package main

import (
	"fmt"
	"math/rand"
	"time"

	"github.com/DATA-DOG/go-txdb"
	"github.com/jinzhu/gorm"

	_ "github.com/jinzhu/gorm/dialects/postgres" // Use PostgreSQL in gorm
)

func main() {
	dial := fmt.Sprintf("postgres://%s:%s@%s:%s/%s?sslmode=%s&statement_timeout=2000", "gorm", "gorm", "localhost", "15432", "test1", "disable")
	{
		conn, err := gorm.Open("postgres", dial)
		if err != nil {
			panic(err)
		}
		conn.AutoMigrate(&User{})
		if err := conn.Close(); err != nil {
			panic(err)
		}
	}
	{
		name := RandStringRunes(100)
		conn1, err := gorm.Open("postgres", dial)
		if err != nil {
			panic(err)
		}
		conn2, err := gorm.Open("postgres", dial)
		if err != nil {
			panic(err)
		}
		err = testExec(conn1, conn2, name)
		fmt.Println(err)
		if err := conn1.Close(); err != nil {
			panic(err)
		}
		if err := conn2.Close(); err != nil {
			panic(err)
		}
	}
	fmt.Println("conn3, conn4")
	{
		name := RandStringRunes(100)
		conn3, err := gorm.Open("postgres", dial)
		if err != nil {
			panic(err)
		}
		conn4, err := gorm.Open("postgres", dial)
		if err != nil {
			panic(err)
		}

		conn3 = conn3.Begin()
		conn4 = conn4.Begin()
		err = testExec(conn3, conn4, name) // conn3 wait lock so we got timeout error
		fmt.Println(err)

		if err := conn3.Rollback().Error; err != nil {
			panic(err)
		}
		if err := conn4.Rollback().Error; err != nil {
			panic(err)
		}
		if err := conn3.Close(); err != nil {
			panic(err)
		}
		if err := conn4.Close(); err != nil {
			panic(err)
		}
	}

	fmt.Println("txdb")
	{
		dbname := "postgreql_txdb"
		txdb.Register(dbname, "postgres", dial)

		dialect, ok := gorm.GetDialect("postgres")
		if !ok {
			panic(fmt.Errorf("dialect not exist"))
		}
		gorm.RegisterDialect(dbname, dialect)

		name := RandStringRunes(100)
		conn5, err := gorm.Open(dbname, "conn1")
		if err != nil {
			panic(err)
		}
		conn6, err := gorm.Open(dbname, "conn2")
		if err != nil {
			panic(err)
		}
		err = testExec(conn5, conn6, name)
		fmt.Println(err) // timeout
		if err := conn5.Close(); err != nil {
			panic(err)
		}
		if err := conn6.Close(); err != nil {
			panic(err)
		}
	}

	fmt.Println("end")
}

func testExec(conn1 *gorm.DB, conn2 *gorm.DB, name string) error {
	err := conn1.Save(&User{Name: name}).Error
	if err != nil {
		panic(err) // should be always succeed
	}

	err = conn2.Save(&User{Name: name}).Error
	if err != nil {
		fmt.Println("save failed")
		return err
	}

	return nil
}

// https://stackoverflow.com/questions/22892120/how-to-generate-a-random-string-of-a-fixed-length-in-go
func init() {
	rand.Seed(time.Now().UnixNano())
}

var letterRunes = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")

func RandStringRunes(n int) string {
	b := make([]rune, n)
	for i := range b {
		b[i] = letterRunes[rand.Intn(len(letterRunes))]
	}
	return string(b)
}

type User struct {
	gorm.Model
	Name string `json:"name" gorm:"unique;not null"`
}