package database

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

	"github.com/go-sql-driver/mysql"
	"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
		}

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

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

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

		return mysql.NewConnector(dbcfg)
	}
}