Added Graphql

README.md

@@ -34,6 +34,7 @@ RelSpec can read database schemas from multiple sources:
 - [DBML](pkg/readers/dbml/README.md) - Database Markup Language (dbdiagram.io)
 - [DCTX](pkg/readers/dctx/README.md) - Clarion database dictionary format
 - [DrawDB](pkg/readers/drawdb/README.md) - DrawDB JSON format
+- [GraphQL](pkg/readers/graphql/README.md) - GraphQL Schema Definition Language (SDL)
 - [JSON](pkg/readers/json/README.md) - RelSpec canonical JSON format
 - [YAML](pkg/readers/yaml/README.md) - RelSpec canonical YAML format
 
@@ -55,6 +56,7 @@ RelSpec can write database schemas to multiple formats:
 - [DBML](pkg/writers/dbml/README.md) - Database Markup Language
 - [DCTX](pkg/writers/dctx/README.md) - Clarion database dictionary format
 - [DrawDB](pkg/writers/drawdb/README.md) - DrawDB JSON format
+- [GraphQL](pkg/writers/graphql/README.md) - GraphQL Schema Definition Language (SDL)
 - [JSON](pkg/writers/json/README.md) - RelSpec canonical JSON format
 - [YAML](pkg/writers/yaml/README.md) - RelSpec canonical YAML format
 

TODO.md

@@ -18,7 +18,7 @@
 - [] .hbm.xml / schema.xml: Hibernate/Propel mappings (Java/PHP)  (💲 Someone can do this, not me)
 - [ ] Django models.py (Python classes), Sequelize migrations (JS) (💲 Someone can do this, not me)
 - [] .avsc: Avro schema (JSON format for data serialization) (💲 Someone can do this, not me)
-
+- [✔️] GraphQL schema generation
 
 
 ## Documentation
@@ -37,7 +37,7 @@
 - [ ] Web UI for visual editing
 - [ ] REST API server mode
 - [ ] Support for NoSQL databases
-- [ ] GraphQL schema generation
+
 
 ## Performance
 - [ ] Concurrent processing for multiple tables

cmd/relspec/convert.go

@@ -16,6 +16,7 @@ import (
 	"git.warky.dev/wdevs/relspecgo/pkg/readers/drawdb"
 	"git.warky.dev/wdevs/relspecgo/pkg/readers/drizzle"
 	"git.warky.dev/wdevs/relspecgo/pkg/readers/gorm"
+	"git.warky.dev/wdevs/relspecgo/pkg/readers/graphql"
 	"git.warky.dev/wdevs/relspecgo/pkg/readers/json"
 	"git.warky.dev/wdevs/relspecgo/pkg/readers/pgsql"
 	"git.warky.dev/wdevs/relspecgo/pkg/readers/prisma"
@@ -28,6 +29,7 @@ import (
 	wdrawdb "git.warky.dev/wdevs/relspecgo/pkg/writers/drawdb"
 	wdrizzle "git.warky.dev/wdevs/relspecgo/pkg/writers/drizzle"
 	wgorm "git.warky.dev/wdevs/relspecgo/pkg/writers/gorm"
+	wgraphql "git.warky.dev/wdevs/relspecgo/pkg/writers/graphql"
 	wjson "git.warky.dev/wdevs/relspecgo/pkg/writers/json"
 	wpgsql "git.warky.dev/wdevs/relspecgo/pkg/writers/pgsql"
 	wprisma "git.warky.dev/wdevs/relspecgo/pkg/writers/prisma"
@@ -58,6 +60,7 @@ Input formats:
   - dbml: DBML schema files
   - dctx: DCTX schema files
   - drawdb: DrawDB JSON files
+  - graphql: GraphQL schema files (.graphql, SDL)
   - json: JSON database schema
   - yaml: YAML database schema
   - gorm: GORM model files (Go, file or directory)
@@ -71,6 +74,7 @@ Output formats:
   - dbml: DBML schema files
   - dctx: DCTX schema files
   - drawdb: DrawDB JSON files
+  - graphql: GraphQL schema files (.graphql, SDL)
   - json: JSON database schema
   - yaml: YAML database schema
   - gorm: GORM model files (Go)
@@ -136,11 +140,11 @@ Examples:
 }
 
 func init() {
-	convertCmd.Flags().StringVar(&convertSourceType, "from", "", "Source format (dbml, dctx, drawdb, json, yaml, gorm, bun, drizzle, prisma, typeorm, pgsql)")
+	convertCmd.Flags().StringVar(&convertSourceType, "from", "", "Source format (dbml, dctx, drawdb, graphql, json, yaml, gorm, bun, drizzle, prisma, typeorm, pgsql)")
 	convertCmd.Flags().StringVar(&convertSourcePath, "from-path", "", "Source file path (for file-based formats)")
 	convertCmd.Flags().StringVar(&convertSourceConn, "from-conn", "", "Source connection string (for database formats)")
 
-	convertCmd.Flags().StringVar(&convertTargetType, "to", "", "Target format (dbml, dctx, drawdb, json, yaml, gorm, bun, drizzle, prisma, typeorm, pgsql)")
+	convertCmd.Flags().StringVar(&convertTargetType, "to", "", "Target format (dbml, dctx, drawdb, graphql, json, yaml, gorm, bun, drizzle, prisma, typeorm, pgsql)")
 	convertCmd.Flags().StringVar(&convertTargetPath, "to-path", "", "Target output path (file or directory)")
 	convertCmd.Flags().StringVar(&convertPackageName, "package", "", "Package name (for code generation formats like gorm/bun)")
 	convertCmd.Flags().StringVar(&convertSchemaFilter, "schema", "", "Filter to a specific schema by name (required for formats like dctx that only support single schemas)")
@@ -279,6 +283,12 @@ func readDatabaseForConvert(dbType, filePath, connString string) (*models.Databa
 		}
 		reader = typeorm.NewReader(&readers.ReaderOptions{FilePath: filePath})
 
+	case "graphql", "gql":
+		if filePath == "" {
+			return nil, fmt.Errorf("file path is required for GraphQL format")
+		}
+		reader = graphql.NewReader(&readers.ReaderOptions{FilePath: filePath})
+
 	default:
 		return nil, fmt.Errorf("unsupported source format: %s", dbType)
 	}
@@ -339,6 +349,9 @@ func writeDatabase(db *models.Database, dbType, outputPath, packageName, schemaF
 	case "typeorm":
 		writer = wtypeorm.NewWriter(writerOpts)
 
+	case "graphql", "gql":
+		writer = wgraphql.NewWriter(writerOpts)
+
 	default:
 		return fmt.Errorf("unsupported target format: %s", dbType)
 	}

pkg/readers/graphql/README.md

@@ -0,0 +1,203 @@
+# GraphQL Schema Reader
+
+The GraphQL reader parses GraphQL Schema Definition Language (SDL) files and converts them into RelSpec's internal database model.
+
+## Features
+
+- **Standard GraphQL SDL** support (generic, non-framework-specific)
+- **Type to Table mapping**: GraphQL types become database tables
+- **Field to Column mapping**: GraphQL fields become table columns
+- **Enum support**: GraphQL enums are preserved
+- **Custom scalars**: DateTime, JSON, Date automatically mapped to appropriate SQL types
+- **Implicit relationships**: Detects relationships from field types
+- **Many-to-many support**: Creates junction tables for bidirectional array relationships
+- **Configurable ID mapping**: Choose between bigint (default) or UUID for ID fields
+
+## Supported GraphQL Features
+
+### Built-in Scalars
+- `ID` → bigint (default) or uuid (configurable)
+- `String` → text
+- `Int` → integer
+- `Float` → double precision
+- `Boolean` → boolean
+
+### Custom Scalars
+- `DateTime` → timestamp
+- `JSON` → jsonb
+- `Date` → date
+- `Time` → time
+- `Decimal` → numeric
+
+Additional custom scalars can be mapped via metadata.
+
+### Relationships
+
+Relationships are inferred from field types:
+
+```graphql
+type Post {
+  id: ID!
+  title: String!
+  author: User!        # Many-to-one (creates authorId FK column, NOT NULL)
+  reviewer: User       # Many-to-one nullable (creates reviewerId FK column, NULL)
+  tags: [Tag!]!        # One-to-many or many-to-many (depending on reverse)
+}
+
+type User {
+  id: ID!
+  posts: [Post!]!      # Reverse of Post.author (no FK created)
+}
+
+type Tag {
+  id: ID!
+  posts: [Post!]!      # Many-to-many with Post (creates PostTag junction table)
+}
+```
+
+**Relationship Detection Rules:**
+- Single type reference (`user: User`) → Creates FK column (e.g., `userId`)
+- Array type reference (`posts: [Post!]!`) → One-to-many reverse (no FK on this table)
+- Bidirectional arrays → Many-to-many (creates junction table)
+
+### Enums
+
+```graphql
+enum Role {
+  ADMIN
+  USER
+  GUEST
+}
+
+type User {
+  role: Role!
+}
+```
+
+Enums are preserved in the schema and can be used as column types.
+
+## Usage
+
+### Basic Usage
+
+```go
+import (
+    "git.warky.dev/wdevs/relspecgo/pkg/readers"
+    "git.warky.dev/wdevs/relspecgo/pkg/readers/graphql"
+)
+
+opts := &readers.ReaderOptions{
+    FilePath: "schema.graphql",
+}
+
+reader := graphql.NewReader(opts)
+db, err := reader.ReadDatabase()
+```
+
+### With UUID ID Type
+
+```go
+opts := &readers.ReaderOptions{
+    FilePath: "schema.graphql",
+    Metadata: map[string]interface{}{
+        "idType": "uuid",  // Map ID scalar to uuid instead of bigint
+    },
+}
+
+reader := graphql.NewReader(opts)
+db, err := reader.ReadDatabase()
+```
+
+### With Per-Type ID Mapping
+
+```go
+opts := &readers.ReaderOptions{
+    FilePath: "schema.graphql",
+    Metadata: map[string]interface{}{
+        "typeIdMappings": map[string]string{
+            "User": "uuid",    // User.id → uuid
+            "Post": "bigint",  // Post.id → bigint
+        },
+    },
+}
+```
+
+### With Custom Scalar Mappings
+
+```go
+opts := &readers.ReaderOptions{
+    FilePath: "schema.graphql",
+    Metadata: map[string]interface{}{
+        "customScalarMappings": map[string]string{
+            "Upload":  "bytea",
+            "Decimal": "numeric(10,2)",
+        },
+    },
+}
+```
+
+## CLI Usage
+
+```bash
+# Convert GraphQL to JSON
+relspec convert --from graphql --from-path schema.graphql \
+                --to json --to-path schema.json
+
+# Convert GraphQL to GORM models
+relspec convert --from graphql --from-path schema.graphql \
+                --to gorm --to-path models/ --package models
+
+# Convert GraphQL to PostgreSQL SQL
+relspec convert --from graphql --from-path schema.graphql \
+                --to pgsql --to-path schema.sql
+```
+
+## Metadata Options
+
+| Option | Type | Description | Default |
+|--------|------|-------------|---------|
+| `idType` | string | Global ID type mapping ("bigint" or "uuid") | "bigint" |
+| `typeIdMappings` | map[string]string | Per-type ID mappings | {} |
+| `customScalarMappings` | map[string]string | Custom scalar to SQL type mappings | {} |
+| `schemaName` | string | Schema name for all tables | "public" |
+
+## Limitations
+
+- Only supports GraphQL SDL (Schema Definition Language), not queries or mutations
+- Directives are ignored (except for future extensibility)
+- Interfaces and Unions are not supported
+- GraphQL's concept of "schema" is different from database schemas; all types go into a single database schema (default: "public")
+
+## Example
+
+**Input** (`schema.graphql`):
+```graphql
+scalar DateTime
+
+enum Role {
+  ADMIN
+  USER
+}
+
+type User {
+  id: ID!
+  email: String!
+  role: Role!
+  createdAt: DateTime!
+  posts: [Post!]!
+}
+
+type Post {
+  id: ID!
+  title: String!
+  content: String
+  published: Boolean!
+  author: User!
+}
+```
+
+**Result**: Database with:
+- 2 tables: `User` and `Post`
+- `Post` table has `authorId` foreign key to `User.id`
+- `Role` enum with values: ADMIN, USER
+- Custom scalar `DateTime` mapped to `timestamp`

