// Copyright 2014 The Gogs 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 (
	"errors"
	"fmt"
	"io"
	"mime/multipart"
	"os"
	"path"
	"strings"
	"time"

	"github.com/Unknwon/com"
	"github.com/go-xorm/xorm"
	api "github.com/gogits/go-gogs-client"
	gouuid "github.com/satori/go.uuid"

	"github.com/gogits/gogs/modules/base"
	"github.com/gogits/gogs/modules/log"
	"github.com/gogits/gogs/modules/setting"
)

var (
	ErrMissingIssueNumber = errors.New("No issue number specified")
)

// Issue represents an issue or pull request of repository.
type Issue struct {
	ID              int64       `xorm:"pk autoincr"`
	RepoID          int64       `xorm:"INDEX UNIQUE(repo_index)"`
	Repo            *Repository `xorm:"-"`
	Index           int64       `xorm:"UNIQUE(repo_index)"` // Index in one repository.
	PosterID        int64
	Poster          *User    `xorm:"-"`
	Title           string   `xorm:"name"`
	Content         string   `xorm:"TEXT"`
	RenderedContent string   `xorm:"-"`
	Labels          []*Label `xorm:"-"`
	MilestoneID     int64
	Milestone       *Milestone `xorm:"-"`
	Priority        int
	AssigneeID      int64
	Assignee        *User `xorm:"-"`
	IsClosed        bool
	IsRead          bool         `xorm:"-"`
	IsPull          bool         // Indicates whether is a pull request or not.
	PullRequest     *PullRequest `xorm:"-"`
	NumComments     int

	Deadline     time.Time `xorm:"-"`
	DeadlineUnix int64
	Created      time.Time `xorm:"-"`
	CreatedUnix  int64
	Updated      time.Time `xorm:"-"`
	UpdatedUnix  int64

	Attachments []*Attachment `xorm:"-"`
	Comments    []*Comment    `xorm:"-"`
}

func (issue *Issue) BeforeInsert() {
	issue.CreatedUnix = time.Now().Unix()
	issue.UpdatedUnix = issue.CreatedUnix
}

func (issue *Issue) BeforeUpdate() {
	issue.UpdatedUnix = time.Now().Unix()
	issue.DeadlineUnix = issue.Deadline.Unix()
}

func (issue *Issue) AfterSet(colName string, _ xorm.Cell) {
	switch colName {
	case "deadline_unix":
		issue.Deadline = time.Unix(issue.DeadlineUnix, 0).Local()
	case "created_unix":
		issue.Created = time.Unix(issue.CreatedUnix, 0).Local()
	case "updated_unix":
		issue.Updated = time.Unix(issue.UpdatedUnix, 0).Local()
	}
}

func (issue *Issue) loadAttributes(e Engine) (err error) {
	if issue.Repo == nil {
		issue.Repo, err = getRepositoryByID(e, issue.RepoID)
		if err != nil {
			return fmt.Errorf("getRepositoryByID [%d]: %v", issue.RepoID, err)
		}
	}

	if issue.Poster == nil {
		issue.Poster, err = getUserByID(e, issue.PosterID)
		if err != nil {
			if IsErrUserNotExist(err) {
				issue.PosterID = -1
				issue.Poster = NewGhostUser()
			} else {
				return fmt.Errorf("getUserByID.(Poster) [%d]: %v", issue.PosterID, err)
			}
			return
		}
	}

	if issue.Labels == nil {
		issue.Labels, err = getLabelsByIssueID(e, issue.ID)
		if err != nil {
			return fmt.Errorf("getLabelsByIssueID [%d]: %v", issue.ID, err)
		}
	}

	if issue.Milestone == nil && issue.MilestoneID > 0 {
		issue.Milestone, err = getMilestoneByRepoID(e, issue.RepoID, issue.MilestoneID)
		if err != nil {
			return fmt.Errorf("getMilestoneByRepoID [repo_id: %d, milestone_id: %d]: %v", issue.RepoID, issue.MilestoneID, err)
		}
	}

	if issue.Assignee == nil && issue.AssigneeID > 0 {
		issue.Assignee, err = getUserByID(e, issue.AssigneeID)
		if err != nil {
			return fmt.Errorf("getUserByID.(assignee) [%d]: %v", issue.AssigneeID, err)
		}
	}

	if issue.IsPull && issue.PullRequest == nil {
		// It is possible pull request is not yet created.
		issue.PullRequest, err = getPullRequestByIssueID(e, issue.ID)
		if err != nil && !IsErrPullRequestNotExist(err) {
			return fmt.Errorf("getPullRequestByIssueID [%d]: %v", issue.ID, err)
		}
	}

	if issue.Attachments == nil {
		issue.Attachments, err = getAttachmentsByIssueID(e, issue.ID)
		if err != nil {
			return fmt.Errorf("getAttachmentsByIssueID [%d]: %v", issue.ID, err)
		}
	}

	if issue.Comments == nil {
		issue.Comments, err = getCommentsByIssueID(e, issue.ID)
		if err != nil {
			return fmt.Errorf("getCommentsByIssueID [%d]: %v", issue.ID, err)
		}
	}

	return nil
}

func (issue *Issue) LoadAttributes() error {
	return issue.loadAttributes(x)
}

func (issue *Issue) HTMLURL() string {
	var path string
	if issue.IsPull {
		path = "pulls"
	} else {
		path = "issues"
	}
	return fmt.Sprintf("%s/%s/%d", issue.Repo.HTMLURL(), path, issue.Index)
}

