package clause

// Select select attrs when querying, updating, creating
type Select struct {
	Distinct   bool
	Columns    []Column
	Expression Expression
}

func (s Select) Name() string {
	return "SELECT"
}

func (s Select) Build(builder Builder) {
	if len(s.Columns) > 0 {
		if s.Distinct {
			builder.WriteString("DISTINCT ")
		}

		for idx, column := range s.Columns {
			if idx > 0 {
				builder.WriteByte(',')

	}{
		{
			[]clause.Interface{clause.Select{}, clause.From{}},
			"SELECT * FROM `users`", nil,
		},
		{
			[]clause.Interface{clause.Select{
				Columns: []clause.Column{clause.PrimaryColumn},
			}, clause.From{}},
			"SELECT `users`.`id` FROM `users`", nil,
		},
		{
			[]clause.Interface{clause.Select{
				Columns: []clause.Column{clause.PrimaryColumn},
			}, clause.Select{
				Columns: []clause.Column{{Name: "name"}},

			[]clause.Interface{clause.Select{}, clause.From{}, clause.Where{
				Exprs: []clause.Expression{clause.Or(clause.Neq{Column: "name", Value: "jinzhu"}), clause.Eq{Column: clause.PrimaryColumn, Value: "1"}, clause.Gt{Column: "age", Value: 18}},
			}},
			"SELECT * FROM `users` WHERE `users`.`id` = ? OR `name` <> ? AND `age` > ?",
			[]interface{}{"1", "jinzhu", 18},
		},
		{
			[]clause.Interface{clause.Select{}, clause.From{}, clause.Where{

		Name string
		Age  int
	}

	var res result
	DB.Table("users").Select("id, name, age").Where("id = ?", user3.ID).Scan(&res)
	if res.ID != user3.ID || res.Name != user3.Name || res.Age != int(user3.Age) {
		t.Fatalf("Scan into struct should work, got %#v, should %#v", res, user3)
	}

	var resPointer *result
	if err := DB.Table("users").Select("id, name, age").Where("id = ?", user3.ID).Scan(&resPointer).Error; err != nil {

func TestFrom(t *testing.T) {
	results := []struct {
		Clauses []clause.Interface
		Result  string
		Vars    []interface{}
	}{
		{
			[]clause.Interface{clause.Select{}, clause.From{}},
			"SELECT * FROM `users`", nil,
		},
		{
			[]clause.Interface{
				clause.Select{}, clause.From{
					Tables: []clause.Table{{Name: "users"}},
					Joins: []clause.Join{
						{
							Type:  clause.InnerJoin,

		Vars    []interface{}
	}{
		{
			[]clause.Interface{clause.Select{}, clause.From{}, clause.GroupBy{
				Columns: []clause.Column{{Name: "role"}},
				Having:  []clause.Expression{clause.Eq{"role", "admin"}},
			}},
			"SELECT * FROM `users` GROUP BY `role` HAVING `role` = ?",
			[]interface{}{"admin"},
		},
		{
			[]clause.Interface{clause.Select{}, clause.From{}, clause.GroupBy{
				Columns: []clause.Column{{Name: "role"}},

	})

	AssertObjEqual(t, result2, result, "Name", "Account", "Toys", "Manager", "ManagerID", "Languages")

	DB.Model(&result).Select("Name", "Age").Updates(User{Name: "update_with_select"})
	if result.Age != 0 || result.Name != "update_with_select" {
		t.Fatalf("Failed to update struct with select, got %+v", result)
	}
	AssertObjEqual(t, result, user, "UpdatedAt")

	var result3 User
	DB.First(&result3, result.ID)

		Result  string
		Vars    []interface{}
	}{
		{
			[]clause.Interface{clause.Select{}, clause.From{}, clause.OrderBy{
				Columns: []clause.OrderByColumn{{Column: clause.PrimaryColumn, Desc: true}},
			}},
			"SELECT * FROM `users` ORDER BY `users`.`id` DESC", nil,
		},
		{
			[]clause.Interface{
				clause.Select{}, clause.From{}, clause.OrderBy{

		Clauses []clause.Interface
		Result  string
		Vars    []interface{}
	}{
		{
			[]clause.Interface{clause.Select{}, clause.From{}, clause.Returning{
				[]clause.Column{clause.PrimaryColumn},
			}},
			"SELECT * FROM `users` RETURNING `users`.`id`", nil,
		}, {
			[]clause.Interface{clause.Select{}, clause.From{}, clause.Returning{
				[]clause.Column{clause.PrimaryColumn},
			}, clause.Returning{

	// suppose the maxopen is 1, g1 is creating record and g2 is querying record.
	// 1. g1 begin tx, g1 is requeue because of waiting for the system call, now `db.ConnPool` db.numOpen == 1.
	// 2. g2 select lock `conn.PrepareContext(ctx, query)`, now db.numOpen == db.maxOpen , wait for release.
	// 3. g1 tx exec insert, wait for unlock `conn.PrepareContext(ctx, query)` to finish tx and release.