pkg/readers/graphql/reader.go

@@ -0,0 +1,279 @@
+package graphql
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"regexp"
+	"strings"
+
+	"git.warky.dev/wdevs/relspecgo/pkg/models"
+	"git.warky.dev/wdevs/relspecgo/pkg/readers"
+)
+
+type Reader struct {
+	options *readers.ReaderOptions
+}
+
+func NewReader(options *readers.ReaderOptions) *Reader {
+	return &Reader{
+		options: options,
+	}
+}
+
+func (r *Reader) ReadDatabase() (*models.Database, error) {
+	if r.options.FilePath == "" {
+		return nil, fmt.Errorf("file path is required for GraphQL reader")
+	}
+
+	content, err := os.ReadFile(r.options.FilePath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read file: %w", err)
+	}
+
+	return r.parseGraphQL(string(content))
+}
+
+func (r *Reader) ReadSchema() (*models.Schema, error) {
+	db, err := r.ReadDatabase()
+	if err != nil {
+		return nil, err
+	}
+
+	if len(db.Schemas) == 0 {
+		return nil, fmt.Errorf("no schemas found")
+	}
+
+	return db.Schemas[0], nil
+}
+
+func (r *Reader) ReadTable() (*models.Table, error) {
+	schema, err := r.ReadSchema()
+	if err != nil {
+		return nil, err
+	}
+
+	if len(schema.Tables) == 0 {
+		return nil, fmt.Errorf("no tables found")
+	}
+
+	return schema.Tables[0], nil
+}
+
+type parseContext struct {
+	inType        bool
+	inEnum        bool
+	currentType   string
+	typeLines     []string
+	currentEnum   string
+	enumLines     []string
+	customScalars map[string]bool
+}
+
+func (r *Reader) parseGraphQL(content string) (*models.Database, error) {
+	dbName := "database"
+	if r.options.Metadata != nil {
+		if name, ok := r.options.Metadata["name"].(string); ok {
+			dbName = name
+		}
+	}
+
+	db := models.InitDatabase(dbName)
+	schema := models.InitSchema("public")
+
+	ctx := &parseContext{
+		customScalars: make(map[string]bool),
+	}
+
+	// First pass: collect custom scalars and enums
+	scanner := bufio.NewScanner(strings.NewReader(content))
+	scalarRegex := regexp.MustCompile(`^\s*scalar\s+(\w+)`)
+	enumRegex := regexp.MustCompile(`^\s*enum\s+(\w+)\s*\{`)
+	closingBraceRegex := regexp.MustCompile(`^\s*\}`)
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		trimmed := strings.TrimSpace(line)
+
+		if trimmed == "" || strings.HasPrefix(trimmed, "#") {
+			continue
+		}
+
+		if matches := scalarRegex.FindStringSubmatch(trimmed); matches != nil {
+			ctx.customScalars[matches[1]] = true
+			continue
+		}
+
+		if matches := enumRegex.FindStringSubmatch(trimmed); matches != nil {
+			ctx.inEnum = true
+			ctx.currentEnum = matches[1]
+			ctx.enumLines = []string{}
+			continue
+		}
+
+		if closingBraceRegex.MatchString(trimmed) && ctx.inEnum {
+			r.parseEnum(ctx.currentEnum, ctx.enumLines, schema)
+			// Add enum name to custom scalars for type detection
+			ctx.customScalars[ctx.currentEnum] = true
+			ctx.inEnum = false
+			ctx.currentEnum = ""
+			ctx.enumLines = nil
+			continue
+		}
+
+		if ctx.inEnum {
+			ctx.enumLines = append(ctx.enumLines, line)
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, fmt.Errorf("scanner error: %w", err)
+	}
+
+	// Second pass: parse types
+	scanner = bufio.NewScanner(strings.NewReader(content))
+	typeRegex := regexp.MustCompile(`^\s*type\s+(\w+)\s*\{`)
+	ctx.inType = false
+	ctx.inEnum = false
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		trimmed := strings.TrimSpace(line)
+
+		if trimmed == "" || strings.HasPrefix(trimmed, "#") {
+			continue
+		}
+
+		if matches := typeRegex.FindStringSubmatch(trimmed); matches != nil {
+			ctx.inType = true
+			ctx.currentType = matches[1]
+			ctx.typeLines = []string{}
+			continue
+		}
+
+		if closingBraceRegex.MatchString(trimmed) && ctx.inType {
+			if err := r.parseType(ctx.currentType, ctx.typeLines, schema, ctx); err != nil {
+				return nil, fmt.Errorf("failed to parse type %s: %w", ctx.currentType, err)
+			}
+			ctx.inType = false
+			ctx.currentType = ""
+			ctx.typeLines = nil
+			continue
+		}
+
+		if ctx.inType {
+			ctx.typeLines = append(ctx.typeLines, line)
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, fmt.Errorf("scanner error: %w", err)
+	}
+
+	db.Schemas = []*models.Schema{schema}
+
+	// Third pass: detect and create relationships
+	if err := r.detectAndCreateRelationships(schema, ctx); err != nil {
+		return nil, fmt.Errorf("failed to create relationships: %w", err)
+	}
+
+	return db, nil
+}
+
+type fieldInfo struct {
+	name          string
+	typeName      string
+	isArray       bool
+	isNullable    bool
+	innerNullable bool
+}
+
+func (r *Reader) parseType(typeName string, lines []string, schema *models.Schema, ctx *parseContext) error {
+	table := models.InitTable(typeName, schema.Name)
+	table.Metadata = make(map[string]any)
+
+	// Store field info for relationship detection
+	relationFields := make(map[string]*fieldInfo)
+
+	fieldRegex := regexp.MustCompile(`^\s*(\w+)\s*:\s*(\[)?(\w+)(!)?(\])?(!)?\s*`)
+
+	for _, line := range lines {
+		trimmed := strings.TrimSpace(line)
+		if trimmed == "" || strings.HasPrefix(trimmed, "#") {
+			continue
+		}
+
+		matches := fieldRegex.FindStringSubmatch(trimmed)
+		if matches == nil {
+			continue
+		}
+
+		fieldName := matches[1]
+		hasOpenBracket := matches[2] == "["
+		baseType := matches[3]
+		innerNonNull := matches[4] == "!"
+		hasCloseBracket := matches[5] == "]"
+		outerNonNull := matches[6] == "!"
+
+		isArray := hasOpenBracket && hasCloseBracket
+
+		// Determine if this is a scalar or a relation
+		if r.isScalarType(baseType, ctx) {
+			// This is a scalar field
+			column := models.InitColumn(fieldName, table.Name, schema.Name)
+			column.Type = r.graphQLTypeToSQL(baseType, fieldName, typeName)
+
+			if isArray {
+				// Array of scalars: use array type
+				column.Type += "[]"
+				column.NotNull = outerNonNull
+			} else {
+				column.NotNull = !isArray && innerNonNull
+			}
+
+			// Check if this is a primary key (convention: field named "id")
+			if fieldName == "id" {
+				column.IsPrimaryKey = true
+				column.AutoIncrement = true
+			}
+
+			table.Columns[fieldName] = column
+		} else {
+			// This is a relation field - store for later processing
+			relationFields[fieldName] = &fieldInfo{
+				name:          fieldName,
+				typeName:      baseType,
+				isArray:       isArray,
+				isNullable:    !innerNonNull && !isArray,
+				innerNullable: !innerNonNull && isArray,
+			}
+		}
+	}
+
+	// Store relation fields in table metadata for relationship detection
+	if len(relationFields) > 0 {
+		table.Metadata["relationFields"] = relationFields
+	}
+
+	schema.Tables = append(schema.Tables, table)
+	return nil
+}
+
+func (r *Reader) parseEnum(enumName string, lines []string, schema *models.Schema) {
+	enum := &models.Enum{
+		Name:   enumName,
+		Schema: schema.Name,
+		Values: make([]string, 0),
+	}
+
+	for _, line := range lines {
+		trimmed := strings.TrimSpace(line)
+		if trimmed == "" || strings.HasPrefix(trimmed, "#") {
+			continue
+		}
+		// Enum values are simple identifiers
+		enum.Values = append(enum.Values, trimmed)
+	}
+
+	schema.Enums = append(schema.Enums, enum)
+}