// State returns string representation of issue status.
func (i *Issue) State() api.StateType {
	if i.IsClosed {
		return api.STATE_CLOSED
	}
	return api.STATE_OPEN
}

// This method assumes some fields assigned with values:
// Required - Poster, Labels,
// Optional - Milestone, Assignee, PullRequest
func (issue *Issue) APIFormat() *api.Issue {
	apiLabels := make([]*api.Label, len(issue.Labels))
	for i := range issue.Labels {
		apiLabels[i] = issue.Labels[i].APIFormat()
	}

	apiIssue := &api.Issue{
		ID:       issue.ID,
		Index:    issue.Index,
		Poster:   issue.Poster.APIFormat(),
		Title:    issue.Title,
		Body:     issue.Content,
		Labels:   apiLabels,
		State:    issue.State(),
		Comments: issue.NumComments,
		Created:  issue.Created,
		Updated:  issue.Updated,
	}

	if issue.Milestone != nil {
		apiIssue.Milestone = issue.Milestone.APIFormat()
	}
	if issue.Assignee != nil {
		apiIssue.Assignee = issue.Assignee.APIFormat()
	}
	if issue.IsPull {
		apiIssue.PullRequest = &api.PullRequestMeta{
			HasMerged: issue.PullRequest.HasMerged,
		}
		if issue.PullRequest.HasMerged {
			apiIssue.PullRequest.Merged = &issue.PullRequest.Merged
		}
	}

	return apiIssue
}

// HashTag returns unique hash tag for issue.
func (i *Issue) HashTag() string {
	return "issue-" + com.ToStr(i.ID)
}

// IsPoster returns true if given user by ID is the poster.
func (i *Issue) IsPoster(uid int64) bool {
	return i.PosterID == uid
}

func (i *Issue) hasLabel(e Engine, labelID int64) bool {
	return hasIssueLabel(e, i.ID, labelID)
}

// HasLabel returns true if issue has been labeled by given ID.
func (i *Issue) HasLabel(labelID int64) bool {
	return i.hasLabel(x, labelID)
}

func (issue *Issue) sendLabelUpdatedWebhook(doer *User) {
	var err error
	if issue.IsPull {
		err = issue.PullRequest.LoadIssue()
		if err != nil {
			log.Error(4, "LoadIssue: %v", err)
			return
		}
		err = PrepareWebhooks(issue.Repo, HOOK_EVENT_PULL_REQUEST, &api.PullRequestPayload{
			Action:      api.HOOK_ISSUE_LABEL_UPDATED,
			Index:       issue.Index,
			PullRequest: issue.PullRequest.APIFormat(),
			Repository:  issue.Repo.APIFormat(nil),
			Sender:      doer.APIFormat(),
		})
	}
	if err != nil {
		log.Error(4, "PrepareWebhooks [is_pull: %v]: %v", issue.IsPull, err)
	} else {
		go HookQueue.Add(issue.RepoID)
	}
}

func (i *Issue) addLabel(e *xorm.Session, label *Label) error {
	return newIssueLabel(e, i, label)
}

// AddLabel adds a new label to the issue.
func (issue *Issue) AddLabel(doer *User, label *Label) error {
	if err := NewIssueLabel(issue, label); err != nil {
		return err
	}

	issue.sendLabelUpdatedWebhook(doer)
	return nil
}

func (issue *Issue) addLabels(e *xorm.Session, labels []*Label) error {
	return newIssueLabels(e, issue, labels)
}

// AddLabels adds a list of new labels to the issue.
func (issue *Issue) AddLabels(doer *User, labels []*Label) error {
	if err := NewIssueLabels(issue, labels); err != nil {
		return err
	}

	issue.sendLabelUpdatedWebhook(doer)
	return nil
}

func (issue *Issue) getLabels(e Engine) (err error) {
	if len(issue.Labels) > 0 {
		return nil
	}

	issue.Labels, err = getLabelsByIssueID(e, issue.ID)
	if err != nil {
		return fmt.Errorf("getLabelsByIssueID: %v", err)
	}
	return nil
}

func (issue *Issue) removeLabel(e *xorm.Session, label *Label) error {
	return deleteIssueLabel(e, issue, label)
}

// RemoveLabel removes a label from issue by given ID.
func (issue *Issue) RemoveLabel(doer *User, label *Label) error {
	if err := DeleteIssueLabel(issue, label); err != nil {
		return err
	}

	issue.sendLabelUpdatedWebhook(doer)
	return nil
}

func (issue *Issue) clearLabels(e *xorm.Session) (err error) {
	if err = issue.getLabels(e); err != nil {
		return fmt.Errorf("getLabels: %v", err)
	}

	for i := range issue.Labels {
		if err = issue.removeLabel(e, issue.Labels[i]); err != nil {
			return fmt.Errorf("removeLabel: %v", err)
		}
	}

	return nil
}

func (issue *Issue) ClearLabels(doer *User) (err error) {
	sess := x.NewSession()
	defer sessionRelease(sess)
	if err = sess.Begin(); err != nil {
		return err
	}

