package prisma

import (
	"bufio"
	"fmt"
	"os"
	"regexp"
	"strings"

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

// Reader implements the readers.Reader interface for Prisma schema format
type Reader struct {
	options *readers.ReaderOptions
}

// NewReader creates a new Prisma reader with the given options
func NewReader(options *readers.ReaderOptions) *Reader {
	return &Reader{
		options: options,
	}
}

// ReadDatabase reads and parses Prisma schema input, returning a Database model
func (r *Reader) ReadDatabase() (*models.Database, error) {
	if r.options.FilePath == "" {
		return nil, fmt.Errorf("file path is required for Prisma reader")
	}

	content, err := os.ReadFile(r.options.FilePath)
	if err != nil {
		return nil, fmt.Errorf("failed to read file: %w", err)
	}

	return r.parsePrisma(string(content))
}

// ReadSchema reads and parses Prisma schema input, returning a Schema model
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 in Prisma schema")
	}

	// Return the first schema
	return db.Schemas[0], nil
}

// ReadTable reads and parses Prisma schema input, returning a Table model
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 in Prisma schema")
	}

	// Return the first table
	return schema.Tables[0], nil
}

// parsePrisma parses Prisma schema content and returns a Database model
func (r *Reader) parsePrisma(content string) (*models.Database, error) {
	db := models.InitDatabase("database")

	if r.options.Metadata != nil {
		if name, ok := r.options.Metadata["name"].(string); ok {
			db.Name = name
		}
	}

	// Default schema for Prisma (doesn't have explicit schema concept in most cases)
	schema := models.InitSchema("public")
	schema.Enums = make([]*models.Enum, 0)

	scanner := bufio.NewScanner(strings.NewReader(content))

	// State tracking
	var currentBlock string // "datasource", "generator", "model", "enum"
	var currentTable *models.Table
	var currentEnum *models.Enum
	var blockContent []string

	// Regex patterns
	datasourceRegex := regexp.MustCompile(`^datasource\s+\w+\s*{`)
	generatorRegex := regexp.MustCompile(`^generator\s+\w+\s*{`)
	modelRegex := regexp.MustCompile(`^model\s+(\w+)\s*{`)
	enumRegex := regexp.MustCompile(`^enum\s+(\w+)\s*{`)

	for scanner.Scan() {
		line := scanner.Text()
		trimmed := strings.TrimSpace(line)

		// Skip empty lines and comments
		if trimmed == "" || strings.HasPrefix(trimmed, "//") {
			continue
		}

		// Check for block start
		if matches := datasourceRegex.FindStringSubmatch(trimmed); matches != nil {
			currentBlock = "datasource"
			blockContent = []string{}
			continue
		}

		if matches := generatorRegex.FindStringSubmatch(trimmed); matches != nil {
			currentBlock = "generator"
			blockContent = []string{}
			continue
		}

		if matches := modelRegex.FindStringSubmatch(trimmed); matches != nil {
			currentBlock = "model"
			tableName := matches[1]
			currentTable = models.InitTable(tableName, "public")
			blockContent = []string{}
			continue
		}

		if matches := enumRegex.FindStringSubmatch(trimmed); matches != nil {
			currentBlock = "enum"
			enumName := matches[1]
			currentEnum = models.InitEnum(enumName, "public")
			blockContent = []string{}
			continue
		}

		// Check for block end
		if trimmed == "}" {
			switch currentBlock {
			case "datasource":
				r.parseDatasource(blockContent, db)
			case "generator":
				// We don't need to do anything with generator blocks
			case "model":
				if currentTable != nil {
					r.parseModelFields(blockContent, currentTable)
					schema.Tables = append(schema.Tables, currentTable)
					currentTable = nil
				}
			case "enum":
				if currentEnum != nil {
					schema.Enums = append(schema.Enums, currentEnum)
					currentEnum = nil
				}
			}
			currentBlock = ""
			blockContent = []string{}
			continue
		}

		// Accumulate block content
		if currentBlock != "" {
			if currentBlock == "enum" && currentEnum != nil {
				// For enums, just add the trimmed value
				if trimmed != "" {
					currentEnum.Values = append(currentEnum.Values, trimmed)
				}
			} else {
				blockContent = append(blockContent, line)
			}
		}
	}

