// Copyright 2018-2022 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.

package models

import (
	"code.gitea.io/gitea/models/db"
	user_model "code.gitea.io/gitea/models/user"
	"code.gitea.io/gitea/modules/timeutil"
)

// IssueParent represents an issue parent
type IssueParent struct {
	ID           int64              `xorm:"pk autoincr"`
	UserID       int64              `xorm:"NOT NULL"`
	IssueID      int64              `xorm:"UNIQUE(issue_parent) NOT NULL"`
	ParentID     int64              `xorm:"UNIQUE(issue_parent) NOT NULL"`
	CreatedUnix  timeutil.TimeStamp `xorm:"created"`
	UpdatedUnix  timeutil.TimeStamp `xorm:"updated"`
}

func init() {
	db.RegisterModel(new(IssueParent))
}

// ParentType Defines Parent Type Constants
type ParentType int

// Define Parent Types
const (
	ParentTypeFather ParentType = iota
	ParentTypeChild
)

// CreateIssueParent creates a new parent for an issue
func CreateIssueParent(user *user_model.User, issue, parent *Issue) error {
	ctx, committer, err := db.TxContext()
	if err != nil {
		return err
	}
	defer committer.Close()
	sess := db.GetEngine(ctx)

	// Check if it aleready exists
	exists, err := issueParentExists(sess, issue.ID, parent.ID)
	if err != nil {
		return err
	}
	if exists {
		return ErrParentExists{issue.ID, parent.ID}
	}
	// And if it would be circular
	circular, err := issueParentExists(sess, parent.ID, issue.ID)
	if err != nil {
		return err
	}
	if circular {
		return ErrCircularParent{issue.ID, parent.ID}
	}

	if err := db.Insert(ctx, &IssueParent{
		UserID:       user.ID,
		IssueID:      issue.ID,
		ParentID:     parent.ID,
	}); err != nil {
		return err
	}

	// Add comment referencing the new parent
	if err = createIssueParentComment(ctx, user, issue, parent, true); err != nil {
		return err
	}

	return committer.Commit()
}

// RemoveIssueParent removes a parent from an issue
func RemoveIssueParent(user *user_model.User, issue, parent *Issue, parentType ParentType) (err error) {
	ctx, committer, err := db.TxContext()
	if err != nil {
		return err
	}
	defer committer.Close()

	var issueParentToDelete IssueParent

	switch parentType {
	case ParentTypeFather:
		issueParentToDelete = IssueParent{IssueID: issue.ID, ParentID: parent.ID}
	case ParentTypeChild:
		issueParentToDelete = IssueParent{IssueID: parent.ID, ParentID: issue.ID}
	default:
		return ErrUnknownParentType{parentType}
	}

	affected, err := db.GetEngine(ctx).Delete(&issueParentToDelete)
	if err != nil {
		return err
	}

	// If we deleted nothing, the parent did not exist
	if affected <= 0 {
		return ErrParentNotExists{issue.ID, parent.ID}
	}

	// Add comment referencing the removed parent
	if err = createIssueParentComment(ctx, user, issue, parent, false); err != nil {
		return err
	}
	return committer.Commit()
}

// Check if the parent already exists
func issueParentExists(e db.Engine, issueID, depID int64) (bool, error) {
	return e.Where("(issue_id = ? AND parent_id = ?)", issueID, depID).Exist(&IssueParent{})
}

// IssueNoParentsLeft checks if issue can be closed
func IssueNoParentsLeft(issue *Issue) (bool, error) {
	return issueNoParentsLeft(db.GetEngine(db.DefaultContext), issue)
}

func issueNoParentsLeft(e db.Engine, issue *Issue) (bool, error) {
	exists, err := e.
		Table("issue_parent").
		Select("issue.*").
		Join("INNER", "issue", "issue.id = issue_parent.parent_id").
		Where("issue_parent.issue_id = ?", issue.ID).
		And("issue.is_closed = ?", "0").
		Exist(&Issue{})

	return !exists, err
}