	if err = issue.clearLabels(sess); err != nil {
		return err
	}

	if err = sess.Commit(); err != nil {
		return fmt.Errorf("Commit: %v", err)
	}

	if issue.IsPull {
		err = issue.PullRequest.LoadIssue()
		if err != nil {
			log.Error(4, "LoadIssue: %v", err)
			return
		}
		err = PrepareWebhooks(issue.Repo, HOOK_EVENT_PULL_REQUEST, &api.PullRequestPayload{
			Action:      api.HOOK_ISSUE_LABEL_CLEARED,
			Index:       issue.Index,
			PullRequest: issue.PullRequest.APIFormat(),
			Repository:  issue.Repo.APIFormat(nil),
			Sender:      doer.APIFormat(),
		})
	}
	if err != nil {
		log.Error(4, "PrepareWebhooks [is_pull: %v]: %v", issue.IsPull, err)
	} else {
		go HookQueue.Add(issue.RepoID)
	}

	return nil
}

// ReplaceLabels removes all current labels and add new labels to the issue.
func (issue *Issue) ReplaceLabels(labels []*Label) (err error) {
	sess := x.NewSession()
	defer sessionRelease(sess)
	if err = sess.Begin(); err != nil {
		return err
	}

	if err = issue.clearLabels(sess); err != nil {
		return fmt.Errorf("clearLabels: %v", err)
	} else if err = issue.addLabels(sess, labels); err != nil {
		return fmt.Errorf("addLabels: %v", err)
	}

	return sess.Commit()
}

func (i *Issue) GetAssignee() (err error) {
	if i.AssigneeID == 0 || i.Assignee != nil {
		return nil
	}

	i.Assignee, err = GetUserByID(i.AssigneeID)
	if IsErrUserNotExist(err) {
		return nil
	}
	return err
}

// ReadBy sets issue to be read by given user.
func (i *Issue) ReadBy(uid int64) error {
	return UpdateIssueUserByRead(uid, i.ID)
}

func updateIssueCols(e Engine, issue *Issue, cols ...string) error {
	_, err := e.Id(issue.ID).Cols(cols...).Update(issue)
	return err
}

// UpdateIssueCols only updates values of specific columns for given issue.
func UpdateIssueCols(issue *Issue, cols ...string) error {
	return updateIssueCols(x, issue, cols...)
}

func (i *Issue) changeStatus(e *xorm.Session, doer *User, repo *Repository, isClosed bool) (err error) {
	// Nothing should be performed if current status is same as target status
	if i.IsClosed == isClosed {
		return nil
	}
	i.IsClosed = isClosed

	if err = updateIssueCols(e, i, "is_closed"); err != nil {
		return err
	} else if err = updateIssueUsersByStatus(e, i.ID, isClosed); err != nil {
		return err
	}

	// Update issue count of labels
	if err = i.getLabels(e); err != nil {
		return err
	}
	for idx := range i.Labels {
		if i.IsClosed {
			i.Labels[idx].NumClosedIssues++
		} else {
			i.Labels[idx].NumClosedIssues--
		}
		if err = updateLabel(e, i.Labels[idx]); err != nil {
			return err
		}
	}

	// Update issue count of milestone
	if err = changeMilestoneIssueStats(e, i); err != nil {
		return err
	}

	// New action comment
	if _, err = createStatusComment(e, doer, repo, i); err != nil {
		return err
	}

	return nil
}

// ChangeStatus changes issue status to open or closed.
func (issue *Issue) ChangeStatus(doer *User, repo *Repository, isClosed bool) (err error) {
	sess := x.NewSession()
	defer sessionRelease(sess)
	if err = sess.Begin(); err != nil {
		return err
	}

	if err = issue.changeStatus(sess, doer, repo, isClosed); err != nil {
		return err
	}

	if err = sess.Commit(); err != nil {
		return fmt.Errorf("Commit: %v", err)
	}

	if issue.IsPull {
		// Merge pull request calls issue.changeStatus so we need to handle separately.
		issue.PullRequest.Issue = issue
		apiPullRequest := &api.PullRequestPayload{
			Index:       issue.Index,
			PullRequest: issue.PullRequest.APIFormat(),
			Repository:  repo.APIFormat(nil),
			Sender:      doer.APIFormat(),
		}
		if isClosed {
			apiPullRequest.Action = api.HOOK_ISSUE_CLOSED
		} else {
			apiPullRequest.Action = api.HOOK_ISSUE_REOPENED
		}
		err = PrepareWebhooks(repo, HOOK_EVENT_PULL_REQUEST, apiPullRequest)
	}
	if err != nil {
		log.Error(4, "PrepareWebhooks [is_pull: %v, is_closed: %v]: %v", issue.IsPull, isClosed, err)
	} else {
		go HookQueue.Add(repo.ID)
	}

	return nil
}

func (issue *Issue) ChangeTitle(doer *User, title string) (err error) {
	oldTitle := issue.Title
	issue.Title = title
	if err = UpdateIssueCols(issue, "name"); err != nil {
		return fmt.Errorf("UpdateIssueCols: %v", err)
	}

	if issue.IsPull {
		issue.PullRequest.Issue = issue
		err = PrepareWebhooks(issue.Repo, HOOK_EVENT_PULL_REQUEST, &api.PullRequestPayload{
			Action: api.HOOK_ISSUE_EDITED,
			Index:  issue.Index,
			Changes: &api.ChangesPayload{
				Title: &api.ChangesFromPayload{
					From: oldTitle,
				},
			},
			PullRequest: issue.PullRequest.APIFormat(),
			Repository:  issue.Repo.APIFormat(nil),
			Sender:      doer.APIFormat(),
		})
	}
	if err != nil {
		log.Error(4, "PrepareWebhooks [is_pull: %v]: %v", issue.IsPull, err)
	} else {
		go HookQueue.Add(issue.RepoID)
	}