	// Second pass: resolve relationships
	r.resolveRelationships(schema)

	db.Schemas = append(db.Schemas, schema)
	return db, nil
}

// parseDatasource extracts database type from datasource block
func (r *Reader) parseDatasource(lines []string, db *models.Database) {
	providerRegex := regexp.MustCompile(`provider\s*=\s*"?(\w+)"?`)

	for _, line := range lines {
		if matches := providerRegex.FindStringSubmatch(line); matches != nil {
			provider := matches[1]
			switch provider {
			case "postgresql", "postgres":
				db.DatabaseType = models.PostgresqlDatabaseType
			case "mysql":
				db.DatabaseType = "mysql"
			case "sqlite":
				db.DatabaseType = models.SqlLiteDatabaseType
			case "sqlserver":
				db.DatabaseType = models.MSSQLDatabaseType
			default:
				db.DatabaseType = models.PostgresqlDatabaseType
			}
			break
		}
	}
}

// parseModelFields parses model field definitions
func (r *Reader) parseModelFields(lines []string, table *models.Table) {
	fieldRegex := regexp.MustCompile(`^(\w+)\s+(\w+)(\?|\[\])?\s*(@.+)?`)
	blockAttrRegex := regexp.MustCompile(`^@@(\w+)\((.*?)\)`)

	for _, line := range lines {
		trimmed := strings.TrimSpace(line)

		// Skip empty lines and comments
		if trimmed == "" || strings.HasPrefix(trimmed, "//") {
			continue
		}

		// Check for block attributes (@@id, @@unique, @@index)
		if matches := blockAttrRegex.FindStringSubmatch(trimmed); matches != nil {
			attrName := matches[1]
			attrContent := matches[2]
			r.parseBlockAttribute(attrName, attrContent, table)
			continue
		}

		// Parse field definition
		if matches := fieldRegex.FindStringSubmatch(trimmed); matches != nil {
			fieldName := matches[1]
			fieldType := matches[2]
			modifier := matches[3]   // ? or []
			attributes := matches[4] // @... part

			column := r.parseField(fieldName, fieldType, modifier, attributes, table)
			if column != nil {
				table.Columns[column.Name] = column
			}
		}
	}
}

// parseField parses a single field definition
func (r *Reader) parseField(name, fieldType, modifier, attributes string, table *models.Table) *models.Column {
	// Check if this is a relation field (array or references another model)
	if modifier == "[]" {
		// Array field - this is a relation field, not a column
		// We'll handle this in relationship resolution
		return nil
	}

	// Check if this is a non-primitive type (relation field)
	// Note: We need to allow enum types through as they're like primitives
	if !r.isPrimitiveType(fieldType) && !r.isEnumType(fieldType, table) {
		// This is a relation field (e.g., user User), not a scalar column
		// Only process this if it has @relation attribute (which means it's the owning side with FK)
		// Otherwise skip it as it's just the inverse relation field
		if attributes == "" || !strings.Contains(attributes, "@relation") {
			return nil
		}
		// If it has @relation, we still don't create a column for it
		// The actual FK column will be in the fields: [...] part of @relation
		return nil
	}

	column := models.InitColumn(name, table.Name, table.Schema)

	// Map Prisma type to SQL type
	column.Type = r.prismaTypeToSQL(fieldType)

	// Handle modifiers
	if modifier == "?" {
		column.NotNull = false
	} else {
		// Default: required fields are NOT NULL
		column.NotNull = true
	}

	// Parse field attributes
	if attributes != "" {
		r.parseFieldAttributes(attributes, column, table)
	}

	return column
}

// prismaTypeToSQL converts Prisma types to SQL types
func (r *Reader) prismaTypeToSQL(prismaType string) string {
	typeMap := map[string]string{
		"String":   "text",
		"Boolean":  "boolean",
		"Int":      "integer",
		"BigInt":   "bigint",
		"Float":    "double precision",
		"Decimal":  "decimal",
		"DateTime": "timestamp",
		"Json":     "jsonb",
		"Bytes":    "bytea",
	}

	if sqlType, ok := typeMap[prismaType]; ok {
		return sqlType
	}

	// If not a built-in type, it might be an enum or model reference
	// For enums, we'll use the enum name directly
	return prismaType
}

