From 9e84e4bb1b69f388788ac0b37dcdc3dcfd17ff05 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Vin=C3=ADcius=20Garcia?= <vingarcia00@gmail.com>
Date: Thu, 26 Nov 2020 22:35:36 -0300
Subject: [PATCH] Remove gorm dependency from Delete()

---
 kiss_orm.go      | 30 ++++++++++++++++++-------
 kiss_orm_test.go | 58 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 80 insertions(+), 8 deletions(-)

diff --git a/kiss_orm.go b/kiss_orm.go
index 748bfae..a619cbb 100644
--- a/kiss_orm.go
+++ b/kiss_orm.go
@@ -48,11 +48,11 @@ func (c Client) ChangeTable(ctx context.Context, tableName string) ORMProvider {
 }
 
 // Query queries several rows from the database,
-// the input should be a slice of structs passed
+// the input should be a slice of structs (or *struct) passed
 // by reference and it will be filled with all the results.
 //
 // Note: it is very important to make sure the query will
-// return a small number of results, otherwise you risk
+// return a small known number of results, otherwise you risk
 // of overloading the available memory.
 func (c Client) Query(
 	ctx context.Context,
@@ -271,14 +271,15 @@ func (c Client) Delete(
 	ctx context.Context,
 	ids ...interface{},
 ) error {
-	for _, id := range ids {
-		r := c.db.Table(c.tableName).Delete(id)
-		if r.Error != nil {
-			return r.Error
-		}
+	if len(ids) == 0 {
+		return nil
 	}
 
-	return nil
+	query := buildDeleteQuery(c.tableName, ids)
+
+	_, err := c.db.DB().ExecContext(ctx, query, ids...)
+
+	return err
 }
 
 // Update updates the given instances on the database by id.
@@ -606,3 +607,16 @@ func getTagInfoWithCache(tagInfoCache map[reflect.Type]structInfo, key reflect.T
 	}
 	return info
 }
+
+func buildDeleteQuery(table string, ids []interface{}) string {
+	values := []string{}
+	for range ids {
+		values = append(values, "?")
+	}
+
+	return fmt.Sprintf(
+		"DELETE FROM `%s` WHERE id IN (%s)",
+		table,
+		strings.Join(values, ","),
+	)
+}
diff --git a/kiss_orm_test.go b/kiss_orm_test.go
index 500b970..6417410 100644
--- a/kiss_orm_test.go
+++ b/kiss_orm_test.go
@@ -294,6 +294,64 @@ func TestDelete(t *testing.T) {
 		assert.Equal(t, uint(0), result.ID)
 		assert.Equal(t, "", result.Name)
 	})
+
+	t.Run("should delete multiple ids correctly", func(t *testing.T) {
+		db := connectDB(t)
+		defer db.Close()
+
+		ctx := context.Background()
+		c := Client{
+			db:        db,
+			tableName: "users",
+		}
+
+		u1 := User{
+			Name: "Fernanda",
+		}
+		err := c.Insert(ctx, &u1)
+		assert.Equal(t, nil, err)
+		assert.NotEqual(t, 0, u1.ID)
+
+		u2 := User{
+			Name: "Juliano",
+		}
+		err = c.Insert(ctx, &u2)
+		assert.Equal(t, nil, err)
+		assert.NotEqual(t, 0, u2.ID)
+
+		u3 := User{
+			Name: "This won't be deleted",
+		}
+		err = c.Insert(ctx, &u3)
+		assert.Equal(t, nil, err)
+		assert.NotEqual(t, 0, u3.ID)
+
+		result := User{}
+		it := c.db.Raw("SELECT * FROM users WHERE id=?", u1.ID)
+		it.Scan(&result)
+		assert.Equal(t, u1.ID, result.ID)
+
+		result = User{}
+		it = c.db.Raw("SELECT * FROM users WHERE id=?", u2.ID)
+		it.Scan(&result)
+		assert.Equal(t, u2.ID, result.ID)
+
+		result = User{}
+		it = c.db.Raw("SELECT * FROM users WHERE id=?", u3.ID)
+		it.Scan(&result)
+		assert.Equal(t, u3.ID, result.ID)
+
+		err = c.Delete(ctx, u1.ID, u2.ID)
+		assert.Equal(t, nil, err)
+
+		results := []User{}
+		it = c.db.Raw("SELECT * FROM users WHERE id IN (?, ?, ?)", u1.ID, u2.ID, u3.ID)
+		it.Scan(&results)
+
+		assert.Equal(t, nil, it.Error)
+		assert.Equal(t, 1, len(results))
+		assert.Equal(t, "This won't be deleted", results[0].Name)
+	})
 }
 
 func TestUpdate(t *testing.T) {