	return nil
}

func (issue *Issue) ChangeContent(doer *User, content string) (err error) {
	oldContent := issue.Content
	issue.Content = content
	if err = UpdateIssueCols(issue, "content"); err != nil {
		return fmt.Errorf("UpdateIssueCols: %v", err)
	}

	if issue.IsPull {
		issue.PullRequest.Issue = issue
		err = PrepareWebhooks(issue.Repo, HOOK_EVENT_PULL_REQUEST, &api.PullRequestPayload{
			Action: api.HOOK_ISSUE_EDITED,
			Index:  issue.Index,
			Changes: &api.ChangesPayload{
				Body: &api.ChangesFromPayload{
					From: oldContent,
				},
			},
			PullRequest: issue.PullRequest.APIFormat(),
			Repository:  issue.Repo.APIFormat(nil),
			Sender:      doer.APIFormat(),
		})
	}
	if err != nil {
		log.Error(4, "PrepareWebhooks [is_pull: %v]: %v", issue.IsPull, err)
	} else {
		go HookQueue.Add(issue.RepoID)
	}

	return nil
}

func (issue *Issue) ChangeAssignee(doer *User, assigneeID int64) (err error) {
	issue.AssigneeID = assigneeID
	if err = UpdateIssueUserByAssignee(issue); err != nil {
		return fmt.Errorf("UpdateIssueUserByAssignee: %v", err)
	}

	issue.Assignee, err = GetUserByID(issue.AssigneeID)
	if err != nil && !IsErrUserNotExist(err) {
		log.Error(4, "GetUserByID [assignee_id: %v]: %v", issue.AssigneeID, err)
		return nil
	}

	// Error not nil here means user does not exist, which is remove assignee.
	isRemoveAssignee := err != nil
	if issue.IsPull {
		issue.PullRequest.Issue = issue
		apiPullRequest := &api.PullRequestPayload{
			Index:       issue.Index,
			PullRequest: issue.PullRequest.APIFormat(),
			Repository:  issue.Repo.APIFormat(nil),
			Sender:      doer.APIFormat(),
		}
		if isRemoveAssignee {
			apiPullRequest.Action = api.HOOK_ISSUE_UNASSIGNED
		} else {
			apiPullRequest.Action = api.HOOK_ISSUE_ASSIGNED
		}
		err = PrepareWebhooks(issue.Repo, HOOK_EVENT_PULL_REQUEST, apiPullRequest)
	}
	if err != nil {
		log.Error(4, "PrepareWebhooks [is_pull: %v, remove_assignee: %v]: %v", issue.IsPull, isRemoveAssignee, err)
	} else {
		go HookQueue.Add(issue.RepoID)
	}

	return nil
}

type NewIssueOptions struct {
	Repo        *Repository
	Issue       *Issue
	LableIDs    []int64
	Attachments []string // In UUID format.
	IsPull      bool
}

func newIssue(e *xorm.Session, opts NewIssueOptions) (err error) {
	opts.Issue.Title = strings.TrimSpace(opts.Issue.Title)
	opts.Issue.Index = opts.Repo.NextIssueIndex()

	if opts.Issue.MilestoneID > 0 {
		milestone, err := getMilestoneByRepoID(e, opts.Issue.RepoID, opts.Issue.MilestoneID)
		if err != nil && !IsErrMilestoneNotExist(err) {
			return fmt.Errorf("getMilestoneByID: %v", err)
		}

		// Assume milestone is invalid and drop silently.
		opts.Issue.MilestoneID = 0
		if milestone != nil {
			opts.Issue.MilestoneID = milestone.ID
			opts.Issue.Milestone = milestone
			if err = changeMilestoneAssign(e, opts.Issue, -1); err != nil {
				return err
			}
		}
	}

	if opts.Issue.AssigneeID > 0 {
		assignee, err := getUserByID(e, opts.Issue.AssigneeID)
		if err != nil && !IsErrUserNotExist(err) {
			return fmt.Errorf("getUserByID: %v", err)
		}

		// Assume assignee is invalid and drop silently.
		opts.Issue.AssigneeID = 0
		if assignee != nil {
			valid, err := hasAccess(e, assignee, opts.Repo, ACCESS_MODE_WRITE)
			if err != nil {
				return fmt.Errorf("hasAccess [user_id: %d, repo_id: %d]: %v", assignee.ID, opts.Repo.ID, err)
			}
			if valid {
				opts.Issue.AssigneeID = assignee.ID
				opts.Issue.Assignee = assignee
			}
		}
	}