// parseFieldAttributes parses field attributes like @id, @unique, @default
func (r *Reader) parseFieldAttributes(attributes string, column *models.Column, table *models.Table) {
	// @id attribute
	if strings.Contains(attributes, "@id") {
		column.IsPrimaryKey = true
		column.NotNull = true
	}

	// @unique attribute
	if regexp.MustCompile(`@unique\b`).MatchString(attributes) {
		uniqueConstraint := models.InitConstraint(
			fmt.Sprintf("uq_%s", column.Name),
			models.UniqueConstraint,
		)
		uniqueConstraint.Schema = table.Schema
		uniqueConstraint.Table = table.Name
		uniqueConstraint.Columns = []string{column.Name}
		table.Constraints[uniqueConstraint.Name] = uniqueConstraint
	}

	// @default attribute - extract value with balanced parentheses
	if strings.Contains(attributes, "@default(") {
		defaultValue := r.extractDefaultValue(attributes)
		if defaultValue != "" {
			r.parseDefaultValue(defaultValue, column)
		}
	}

	// @updatedAt attribute - store in comment for now
	if strings.Contains(attributes, "@updatedAt") {
		if column.Comment != "" {
			column.Comment += "; @updatedAt"
		} else {
			column.Comment = "@updatedAt"
		}
	}

	// @relation attribute - we'll handle this in relationship resolution
	// For now, just note that this field is part of a relation
}

// extractDefaultValue extracts the default value from @default(...) handling nested parentheses
func (r *Reader) extractDefaultValue(attributes string) string {
	idx := strings.Index(attributes, "@default(")
	if idx == -1 {
		return ""
	}

	start := idx + len("@default(")
	depth := 1
	i := start

	for i < len(attributes) && depth > 0 {
		switch attributes[i] {
		case '(':
			depth++
		case ')':
			depth--
		}
		i++
	}

	if depth == 0 {
		return attributes[start : i-1]
	}

	return ""
}

// parseDefaultValue parses Prisma default value expressions
func (r *Reader) parseDefaultValue(defaultExpr string, column *models.Column) {
	defaultExpr = strings.TrimSpace(defaultExpr)

	switch defaultExpr {
	case "autoincrement()":
		column.AutoIncrement = true
	case "now()":
		column.Default = "now()"
	case "uuid()":
		column.Default = "gen_random_uuid()"
	case "cuid()":
		// CUID is Prisma-specific, store in comment
		if column.Comment != "" {
			column.Comment += "; default(cuid())"
		} else {
			column.Comment = "default(cuid())"
		}
	case "true":
		column.Default = true
	case "false":
		column.Default = false
	default:
		// Check if it's a string literal
		if strings.HasPrefix(defaultExpr, "\"") && strings.HasSuffix(defaultExpr, "\"") {
			column.Default = defaultExpr[1 : len(defaultExpr)-1]
		} else if strings.HasPrefix(defaultExpr, "'") && strings.HasSuffix(defaultExpr, "'") {
			column.Default = defaultExpr[1 : len(defaultExpr)-1]
		} else {
			// Try to parse as number or enum value
			column.Default = defaultExpr
		}
	}
}

// parseBlockAttribute parses block-level attributes like @@id, @@unique, @@index
func (r *Reader) parseBlockAttribute(attrName, content string, table *models.Table) {
	// Extract column list from brackets [col1, col2]
	colListRegex := regexp.MustCompile(`\[(.*?)\]`)
	matches := colListRegex.FindStringSubmatch(content)
	if matches == nil {
		return
	}

	columnList := strings.Split(matches[1], ",")
	columns := make([]string, 0)
	for _, col := range columnList {
		columns = append(columns, strings.TrimSpace(col))
	}