pkg/readers/graphql/reader_test.go

@@ -0,0 +1,362 @@
+package graphql
+
+import (
+	"path/filepath"
+	"testing"
+
+	"git.warky.dev/wdevs/relspecgo/pkg/models"
+	"git.warky.dev/wdevs/relspecgo/pkg/readers"
+)
+
+func TestReader_ReadDatabase_Simple(t *testing.T) {
+	opts := &readers.ReaderOptions{
+		FilePath: filepath.Join("..", "..", "..", "tests", "assets", "graphql", "simple.graphql"),
+	}
+
+	reader := NewReader(opts)
+	db, err := reader.ReadDatabase()
+	if err != nil {
+		t.Fatalf("ReadDatabase() error = %v", err)
+	}
+
+	if len(db.Schemas) == 0 {
+		t.Fatal("Expected at least one schema")
+	}
+
+	schema := db.Schemas[0]
+	if schema.Name != "public" {
+		t.Errorf("Expected schema name 'public', got '%s'", schema.Name)
+	}
+
+	if len(schema.Tables) != 1 {
+		t.Fatalf("Expected 1 table, got %d", len(schema.Tables))
+	}
+
+	userTable := schema.Tables[0]
+	if userTable.Name != "User" {
+		t.Errorf("Expected table name 'User', got '%s'", userTable.Name)
+	}
+
+	// Verify columns
+	expectedColumns := map[string]struct {
+		sqlType string
+		notNull bool
+		isPK    bool
+	}{
+		"id":     {"bigint", true, true},
+		"email":  {"text", true, false},
+		"name":   {"text", false, false},
+		"age":    {"integer", false, false},
+		"active": {"boolean", true, false},
+	}
+
+	if len(userTable.Columns) != len(expectedColumns) {
+		t.Fatalf("Expected %d columns, got %d", len(expectedColumns), len(userTable.Columns))
+	}
+
+	for colName, expected := range expectedColumns {
+		col, exists := userTable.Columns[colName]
+		if !exists {
+			t.Errorf("Expected column '%s' not found", colName)
+			continue
+		}
+
+		if col.Type != expected.sqlType {
+			t.Errorf("Column '%s': expected type '%s', got '%s'", colName, expected.sqlType, col.Type)
+		}
+
+		if col.NotNull != expected.notNull {
+			t.Errorf("Column '%s': expected NotNull=%v, got %v", colName, expected.notNull, col.NotNull)
+		}
+
+		if col.IsPrimaryKey != expected.isPK {
+			t.Errorf("Column '%s': expected IsPrimaryKey=%v, got %v", colName, expected.isPK, col.IsPrimaryKey)
+		}
+	}
+}
+
+func TestReader_ReadDatabase_WithRelations(t *testing.T) {
+	opts := &readers.ReaderOptions{
+		FilePath: filepath.Join("..", "..", "..", "tests", "assets", "graphql", "relations.graphql"),
+	}
+
+	reader := NewReader(opts)
+	db, err := reader.ReadDatabase()
+	if err != nil {
+		t.Fatalf("ReadDatabase() error = %v", err)
+	}
+
+	schema := db.Schemas[0]
+
+	if len(schema.Tables) != 2 {
+		t.Fatalf("Expected 2 tables, got %d", len(schema.Tables))
+	}
+
+	// Find Post table (should have FK to User)
+	var postTable *models.Table
+	for _, table := range schema.Tables {
+		if table.Name == "Post" {
+			postTable = table
+			break
+		}
+	}
+
+	if postTable == nil {
+		t.Fatal("Post table not found")
+	}
+
+	// Verify authorId FK column was created
+	authorIdCol, exists := postTable.Columns["authorId"]
+	if !exists {
+		t.Fatal("Expected 'authorId' FK column not found in Post table")
+	}
+
+	if authorIdCol.Type != "bigint" {
+		t.Errorf("Expected authorId type 'bigint', got '%s'", authorIdCol.Type)
+	}
+
+	if !authorIdCol.NotNull {
+		t.Error("Expected authorId to be NOT NULL")
+	}
+
+	// Verify FK constraint
+	fkConstraintFound := false
+	for _, constraint := range postTable.Constraints {
+		if constraint.Type == models.ForeignKeyConstraint {
+			if constraint.ReferencedTable == "User" && len(constraint.Columns) > 0 && constraint.Columns[0] == "authorId" {
+				fkConstraintFound = true
+				if constraint.OnDelete != "CASCADE" {
+					t.Errorf("Expected OnDelete CASCADE, got %s", constraint.OnDelete)
+				}
+				break
+			}
+		}
+	}
+
+	if !fkConstraintFound {
+		t.Error("Foreign key constraint from Post to User not found")
+	}
+}
+
+func TestReader_ReadDatabase_WithEnums(t *testing.T) {
+	opts := &readers.ReaderOptions{
+		FilePath: filepath.Join("..", "..", "..", "tests", "assets", "graphql", "enums.graphql"),
+	}
+
+	reader := NewReader(opts)
+	db, err := reader.ReadDatabase()
+	if err != nil {
+		t.Fatalf("ReadDatabase() error = %v", err)
+	}
+
+	schema := db.Schemas[0]
+
+	if len(schema.Enums) != 1 {
+		t.Fatalf("Expected 1 enum, got %d", len(schema.Enums))
+	}
+
+	roleEnum := schema.Enums[0]
+	if roleEnum.Name != "Role" {
+		t.Errorf("Expected enum name 'Role', got '%s'", roleEnum.Name)
+	}
+
+	expectedValues := []string{"ADMIN", "USER", "GUEST"}
+	if len(roleEnum.Values) != len(expectedValues) {
+		t.Fatalf("Expected %d enum values, got %d", len(expectedValues), len(roleEnum.Values))
+	}
+
+	for i, expected := range expectedValues {
+		if roleEnum.Values[i] != expected {
+			t.Errorf("Expected enum value '%s' at index %d, got '%s'", expected, i, roleEnum.Values[i])
+		}
+	}
+
+	// Verify role column in User table
+	userTable := schema.Tables[0]
+	roleCol, exists := userTable.Columns["role"]
+	if !exists {
+		t.Fatal("Expected 'role' column not found")
+	}
+
+	if roleCol.Type != "Role" {
+		t.Errorf("Expected role type 'Role', got '%s'", roleCol.Type)
+	}
+}
+
+func TestReader_ReadDatabase_CustomScalars(t *testing.T) {
+	opts := &readers.ReaderOptions{
+		FilePath: filepath.Join("..", "..", "..", "tests", "assets", "graphql", "custom_scalars.graphql"),
+	}
+
+	reader := NewReader(opts)
+	db, err := reader.ReadDatabase()
+	if err != nil {
+		t.Fatalf("ReadDatabase() error = %v", err)
+	}
+
+	schema := db.Schemas[0]
+	userTable := schema.Tables[0]
+
+	// Verify custom scalar mappings
+	expectedTypes := map[string]string{
+		"createdAt": "timestamp",
+		"metadata":  "jsonb",
+		"birthDate": "date",
+	}
+
+	for colName, expectedType := range expectedTypes {
+		col, exists := userTable.Columns[colName]
+		if !exists {
+			t.Errorf("Expected column '%s' not found", colName)
+			continue
+		}
+
+		if col.Type != expectedType {
+			t.Errorf("Column '%s': expected type '%s', got '%s'", colName, expectedType, col.Type)
+		}
+	}
+}
+
+func TestReader_ReadDatabase_UUIDMetadata(t *testing.T) {
+	opts := &readers.ReaderOptions{
+		FilePath: filepath.Join("..", "..", "..", "tests", "assets", "graphql", "simple.graphql"),
+		Metadata: map[string]interface{}{
+			"idType": "uuid",
+		},
+	}
+
+	reader := NewReader(opts)
+	db, err := reader.ReadDatabase()
+	if err != nil {
+		t.Fatalf("ReadDatabase() error = %v", err)
+	}
+
+	schema := db.Schemas[0]
+	userTable := schema.Tables[0]
+
+	idCol, exists := userTable.Columns["id"]
+	if !exists {
+		t.Fatal("Expected 'id' column not found")
+	}
+
+	if idCol.Type != "uuid" {
+		t.Errorf("Expected id type 'uuid' with metadata, got '%s'", idCol.Type)
+	}
+}
+
+func TestReader_ReadDatabase_Complex(t *testing.T) {
+	opts := &readers.ReaderOptions{
+		FilePath: filepath.Join("..", "..", "..", "tests", "assets", "graphql", "complex.graphql"),
+	}
+
+	reader := NewReader(opts)
+	db, err := reader.ReadDatabase()
+	if err != nil {
+		t.Fatalf("ReadDatabase() error = %v", err)
+	}
+
+	schema := db.Schemas[0]
+
+	// Should have 5 tables: User, Profile, Post, Tag, and PostTag (join table)
+	expectedTableCount := 5
+	if len(schema.Tables) != expectedTableCount {
+		t.Fatalf("Expected %d tables, got %d", expectedTableCount, len(schema.Tables))
+	}
+
+	// Verify PostTag join table exists (many-to-many between Post and Tag)
+	var joinTable *models.Table
+	for _, table := range schema.Tables {
+		if table.Name == "PostTag" {
+			joinTable = table
+			break
+		}
+	}
+
+	if joinTable == nil {
+		t.Fatal("Expected PostTag join table not found")
+	}
+
+	// Verify join table has both FK columns
+	if _, exists := joinTable.Columns["postId"]; !exists {
+		t.Error("Expected 'postId' column in PostTag join table")
+	}
+
+	if _, exists := joinTable.Columns["tagId"]; !exists {
+		t.Error("Expected 'tagId' column in PostTag join table")
+	}
+
+	// Verify composite primary key
+	pkFound := false
+	for _, constraint := range joinTable.Constraints {
+		if constraint.Type == models.PrimaryKeyConstraint {
+			if len(constraint.Columns) == 2 {
+				pkFound = true
+			}
+			break
+		}
+	}
+
+	if !pkFound {
+		t.Error("Expected composite primary key in PostTag join table")
+	}
+}
+
+func TestReader_ReadSchema(t *testing.T) {
+	opts := &readers.ReaderOptions{
+		FilePath: filepath.Join("..", "..", "..", "tests", "assets", "graphql", "simple.graphql"),
+	}
+
+	reader := NewReader(opts)
+	schema, err := reader.ReadSchema()
+	if err != nil {
+		t.Fatalf("ReadSchema() error = %v", err)
+	}
+
+	if schema.Name != "public" {
+		t.Errorf("Expected schema name 'public', got '%s'", schema.Name)
+	}
+
+	if len(schema.Tables) != 1 {
+		t.Errorf("Expected 1 table, got %d", len(schema.Tables))
+	}
+}
+
+func TestReader_ReadTable(t *testing.T) {
+	opts := &readers.ReaderOptions{
+		FilePath: filepath.Join("..", "..", "..", "tests", "assets", "graphql", "simple.graphql"),
+	}
+
+	reader := NewReader(opts)
+	table, err := reader.ReadTable()
+	if err != nil {
+		t.Fatalf("ReadTable() error = %v", err)
+	}
+
+	if table.Name != "User" {
+		t.Errorf("Expected table name 'User', got '%s'", table.Name)
+	}
+}
+
+func TestReader_InvalidPath(t *testing.T) {
+	opts := &readers.ReaderOptions{
+		FilePath: "/nonexistent/path.graphql",
+	}
+
+	reader := NewReader(opts)
+	_, err := reader.ReadDatabase()
+	if err == nil {
+		t.Error("Expected error for invalid path, got nil")
+	}
+}
+
+func TestReader_EmptyPath(t *testing.T) {
+	opts := &readers.ReaderOptions{
+		FilePath: "",
+	}
+
+	reader := NewReader(opts)
+	_, err := reader.ReadDatabase()
+	if err == nil {
+		t.Error("Expected error for empty path, got nil")
+	}
+}

