package prisma

import (
	"fmt"
	"os"
	"sort"
	"strings"

	"git.warky.dev/wdevs/relspecgo/pkg/models"
	"git.warky.dev/wdevs/relspecgo/pkg/writers"
)

// Writer implements the writers.Writer interface for Prisma schema format
type Writer struct {
	options *writers.WriterOptions
}

// NewWriter creates a new Prisma writer with the given options
func NewWriter(options *writers.WriterOptions) *Writer {
	return &Writer{
		options: options,
	}
}

// WriteDatabase writes a Database model to Prisma schema format
func (w *Writer) WriteDatabase(db *models.Database) error {
	content := w.databaseToPrisma(db)

	if w.options.OutputPath != "" {
		return os.WriteFile(w.options.OutputPath, []byte(content), 0644)
	}

	fmt.Print(content)
	return nil
}

// WriteSchema writes a Schema model to Prisma schema format
func (w *Writer) WriteSchema(schema *models.Schema) error {
	// Create temporary database for schema
	db := models.InitDatabase("database")
	db.Schemas = []*models.Schema{schema}

	return w.WriteDatabase(db)
}

// WriteTable writes a Table model to Prisma schema format
func (w *Writer) WriteTable(table *models.Table) error {
	// Create temporary schema and database for table
	schema := models.InitSchema(table.Schema)
	schema.Tables = []*models.Table{table}

	return w.WriteSchema(schema)
}

// databaseToPrisma converts a Database to Prisma schema format string
func (w *Writer) databaseToPrisma(db *models.Database) string {
	var sb strings.Builder

	// Write datasource block
	sb.WriteString(w.generateDatasource(db))
	sb.WriteString("\n")

	// Write generator block
	sb.WriteString(w.generateGenerator())
	sb.WriteString("\n")

	// Process all schemas (typically just one in Prisma)
	for _, schema := range db.Schemas {
		// Write enums
		if len(schema.Enums) > 0 {
			for _, enum := range schema.Enums {
				sb.WriteString(w.enumToPrisma(enum))
				sb.WriteString("\n")
			}
		}

		// Identify join tables for implicit M2M
		joinTables := w.identifyJoinTables(schema)

		// Write models (excluding join tables)
		for _, table := range schema.Tables {
			if joinTables[table.Name] {
				continue // Skip join tables
			}
			sb.WriteString(w.tableToPrisma(table, schema, joinTables))
			sb.WriteString("\n")
		}
	}

	return sb.String()
}

// generateDatasource generates the datasource block
func (w *Writer) generateDatasource(db *models.Database) string {
	provider := "postgresql"

	// Map database type to Prisma provider
	switch db.DatabaseType {
	case models.PostgresqlDatabaseType:
		provider = "postgresql"
	case models.MSSQLDatabaseType:
		provider = "sqlserver"
	case models.SqlLiteDatabaseType:
		provider = "sqlite"
	case "mysql":
		provider = "mysql"
	}

	return fmt.Sprintf(`datasource db {
  provider = "%s"
  url      = env("DATABASE_URL")
}
`, provider)
}

// generateGenerator generates the generator block
func (w *Writer) generateGenerator() string {
	return `generator client {
  provider = "prisma-client-js"
}
`
}

// enumToPrisma converts an Enum to Prisma enum block
func (w *Writer) enumToPrisma(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()
}

// identifyJoinTables identifies tables that are join tables for M2M relations
func (w *Writer) identifyJoinTables(schema *models.Schema) map[string]bool {
	joinTables := make(map[string]bool)

	for _, table := range schema.Tables {
		// Check if this is a join table:
		// 1. Starts with _ (Prisma convention)
		// 2. Has exactly 2 FK constraints
		// 3. Has composite PK with those 2 columns
		// 4. Has no other columns except the FK columns

		if !strings.HasPrefix(table.Name, "_") {
			continue
		}

		fks := table.GetForeignKeys()
		if len(fks) != 2 {
			continue
		}

		// Check if columns are only the FK columns
		if len(table.Columns) != 2 {
			continue
		}

		// Check if both FK columns are part of PK
		pkCols := 0
		for _, col := range table.Columns {
			if col.IsPrimaryKey {
				pkCols++
			}
		}

		if pkCols == 2 {
			joinTables[table.Name] = true
		}
	}

	return joinTables
}

// tableToPrisma converts a Table to Prisma model block
func (w *Writer) tableToPrisma(table *models.Table, schema *models.Schema, joinTables map[string]bool) string {
	var sb strings.Builder

	sb.WriteString(fmt.Sprintf("model %s {\n", table.Name))

	// Collect columns to write
	columns := make([]*models.Column, 0, len(table.Columns))
	for _, col := range table.Columns {
		columns = append(columns, col)
	}

	// Sort columns for consistent output
	sort.Slice(columns, func(i, j int) bool {
		return columns[i].Name < columns[j].Name
	})

	// Write scalar fields
	for _, col := range columns {
		// Skip if this column is part of a relation that will be output as array field
		if w.isRelationColumn(col, table) {
			// We'll output this with the relation field
			continue
		}

		sb.WriteString(w.columnToField(col, table, schema))
	}

	// Write relation fields
	sb.WriteString(w.generateRelationFields(table, schema, joinTables))