	switch attrName {
	case "id":
		// Composite primary key
		for _, colName := range columns {
			if col, exists := table.Columns[colName]; exists {
				col.IsPrimaryKey = true
				col.NotNull = true
			}
		}
		// Also create a PK constraint
		pkConstraint := models.InitConstraint(
			fmt.Sprintf("pk_%s", table.Name),
			models.PrimaryKeyConstraint,
		)
		pkConstraint.Schema = table.Schema
		pkConstraint.Table = table.Name
		pkConstraint.Columns = columns
		table.Constraints[pkConstraint.Name] = pkConstraint

	case "unique":
		// Multi-column unique constraint
		uniqueConstraint := models.InitConstraint(
			fmt.Sprintf("uq_%s_%s", table.Name, strings.Join(columns, "_")),
			models.UniqueConstraint,
		)
		uniqueConstraint.Schema = table.Schema
		uniqueConstraint.Table = table.Name
		uniqueConstraint.Columns = columns
		table.Constraints[uniqueConstraint.Name] = uniqueConstraint

	case "index":
		// Index
		index := models.InitIndex(
			fmt.Sprintf("idx_%s_%s", table.Name, strings.Join(columns, "_")),
			table.Name,
			table.Schema,
		)
		index.Columns = columns
		table.Indexes[index.Name] = index
	}
}

// relationField stores information about a relation field for second-pass processing
type relationField struct {
	tableName    string
	fieldName    string
	relatedModel string
	isArray      bool
	relationAttr string
}

// resolveRelationships performs a second pass to resolve @relation attributes
func (r *Reader) resolveRelationships(schema *models.Schema) {
	// Build a map of table names for quick lookup
	tableMap := make(map[string]*models.Table)
	for _, table := range schema.Tables {
		tableMap[table.Name] = table
	}

	// First, we need to re-parse to find relation fields
	// We'll re-read the file to extract relation information
	if r.options.FilePath == "" {
		return
	}

	content, err := os.ReadFile(r.options.FilePath)
	if err != nil {
		return
	}

	relations := r.extractRelationFields(string(content))

	// Process explicit @relation attributes to create FK constraints
	for _, rel := range relations {
		if rel.relationAttr != "" {
			r.createConstraintFromRelation(rel, tableMap, schema)
		}
	}

	// Detect implicit many-to-many relationships
	r.detectImplicitManyToMany(relations, tableMap, schema)
}

// extractRelationFields extracts relation field information from the schema
func (r *Reader) extractRelationFields(content string) []relationField {
	relations := make([]relationField, 0)
	scanner := bufio.NewScanner(strings.NewReader(content))

	modelRegex := regexp.MustCompile(`^model\s+(\w+)\s*{`)
	fieldRegex := regexp.MustCompile(`^(\w+)\s+(\w+)(\?|\[\])?\s*(@.+)?`)

	var currentModel string
	inModel := false

	for scanner.Scan() {
		line := scanner.Text()
		trimmed := strings.TrimSpace(line)

		if trimmed == "" || strings.HasPrefix(trimmed, "//") {
			continue
		}

		if matches := modelRegex.FindStringSubmatch(trimmed); matches != nil {
			currentModel = matches[1]
			inModel = true
			continue
		}

		if trimmed == "}" {
			inModel = false
			currentModel = ""
			continue
		}

		if inModel && currentModel != "" {
			if matches := fieldRegex.FindStringSubmatch(trimmed); matches != nil {
				fieldName := matches[1]
				fieldType := matches[2]
				modifier := matches[3]
				attributes := matches[4]

				// Check if this is a relation field (references another model or is an array)
				isPotentialRelation := modifier == "[]" || !r.isPrimitiveType(fieldType)

				if isPotentialRelation {
					rel := relationField{
						tableName:    currentModel,
						fieldName:    fieldName,
						relatedModel: fieldType,
						isArray:      modifier == "[]",
						relationAttr: attributes,
					}
					relations = append(relations, rel)
				}
			}
		}
	}

	return relations
}

// isPrimitiveType checks if a type is a Prisma primitive type
func (r *Reader) isPrimitiveType(typeName string) bool {
	primitives := []string{"String", "Boolean", "Int", "BigInt", "Float", "Decimal", "DateTime", "Json", "Bytes"}
	for _, p := range primitives {
		if typeName == p {
			return true
		}
	}
	return false
}

