package database

import (
	"context"
	"database/sql/driver"
	"errors"
	"fmt"
	"os"

	"github.com/go-sql-driver/mysql"
	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/stdlib"
	"gopkg.in/yaml.v3"
)

// from https://github.com/Boostport/dynamic-database-config

// CreateConnectorFunc is a function that creates a database connector
type CreateConnectorFunc func() (driver.Connector, error)

// Driver implements the sql/driver interface with dynamic configuration
type Driver struct {
	CreateConnectorFunc CreateConnectorFunc
}

// Driver returns the driver instance
func (d Driver) Driver() driver.Driver {
	return d
}

// Connect creates a new database connection using the dynamic connector
func (d Driver) Connect(ctx context.Context) (driver.Conn, error) {
	connector, err := d.CreateConnectorFunc()
	if err != nil {
		return nil, fmt.Errorf("error creating connector from function: %w", err)
	}

	return connector.Connect(ctx)
}

// Open is not supported for dynamic configuration
func (d Driver) Open(name string) (driver.Conn, error) {
	return nil, errors.New("open is not supported")
}

// createConnector creates a connector function that reads configuration from a file
func createConnector(configFile string) CreateConnectorFunc {
	return func() (driver.Connector, error) {
		dbFile, err := os.Open(configFile)
		if err != nil {
			return nil, err
		}
		defer dbFile.Close()

		dec := yaml.NewDecoder(dbFile)
		cfg := Config{}

		err = dec.Decode(&cfg)
		if err != nil {
			return nil, err
		}

		// Validate configuration
		if err := cfg.Validate(); err != nil {
			return nil, fmt.Errorf("invalid configuration: %w", err)
		}

		// Determine database type and create appropriate connector
		if cfg.MySQL != nil {
			return createMySQLConnector(cfg.MySQL)
		} else if cfg.Postgres != nil {
			return createPostgresConnector(cfg.Postgres)
		} else if cfg.User != "" && cfg.Name != "" {
			// Legacy flat PostgreSQL format (requires at minimum user and dbname)
			return createPostgresConnectorFromFlat(&cfg)
		}

		return nil, fmt.Errorf("no valid database configuration found (mysql or postgres section required)")
	}
}

// createMySQLConnector creates a MySQL connector from configuration
func createMySQLConnector(cfg *MySQLConfig) (driver.Connector, error) {
	dsn := cfg.DSN
	if len(dsn) == 0 {
		dsn = os.Getenv("DATABASE_DSN")
		if len(dsn) == 0 {
			return nil, fmt.Errorf("dsn config in database.yaml or DATABASE_DSN environment variable required")
		}
	}

	dbcfg, err := mysql.ParseDSN(dsn)
	if err != nil {
		return nil, err
	}

	if user := cfg.User; len(user) > 0 {
		dbcfg.User = user
	}

	if pass := cfg.Pass; len(pass) > 0 {
		dbcfg.Passwd = pass
	}

	if name := cfg.DBName; len(name) > 0 {
		dbcfg.DBName = name
	}

	return mysql.NewConnector(dbcfg)
}

// createPostgresConnector creates a PostgreSQL connector from configuration
func createPostgresConnector(cfg *PostgresConfig) (driver.Connector, error) {
	// Validate required fields
	if cfg.Host == "" {
		return nil, fmt.Errorf("postgres: host is required")
	}
	if cfg.User == "" {
		return nil, fmt.Errorf("postgres: user is required")
	}
	if cfg.Name == "" {
		return nil, fmt.Errorf("postgres: database name is required")
	}

	// Validate SSLMode
	validSSLModes := map[string]bool{
		"disable": true, "allow": true, "prefer": true,
		"require": true, "verify-ca": true, "verify-full": true,
	}
	if cfg.SSLMode != "" && !validSSLModes[cfg.SSLMode] {
		return nil, fmt.Errorf("postgres: invalid sslmode: %s", cfg.SSLMode)
	}

	// Build config directly (security: no DSN string with password)
	connConfig, err := pgx.ParseConfig("")
	if err != nil {
		return nil, fmt.Errorf("postgres: failed to create pgx config: %w", err)
	}

	connConfig.Host = cfg.Host
	connConfig.Port = cfg.Port
	connConfig.User = cfg.User
	connConfig.Password = cfg.Pass
	connConfig.Database = cfg.Name

	// Map SSLMode to pgx configuration
	// Note: pgx uses different SSL handling than libpq
	// For now, we'll construct a minimal DSN with sslmode for ParseConfig
	if cfg.SSLMode != "" {
		// Reconstruct with sslmode only (no password in DSN)
		dsnWithoutPassword := fmt.Sprintf("host=%s port=%d user=%s dbname=%s sslmode=%s",
			cfg.Host, cfg.Port, cfg.User, cfg.Name, cfg.SSLMode)
		connConfig, err = pgx.ParseConfig(dsnWithoutPassword)
		if err != nil {
			return nil, fmt.Errorf("postgres: failed to parse config with sslmode: %w", err)
		}
		// Set password separately after parsing
		connConfig.Password = cfg.Pass
	}

	return stdlib.GetConnector(*connConfig), nil
}

// createPostgresConnectorFromFlat creates a PostgreSQL connector from flat config format
func createPostgresConnectorFromFlat(cfg *Config) (driver.Connector, error) {
	pgCfg := &PostgresConfig{
		User:    cfg.User,
		Pass:    cfg.Pass,
		Host:    cfg.Host,
		Port:    cfg.Port,
		Name:    cfg.Name,
		SSLMode: cfg.SSLMode,
	}

	// Set defaults for PostgreSQL
	if pgCfg.Host == "" {
		pgCfg.Host = "localhost"
	}
	if pgCfg.Port == 0 {
		pgCfg.Port = 5432
	}
	if pgCfg.SSLMode == "" {
		pgCfg.SSLMode = "prefer"
	}

	return createPostgresConnector(pgCfg)
}