package mysql

import (
	"fmt"

	"gorm.io/driver/mysql"
	"gorm.io/gorm"
	"gorm.io/gorm/schema"
	"gorm.io/plugin/dbresolver"
)

type Config struct {
	Host     string
	Port     int
	User     string
	Password string
	Database string
	Charset  string
	Prefix   string

	ReadHost     string
	ReadPort     int
	ReadUser     string
	ReadPassword string
	ReadDatabase string
}

func New(c Config) (*gorm.DB, error) {

	dsn := buildDSN(c.User, c.Password, c.Host, c.Port, c.Database, c.Charset)
	db, err := gorm.Open(mysql.New(mysql.Config{
		DSN:                       dsn,
		DefaultStringSize:         256,
		DisableDatetimePrecision:  true,
		DontSupportRenameIndex:    true,
		DontSupportRenameColumn:   true,
		SkipInitializeWithVersion: false,
	}), &gorm.Config{
		NamingStrategy: schema.NamingStrategy{
			TablePrefix: c.Prefix,
		},
	})
	if err != nil {
		return nil, fmt.Errorf("mysql open: %w", err)
	}

	readDSN := buildReadDSN(c)
	if readDSN != "" {
		if err := db.Use(dbresolver.Register(dbresolver.Config{
			Sources:  []gorm.Dialector{mysql.Open(dsn)},
			Replicas: []gorm.Dialector{mysql.Open(readDSN)},
			Policy:   dbresolver.RandomPolicy{},
		})); err != nil {
			return nil, fmt.Errorf("mysql dbresolver: %w", err)
		}
	}

	return db, nil
}

func buildReadDSN(c Config) string {
	if c.ReadHost == "" {
		return ""
	}

	port := c.ReadPort
	if port == 0 {
		port = c.Port
	}
	user := c.ReadUser
	if user == "" {
		user = c.User
	}
	password := c.ReadPassword
	if password == "" {
		password = c.Password
	}
	database := c.ReadDatabase
	if database == "" {
		database = c.Database
	}
	charset := c.Charset
	if charset == "" {
		charset = "utf8mb4"
	}
	return buildDSN(user, password, c.ReadHost, port, database, charset)
}

func buildDSN(user, password, host string, port int, database, charset string) string {
	return fmt.Sprintf("%s:%s@tcp(%s:%d)/%s?charset=%s&parseTime=True&loc=Local",
		user, password, host, port, database, charset)
}