package main

import (
	"database/sql"
	"fmt"
	"github.com/google/uuid"
	"gorm.io/driver/mysql"
	"gorm.io/gorm"
	"gorm.io/gorm/clause"
	"log"
	"time"
)

type Model struct {
	ID        uuid.UUID `gorm:"type:char(36);primary_key"`
}

// BeforeCreate will set a UUID rather than numeric ID.
func (m *Model) BeforeCreate(tx *gorm.DB) (err error) {
	m.ID = uuid.New()
	return
}

type Foo struct {
	Model
	Name string `gorm:"type:varchar(45)"`
	Bars []*Bar `gorm:"many2many:foo_bar;"`
}

type Bar struct {
	Model
	Name string `gorm:"type:varchar(45)"`
	Foos []*Foo `gorm:"many2many:foo_bar;"`
}

func main() {
	db := provideDatabase()
	foos := map[string]*Foo{}
	for _, f := range []string{"a", "b", "c", "d", "e"} {
		id := uuid.New()
		foo := Foo{Model: Model{ID: id}, Name: f}
		db.Omit(clause.Associations).Create(&foo)
		foos[f] = &foo
	}
	for _, b := range []string{"z", "y", "x", "w", "v"} {
		bar := Bar{
			Model: Model{ID: uuid.New()},
			Name:  b,
			Foos: []*Foo{
				foos["a"],
				foos["e"],
			},
		}
		db.Create(&bar)
	}
}

// create the database and truncate the tables
func provideDatabase() *gorm.DB {
	log.Println("Connecting to database...")
	connectionString :=
		fmt.Sprintf("%s:%s@tcp(%s:%d)/%s?parseTime=true",
			"root", "letmein", "127.0.0.1", 33070, "test")
	var err error
	sqlDB, err := sql.Open("mysql", connectionString)
	if err != nil {
		panic("Could not connect to database")
	}
	db, err := gorm.Open(mysql.New(mysql.Config{
		Conn: sqlDB,
	}), &gorm.Config{})
	db.AutoMigrate(Foo{}, Bar{})
	db.Exec("SET FOREIGN_KEY_CHECKS=0")
	tables := []string{"foos", "bars", "foo_bar"}
	for _, table := range tables {
		db.Exec("TRUNCATE TABLE " + table)
	}
	return db
}