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"
}