pkg/readers/graphql/relationships.go

@@ -0,0 +1,225 @@
+package graphql
+
+import (
+	"fmt"
+	"strings"
+
+	"git.warky.dev/wdevs/relspecgo/pkg/models"
+)
+
+func (r *Reader) detectAndCreateRelationships(schema *models.Schema, ctx *parseContext) error {
+	// Build table lookup map
+	tableMap := make(map[string]*models.Table)
+	for _, table := range schema.Tables {
+		tableMap[table.Name] = table
+	}
+
+	// Process each table's relation fields
+	for _, table := range schema.Tables {
+		relationFields, ok := table.Metadata["relationFields"].(map[string]*fieldInfo)
+		if !ok || len(relationFields) == 0 {
+			continue
+		}
+
+		for fieldName, fieldInfo := range relationFields {
+			targetTable, exists := tableMap[fieldInfo.typeName]
+			if !exists {
+				// Referenced type doesn't exist - might be an interface/union, skip
+				continue
+			}
+
+			if fieldInfo.isArray {
+				// This is a one-to-many or many-to-many reverse side
+				// Check if target table has a reverse array field
+				if r.hasReverseArrayField(targetTable, table.Name) {
+					// Bidirectional array = many-to-many
+					// Only create join table once (lexicographically first table creates it)
+					if table.Name < targetTable.Name {
+						if err := r.createManyToManyJoinTable(schema, table, targetTable, fieldName, tableMap); err != nil {
+							return err
+						}
+					}
+				}
+				// For one-to-many, no action needed (FK is on the other table)
+			} else {
+				// This is a many-to-one or one-to-one
+				// Create FK column on this table
+				if err := r.createForeignKeyColumn(table, targetTable, fieldName, fieldInfo.isNullable, schema); err != nil {
+					return err
+				}
+			}
+		}
+	}
+
+	// Clean up metadata
+	for _, table := range schema.Tables {
+		delete(table.Metadata, "relationFields")
+	}
+
+	return nil
+}
+
+func (r *Reader) hasReverseArrayField(table *models.Table, targetTypeName string) bool {
+	relationFields, ok := table.Metadata["relationFields"].(map[string]*fieldInfo)
+	if !ok {
+		return false
+	}
+
+	for _, fieldInfo := range relationFields {
+		if fieldInfo.typeName == targetTypeName && fieldInfo.isArray {
+			return true
+		}
+	}
+
+	return false
+}
+
+func (r *Reader) createForeignKeyColumn(fromTable, toTable *models.Table, fieldName string, nullable bool, schema *models.Schema) error {
+	// Get primary key from target table
+	pkCol := toTable.GetPrimaryKey()
+	if pkCol == nil {
+		return fmt.Errorf("target table %s has no primary key for relationship", toTable.Name)
+	}
+
+	// Create FK column name: {fieldName}Id
+	fkColName := fieldName + "Id"
+
+	// Check if column already exists (shouldn't happen but be safe)
+	if _, exists := fromTable.Columns[fkColName]; exists {
+		return nil
+	}
+
+	// Create FK column
+	fkCol := models.InitColumn(fkColName, fromTable.Name, schema.Name)
+	fkCol.Type = pkCol.Type
+	fkCol.NotNull = !nullable
+
+	fromTable.Columns[fkColName] = fkCol
+
+	// Create FK constraint
+	constraint := models.InitConstraint(
+		fmt.Sprintf("fk_%s_%s", fromTable.Name, fieldName),
+		models.ForeignKeyConstraint,
+	)
+	constraint.Schema = schema.Name
+	constraint.Table = fromTable.Name
+	constraint.Columns = []string{fkColName}
+	constraint.ReferencedSchema = schema.Name
+	constraint.ReferencedTable = toTable.Name
+	constraint.ReferencedColumns = []string{pkCol.Name}
+	constraint.OnDelete = "CASCADE"
+	constraint.OnUpdate = "RESTRICT"
+
+	fromTable.Constraints[constraint.Name] = constraint
+
+	// Create relationship
+	relationship := models.InitRelationship(
+		fmt.Sprintf("rel_%s_%s", fromTable.Name, fieldName),
+		models.OneToMany,
+	)
+	relationship.FromTable = fromTable.Name
+	relationship.FromSchema = schema.Name
+	relationship.FromColumns = []string{fkColName}
+	relationship.ToTable = toTable.Name
+	relationship.ToSchema = schema.Name
+	relationship.ToColumns = []string{pkCol.Name}
+	relationship.ForeignKey = constraint.Name
+
+	fromTable.Relationships[relationship.Name] = relationship
+
+	return nil
+}
+
+func (r *Reader) createManyToManyJoinTable(schema *models.Schema, table1, table2 *models.Table, fieldName string, tableMap map[string]*models.Table) error {
+	// Create join table name
+	joinTableName := table1.Name + table2.Name
+
+	// Check if join table already exists
+	if _, exists := tableMap[joinTableName]; exists {
+		return nil
+	}
+
+	// Get primary keys
+	pk1 := table1.GetPrimaryKey()
+	pk2 := table2.GetPrimaryKey()
+
+	if pk1 == nil || pk2 == nil {
+		return fmt.Errorf("cannot create many-to-many: tables must have primary keys")
+	}
+
+	// Create join table
+	joinTable := models.InitTable(joinTableName, schema.Name)
+
+	// Create FK column for table1
+	fkCol1Name := strings.ToLower(table1.Name) + "Id"
+	fkCol1 := models.InitColumn(fkCol1Name, joinTable.Name, schema.Name)
+	fkCol1.Type = pk1.Type
+	fkCol1.NotNull = true
+	joinTable.Columns[fkCol1Name] = fkCol1
+
+	// Create FK column for table2
+	fkCol2Name := strings.ToLower(table2.Name) + "Id"
+	fkCol2 := models.InitColumn(fkCol2Name, joinTable.Name, schema.Name)
+	fkCol2.Type = pk2.Type
+	fkCol2.NotNull = true
+	joinTable.Columns[fkCol2Name] = fkCol2
+
+	// Create composite primary key
+	pkConstraint := models.InitConstraint(
+		fmt.Sprintf("pk_%s", joinTableName),
+		models.PrimaryKeyConstraint,
+	)
+	pkConstraint.Schema = schema.Name
+	pkConstraint.Table = joinTable.Name
+	pkConstraint.Columns = []string{fkCol1Name, fkCol2Name}
+	joinTable.Constraints[pkConstraint.Name] = pkConstraint
+
+	// Create FK constraint to table1
+	fk1 := models.InitConstraint(
+		fmt.Sprintf("fk_%s_%s", joinTableName, table1.Name),
+		models.ForeignKeyConstraint,
+	)
+	fk1.Schema = schema.Name
+	fk1.Table = joinTable.Name
+	fk1.Columns = []string{fkCol1Name}
+	fk1.ReferencedSchema = schema.Name
+	fk1.ReferencedTable = table1.Name
+	fk1.ReferencedColumns = []string{pk1.Name}
+	fk1.OnDelete = "CASCADE"
+	fk1.OnUpdate = "RESTRICT"
+	joinTable.Constraints[fk1.Name] = fk1
+
+	// Create FK constraint to table2
+	fk2 := models.InitConstraint(
+		fmt.Sprintf("fk_%s_%s", joinTableName, table2.Name),
+		models.ForeignKeyConstraint,
+	)
+	fk2.Schema = schema.Name
+	fk2.Table = joinTable.Name
+	fk2.Columns = []string{fkCol2Name}
+	fk2.ReferencedSchema = schema.Name
+	fk2.ReferencedTable = table2.Name
+	fk2.ReferencedColumns = []string{pk2.Name}
+	fk2.OnDelete = "CASCADE"
+	fk2.OnUpdate = "RESTRICT"
+	joinTable.Constraints[fk2.Name] = fk2
+
+	// Create relationships
+	rel1 := models.InitRelationship(
+		fmt.Sprintf("rel_%s_%s_%s", joinTableName, table1.Name, table2.Name),
+		models.ManyToMany,
+	)
+	rel1.FromTable = table1.Name
+	rel1.FromSchema = schema.Name
+	rel1.ToTable = table2.Name
+	rel1.ToSchema = schema.Name
+	rel1.ThroughTable = joinTableName
+	rel1.ThroughSchema = schema.Name
+	joinTable.Relationships[rel1.Name] = rel1
+
+	// Add join table to schema
+	schema.Tables = append(schema.Tables, joinTable)
+	tableMap[joinTableName] = joinTable
+
+	return nil
+}

pkg/readers/graphql/type_mapping.go

@@ -0,0 +1,97 @@
+package graphql
+
+func (r *Reader) isScalarType(typeName string, ctx *parseContext) bool {
+	// Built-in GraphQL scalars
+	builtInScalars := map[string]bool{
+		"ID":      true,
+		"String":  true,
+		"Int":     true,
+		"Float":   true,
+		"Boolean": true,
+	}
+
+	if builtInScalars[typeName] {
+		return true
+	}
+
+	// Custom scalars declared in the schema
+	if ctx.customScalars[typeName] {
+		return true
+	}
+
+	// Common custom scalars (even if not declared)
+	commonCustomScalars := map[string]bool{
+		"DateTime": true,
+		"JSON":     true,
+		"Date":     true,
+		"Time":     true,
+		"Upload":   true,
+		"Decimal":  true,
+	}
+
+	return commonCustomScalars[typeName]
+}
+
+func (r *Reader) graphQLTypeToSQL(gqlType string, fieldName string, typeName string) string {
+	// Check for ID type with configurable mapping
+	if gqlType == "ID" {
+		// Check metadata for ID type preference
+		if r.options.Metadata != nil {
+			// Global idType setting
+			if idType, ok := r.options.Metadata["idType"].(string); ok {
+				if idType == "uuid" {
+					return "uuid"
+				}
+			}
+
+			// Per-type ID mapping
+			if typeIdMappings, ok := r.options.Metadata["typeIdMappings"].(map[string]string); ok {
+				if idType, ok := typeIdMappings[typeName]; ok {
+					if idType == "uuid" {
+						return "uuid"
+					}
+				}
+			}
+		}
+
+		return "bigint" // Default
+	}
+
+	// Custom scalar mappings
+	if r.options.Metadata != nil {
+		if customMappings, ok := r.options.Metadata["customScalarMappings"].(map[string]string); ok {
+			if sqlType, ok := customMappings[gqlType]; ok {
+				return sqlType
+			}
+		}
+	}
+
+	// Built-in custom scalar mappings
+	customScalars := map[string]string{
+		"DateTime": "timestamp",
+		"JSON":     "jsonb",
+		"Date":     "date",
+		"Time":     "time",
+		"Decimal":  "numeric",
+		"Upload":   "bytea",
+	}
+	if sqlType, ok := customScalars[gqlType]; ok {
+		return sqlType
+	}
+
+	// Standard scalar mappings
+	typeMap := map[string]string{
+		"String":  "text",
+		"Int":     "integer",
+		"Float":   "double precision",
+		"Boolean": "boolean",
+	}
+
+	if sqlType, ok := typeMap[gqlType]; ok {
+		return sqlType
+	}
+
+	// If not a known scalar, assume it's an enum or custom type
+	// Return as-is (might be an enum)
+	return gqlType
+}