	// Write block attributes (@@id, @@unique, @@index)
	sb.WriteString(w.generateBlockAttributes(table))

	sb.WriteString("}\n")

	return sb.String()
}

// columnToField converts a Column to a Prisma field definition
func (w *Writer) columnToField(col *models.Column, table *models.Table, schema *models.Schema) string {
	var sb strings.Builder

	// Field name
	sb.WriteString(fmt.Sprintf("  %s", col.Name))

	// Field type
	prismaType := w.sqlTypeToPrisma(col.Type, schema)
	sb.WriteString(fmt.Sprintf(" %s", prismaType))

	// Optional modifier
	if !col.NotNull && !col.IsPrimaryKey {
		sb.WriteString("?")
	}

	// Field attributes
	attributes := w.generateFieldAttributes(col, table)
	if attributes != "" {
		sb.WriteString(" ")
		sb.WriteString(attributes)
	}

	sb.WriteString("\n")

	return sb.String()
}

// sqlTypeToPrisma converts SQL types to Prisma types
func (w *Writer) sqlTypeToPrisma(sqlType string, schema *models.Schema) string {
	// Check if it's an enum
	for _, enum := range schema.Enums {
		if strings.EqualFold(sqlType, enum.Name) {
			return enum.Name
		}
	}

	// Standard type mapping
	typeMap := map[string]string{
		"text":              "String",
		"varchar":           "String",
		"character varying": "String",
		"char":              "String",
		"boolean":           "Boolean",
		"bool":              "Boolean",
		"integer":           "Int",
		"int":               "Int",
		"int4":              "Int",
		"bigint":            "BigInt",
		"int8":              "BigInt",
		"double precision":  "Float",
		"float":             "Float",
		"float8":            "Float",
		"decimal":           "Decimal",
		"numeric":           "Decimal",
		"timestamp":         "DateTime",
		"timestamptz":       "DateTime",
		"date":              "DateTime",
		"jsonb":             "Json",
		"json":              "Json",
		"bytea":             "Bytes",
	}

	for sqlPattern, prismaType := range typeMap {
		if strings.Contains(strings.ToLower(sqlType), sqlPattern) {
			return prismaType
		}
	}

	// Default to String for unknown types
	return "String"
}

// generateFieldAttributes generates field attributes like @id, @unique, @default
func (w *Writer) generateFieldAttributes(col *models.Column, table *models.Table) string {
	attrs := make([]string, 0)

	// @id
	if col.IsPrimaryKey {
		// Check if this is part of a composite key
		pkCount := 0
		for _, c := range table.Columns {
			if c.IsPrimaryKey {
				pkCount++
			}
		}
		if pkCount == 1 {
			attrs = append(attrs, "@id")
		}
	}

	// @unique
	if w.hasUniqueConstraint(col.Name, table) {
		attrs = append(attrs, "@unique")
	}

	// @default
	if col.AutoIncrement {
		attrs = append(attrs, "@default(autoincrement())")
	} else if col.Default != nil {
		defaultAttr := w.formatDefaultValue(col.Default)
		if defaultAttr != "" {
			attrs = append(attrs, fmt.Sprintf("@default(%s)", defaultAttr))
		}
	}

	// @updatedAt (check comment)
	if strings.Contains(col.Comment, "@updatedAt") {
		attrs = append(attrs, "@updatedAt")
	}

	return strings.Join(attrs, " ")
}

// formatDefaultValue formats a default value for Prisma
func (w *Writer) formatDefaultValue(defaultValue any) string {
	switch v := defaultValue.(type) {
	case string:
		if v == "now()" {
			return "now()"
		} else if v == "gen_random_uuid()" {
			return "uuid()"
		} else if strings.Contains(strings.ToLower(v), "uuid") {
			return "uuid()"
		} else {
			// String literal
			return fmt.Sprintf(`"%s"`, v)
		}
	case bool:
		if v {
			return "true"
		}
		return "false"
	case int, int64, int32:
		return fmt.Sprintf("%v", v)
	default:
		return fmt.Sprintf("%v", v)
	}
}

// hasUniqueConstraint checks if a column has a unique constraint
func (w *Writer) hasUniqueConstraint(colName string, table *models.Table) bool {
	for _, constraint := range table.Constraints {
		if constraint.Type == models.UniqueConstraint &&
			len(constraint.Columns) == 1 &&
			constraint.Columns[0] == colName {
			return true
		}
	}
	return false
}

// isRelationColumn checks if a column is a FK column
func (w *Writer) isRelationColumn(col *models.Column, table *models.Table) bool {
	for _, constraint := range table.Constraints {
		if constraint.Type == models.ForeignKeyConstraint {
			for _, fkCol := range constraint.Columns {
				if fkCol == col.Name {
					return true
				}
			}
		}
	}
	return false
}

// generateRelationFields generates relation fields and their FK columns
func (w *Writer) generateRelationFields(table *models.Table, schema *models.Schema, joinTables map[string]bool) string {
	var sb strings.Builder