	// Milestone and assignee validation should happen before insert actual object.
	if _, err = e.Insert(opts.Issue); err != nil {
		return err
	}

	if opts.IsPull {
		_, err = e.Exec("UPDATE `repository` SET num_pulls = num_pulls + 1 WHERE id = ?", opts.Issue.RepoID)
	} else {
		_, err = e.Exec("UPDATE `repository` SET num_issues = num_issues + 1 WHERE id = ?", opts.Issue.RepoID)
	}
	if err != nil {
		return err
	}

	if len(opts.LableIDs) > 0 {
		// During the session, SQLite3 driver cannot handle retrieve objects after update something.
		// So we have to get all needed labels first.
		labels := make([]*Label, 0, len(opts.LableIDs))
		if err = e.In("id", opts.LableIDs).Find(&labels); err != nil {
			return fmt.Errorf("find all labels [label_ids: %v]: %v", opts.LableIDs, err)
		}

		for _, label := range labels {
			// Silently drop invalid labels.
			if label.RepoID != opts.Repo.ID {
				continue
			}

			if err = opts.Issue.addLabel(e, label); err != nil {
				return fmt.Errorf("addLabel [id: %d]: %v", label.ID, err)
			}
		}
	}

	if err = newIssueUsers(e, opts.Repo, opts.Issue); err != nil {
		return err
	}

	if len(opts.Attachments) > 0 {
		attachments, err := getAttachmentsByUUIDs(e, opts.Attachments)
		if err != nil {
			return fmt.Errorf("getAttachmentsByUUIDs [uuids: %v]: %v", opts.Attachments, err)
		}

		for i := 0; i < len(attachments); i++ {
			attachments[i].IssueID = opts.Issue.ID
			if _, err = e.Id(attachments[i].ID).Update(attachments[i]); err != nil {
				return fmt.Errorf("update attachment [id: %d]: %v", attachments[i].ID, err)
			}
		}
	}

	return opts.Issue.loadAttributes(e)
}

// NewIssue creates new issue with labels for repository.
func NewIssue(repo *Repository, issue *Issue, labelIDs []int64, uuids []string) (err error) {
	sess := x.NewSession()
	defer sessionRelease(sess)
	if err = sess.Begin(); err != nil {
		return err
	}

	if err = newIssue(sess, NewIssueOptions{
		Repo:        repo,
		Issue:       issue,
		LableIDs:    labelIDs,
		Attachments: uuids,
	}); err != nil {
		return fmt.Errorf("newIssue: %v", err)
	}

	if err = sess.Commit(); err != nil {
		return fmt.Errorf("Commit: %v", err)
	}

	if err = NotifyWatchers(&Action{
		ActUserID:    issue.Poster.ID,
		ActUserName:  issue.Poster.Name,
		OpType:       ACTION_CREATE_ISSUE,
		Content:      fmt.Sprintf("%d|%s", issue.Index, issue.Title),
		RepoID:       repo.ID,
		RepoUserName: repo.Owner.Name,
		RepoName:     repo.Name,
		IsPrivate:    repo.IsPrivate,
	}); err != nil {
		log.Error(4, "NotifyWatchers: %v", err)
	}
	if err = issue.MailParticipants(); err != nil {
		log.Error(4, "MailParticipants: %v", err)
	}

	return nil
}

// GetIssueByRef returns an Issue specified by a GFM reference.
// See https://help.github.com/articles/writing-on-github#references for more information on the syntax.
func GetIssueByRef(ref string) (*Issue, error) {
	n := strings.IndexByte(ref, byte('#'))
	if n == -1 {
		return nil, ErrMissingIssueNumber
	}

	index, err := com.StrTo(ref[n+1:]).Int64()
	if err != nil {
		return nil, err
	}

	repo, err := GetRepositoryByRef(ref[:n])
	if err != nil {
		return nil, err
	}

	issue, err := GetIssueByIndex(repo.ID, index)
	if err != nil {
		return nil, err
	}

	return issue, issue.LoadAttributes()
}

// GetIssueByIndex returns raw issue without loading attributes by index in a repository.
func GetRawIssueByIndex(repoID, index int64) (*Issue, error) {
	issue := &Issue{
		RepoID: repoID,
		Index:  index,
	}
	has, err := x.Get(issue)
	if err != nil {
		return nil, err
	} else if !has {
		return nil, ErrIssueNotExist{0, repoID, index}
	}
	return issue, nil
}

// GetIssueByIndex returns issue by index in a repository.
func GetIssueByIndex(repoID, index int64) (*Issue, error) {
	issue, err := GetRawIssueByIndex(repoID, index)
	if err != nil {
		return nil, err
	}
	return issue, issue.LoadAttributes()
}

func getRawIssueByID(e Engine, id int64) (*Issue, error) {
	issue := new(Issue)
	has, err := e.Id(id).Get(issue)
	if err != nil {
		return nil, err
	} else if !has {
		return nil, ErrIssueNotExist{id, 0, 0}
	}
	return issue, nil
}

func getIssueByID(e Engine, id int64) (*Issue, error) {
	issue, err := getRawIssueByID(e, id)
	if err != nil {
		return nil, err
	}
	return issue, issue.loadAttributes(e)
}

// GetIssueByID returns an issue by given ID.
func GetIssueByID(id int64) (*Issue, error) {
	return getIssueByID(x, id)
}

type IssuesOptions struct {
	UserID      int64
	AssigneeID  int64
	RepoID      int64
	PosterID    int64
	MilestoneID int64
	RepoIDs     []int64
	Page        int
	IsClosed    bool
	IsMention   bool
	IsPull      bool
	Labels      string
	SortType    string
}