// isEnumType checks if a type name might be an enum
// Note: We can't definitively check against schema.Enums at parse time
// because enums might be defined after the model, so we just check
// if it starts with uppercase (Prisma convention for enums)
func (r *Reader) isEnumType(typeName string, table *models.Table) bool {
	// Simple heuristic: enum types start with uppercase letter
	// and are not known model names (though we can't check that yet)
	if len(typeName) > 0 && typeName[0] >= 'A' && typeName[0] <= 'Z' {
		// Additional check: primitive types are already handled above
		// So if it's uppercase and not primitive, it's likely an enum or model
		// We'll assume it's an enum if it's a single word
		return !strings.Contains(typeName, "_")
	}
	return false
}

// createConstraintFromRelation creates a FK constraint from a @relation attribute
func (r *Reader) createConstraintFromRelation(rel relationField, tableMap map[string]*models.Table, schema *models.Schema) {
	// Skip array fields (they are the inverse side of the relation)
	if rel.isArray {
		return
	}

	if rel.relationAttr == "" {
		return
	}

	// Parse @relation attribute
	relationRegex := regexp.MustCompile(`@relation\((.*?)\)`)
	matches := relationRegex.FindStringSubmatch(rel.relationAttr)
	if matches == nil {
		return
	}

	relationContent := matches[1]

	// Extract fields and references
	fieldsRegex := regexp.MustCompile(`fields:\s*\[(.*?)\]`)
	referencesRegex := regexp.MustCompile(`references:\s*\[(.*?)\]`)
	nameRegex := regexp.MustCompile(`name:\s*"([^"]+)"`)
	onDeleteRegex := regexp.MustCompile(`onDelete:\s*(\w+)`)
	onUpdateRegex := regexp.MustCompile(`onUpdate:\s*(\w+)`)

	fieldsMatch := fieldsRegex.FindStringSubmatch(relationContent)
	referencesMatch := referencesRegex.FindStringSubmatch(relationContent)

	if fieldsMatch == nil || referencesMatch == nil {
		return
	}

	// Parse field and reference column lists
	fieldCols := r.parseColumnList(fieldsMatch[1])
	refCols := r.parseColumnList(referencesMatch[1])

	if len(fieldCols) == 0 || len(refCols) == 0 {
		return
	}

	// Create FK constraint
	constraintName := fmt.Sprintf("fk_%s_%s", rel.tableName, fieldCols[0])

	// Check for custom name
	if nameMatch := nameRegex.FindStringSubmatch(relationContent); nameMatch != nil {
		constraintName = nameMatch[1]
	}

	constraint := models.InitConstraint(constraintName, models.ForeignKeyConstraint)
	constraint.Schema = "public"
	constraint.Table = rel.tableName
	constraint.Columns = fieldCols
	constraint.ReferencedSchema = "public"
	constraint.ReferencedTable = rel.relatedModel
	constraint.ReferencedColumns = refCols

	// Parse referential actions
	if onDeleteMatch := onDeleteRegex.FindStringSubmatch(relationContent); onDeleteMatch != nil {
		constraint.OnDelete = onDeleteMatch[1]
	}

	if onUpdateMatch := onUpdateRegex.FindStringSubmatch(relationContent); onUpdateMatch != nil {
		constraint.OnUpdate = onUpdateMatch[1]
	}

	// Add constraint to table
	if table, exists := tableMap[rel.tableName]; exists {
		table.Constraints[constraint.Name] = constraint
	}
}

// parseColumnList parses a comma-separated list of column names
func (r *Reader) parseColumnList(list string) []string {
	parts := strings.Split(list, ",")
	result := make([]string, 0)
	for _, part := range parts {
		trimmed := strings.TrimSpace(part)
		if trimmed != "" {
			result = append(result, trimmed)
		}
	}
	return result
}

