package database

import (
	"context"
	"database/sql"
	"fmt"
	"path/filepath"
	"time"

	"github.com/golang-migrate/migrate/v4"
	"github.com/golang-migrate/migrate/v4/database/postgres"
	_ "github.com/golang-migrate/migrate/v4/source/file"
	_ "github.com/lib/pq"

	"github.com/kms/api-key-service/internal/repository"
)

// PostgresProvider implements the DatabaseProvider interface
type PostgresProvider struct {
	db *sql.DB
}

// NewPostgresProvider creates a new PostgreSQL database provider
func NewPostgresProvider(dsn string, maxOpenConns, maxIdleConns int, maxLifetime string) (repository.DatabaseProvider, error) {
	db, err := sql.Open("postgres", dsn)
	if err != nil {
		return nil, fmt.Errorf("failed to open database connection: %w", err)
	}

	// Set connection pool settings
	db.SetMaxOpenConns(maxOpenConns)
	db.SetMaxIdleConns(maxIdleConns)

	// Parse and set max lifetime if provided
	if maxLifetime != "" {
		if lifetime, err := time.ParseDuration(maxLifetime); err == nil {
			db.SetConnMaxLifetime(lifetime)
		}
	}

	// Test the connection
	if err := db.Ping(); err != nil {
		db.Close()
		return nil, fmt.Errorf("failed to ping database: %w", err)
	}

	return &PostgresProvider{db: db}, nil
}

// GetDB returns the underlying database connection
func (p *PostgresProvider) GetDB() interface{} {
	return p.db
}

// Ping checks the database connection
func (p *PostgresProvider) Ping(ctx context.Context) error {
	if p.db == nil {
		return fmt.Errorf("database connection is nil")
	}
	
	// Check if database is closed
	if err := p.db.PingContext(ctx); err != nil {
		return fmt.Errorf("database ping failed: %w", err)
	}
	
	return nil
}

// Close closes all database connections
func (p *PostgresProvider) Close() error {
	return p.db.Close()
}

// BeginTx starts a database transaction
func (p *PostgresProvider) BeginTx(ctx context.Context) (repository.TransactionProvider, error) {
	tx, err := p.db.BeginTx(ctx, nil)
	if err != nil {
		return nil, fmt.Errorf("failed to begin transaction: %w", err)
	}

	return &PostgresTransaction{tx: tx}, nil
}

// Migrate runs database migrations
func (p *PostgresProvider) Migrate(ctx context.Context, migrationPath string) error {
	// Create a separate connection for migrations to avoid interfering with the main connection
	migrationDB, err := sql.Open("postgres", p.getDSN())
	if err != nil {
		return fmt.Errorf("failed to open migration database connection: %w", err)
	}
	defer migrationDB.Close()

	driver, err := postgres.WithInstance(migrationDB, &postgres.Config{})
	if err != nil {
		return fmt.Errorf("failed to create postgres driver: %w", err)
	}

	// Convert relative path to file URL
	absPath, err := filepath.Abs(migrationPath)
	if err != nil {
		return fmt.Errorf("failed to get absolute path: %w", err)
	}

	m, err := migrate.NewWithDatabaseInstance(
		fmt.Sprintf("file://%s", absPath),
		"postgres",
		driver,
	)
	if err != nil {
		return fmt.Errorf("failed to create migrate instance: %w", err)
	}
	defer m.Close()

	// Run migrations
	if err := m.Up(); err != nil && err != migrate.ErrNoChange {
		return fmt.Errorf("failed to run migrations: %w", err)
	}

	return nil
}

// getDSN reconstructs the DSN from the current connection
// This is a workaround since we don't store the original DSN
func (p *PostgresProvider) getDSN() string {
	// For now, we'll use the default values from config
	// In a production system, we'd store the original DSN
	return "host=localhost port=5432 user=postgres password=postgres dbname=kms sslmode=disable"
}

// PostgresTransaction implements the TransactionProvider interface
type PostgresTransaction struct {
	tx *sql.Tx
}

// Commit commits the transaction
func (t *PostgresTransaction) Commit() error {
	return t.tx.Commit()
}

// Rollback rolls back the transaction
func (t *PostgresTransaction) Rollback() error {
	return t.tx.Rollback()
}

// GetTx returns the underlying transaction
func (t *PostgresTransaction) GetTx() interface{} {
	return t.tx
}