	// Get all FK constraints
	fks := table.GetForeignKeys()

	for _, fk := range fks {
		// Generate the FK scalar field
		for _, fkCol := range fk.Columns {
			if col, exists := table.Columns[fkCol]; exists {
				sb.WriteString(w.columnToField(col, table, schema))
			}
		}

		// Generate the relation field
		relationType := fk.ReferencedTable
		isOptional := false

		// Check if FK column is nullable
		for _, fkCol := range fk.Columns {
			if col, exists := table.Columns[fkCol]; exists {
				if !col.NotNull {
					isOptional = true
				}
			}
		}

		relationName := relationType
		if strings.HasSuffix(strings.ToLower(relationName), "s") {
			relationName = relationName[:len(relationName)-1]
		}

		sb.WriteString(fmt.Sprintf("  %s %s", strings.ToLower(relationName), relationType))

		if isOptional {
			sb.WriteString("?")
		}

		// @relation attribute
		relationAttr := w.generateRelationAttribute(fk)
		if relationAttr != "" {
			sb.WriteString(" ")
			sb.WriteString(relationAttr)
		}

		sb.WriteString("\n")
	}

	// Generate inverse relations (arrays) for tables that reference this one
	sb.WriteString(w.generateInverseRelations(table, schema, joinTables))

	return sb.String()
}

// generateRelationAttribute generates the @relation(...) attribute
func (w *Writer) generateRelationAttribute(fk *models.Constraint) string {
	parts := make([]string, 0)

	// fields
	fieldsStr := strings.Join(fk.Columns, ", ")
	parts = append(parts, fmt.Sprintf("fields: [%s]", fieldsStr))

	// references
	referencesStr := strings.Join(fk.ReferencedColumns, ", ")
	parts = append(parts, fmt.Sprintf("references: [%s]", referencesStr))

	// onDelete
	if fk.OnDelete != "" {
		parts = append(parts, fmt.Sprintf("onDelete: %s", fk.OnDelete))
	}

	// onUpdate
	if fk.OnUpdate != "" {
		parts = append(parts, fmt.Sprintf("onUpdate: %s", fk.OnUpdate))
	}

	return fmt.Sprintf("@relation(%s)", strings.Join(parts, ", "))
}

// generateInverseRelations generates array fields for reverse relationships
func (w *Writer) generateInverseRelations(table *models.Table, schema *models.Schema, joinTables map[string]bool) string {
	var sb strings.Builder

	// Find all tables that have FKs pointing to this table
	for _, otherTable := range schema.Tables {
		if otherTable.Name == table.Name {
			continue
		}

		// Check if this is a join table
		if joinTables[otherTable.Name] {
			// Handle implicit M2M
			if w.isJoinTableFor(otherTable, table.Name) {
				// Find the other side of the M2M
				for _, fk := range otherTable.GetForeignKeys() {
					if fk.ReferencedTable != table.Name {
						// This is the other side
						otherSide := fk.ReferencedTable
						sb.WriteString(fmt.Sprintf("  %ss %s[]\n",
							strings.ToLower(otherSide), otherSide))
						break
					}
				}
			}
			continue
		}

		// Regular one-to-many inverse relation
		for _, fk := range otherTable.GetForeignKeys() {
			if fk.ReferencedTable == table.Name {
				// This table is referenced by otherTable
				pluralName := otherTable.Name
				if !strings.HasSuffix(pluralName, "s") {
					pluralName += "s"
				}

				sb.WriteString(fmt.Sprintf("  %s %s[]\n",
					strings.ToLower(pluralName), otherTable.Name))
			}
		}
	}

	return sb.String()
}

// isJoinTableFor checks if a table is a join table involving the specified model
func (w *Writer) isJoinTableFor(joinTable *models.Table, modelName string) bool {
	for _, fk := range joinTable.GetForeignKeys() {
		if fk.ReferencedTable == modelName {
			return true
		}
	}
	return false
}

// generateBlockAttributes generates block-level attributes like @@id, @@unique, @@index
func (w *Writer) generateBlockAttributes(table *models.Table) string {
	var sb strings.Builder

	// @@id for composite primary key
	pkCols := make([]string, 0)
	for _, col := range table.Columns {
		if col.IsPrimaryKey {
			pkCols = append(pkCols, col.Name)
		}
	}

	if len(pkCols) > 1 {
		sort.Strings(pkCols)
		sb.WriteString(fmt.Sprintf("  @@id([%s])\n", strings.Join(pkCols, ", ")))
	}

	// @@unique for multi-column unique constraints
	for _, constraint := range table.Constraints {
		if constraint.Type == models.UniqueConstraint && len(constraint.Columns) > 1 {
			sb.WriteString(fmt.Sprintf("  @@unique([%s])\n", strings.Join(constraint.Columns, ", ")))
		}
	}

	// @@index for indexes
	for _, index := range table.Indexes {
		if !index.Unique { // Unique indexes are handled by @@unique
			sb.WriteString(fmt.Sprintf("  @@index([%s])\n", strings.Join(index.Columns, ", ")))
		}
	}

	return sb.String()
}