Add put task endpoint (#33)

Closes #23

Reviewed-on: #33

backend/db.go

@@ -102,7 +102,7 @@ func (db *Db) CreateGoal(userId int, goal *CreateGoalRequest) (int, error) {
 	if err != nil {
 		return 0, err
 	}
-	defer tx.Rollback()
+	defer tx.MustRollback()
 
 	// Insert the new goal
 	err = tx.Query("insert into goals (user_id, name, target, progress, weight) values (?, ?, ?, 0, ?)").
@@ -156,7 +156,7 @@ func (db *Db) CreateTask(task *CreateTaskRequest) (int, error) {
 	if err != nil {
 		return 0, err
 	}
-	defer tx.Rollback()
+	defer tx.MustRollback()
 
 	// Insert the new task
 	err = tx.Query("insert into tasks (name, reward, assigned) values (?, ?, ?)").
@@ -211,3 +211,29 @@ func (db *Db) GetTask(id int) (Task, error) {
 	}
 	return task, nil
 }
+
+func (db *Db) HasTask(id int) (bool, error) {
+	count := 0
+	err := db.db.Query("select count(*) from tasks where id = ?").
+		Bind(id).ScanSingle(&count)
+	if err != nil {
+		return false, err
+	}
+	return count > 0, nil
+}
+
+func (db *Db) UpdateTask(id int, task *CreateTaskRequest) error {
+	tx, err := db.db.Begin()
+	if err != nil {
+		return err
+	}
+	defer tx.MustRollback()
+
+	err = tx.Query("update tasks set name=?, reward=?, assigned=? where id = ?").
+		Bind(task.Name, task.Reward, task.Assigned, id).
+		Exec()
+	if err != nil {
+		return err
+	}
+	return tx.Commit()
+}