feat(views)!: move task position handling to its own crud entity

BREAKING CHANGE: the position of tasks now can't be updated anymore via the task update endpoint. Instead, there is a new endpoint which takes the project view into account as well.

pkg/models/task_position.go

@@ -0,0 +1,115 @@
+// Vikunja is a to-do list application to facilitate your life.
+// Copyright 2018-present Vikunja and contributors. All rights reserved.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public Licensee as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public Licensee for more details.
+//
+// You should have received a copy of the GNU Affero General Public Licensee
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package models
+
+import (
+	"code.vikunja.io/web"
+	"math"
+	"xorm.io/xorm"
+)
+
+type TaskPosition struct {
+	// The ID of the task this position is for
+	TaskID int64 `xorm:"bigint not null index" json:"task_id" param:"task"`
+	// The project view this task is related to
+	ProjectViewID int64 `xorm:"bigint not null index" json:"project_view_id"`
+	// The position of the task - any task project can be sorted as usual by this parameter.
+	// When accessing tasks via kanban buckets, this is primarily used to sort them based on a range
+	// We're using a float64 here to make it possible to put any task within any two other tasks (by changing the number).
+	// You would calculate the new position between two tasks with something like task3.position = (task2.position - task1.position) / 2.
+	// A 64-Bit float leaves plenty of room to initially give tasks a position with 2^16 difference to the previous task
+	// which also leaves a lot of room for rearranging and sorting later.
+	// Positions are always saved per view. They will automatically be set if you request the tasks through a view
+	// endpoint, otherwise they will always be 0. To update them, take a look at the Task Position endpoint.
+	Position float64 `xorm:"double not null" json:"position"`
+
+	web.CRUDable `xorm:"-" json:"-"`
+	web.Rights   `xorm:"-" json:"-"`
+}
+
+func (tp *TaskPosition) TableName() string {
+	return "task_positions"
+}
+
+func (tp *TaskPosition) CanUpdate(s *xorm.Session, a web.Auth) (bool, error) {
+	pv := &ProjectView{ID: tp.ProjectViewID}
+	return pv.CanUpdate(s, a)
+}
+
+// Update is the handler to update a task position
+// @Summary Updates a task position
+// @Description Updates a task position.
+// @tags task
+// @Accept json
+// @Produce json
+// @Security JWTKeyAuth
+// @Param id path int true "Task ID"
+// @Param view body models.TaskPosition true "The task position with updated values you want to change."
+// @Success 200 {object} models.TaskPosition "The updated task position."
+// @Failure 400 {object} web.HTTPError "Invalid task position object provided."
+// @Failure 500 {object} models.Message "Internal error"
+// @Router /tasks/{id}/position [post]
+func (tp *TaskPosition) Update(s *xorm.Session, _ web.Auth) (err error) {
+	exists, err := s.
+		Where("task_id = ? AND project_view_id = ?", tp.TaskID, tp.ProjectViewID).
+		Get(&TaskPosition{})
+	if err != nil {
+		return err
+	}
+
+	if !exists {
+		_, err = s.Insert(tp)
+		return
+	}
+
+	_, err = s.
+		Where("task_id = ?", tp.TaskID).
+		Cols("project_view_id", "position").
+		Update(tp)
+	return
+}
+
+func RecalculateTaskPositions(s *xorm.Session, view *ProjectView) (err error) {
+
+	allTasks := []*Task{}
+	err = s.
+		Select("tasks.*, task_positions.position AS position").
+		Join("LEFT", "task_positions", "task_positions.task_id = tasks.id AND task_positions.project_view_id = ?", view.ID).
+		Where("project_id = ?", view.ProjectID).
+		OrderBy("position asc").
+		Find(&allTasks)
+	if err != nil {
+		return
+	}
+
+	maxPosition := math.Pow(2, 32)
+	newPositions := make([]*TaskPosition, 0, len(allTasks))
+
+	for i, task := range allTasks {
+
+		currentPosition := maxPosition / float64(len(allTasks)) * (float64(i + 1))
+
+		newPositions = append(newPositions, &TaskPosition{
+			TaskID:        task.ID,
+			ProjectViewID: view.ID,
+			Position:      currentPosition,
+		})
+	}
+
+	_, err = s.Insert(newPositions)
+	return
+}