package migrate

import (
	"fmt"
	"strings"
)

// Postgres returns a PostgreSQL dialect implementation
func Postgres() Dialect {
	return postgres{}
}

type postgres struct{}

// quoteIdentifier safely quotes a SQL identifier to prevent SQL injection
// PostgreSQL uses double quotes for identifiers and doubles them for escaping
func (p postgres) quoteIdentifier(identifier string) string {
	// Replace any existing quotes with double quotes (SQL escape mechanism)
	escaped := strings.ReplaceAll(identifier, `"`, `""`)
	return fmt.Sprintf(`"%s"`, escaped)
}

func (p postgres) CreateTable(table string) string {
	return fmt.Sprintf(`CREATE TABLE %s (
	id SERIAL PRIMARY KEY,
	description VARCHAR,
	applied TIMESTAMP);`, p.quoteIdentifier(table))
}

func (p postgres) TableExists(table string) string {
	// PostgreSQL-specific way to check if table exists
	return fmt.Sprintf("SELECT 1 FROM %s LIMIT 1;", p.quoteIdentifier(table))
}

func (p postgres) CheckVersion(table string) string {
	return fmt.Sprintf("SELECT id FROM %s ORDER BY id DESC LIMIT 1;", p.quoteIdentifier(table))
}

func (p postgres) InsertVersion(table string) string {
	// PostgreSQL uses $1, $2 for placeholders instead of ?
	return fmt.Sprintf("INSERT INTO %s(description, applied) VALUES ($1, $2);", p.quoteIdentifier(table))
}