// Issues returns a list of issues by given conditions.
func Issues(opts *IssuesOptions) ([]*Issue, error) {
	if opts.Page <= 0 {
		opts.Page = 1
	}

	sess := x.Limit(setting.UI.IssuePagingNum, (opts.Page-1)*setting.UI.IssuePagingNum)

	if opts.RepoID > 0 {
		sess.Where("issue.repo_id=?", opts.RepoID).And("issue.is_closed=?", opts.IsClosed)
	} else if opts.RepoIDs != nil {
		// In case repository IDs are provided but actually no repository has issue.
		if len(opts.RepoIDs) == 0 {
			return make([]*Issue, 0), nil
		}
		sess.In("issue.repo_id", base.Int64sToStrings(opts.RepoIDs)).And("issue.is_closed=?", opts.IsClosed)
	} else {
		sess.Where("issue.is_closed=?", opts.IsClosed)
	}

	if opts.AssigneeID > 0 {
		sess.And("issue.assignee_id=?", opts.AssigneeID)
	} else if opts.PosterID > 0 {
		sess.And("issue.poster_id=?", opts.PosterID)
	}

	if opts.MilestoneID > 0 {
		sess.And("issue.milestone_id=?", opts.MilestoneID)
	}

	sess.And("issue.is_pull=?", opts.IsPull)

	switch opts.SortType {
	case "oldest":
		sess.Asc("issue.created_unix")
	case "recentupdate":
		sess.Desc("issue.updated_unix")
	case "leastupdate":
		sess.Asc("issue.updated_unix")
	case "mostcomment":
		sess.Desc("issue.num_comments")
	case "leastcomment":
		sess.Asc("issue.num_comments")
	case "priority":
		sess.Desc("issue.priority")
	default:
		sess.Desc("issue.created_unix")
	}

	if len(opts.Labels) > 0 && opts.Labels != "0" {
		labelIDs := base.StringsToInt64s(strings.Split(opts.Labels, ","))
		if len(labelIDs) > 0 {
			sess.Join("INNER", "issue_label", "issue.id = issue_label.issue_id").In("issue_label.label_id", labelIDs)
		}
	}

	if opts.IsMention {
		sess.Join("INNER", "issue_user", "issue.id = issue_user.issue_id").And("issue_user.is_mentioned = ?", true)

		if opts.UserID > 0 {
			sess.And("issue_user.uid = ?", opts.UserID)
		}
	}

	issues := make([]*Issue, 0, setting.UI.IssuePagingNum)
	if err := sess.Find(&issues); err != nil {
		return nil, fmt.Errorf("Find: %v", err)
	}

	// FIXME: use IssueList to improve performance.
	for i := range issues {
		if err := issues[i].LoadAttributes(); err != nil {
			return nil, fmt.Errorf("LoadAttributes [%d]: %v", issues[i].ID, err)
		}
	}

	return issues, nil
}

// .___                             ____ ___
// |   | ______ ________ __   ____ |    |   \______ ___________
// |   |/  ___//  ___/  |  \_/ __ \|    |   /  ___// __ \_  __ \
// |   |\___ \ \___ \|  |  /\  ___/|    |  /\___ \\  ___/|  | \/
// |___/____  >____  >____/  \___  >______//____  >\___  >__|
//          \/     \/            \/             \/     \/

// IssueUser represents an issue-user relation.
type IssueUser struct {
	ID          int64 `xorm:"pk autoincr"`
	UID         int64 `xorm:"INDEX"` // User ID.
	IssueID     int64
	RepoID      int64 `xorm:"INDEX"`
	MilestoneID int64
	IsRead      bool
	IsAssigned  bool
	IsMentioned bool
	IsPoster    bool
	IsClosed    bool
}

func newIssueUsers(e *xorm.Session, repo *Repository, issue *Issue) error {
	assignees, err := repo.getAssignees(e)
	if err != nil {
		return fmt.Errorf("getAssignees: %v", err)
	}

	// Poster can be anyone, append later if not one of assignees.
	isPosterAssignee := false

	// Leave a seat for poster itself to append later, but if poster is one of assignee
	// and just waste 1 unit is cheaper than re-allocate memory once.
	issueUsers := make([]*IssueUser, 0, len(assignees)+1)
	for _, assignee := range assignees {
		isPoster := assignee.ID == issue.PosterID
		issueUsers = append(issueUsers, &IssueUser{
			IssueID:    issue.ID,
			RepoID:     repo.ID,
			UID:        assignee.ID,
			IsPoster:   isPoster,
			IsAssigned: assignee.ID == issue.AssigneeID,
		})
		if !isPosterAssignee && isPoster {
			isPosterAssignee = true
		}
	}
	if !isPosterAssignee {
		issueUsers = append(issueUsers, &IssueUser{
			IssueID:  issue.ID,
			RepoID:   repo.ID,
			UID:      issue.PosterID,
			IsPoster: true,
		})
	}

	if _, err = e.Insert(issueUsers); err != nil {
		return err
	}
	return nil
}

// NewIssueUsers adds new issue-user relations for new issue of repository.
func NewIssueUsers(repo *Repository, issue *Issue) (err error) {
	sess := x.NewSession()
	defer sessionRelease(sess)
	if err = sess.Begin(); err != nil {
		return err
	}

	if err = newIssueUsers(sess, repo, issue); err != nil {
		return err
	}

	return sess.Commit()
}

// PairsContains returns true when pairs list contains given issue.
func PairsContains(ius []*IssueUser, issueId, uid int64) int {
	for i := range ius {
		if ius[i].IssueID == issueId &&
			ius[i].UID == uid {
			return i
		}
	}
	return -1
}