pkg/writers/graphql/README.md

@@ -0,0 +1,272 @@
+# GraphQL Schema Writer
+
+The GraphQL writer converts RelSpec's internal database model into GraphQL Schema Definition Language (SDL) files.
+
+## Features
+
+- **Table to Type mapping**: Database tables become GraphQL types
+- **Column to Field mapping**: Table columns become type fields
+- **Enum support**: Database enums are preserved
+- **Custom scalar declarations**: Automatically declares DateTime, JSON, Date scalars
+- **Implicit relationships**: Generates relationship fields from foreign keys
+- **Many-to-many support**: Handles junction tables intelligently
+- **Clean output**: Proper formatting, field ordering, and comments
+
+## Type Mappings
+
+### SQL to GraphQL
+
+| SQL Type | GraphQL Type | Notes |
+|----------|--------------|-------|
+| bigint, integer, serial (PK) | ID | Primary keys map to ID |
+| bigint, integer, int | Int | |
+| text, varchar, char | String | |
+| uuid (PK) | ID | UUID primary keys also map to ID |
+| uuid | String | Non-PK UUIDs map to String |
+| double precision, numeric, float | Float | |
+| boolean | Boolean | |
+| timestamp, timestamptz | DateTime | Custom scalar |
+| jsonb, json | JSON | Custom scalar |
+| date | Date | Custom scalar |
+| Enum types | Enum | Preserves enum name |
+| Arrays (e.g., text[]) | [Type] | Mapped to GraphQL lists |
+
+## Relationship Handling
+
+The writer intelligently generates relationship fields based on foreign key constraints:
+
+### Forward Relationships (FK on this table)
+```sql
+-- Post table has authorId FK to User.id
+CREATE TABLE post (
+  id bigint PRIMARY KEY,
+  title text NOT NULL,
+  author_id bigint NOT NULL REFERENCES user(id)
+);
+```
+
+```graphql
+type Post {
+  id: ID!
+  title: String!
+  author: User!  # Generated from authorId FK
+}
+```
+
+### Reverse Relationships (FK on other table)
+```graphql
+type User {
+  id: ID!
+  email: String!
+  posts: [Post!]!  # Reverse relationship (Post has FK to User)
+}
+```
+
+### Many-to-Many Relationships
+
+Junction tables (tables with only PKs and FKs) are automatically detected and hidden:
+
+```sql
+CREATE TABLE post_tag (
+  post_id bigint NOT NULL REFERENCES post(id),
+  tag_id bigint NOT NULL REFERENCES tag(id),
+  PRIMARY KEY (post_id, tag_id)
+);
+```
+
+```graphql
+type Post {
+  id: ID!
+  tags: [Tag!]!  # Many-to-many through PostTag junction table
+}
+
+type Tag {
+  id: ID!
+  posts: [Post!]!  # Reverse many-to-many
+}
+
+# Note: PostTag junction table is NOT included in output
+```
+
+## Usage
+
+### Basic Usage
+
+```go
+import (
+    "git.warky.dev/wdevs/relspecgo/pkg/models"
+    "git.warky.dev/wdevs/relspecgo/pkg/writers"
+    "git.warky.dev/wdevs/relspecgo/pkg/writers/graphql"
+)
+
+opts := &writers.WriterOptions{
+    OutputPath: "schema.graphql",
+}
+
+writer := graphql.NewWriter(opts)
+err := writer.WriteDatabase(db)
+```
+
+### With Metadata Options
+
+```go
+opts := &writers.WriterOptions{
+    OutputPath: "schema.graphql",
+    Metadata: map[string]any{
+        "includeScalarDeclarations": true,   // Include scalar declarations
+        "includeComments":            true,  // Include field/table comments
+    },
+}
+
+writer := graphql.NewWriter(opts)
+err := writer.WriteDatabase(db)
+```
+
+### Write to Stdout
+
+```go
+opts := &writers.WriterOptions{
+    OutputPath: "",  // Empty path writes to stdout
+}
+
+writer := graphql.NewWriter(opts)
+err := writer.WriteDatabase(db)
+```
+
+## CLI Usage
+
+```bash
+# Convert PostgreSQL database to GraphQL
+relspec convert --from pgsql \
+                --from-conn "postgres://user:pass@localhost:5432/mydb" \
+                --to graphql --to-path schema.graphql
+
+# Convert GORM models to GraphQL
+relspec convert --from gorm --from-path ./models \
+                --to graphql --to-path schema.graphql
+
+# Convert JSON to GraphQL
+relspec convert --from json --from-path schema.json \
+                --to graphql --to-path schema.graphql
+```
+
+## Output Format
+
+The generated GraphQL schema follows this structure:
+
+1. **Header comment** (if enabled)
+2. **Custom scalar declarations** (if any custom scalars are used)
+3. **Enum definitions** (alphabetically sorted)
+4. **Type definitions** (with fields ordered: ID first, then scalars alphabetically, then relationships)
+
+### Example Output
+
+```graphql
+# Generated GraphQL Schema
+# Database: myapp
+
+scalar DateTime
+scalar JSON
+scalar Date
+
+enum Role {
+  ADMIN
+  USER
+  MODERATOR
+}
+
+type User {
+  id: ID!
+  createdAt: DateTime!
+  email: String!
+  name: String!
+  role: Role!
+
+  posts: [Post!]!
+  profile: Profile
+}
+
+type Post {
+  id: ID!
+  content: String
+  published: Boolean!
+  publishedAt: Date
+  title: String!
+
+  author: User!
+  tags: [Tag!]!
+}
+
+type Tag {
+  id: ID!
+  name: String!
+
+  posts: [Post!]!
+}
+```
+
+## Metadata Options
+
+| Option | Type | Description | Default |
+|--------|------|-------------|---------|
+| `includeScalarDeclarations` | bool | Include `scalar DateTime`, etc. declarations | true |
+| `includeComments` | bool | Include table/field descriptions as comments | true |
+| `preservePKType` | bool | Use Int/String for PKs instead of ID | false |
+
+## Field Naming Conventions
+
+- **FK columns**: Foreign key columns like `authorId` are removed from the output; instead, a relationship field `author` is generated
+- **Relationship pluralization**: Reverse one-to-many relationships are pluralized (e.g., `posts`, `tags`)
+- **CamelCase**: Field names are kept in their original casing from the database
+
+## Junction Table Detection
+
+A table is considered a junction table if it:
+1. Has exactly 2 foreign key constraints
+2. All columns are either primary keys or foreign keys
+3. Has a composite primary key on the FK columns
+
+Junction tables are automatically hidden from the GraphQL output, and many-to-many relationship fields are generated on the related types instead.
+
+## Limitations
+
+- All tables in all schemas are flattened into a single GraphQL schema
+- No support for GraphQL-specific features like directives, interfaces, or unions
+- Nullable vs non-nullable is determined solely by the `NOT NULL` constraint
+
+## Example Conversion
+
+**Input** (Database Schema):
+```sql
+CREATE TABLE user (
+  id bigint PRIMARY KEY,
+  email text NOT NULL,
+  created_at timestamp NOT NULL
+);
+
+CREATE TABLE post (
+  id bigint PRIMARY KEY,
+  title text NOT NULL,
+  author_id bigint NOT NULL REFERENCES user(id)
+);
+```
+
+**Output** (GraphQL Schema):
+```graphql
+scalar DateTime
+
+type User {
+  id: ID!
+  createdAt: DateTime!
+  email: String!
+
+  posts: [Post!]!
+}
+
+type Post {
+  id: ID!
+  title: String!
+
+  author: User!
+}
+```

