package infrastructure

import (
	"database/sql"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"runtime"

	"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"
)

// Config holds database configuration
type Config struct {
	Host     string
	Port     string
	User     string
	Password string
	DBName   string
	SSLMode  string
}

// NewConnection creates a new database connection
func NewConnection(config Config) (*sql.DB, error) {
	dsn := fmt.Sprintf("host=%s port=%s user=%s password=%s dbname=%s sslmode=%s",
		config.Host, config.Port, config.User, config.Password, config.DBName, config.SSLMode)

	db, err := sql.Open("postgres", dsn)
	if err != nil {
		return nil, fmt.Errorf("failed to open database connection: %w", err)
	}

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

	return db, nil
}

// LoadConfigFromEnv loads database configuration from environment variables
func LoadConfigFromEnv() Config {
	return Config{
		Host:     getEnv("DB_HOST", "localhost"),
		Port:     getEnv("DB_PORT", "5432"),
		User:     getEnv("DB_USER", "postgres"),
		Password: getEnv("DB_PASSWORD", "password"),
		DBName:   getEnv("DB_NAME", "linkedin_jobs"),
		SSLMode:  getEnv("DB_SSLMODE", "disable"),
	}
}

func getEnv(key, defaultValue string) string {
	if value := os.Getenv(key); value != "" {
		return value
	}
	return defaultValue
}

// RunMigrations runs all pending migrations
func RunMigrations(db *sql.DB) error {
	driver, err := postgres.WithInstance(db, &postgres.Config{})
	if err != nil {
		return fmt.Errorf("failed to create postgres driver: %w", err)
	}

	// Get the migrations directory path
	migrationsPath, err := getMigrationsPath()
	if err != nil {
		return fmt.Errorf("failed to get migrations path: %w", err)
	}

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

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

	return nil
}

// RollbackMigrations rolls back migrations by the specified number of steps
func RollbackMigrations(db *sql.DB, steps int) error {
	driver, err := postgres.WithInstance(db, &postgres.Config{})
	if err != nil {
		return fmt.Errorf("failed to create postgres driver: %w", err)
	}

	migrationsPath, err := getMigrationsPath()
	if err != nil {
		return fmt.Errorf("failed to get migrations path: %w", err)
	}

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

	if err := m.Steps(-steps); err != nil && !errors.Is(err, migrate.ErrNoChange) {
		return fmt.Errorf("failed to rollback migrations: %w", err)
	}

	return nil
}

// GetMigrationVersion returns the current migration version
func GetMigrationVersion(db *sql.DB) (uint, bool, error) {
	driver, err := postgres.WithInstance(db, &postgres.Config{})
	if err != nil {
		return 0, false, fmt.Errorf("failed to create postgres driver: %w", err)
	}

	migrationsPath, err := getMigrationsPath()
	if err != nil {
		return 0, false, fmt.Errorf("failed to get migrations path: %w", err)
	}

	m, err := migrate.NewWithDatabaseInstance(
		fmt.Sprintf("file://%s", migrationsPath),
		"postgres",
		driver,
	)
	if err != nil {
		return 0, false, fmt.Errorf("failed to create migrate instance: %w", err)
	}
	defer m.Close()

	version, dirty, err := m.Version()
	if err != nil {
		if errors.Is(err, migrate.ErrNilVersion) {
			return 0, false, nil
		}
		return 0, false, fmt.Errorf("failed to get migration version: %w", err)
	}

	return version, dirty, nil
}

func getMigrationsPath() (string, error) {
	// Get the directory of the current source file
	_, filename, _, ok := runtime.Caller(0)
	if !ok {
		return "", fmt.Errorf("failed to get current file path")
	}
	
	// Get the project root (go up from infrastructure/ to project root)
	projectRoot := filepath.Dir(filepath.Dir(filename))
	migrationsPath := filepath.Join(projectRoot, "migrations")
	
	// Verify the migrations directory exists
	if _, err := os.Stat(migrationsPath); err != nil {
		return "", fmt.Errorf("migrations directory not found at %s: %w", migrationsPath, err)
	}

	return migrationsPath, nil
}