// GetIssueUsers returns issue-user pairs by given repository and user.
func GetIssueUsers(rid, uid int64, isClosed bool) ([]*IssueUser, error) {
	ius := make([]*IssueUser, 0, 10)
	err := x.Where("is_closed=?", isClosed).Find(&ius, &IssueUser{RepoID: rid, UID: uid})
	return ius, err
}

// GetIssueUserPairsByRepoIds returns issue-user pairs by given repository IDs.
func GetIssueUserPairsByRepoIds(rids []int64, isClosed bool, page int) ([]*IssueUser, error) {
	if len(rids) == 0 {
		return []*IssueUser{}, nil
	}

	ius := make([]*IssueUser, 0, 10)
	sess := x.Limit(20, (page-1)*20).Where("is_closed=?", isClosed).In("repo_id", rids)
	err := sess.Find(&ius)
	return ius, err
}

// GetIssueUserPairsByMode returns issue-user pairs by given repository and user.
func GetIssueUserPairsByMode(uid, rid int64, isClosed bool, page, filterMode int) ([]*IssueUser, error) {
	ius := make([]*IssueUser, 0, 10)
	sess := x.Limit(20, (page-1)*20).Where("uid=?", uid).And("is_closed=?", isClosed)
	if rid > 0 {
		sess.And("repo_id=?", rid)
	}

	switch filterMode {
	case FM_ASSIGN:
		sess.And("is_assigned=?", true)
	case FM_CREATE:
		sess.And("is_poster=?", true)
	default:
		return ius, nil
	}
	err := sess.Find(&ius)
	return ius, err
}

// updateIssueMentions extracts mentioned people from content and
// updates issue-user relations for them.
func updateIssueMentions(e Engine, issueID int64, mentions []string) error {
	if len(mentions) == 0 {
		return nil
	}

	for i := range mentions {
		mentions[i] = strings.ToLower(mentions[i])
	}
	users := make([]*User, 0, len(mentions))

	if err := e.In("lower_name", mentions).Asc("lower_name").Find(&users); err != nil {
		return fmt.Errorf("find mentioned users: %v", err)
	}

	ids := make([]int64, 0, len(mentions))
	for _, user := range users {
		ids = append(ids, user.ID)
		if !user.IsOrganization() || user.NumMembers == 0 {
			continue
		}

		memberIDs := make([]int64, 0, user.NumMembers)
		orgUsers, err := getOrgUsersByOrgID(e, user.ID)
		if err != nil {
			return fmt.Errorf("getOrgUsersByOrgID [%d]: %v", user.ID, err)
		}

		for _, orgUser := range orgUsers {
			memberIDs = append(memberIDs, orgUser.ID)
		}

		ids = append(ids, memberIDs...)
	}

	if err := updateIssueUsersByMentions(e, issueID, ids); err != nil {
		return fmt.Errorf("UpdateIssueUsersByMentions: %v", err)
	}

	return nil
}

// IssueStats represents issue statistic information.
type IssueStats struct {
	OpenCount, ClosedCount int64
	AllCount               int64
	AssignCount            int64
	CreateCount            int64
	MentionCount           int64
}

// Filter modes.
const (
	FM_ALL = iota
	FM_ASSIGN
	FM_CREATE
	FM_MENTION
)

func parseCountResult(results []map[string][]byte) int64 {
	if len(results) == 0 {
		return 0
	}
	for _, result := range results[0] {
		return com.StrTo(string(result)).MustInt64()
	}
	return 0
}

type IssueStatsOptions struct {
	RepoID      int64
	UserID      int64
	Labels      string
	MilestoneID int64
	AssigneeID  int64
	FilterMode  int
	IsPull      bool
}

// GetIssueStats returns issue statistic information by given conditions.
func GetIssueStats(opts *IssueStatsOptions) *IssueStats {
	stats := &IssueStats{}

	countSession := func(opts *IssueStatsOptions) *xorm.Session {
		sess := x.Where("issue.repo_id = ?", opts.RepoID).And("is_pull = ?", opts.IsPull)

		if len(opts.Labels) > 0 && opts.Labels != "0" {
			labelIDs := base.StringsToInt64s(strings.Split(opts.Labels, ","))
			if len(labelIDs) > 0 {
				sess.Join("INNER", "issue_label", "issue.id = issue_id").In("label_id", labelIDs)
			}
		}

		if opts.MilestoneID > 0 {
			sess.And("issue.milestone_id = ?", opts.MilestoneID)
		}

		if opts.AssigneeID > 0 {
			sess.And("assignee_id = ?", opts.AssigneeID)
		}

		return sess
	}

	switch opts.FilterMode {
	case FM_ALL, FM_ASSIGN:
		stats.OpenCount, _ = countSession(opts).
			And("is_closed = ?", false).
			Count(&Issue{})

		stats.ClosedCount, _ = countSession(opts).
			And("is_closed = ?", true).
			Count(&Issue{})
	case FM_CREATE:
		stats.OpenCount, _ = countSession(opts).
			And("poster_id = ?", opts.UserID).
			And("is_closed = ?", false).
			Count(&Issue{})

		stats.ClosedCount, _ = countSession(opts).
			And("poster_id = ?", opts.UserID).
			And("is_closed = ?", true).
			Count(&Issue{})
	case FM_MENTION:
		stats.OpenCount, _ = countSession(opts).
			Join("INNER", "issue_user", "issue.id = issue_user.issue_id").
			And("issue_user.uid = ?", opts.UserID).
			And("issue_user.is_mentioned = ?", true).
			And("issue.is_closed = ?", false).
			Count(&Issue{})

		stats.ClosedCount, _ = countSession(opts).
			Join("INNER", "issue_user", "issue.id = issue_user.issue_id").
			And("issue_user.uid = ?", opts.UserID).
			And("issue_user.is_mentioned = ?", true).
			And("issue.is_closed = ?", true).
			Count(&Issue{})
	}
	return stats
}