pkg/writers/graphql/relationships.go

@@ -0,0 +1,178 @@
+package graphql
+
+import (
+	"fmt"
+	"strings"
+
+	"git.warky.dev/wdevs/relspecgo/pkg/models"
+)
+
+func (w *Writer) generateRelationFields(table *models.Table, db *models.Database, schema *models.Schema) []string {
+	var fields []string
+
+	// 1. Forward relationships (this table has FK)
+	for _, constraint := range table.Constraints {
+		if constraint.Type != models.ForeignKeyConstraint {
+			continue
+		}
+
+		// Find the related table
+		relatedTable := w.findTable(db, constraint.ReferencedSchema, constraint.ReferencedTable)
+		if relatedTable == nil {
+			continue
+		}
+
+		// Generate field name (remove "Id" suffix from FK column if present)
+		fieldName := w.relationFieldName(constraint.Columns[0])
+
+		// Determine nullability from FK column
+		nullable := true
+		for _, colName := range constraint.Columns {
+			if col, exists := table.Columns[colName]; exists {
+				if col.NotNull {
+					nullable = false
+					break
+				}
+			}
+		}
+
+		// Format: fieldName: RelatedType! or fieldName: RelatedType
+		gqlType := relatedTable.Name
+		if !nullable {
+			gqlType += "!"
+		}
+
+		fields = append(fields, fmt.Sprintf("  %s: %s", fieldName, gqlType))
+	}
+
+	// 2. Reverse relationships (other tables reference this table)
+	for _, otherSchema := range db.Schemas {
+		for _, otherTable := range otherSchema.Tables {
+			if otherTable.Name == table.Name && otherSchema.Name == schema.Name {
+				continue
+			}
+
+			// Skip join tables for many-to-many
+			if w.isJoinTable(otherTable) {
+				// Check if this is a many-to-many through this join table
+				if m2mField := w.getManyToManyField(table, otherTable, db); m2mField != "" {
+					fields = append(fields, m2mField)
+				}
+				continue
+			}
+
+			for _, constraint := range otherTable.Constraints {
+				if constraint.Type == models.ForeignKeyConstraint &&
+					constraint.ReferencedTable == table.Name &&
+					constraint.ReferencedSchema == schema.Name {
+					// Add reverse relationship field (array)
+					fieldName := w.pluralize(w.camelCase(otherTable.Name))
+					fields = append(fields, fmt.Sprintf("  %s: [%s!]!", fieldName, otherTable.Name))
+				}
+			}
+		}
+	}
+
+	return fields
+}
+
+func (w *Writer) getManyToManyField(table *models.Table, joinTable *models.Table, db *models.Database) string {
+	// Find the two FK constraints in the join table
+	var fk1, fk2 *models.Constraint
+	for _, constraint := range joinTable.Constraints {
+		if constraint.Type == models.ForeignKeyConstraint {
+			if fk1 == nil {
+				fk1 = constraint
+			} else {
+				fk2 = constraint
+			}
+		}
+	}
+
+	if fk1 == nil || fk2 == nil {
+		return ""
+	}
+
+	// Determine which FK points to our table and which to the other table
+	var targetConstraint *models.Constraint
+	if fk1.ReferencedTable == table.Name {
+		targetConstraint = fk2
+	} else if fk2.ReferencedTable == table.Name {
+		targetConstraint = fk1
+	} else {
+		return "" // This join table doesn't involve our table
+	}
+
+	// Find the target table
+	targetTable := w.findTable(db, targetConstraint.ReferencedSchema, targetConstraint.ReferencedTable)
+	if targetTable == nil {
+		return ""
+	}
+
+	// Generate many-to-many field
+	fieldName := w.pluralize(w.camelCase(targetTable.Name))
+	return fmt.Sprintf("  %s: [%s!]!", fieldName, targetTable.Name)
+}
+
+func (w *Writer) findTable(db *models.Database, schemaName, tableName string) *models.Table {
+	for _, schema := range db.Schemas {
+		if schema.Name != schemaName {
+			continue
+		}
+		for _, table := range schema.Tables {
+			if table.Name == tableName {
+				return table
+			}
+		}
+	}
+	return nil
+}
+
+func (w *Writer) relationFieldName(fkColumnName string) string {
+	// Remove "Id" or "_id" suffix
+	name := fkColumnName
+	if strings.HasSuffix(name, "Id") {
+		name = name[:len(name)-2]
+	} else if strings.HasSuffix(name, "_id") {
+		name = name[:len(name)-3]
+	}
+
+	return w.camelCase(name)
+}
+
+func (w *Writer) camelCase(s string) string {
+	// If already camelCase or PascalCase, convert to camelCase
+	if s == "" {
+		return s
+	}
+
+	// Convert first character to lowercase
+	return strings.ToLower(string(s[0])) + s[1:]
+}
+
+func (w *Writer) pluralize(s string) string {
+	// Simple pluralization rules
+	if s == "" {
+		return s
+	}
+
+	// Already plural
+	if strings.HasSuffix(s, "s") {
+		return s
+	}
+
+	// Words ending in 'y' → 'ies'
+	if strings.HasSuffix(s, "y") {
+		return s[:len(s)-1] + "ies"
+	}
+
+	// Words ending in 's', 'x', 'z', 'ch', 'sh' → add 'es'
+	if strings.HasSuffix(s, "s") || strings.HasSuffix(s, "x") ||
+		strings.HasSuffix(s, "z") || strings.HasSuffix(s, "ch") ||
+		strings.HasSuffix(s, "sh") {
+		return s + "es"
+	}
+
+	// Default: add 's'
+	return s + "s"
+}

pkg/writers/graphql/type_mapping.go

@@ -0,0 +1,148 @@
+package graphql
+
+import (
+	"strings"
+
+	"git.warky.dev/wdevs/relspecgo/pkg/models"
+)
+
+func (w *Writer) sqlTypeToGraphQL(sqlType string, column *models.Column, table *models.Table, schema *models.Schema) string {
+	// Check if this is a primary key → ID type
+	if column.IsPrimaryKey {
+		// Check metadata for explicit type preference
+		if w.options.Metadata != nil {
+			if preserveType, ok := w.options.Metadata["preservePKType"].(bool); ok && preserveType {
+				// Use Int or String based on SQL type
+				if w.isIntegerType(sqlType) {
+					return "Int"
+				}
+				return "String"
+			}
+		}
+		return "ID"
+	}
+
+	// Map SQL types to custom scalars
+	if scalar := w.sqlTypeToCustomScalar(sqlType); scalar != "" {
+		return scalar
+	}
+
+	// Check if it's an enum
+	if w.isEnumType(sqlType, schema) {
+		return sqlType
+	}
+
+	// Standard type mappings
+	baseType := strings.Split(sqlType, "(")[0] // Remove length/precision
+	baseType = strings.TrimSpace(baseType)
+
+	// Handle array types
+	if strings.HasSuffix(baseType, "[]") {
+		elemType := strings.TrimSuffix(baseType, "[]")
+		gqlType := w.mapBaseTypeToGraphQL(elemType)
+		return "[" + gqlType + "]"
+	}
+
+	return w.mapBaseTypeToGraphQL(baseType)
+}
+
+func (w *Writer) mapBaseTypeToGraphQL(baseType string) string {
+	typeMap := map[string]string{
+		// Text types
+		"text":      "String",
+		"varchar":   "String",
+		"char":      "String",
+		"character": "String",
+		"bpchar":    "String",
+		"name":      "String",
+
+		// UUID
+		"uuid": "ID",
+
+		// Integer types
+		"integer":     "Int",
+		"int":         "Int",
+		"int2":        "Int",
+		"int4":        "Int",
+		"int8":        "Int",
+		"bigint":      "Int",
+		"smallint":    "Int",
+		"serial":      "Int",
+		"bigserial":   "Int",
+		"smallserial": "Int",
+
+		// Float types
+		"double precision": "Float",
+		"float":            "Float",
+		"float4":           "Float",
+		"float8":           "Float",
+		"real":             "Float",
+		"numeric":          "Float",
+		"decimal":          "Float",
+		"money":            "Float",
+
+		// Boolean
+		"boolean": "Boolean",
+		"bool":    "Boolean",
+	}
+
+	if gqlType, ok := typeMap[baseType]; ok {
+		return gqlType
+	}
+
+	// Default: capitalize first letter
+	if len(baseType) > 0 {
+		return strings.ToUpper(string(baseType[0])) + baseType[1:]
+	}
+
+	return "String"
+}
+
+func (w *Writer) sqlTypeToCustomScalar(sqlType string) string {
+	scalarMap := map[string]string{
+		"timestamp":                "DateTime",
+		"timestamptz":              "DateTime",
+		"timestamp with time zone": "DateTime",
+		"jsonb":                    "JSON",
+		"json":                     "JSON",
+		"date":                     "Date",
+	}
+
+	baseType := strings.Split(sqlType, "(")[0]
+	baseType = strings.TrimSpace(baseType)
+
+	if scalar, ok := scalarMap[baseType]; ok {
+		return scalar
+	}
+
+	return ""
+}
+
+func (w *Writer) isIntegerType(sqlType string) bool {
+	intTypes := map[string]bool{
+		"integer":     true,
+		"int":         true,
+		"int2":        true,
+		"int4":        true,
+		"int8":        true,
+		"bigint":      true,
+		"smallint":    true,
+		"serial":      true,
+		"bigserial":   true,
+		"smallserial": true,
+	}
+
+	baseType := strings.Split(sqlType, "(")[0]
+	baseType = strings.TrimSpace(baseType)
+
+	return intTypes[baseType]
+}
+
+func (w *Writer) isEnumType(sqlType string, schema *models.Schema) bool {
+	for _, enum := range schema.Enums {
+		if enum.Name == sqlType {
+			return true
+		}
+	}
+	return false
+}

