package common

import (
	"errors"
	"strings"
	"time"

	"laic-backend/logger"

	mysql_ "github.com/go-sql-driver/mysql"
	"gorm.io/driver/mysql"
	"gorm.io/gorm"
)

var DB *gorm.DB
var err error

func InitConnection(config *Mysql) {
	url := config.Url
	if !strings.Contains(url, "loc=") && !strings.Contains(url, "time_zone=") {
		if strings.Contains(url, "?") {
			url += "&loc=Local"
		} else {
			url += "?loc=Local"
		}
	}
	idle := config.Idle
	maxConn := config.MaxConn
	maxWait := time.Duration(config.MaxWait)
	logger.DEBUG("mysql config:", config)

	gConfig := &gorm.Config{
		Logger: logger.NewGormLogger(),
	}
	DB, err = gorm.Open(mysql.Open(url), gConfig)
	if err != nil {
		logger.ERROR("mysql connect error", err)
		panic(err)
	}
	DB = DB.Debug()

	sqlDB, err := DB.DB()
	if err != nil {
		logger.ERROR("init mysql data pool error", err)
		panic(err)
	}
	sqlDB.SetMaxIdleConns(idle)
	sqlDB.SetMaxOpenConns(maxConn)
	sqlDB.SetConnMaxLifetime(maxWait * time.Second)

	logger.INFO("mysql ready")
}

type Pagination struct {
	PageNum  int64 `json:"pageNum" form:"pageNum" binding:"required" minimum:"1"`
	PageSize int64 `json:"pageSize" form:"pageSize" binding:"required" minimum:"1"`
}

func (p *Pagination) Paginate(db *gorm.DB) *gorm.DB {
	offset := int((p.PageNum - 1) * p.PageSize)
	return db.Offset(offset).Limit(int(p.PageSize))
}

// ParseError 解析 MySQL 唯一键冲突等错误，返回错误号和约束名
func ParseError(err error) (uint16, string) {
	if err != nil {
		var mysqlErr *mysql_.MySQLError
		if errors.As(err, &mysqlErr) {
			if mysqlErr.Number == 1062 {
				return mysqlErr.Number, extractConstraintName(mysqlErr.Message)
			}
			return mysqlErr.Number, ""
		} else {
			logger.ERROR("未知错误，gorm error:", err)
		}
	}
	return 0, ""
}

func extractConstraintName(errMsg string) string {
	start := strings.LastIndex(errMsg, "for key '") + len("for key '")
	end := strings.LastIndex(errMsg, "'")
	if start < end {
		return errMsg[start:end]
	}
	return ""
}