// detectImplicitManyToMany detects implicit M2M relationships and creates join tables
func (r *Reader) detectImplicitManyToMany(relations []relationField, tableMap map[string]*models.Table, schema *models.Schema) {
	// Group relations by model pairs
	type modelPair struct {
		model1 string
		model2 string
	}

	pairMap := make(map[modelPair][]relationField)

	for _, rel := range relations {
		if !rel.isArray || rel.relationAttr != "" {
			// Skip non-array fields and explicit relations
			continue
		}

		// Create a normalized pair (alphabetically sorted to avoid duplicates)
		pair := modelPair{}
		if rel.tableName < rel.relatedModel {
			pair.model1 = rel.tableName
			pair.model2 = rel.relatedModel
		} else {
			pair.model1 = rel.relatedModel
			pair.model2 = rel.tableName
		}

		pairMap[pair] = append(pairMap[pair], rel)
	}

	// Check for pairs with arrays on both sides (implicit M2M)
	for pair, rels := range pairMap {
		if len(rels) >= 2 {
			// This is an implicit many-to-many relationship
			r.createImplicitJoinTable(pair.model1, pair.model2, tableMap, schema)
		}
	}
}

// createImplicitJoinTable creates a virtual join table for implicit M2M relations
func (r *Reader) createImplicitJoinTable(model1, model2 string, tableMap map[string]*models.Table, schema *models.Schema) {
	// Prisma naming convention: _Model1ToModel2 (alphabetically sorted)
	joinTableName := fmt.Sprintf("_%sTo%s", model1, model2)

	// Check if join table already exists
	if _, exists := tableMap[joinTableName]; exists {
		return
	}

	// Create join table
	joinTable := models.InitTable(joinTableName, "public")

	// Get primary keys from both tables
	pk1 := r.getPrimaryKeyColumn(tableMap[model1])
	pk2 := r.getPrimaryKeyColumn(tableMap[model2])

	if pk1 == nil || pk2 == nil {
		return // Can't create join table without PKs
	}

	// Create FK columns in join table
	fkCol1Name := fmt.Sprintf("%sId", model1)
	fkCol1 := models.InitColumn(fkCol1Name, joinTableName, "public")
	fkCol1.Type = pk1.Type
	fkCol1.NotNull = true
	joinTable.Columns[fkCol1Name] = fkCol1

	fkCol2Name := fmt.Sprintf("%sId", model2)
	fkCol2 := models.InitColumn(fkCol2Name, joinTableName, "public")
	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 = "public"
	pkConstraint.Table = joinTableName
	pkConstraint.Columns = []string{fkCol1Name, fkCol2Name}
	joinTable.Constraints[pkConstraint.Name] = pkConstraint

	// Mark columns as PK
	fkCol1.IsPrimaryKey = true
	fkCol2.IsPrimaryKey = true

	// Create FK constraints
	fk1 := models.InitConstraint(
		fmt.Sprintf("fk_%s_%s", joinTableName, model1),
		models.ForeignKeyConstraint,
	)
	fk1.Schema = "public"
	fk1.Table = joinTableName
	fk1.Columns = []string{fkCol1Name}
	fk1.ReferencedSchema = "public"
	fk1.ReferencedTable = model1
	fk1.ReferencedColumns = []string{pk1.Name}
	fk1.OnDelete = "Cascade"
	joinTable.Constraints[fk1.Name] = fk1

	fk2 := models.InitConstraint(
		fmt.Sprintf("fk_%s_%s", joinTableName, model2),
		models.ForeignKeyConstraint,
	)
	fk2.Schema = "public"
	fk2.Table = joinTableName
	fk2.Columns = []string{fkCol2Name}
	fk2.ReferencedSchema = "public"
	fk2.ReferencedTable = model2
	fk2.ReferencedColumns = []string{pk2.Name}
	fk2.OnDelete = "Cascade"
	joinTable.Constraints[fk2.Name] = fk2

	// Add join table to schema
	schema.Tables = append(schema.Tables, joinTable)
	tableMap[joinTableName] = joinTable
}

// getPrimaryKeyColumn returns the primary key column of a table
func (r *Reader) getPrimaryKeyColumn(table *models.Table) *models.Column {
	if table == nil {
		return nil
	}

	for _, col := range table.Columns {
		if col.IsPrimaryKey {
			return col
		}
	}

	return nil
}