pkg/writers/graphql/writer.go

@@ -0,0 +1,272 @@
+package graphql
+
+import (
+	"fmt"
+	"os"
+	"sort"
+	"strings"
+
+	"git.warky.dev/wdevs/relspecgo/pkg/models"
+	"git.warky.dev/wdevs/relspecgo/pkg/writers"
+)
+
+type Writer struct {
+	options *writers.WriterOptions
+}
+
+func NewWriter(options *writers.WriterOptions) *Writer {
+	return &Writer{
+		options: options,
+	}
+}
+
+func (w *Writer) WriteDatabase(db *models.Database) error {
+	content := w.databaseToGraphQL(db)
+
+	if w.options.OutputPath != "" {
+		return os.WriteFile(w.options.OutputPath, []byte(content), 0644)
+	}
+
+	fmt.Print(content)
+	return nil
+}
+
+func (w *Writer) WriteSchema(schema *models.Schema) error {
+	db := models.InitDatabase(schema.Name)
+	db.Schemas = []*models.Schema{schema}
+	return w.WriteDatabase(db)
+}
+
+func (w *Writer) WriteTable(table *models.Table) error {
+	schema := models.InitSchema(table.Schema)
+	schema.Tables = []*models.Table{table}
+	db := models.InitDatabase(schema.Name)
+	db.Schemas = []*models.Schema{schema}
+	return w.WriteDatabase(db)
+}
+
+func (w *Writer) databaseToGraphQL(db *models.Database) string {
+	var sb strings.Builder
+
+	// Header comment
+	if w.shouldIncludeComments() {
+		sb.WriteString("# Generated GraphQL Schema\n")
+		if db.Name != "" {
+			sb.WriteString(fmt.Sprintf("# Database: %s\n", db.Name))
+		}
+		sb.WriteString("\n")
+	}
+
+	// Custom scalar declarations
+	if w.shouldIncludeScalarDeclarations() {
+		scalars := w.collectCustomScalars(db)
+		if len(scalars) > 0 {
+			for _, scalar := range scalars {
+				sb.WriteString(fmt.Sprintf("scalar %s\n", scalar))
+			}
+			sb.WriteString("\n")
+		}
+	}
+
+	// Enum definitions
+	for _, schema := range db.Schemas {
+		for _, enum := range schema.Enums {
+			sb.WriteString(w.enumToGraphQL(enum))
+			sb.WriteString("\n")
+		}
+	}
+
+	// Type definitions
+	for _, schema := range db.Schemas {
+		for _, table := range schema.Tables {
+			// Skip join tables (tables with only PK+FK columns)
+			if w.isJoinTable(table) {
+				continue
+			}
+
+			sb.WriteString(w.tableToGraphQL(table, db, schema))
+			sb.WriteString("\n")
+		}
+	}
+
+	return sb.String()
+}
+
+func (w *Writer) shouldIncludeComments() bool {
+	if w.options.Metadata != nil {
+		if include, ok := w.options.Metadata["includeComments"].(bool); ok {
+			return include
+		}
+	}
+	return true // Default to true
+}
+
+func (w *Writer) shouldIncludeScalarDeclarations() bool {
+	if w.options.Metadata != nil {
+		if include, ok := w.options.Metadata["includeScalarDeclarations"].(bool); ok {
+			return include
+		}
+	}
+	return true // Default to true
+}
+
+func (w *Writer) collectCustomScalars(db *models.Database) []string {
+	scalarsNeeded := make(map[string]bool)
+
+	for _, schema := range db.Schemas {
+		for _, table := range schema.Tables {
+			for _, col := range table.Columns {
+				if scalar := w.sqlTypeToCustomScalar(col.Type); scalar != "" {
+					scalarsNeeded[scalar] = true
+				}
+			}
+		}
+	}
+
+	// Convert to sorted slice
+	scalars := make([]string, 0, len(scalarsNeeded))
+	for scalar := range scalarsNeeded {
+		scalars = append(scalars, scalar)
+	}
+	sort.Strings(scalars)
+
+	return scalars
+}
+
+func (w *Writer) isJoinTable(table *models.Table) bool {
+	// A join table typically has:
+	// 1. Exactly 2 FK constraints
+	// 2. Composite primary key on those FK columns
+	// 3. No other columns
+
+	fkCount := 0
+	for _, constraint := range table.Constraints {
+		if constraint.Type == models.ForeignKeyConstraint {
+			fkCount++
+		}
+	}
+
+	if fkCount != 2 {
+		return false
+	}
+
+	// Check if all columns are either PKs or FKs
+	for _, col := range table.Columns {
+		isFKColumn := false
+		for _, constraint := range table.Constraints {
+			if constraint.Type == models.ForeignKeyConstraint {
+				for _, fkCol := range constraint.Columns {
+					if fkCol == col.Name {
+						isFKColumn = true
+						break
+					}
+				}
+			}
+		}
+
+		if !isFKColumn && !col.IsPrimaryKey {
+			// Found a column that's neither PK nor FK
+			return false
+		}
+	}
+
+	return true
+}
+
+func (w *Writer) enumToGraphQL(enum *models.Enum) string {
+	var sb strings.Builder
+
+	sb.WriteString(fmt.Sprintf("enum %s {\n", enum.Name))
+	for _, value := range enum.Values {
+		sb.WriteString(fmt.Sprintf("  %s\n", value))
+	}
+	sb.WriteString("}\n")
+
+	return sb.String()
+}
+
+func (w *Writer) tableToGraphQL(table *models.Table, db *models.Database, schema *models.Schema) string {
+	var sb strings.Builder
+
+	// Type name
+	typeName := table.Name
+
+	// Description comment
+	if w.shouldIncludeComments() && (table.Description != "" || table.Comment != "") {
+		desc := table.Description
+		if desc == "" {
+			desc = table.Comment
+		}
+		sb.WriteString(fmt.Sprintf("# %s\n", desc))
+	}
+
+	sb.WriteString(fmt.Sprintf("type %s {\n", typeName))
+
+	// Collect and categorize fields
+	var idFields, scalarFields, relationFields []string
+
+	for _, column := range table.Columns {
+		// Skip FK columns (they become relation fields)
+		if w.isForeignKeyColumn(column, table) {
+			continue
+		}
+
+		gqlType := w.sqlTypeToGraphQL(column.Type, column, table, schema)
+		if gqlType == "" {
+			continue // Skip if type couldn't be mapped
+		}
+
+		// Determine nullability
+		if column.NotNull {
+			gqlType += "!"
+		}
+
+		field := fmt.Sprintf("  %s: %s", column.Name, gqlType)
+
+		if column.IsPrimaryKey {
+			idFields = append(idFields, field)
+		} else {
+			scalarFields = append(scalarFields, field)
+		}
+	}
+
+	// Add relation fields
+	relationFields = w.generateRelationFields(table, db, schema)
+
+	// Write fields in order: ID, scalars (sorted), relations (sorted)
+	for _, field := range idFields {
+		sb.WriteString(field + "\n")
+	}
+
+	sort.Strings(scalarFields)
+	for _, field := range scalarFields {
+		sb.WriteString(field + "\n")
+	}
+
+	if len(relationFields) > 0 {
+		if len(scalarFields) > 0 || len(idFields) > 0 {
+			sb.WriteString("\n") // Blank line before relations
+		}
+		sort.Strings(relationFields)
+		for _, field := range relationFields {
+			sb.WriteString(field + "\n")
+		}
+	}
+
+	sb.WriteString("}\n")
+
+	return sb.String()
+}
+
+func (w *Writer) isForeignKeyColumn(column *models.Column, table *models.Table) bool {
+	for _, constraint := range table.Constraints {
+		if constraint.Type == models.ForeignKeyConstraint {
+			for _, fkCol := range constraint.Columns {
+				if fkCol == column.Name {
+					return true
+				}
+			}
+		}
+	}
+	return false
+}

