// Package mysql is a library wrapped on top of gorm.io/gorm, with added features such as link tracing, paging queries, etc.
package mysql

import (
	"database/sql"
	"fmt"

	"github.com/uptrace/opentelemetry-go-extra/otelgorm"
	mysqlDriver "gorm.io/driver/mysql"
	"gorm.io/gorm"
	"gorm.io/gorm/logger"
	"gorm.io/gorm/schema"
	"gorm.io/plugin/dbresolver"
)

// Init mysql
func Init(opts ...Option) (*gorm.DB, error) {
	o := defaultOptions()
	o.apply(opts...)
	writeDns := o.mastersDsn[0]

	sqlDB, err := sql.Open("mysql", writeDns)
	if err != nil {
		return nil, err
	}

	sqlDB.SetConnMaxIdleTime(o.connMaxIdleTime) //连接池里面的连接最大空闲时长  当连接持续空闲时长达到maxIdleTime后，该连接就会被关闭并从连接池移除，哪怕当前空闲连接数已经小 SetMaxIdleConns(maxIdleConns)设置的值 连接每次被使用后，持续空闲时长会被重置，从0开始从新计算
	sqlDB.SetMaxIdleConns(o.maxIdleConns)       //连接池里最大空闲连接数。必须要比maxOpenConns小；
	sqlDB.SetMaxOpenConns(o.maxOpenConns)       //连接池最多同时打开的连接数。  服务器cpu核心数 * 2 + 服务器有效磁盘数。 可用show variables like ‘max_connections’; 查看服务器当前设置的最大连接数。
	sqlDB.SetConnMaxLifetime(o.connMaxLifetime) //连接池里面的连接最大存活时长。 maxLifeTime必须要比mysql服务器设置的wait_timeout小，否则会导致golang侧连接池依然保留已被mysql服务器关闭了的连接。 mysql服务器的wait_timeout默认是8 hour，可通过show variables like 'wait_timeout’查看。

	db, err := gorm.Open(mysqlDriver.New(mysqlDriver.Config{Conn: sqlDB}), gormConfig(o))
	if err != nil {
		return nil, err
	}
	db.Set("gorm:table_options", "CHARSET=utf8mb4") // automatic appending of table suffixes when creating tables

	if o.enableTrace {
		err = db.Use(otelgorm.NewPlugin())
		if err != nil {
			return nil, fmt.Errorf("using gorm opentelemetry, err: %v", err)
		}
	}

	// 如果开启了读写分离，配置读数据库（resource、read、replicas）
	// 读写分离配置只
	if o.isOpenReadDb {
		err = db.Use(rwSeparationPlugin(o))
		if err != nil {
			return nil, err
		}
	}

	// register plugins
	for _, plugin := range o.plugins {
		err = db.Use(plugin)
		if err != nil {
			return nil, err
		}
	}
	return db, nil
}

// gorm setting
func gormConfig(o *options) *gorm.Config {
	config := &gorm.Config{
		//是否跳过默认事务
		SkipDefaultTransaction: true,
		// 执行任何SQL时都会创建一个prepared statement并将其缓存，以提高后续的效率
		PrepareStmt: true,
		// disable foreign key constraints, not recommended for production environments
		DisableForeignKeyConstraintWhenMigrating: o.disableForeignKey,
		// removing the plural of an epithet
		NamingStrategy: schema.NamingStrategy{SingularTable: true},
	}

	// print SQL
	if o.isLog {
		if o.gLog == nil {
			config.Logger = logger.Default.LogMode(o.logLevel)
		} else {
			config.Logger = NewCustomGormLogger(o)
		}
	} else {
		config.Logger = logger.Default.LogMode(logger.Silent)
	}

	// print only slow queries
	if o.slowThreshold > 0 {
		config.Logger = NewCustomGormLogger(o)
		//config.Logger = logger.New(
		//	log.New(os.Stdout, "\r\n", log.LstdFlags), // use the standard output asWriter
		//	logger.Config{
		//		SlowThreshold: o.slowThreshold,
		//		Colorful:      true,
		//		LogLevel:      logger.Warn, // set the logging level, only above the specified level will output the slow query log
		//	},
		//)
	}

	return config
}

func rwSeparationPlugin(o *options) gorm.Plugin {
	slaves := []gorm.Dialector{}
	for _, dsn := range o.slavesDsn {
		slaves = append(slaves, mysqlDriver.New(mysqlDriver.Config{
			DSN: dsn,
		}))
	}

	masters := []gorm.Dialector{}
	for _, dsn := range o.mastersDsn {
		masters = append(masters, mysqlDriver.New(mysqlDriver.Config{
			DSN: dsn,
		}))
	}

	return dbresolver.Register(dbresolver.Config{
		Sources:  masters,
		Replicas: slaves,
		Policy:   dbresolver.RandomPolicy{},
	})
}