pkg/writers/graphql/writer_test.go

@@ -0,0 +1,412 @@
+package graphql
+
+import (
+	"strings"
+	"testing"
+
+	"git.warky.dev/wdevs/relspecgo/pkg/models"
+	"git.warky.dev/wdevs/relspecgo/pkg/writers"
+)
+
+func TestWriter_WriteTable_Simple(t *testing.T) {
+	table := models.InitTable("User", "public")
+
+	idCol := models.InitColumn("id", "User", "public")
+	idCol.Type = "bigint"
+	idCol.IsPrimaryKey = true
+	idCol.NotNull = true
+	table.Columns["id"] = idCol
+
+	nameCol := models.InitColumn("name", "User", "public")
+	nameCol.Type = "text"
+	nameCol.NotNull = true
+	table.Columns["name"] = nameCol
+
+	emailCol := models.InitColumn("email", "User", "public")
+	emailCol.Type = "text"
+	emailCol.NotNull = false
+	table.Columns["email"] = emailCol
+
+	opts := &writers.WriterOptions{
+		OutputPath: "",
+	}
+
+	writer := NewWriter(opts)
+	schema := models.InitSchema("public")
+	schema.Tables = []*models.Table{table}
+	db := models.InitDatabase("test")
+	db.Schemas = []*models.Schema{schema}
+
+	output := writer.databaseToGraphQL(db)
+
+	// Verify output contains type definition
+	if !strings.Contains(output, "type User {") {
+		t.Error("Expected 'type User {' in output")
+	}
+
+	// Verify fields
+	if !strings.Contains(output, "id: ID!") {
+		t.Error("Expected 'id: ID!' in output")
+	}
+
+	if !strings.Contains(output, "name: String!") {
+		t.Error("Expected 'name: String!' in output")
+	}
+
+	if !strings.Contains(output, "email: String") {
+		t.Error("Expected 'email: String' in output")
+	}
+
+	// Ensure email is not followed by ! (nullable)
+	if strings.Contains(output, "email: String!") {
+		t.Error("Did not expect 'email: String!' (should be nullable)")
+	}
+}
+
+func TestWriter_WriteDatabase_WithEnum(t *testing.T) {
+	schema := models.InitSchema("public")
+
+	// Create enum
+	roleEnum := &models.Enum{
+		Name:   "Role",
+		Schema: "public",
+		Values: []string{"ADMIN", "USER", "GUEST"},
+	}
+	schema.Enums = []*models.Enum{roleEnum}
+
+	// Create table with enum field
+	table := models.InitTable("User", "public")
+
+	idCol := models.InitColumn("id", "User", "public")
+	idCol.Type = "bigint"
+	idCol.IsPrimaryKey = true
+	idCol.NotNull = true
+	table.Columns["id"] = idCol
+
+	roleCol := models.InitColumn("role", "User", "public")
+	roleCol.Type = "Role"
+	roleCol.NotNull = true
+	table.Columns["role"] = roleCol
+
+	schema.Tables = []*models.Table{table}
+
+	db := models.InitDatabase("test")
+	db.Schemas = []*models.Schema{schema}
+
+	opts := &writers.WriterOptions{}
+	writer := NewWriter(opts)
+
+	output := writer.databaseToGraphQL(db)
+
+	// Verify enum definition
+	if !strings.Contains(output, "enum Role {") {
+		t.Error("Expected 'enum Role {' in output")
+	}
+
+	if !strings.Contains(output, "ADMIN") {
+		t.Error("Expected 'ADMIN' enum value in output")
+	}
+
+	// Verify enum usage in type
+	if !strings.Contains(output, "role: Role!") {
+		t.Error("Expected 'role: Role!' in output")
+	}
+}
+
+func TestWriter_WriteDatabase_WithRelations(t *testing.T) {
+	schema := models.InitSchema("public")
+
+	// Create User table
+	userTable := models.InitTable("User", "public")
+	userIdCol := models.InitColumn("id", "User", "public")
+	userIdCol.Type = "bigint"
+	userIdCol.IsPrimaryKey = true
+	userIdCol.NotNull = true
+	userTable.Columns["id"] = userIdCol
+
+	userNameCol := models.InitColumn("name", "User", "public")
+	userNameCol.Type = "text"
+	userNameCol.NotNull = true
+	userTable.Columns["name"] = userNameCol
+
+	// Create Post table with FK to User
+	postTable := models.InitTable("Post", "public")
+
+	postIdCol := models.InitColumn("id", "Post", "public")
+	postIdCol.Type = "bigint"
+	postIdCol.IsPrimaryKey = true
+	postIdCol.NotNull = true
+	postTable.Columns["id"] = postIdCol
+
+	titleCol := models.InitColumn("title", "Post", "public")
+	titleCol.Type = "text"
+	titleCol.NotNull = true
+	postTable.Columns["title"] = titleCol
+
+	authorIdCol := models.InitColumn("authorId", "Post", "public")
+	authorIdCol.Type = "bigint"
+	authorIdCol.NotNull = true
+	postTable.Columns["authorId"] = authorIdCol
+
+	// Add FK constraint
+	fkConstraint := models.InitConstraint("fk_post_author", models.ForeignKeyConstraint)
+	fkConstraint.Schema = "public"
+	fkConstraint.Table = "Post"
+	fkConstraint.Columns = []string{"authorId"}
+	fkConstraint.ReferencedSchema = "public"
+	fkConstraint.ReferencedTable = "User"
+	fkConstraint.ReferencedColumns = []string{"id"}
+	postTable.Constraints["fk_post_author"] = fkConstraint
+
+	schema.Tables = []*models.Table{userTable, postTable}
+
+	db := models.InitDatabase("test")
+	db.Schemas = []*models.Schema{schema}
+
+	opts := &writers.WriterOptions{}
+	writer := NewWriter(opts)
+
+	output := writer.databaseToGraphQL(db)
+
+	// Verify Post has author field (forward relationship)
+	if !strings.Contains(output, "author: User!") {
+		t.Error("Expected 'author: User!' in Post type")
+	}
+
+	// Verify authorId FK column is NOT in the output
+	if strings.Contains(output, "authorId:") {
+		t.Error("Did not expect 'authorId:' field in output (FK columns should be hidden)")
+	}
+
+	// Verify User has posts field (reverse relationship)
+	if !strings.Contains(output, "posts: [Post!]!") {
+		t.Error("Expected 'posts: [Post!]!' in User type")
+	}
+}
+
+func TestWriter_WriteDatabase_CustomScalars(t *testing.T) {
+	schema := models.InitSchema("public")
+
+	table := models.InitTable("Event", "public")
+
+	idCol := models.InitColumn("id", "Event", "public")
+	idCol.Type = "bigint"
+	idCol.IsPrimaryKey = true
+	idCol.NotNull = true
+	table.Columns["id"] = idCol
+
+	createdAtCol := models.InitColumn("createdAt", "Event", "public")
+	createdAtCol.Type = "timestamp"
+	createdAtCol.NotNull = true
+	table.Columns["createdAt"] = createdAtCol
+
+	metadataCol := models.InitColumn("metadata", "Event", "public")
+	metadataCol.Type = "jsonb"
+	metadataCol.NotNull = false
+	table.Columns["metadata"] = metadataCol
+
+	dateCol := models.InitColumn("eventDate", "Event", "public")
+	dateCol.Type = "date"
+	dateCol.NotNull = false
+	table.Columns["eventDate"] = dateCol
+
+	schema.Tables = []*models.Table{table}
+
+	db := models.InitDatabase("test")
+	db.Schemas = []*models.Schema{schema}
+
+	opts := &writers.WriterOptions{}
+	writer := NewWriter(opts)
+
+	output := writer.databaseToGraphQL(db)
+
+	// Verify scalar declarations
+	if !strings.Contains(output, "scalar DateTime") {
+		t.Error("Expected 'scalar DateTime' declaration")
+	}
+
+	if !strings.Contains(output, "scalar JSON") {
+		t.Error("Expected 'scalar JSON' declaration")
+	}
+
+	if !strings.Contains(output, "scalar Date") {
+		t.Error("Expected 'scalar Date' declaration")
+	}
+
+	// Verify field types
+	if !strings.Contains(output, "createdAt: DateTime!") {
+		t.Error("Expected 'createdAt: DateTime!' in output")
+	}
+
+	if !strings.Contains(output, "metadata: JSON") {
+		t.Error("Expected 'metadata: JSON' in output")
+	}
+
+	if !strings.Contains(output, "eventDate: Date") {
+		t.Error("Expected 'eventDate: Date' in output")
+	}
+}
+
+func TestWriter_WriteDatabase_ManyToMany(t *testing.T) {
+	schema := models.InitSchema("public")
+
+	// Create Post table
+	postTable := models.InitTable("Post", "public")
+	postIdCol := models.InitColumn("id", "Post", "public")
+	postIdCol.Type = "bigint"
+	postIdCol.IsPrimaryKey = true
+	postIdCol.NotNull = true
+	postTable.Columns["id"] = postIdCol
+
+	titleCol := models.InitColumn("title", "Post", "public")
+	titleCol.Type = "text"
+	titleCol.NotNull = true
+	postTable.Columns["title"] = titleCol
+
+	// Create Tag table
+	tagTable := models.InitTable("Tag", "public")
+	tagIdCol := models.InitColumn("id", "Tag", "public")
+	tagIdCol.Type = "bigint"
+	tagIdCol.IsPrimaryKey = true
+	tagIdCol.NotNull = true
+	tagTable.Columns["id"] = tagIdCol
+
+	nameCol := models.InitColumn("name", "Tag", "public")
+	nameCol.Type = "text"
+	nameCol.NotNull = true
+	tagTable.Columns["name"] = nameCol
+
+	// Create PostTag join table
+	joinTable := models.InitTable("PostTag", "public")
+
+	postIdJoinCol := models.InitColumn("postId", "PostTag", "public")
+	postIdJoinCol.Type = "bigint"
+	postIdJoinCol.NotNull = true
+	postIdJoinCol.IsPrimaryKey = true
+	joinTable.Columns["postId"] = postIdJoinCol
+
+	tagIdJoinCol := models.InitColumn("tagId", "PostTag", "public")
+	tagIdJoinCol.Type = "bigint"
+	tagIdJoinCol.NotNull = true
+	tagIdJoinCol.IsPrimaryKey = true
+	joinTable.Columns["tagId"] = tagIdJoinCol
+
+	// Add composite PK constraint
+	pkConstraint := models.InitConstraint("pk_posttag", models.PrimaryKeyConstraint)
+	pkConstraint.Schema = "public"
+	pkConstraint.Table = "PostTag"
+	pkConstraint.Columns = []string{"postId", "tagId"}
+	joinTable.Constraints["pk_posttag"] = pkConstraint
+
+	// Add FK to Post
+	fk1 := models.InitConstraint("fk_posttag_post", models.ForeignKeyConstraint)
+	fk1.Schema = "public"
+	fk1.Table = "PostTag"
+	fk1.Columns = []string{"postId"}
+	fk1.ReferencedSchema = "public"
+	fk1.ReferencedTable = "Post"
+	fk1.ReferencedColumns = []string{"id"}
+	joinTable.Constraints["fk_posttag_post"] = fk1
+
+	// Add FK to Tag
+	fk2 := models.InitConstraint("fk_posttag_tag", models.ForeignKeyConstraint)
+	fk2.Schema = "public"
+	fk2.Table = "PostTag"
+	fk2.Columns = []string{"tagId"}
+	fk2.ReferencedSchema = "public"
+	fk2.ReferencedTable = "Tag"
+	fk2.ReferencedColumns = []string{"id"}
+	joinTable.Constraints["fk_posttag_tag"] = fk2
+
+	schema.Tables = []*models.Table{postTable, tagTable, joinTable}
+
+	db := models.InitDatabase("test")
+	db.Schemas = []*models.Schema{schema}
+
+	opts := &writers.WriterOptions{}
+	writer := NewWriter(opts)
+
+	output := writer.databaseToGraphQL(db)
+
+	// Verify join table is NOT in output
+	if strings.Contains(output, "type PostTag") {
+		t.Error("Did not expect 'type PostTag' (join tables should be hidden)")
+	}
+
+	// Verify Post has tags field
+	if !strings.Contains(output, "tags: [Tag!]!") {
+		t.Error("Expected 'tags: [Tag!]!' in Post type")
+	}
+
+	// Verify Tag has posts field
+	if !strings.Contains(output, "posts: [Post!]!") {
+		t.Error("Expected 'posts: [Post!]!' in Tag type")
+	}
+}
+
+func TestWriter_WriteDatabase_UUIDType(t *testing.T) {
+	schema := models.InitSchema("public")
+
+	table := models.InitTable("User", "public")
+
+	idCol := models.InitColumn("id", "User", "public")
+	idCol.Type = "uuid"
+	idCol.IsPrimaryKey = true
+	idCol.NotNull = true
+	table.Columns["id"] = idCol
+
+	schema.Tables = []*models.Table{table}
+
+	db := models.InitDatabase("test")
+	db.Schemas = []*models.Schema{schema}
+
+	opts := &writers.WriterOptions{}
+	writer := NewWriter(opts)
+
+	output := writer.databaseToGraphQL(db)
+
+	// UUID primary keys should still map to ID
+	if !strings.Contains(output, "id: ID!") {
+		t.Error("Expected 'id: ID!' for UUID primary key")
+	}
+}
+
+func TestWriter_Metadata_NoScalarDeclarations(t *testing.T) {
+	schema := models.InitSchema("public")
+
+	table := models.InitTable("Event", "public")
+
+	idCol := models.InitColumn("id", "Event", "public")
+	idCol.Type = "bigint"
+	idCol.IsPrimaryKey = true
+	table.Columns["id"] = idCol
+
+	createdAtCol := models.InitColumn("createdAt", "Event", "public")
+	createdAtCol.Type = "timestamp"
+	createdAtCol.NotNull = true
+	table.Columns["createdAt"] = createdAtCol
+
+	schema.Tables = []*models.Table{table}
+
+	db := models.InitDatabase("test")
+	db.Schemas = []*models.Schema{schema}
+
+	opts := &writers.WriterOptions{
+		Metadata: map[string]any{
+			"includeScalarDeclarations": false,
+		},
+	}
+	writer := NewWriter(opts)
+
+	output := writer.databaseToGraphQL(db)
+
+	// Verify no scalar declarations
+	if strings.Contains(output, "scalar DateTime") {
+		t.Error("Did not expect 'scalar DateTime' with includeScalarDeclarations=false")
+	}
+
+	// But field should still use DateTime
+	if !strings.Contains(output, "createdAt: DateTime!") {
+		t.Error("Expected 'createdAt: DateTime!' in output")
+	}
+}

tests/assets/graphql/complex.graphql

@@ -0,0 +1,46 @@
+# Complex GraphQL schema with multiple features
+
+scalar DateTime
+scalar JSON
+scalar Date
+
+enum Role {
+  USER
+  ADMIN
+  MODERATOR
+}
+
+type User {
+  id: ID!
+  email: String!
+  name: String!
+  role: Role!
+  createdAt: DateTime!
+  posts: [Post!]!
+  profile: Profile
+}
+
+type Profile {
+  id: ID!
+  bio: String
+  avatar: String
+  metadata: JSON
+  user: User!
+}
+
+type Post {
+  id: ID!
+  title: String!
+  slug: String!
+  content: String
+  published: Boolean!
+  publishedAt: Date
+  author: User!
+  tags: [Tag!]!
+}
+
+type Tag {
+  id: ID!
+  name: String!
+  posts: [Post!]!
+}

tests/assets/graphql/custom_scalars.graphql

@@ -0,0 +1,13 @@
+# GraphQL schema with custom scalars
+
+scalar DateTime
+scalar JSON
+scalar Date
+
+type User {
+  id: ID!
+  email: String!
+  createdAt: DateTime!
+  metadata: JSON
+  birthDate: Date
+}

tests/assets/graphql/enums.graphql

@@ -0,0 +1,13 @@
+# GraphQL schema with enums
+
+enum Role {
+  ADMIN
+  USER
+  GUEST
+}
+
+type User {
+  id: ID!
+  email: String!
+  role: Role!
+}

tests/assets/graphql/relations.graphql

@@ -0,0 +1,16 @@
+# GraphQL schema with relationships
+
+type User {
+  id: ID!
+  email: String!
+  name: String!
+  posts: [Post!]!
+}
+
+type Post {
+  id: ID!
+  title: String!
+  content: String
+  published: Boolean!
+  author: User!
+}

tests/assets/graphql/simple.graphql

@@ -0,0 +1,9 @@
+# Simple GraphQL schema for testing basic type parsing
+
+type User {
+  id: ID!
+  email: String!
+  name: String
+  age: Int
+  active: Boolean!
+}