// GetUserIssueStats returns issue statistic information for dashboard by given conditions.
func GetUserIssueStats(repoID, uid int64, repoIDs []int64, filterMode int, isPull bool) *IssueStats {
	stats := &IssueStats{}

	countSession := func(isClosed, isPull bool, repoID int64, repoIDs []int64) *xorm.Session {
		sess := x.Where("issue.is_closed = ?", isClosed).And("issue.is_pull = ?", isPull)

		if repoID > 0 || len(repoIDs) == 0 {
			sess.And("repo_id = ?", repoID)
		} else {
			sess.In("repo_id", repoIDs)
		}

		return sess
	}

	stats.AssignCount, _ = countSession(false, isPull, repoID, repoIDs).
		And("assignee_id = ?", uid).
		Count(&Issue{})

	stats.CreateCount, _ = countSession(false, isPull, repoID, repoIDs).
		And("poster_id = ?", uid).
		Count(&Issue{})

	openCountSession := countSession(false, isPull, repoID, repoIDs)
	closedCountSession := countSession(true, isPull, repoID, repoIDs)

	switch filterMode {
	case FM_ASSIGN:
		openCountSession.And("assignee_id = ?", uid)
		closedCountSession.And("assignee_id = ?", uid)
	case FM_CREATE:
		openCountSession.And("poster_id = ?", uid)
		closedCountSession.And("poster_id = ?", uid)
	}

	stats.OpenCount, _ = openCountSession.Count(&Issue{})
	stats.ClosedCount, _ = closedCountSession.Count(&Issue{})

	return stats
}

// GetRepoIssueStats returns number of open and closed repository issues by given filter mode.
func GetRepoIssueStats(repoID, uid int64, filterMode int, isPull bool) (numOpen int64, numClosed int64) {
	countSession := func(isClosed, isPull bool, repoID int64) *xorm.Session {
		sess := x.Where("issue.repo_id = ?", isClosed).
			And("is_pull = ?", isPull).
			And("repo_id = ?", repoID)

		return sess
	}

	openCountSession := countSession(false, isPull, repoID)
	closedCountSession := countSession(true, isPull, repoID)

	switch filterMode {
	case FM_ASSIGN:
		openCountSession.And("assignee_id = ?", uid)
		closedCountSession.And("assignee_id = ?", uid)
	case FM_CREATE:
		openCountSession.And("poster_id = ?", uid)
		closedCountSession.And("poster_id = ?", uid)
	}

	openResult, _ := openCountSession.Count(&Issue{})
	closedResult, _ := closedCountSession.Count(&Issue{})

	return openResult, closedResult
}

func updateIssue(e Engine, issue *Issue) error {
	_, err := e.Id(issue.ID).AllCols().Update(issue)
	return err
}

// UpdateIssue updates all fields of given issue.
func UpdateIssue(issue *Issue) error {
	return updateIssue(x, issue)
}

func updateIssueUsersByStatus(e Engine, issueID int64, isClosed bool) error {
	_, err := e.Exec("UPDATE `issue_user` SET is_closed=? WHERE issue_id=?", isClosed, issueID)
	return err
}

// UpdateIssueUsersByStatus updates issue-user relations by issue status.
func UpdateIssueUsersByStatus(issueID int64, isClosed bool) error {
	return updateIssueUsersByStatus(x, issueID, isClosed)
}

func updateIssueUserByAssignee(e *xorm.Session, issue *Issue) (err error) {
	if _, err = e.Exec("UPDATE `issue_user` SET is_assigned = ? WHERE issue_id = ?", false, issue.ID); err != nil {
		return err
	}

	// Assignee ID equals to 0 means clear assignee.
	if issue.AssigneeID > 0 {
		if _, err = e.Exec("UPDATE `issue_user` SET is_assigned = ? WHERE uid = ? AND issue_id = ?", true, issue.AssigneeID, issue.ID); err != nil {
			return err
		}
	}

	return updateIssue(e, issue)
}

// UpdateIssueUserByAssignee updates issue-user relation for assignee.
func UpdateIssueUserByAssignee(issue *Issue) (err error) {
	sess := x.NewSession()
	defer sessionRelease(sess)
	if err = sess.Begin(); err != nil {
		return err
	}

	if err = updateIssueUserByAssignee(sess, issue); err != nil {
		return err
	}

	return sess.Commit()
}

// UpdateIssueUserByRead updates issue-user relation for reading.
func UpdateIssueUserByRead(uid, issueID int64) error {
	_, err := x.Exec("UPDATE `issue_user` SET is_read=? WHERE uid=? AND issue_id=?", true, uid, issueID)
	return err
}

// updateIssueUsersByMentions updates issue-user pairs by mentioning.
func updateIssueUsersByMentions(e Engine, issueID int64, uids []int64) error {
	for _, uid := range uids {
		iu := &IssueUser{
			UID:     uid,
			IssueID: issueID,
		}
		has, err := e.Get(iu)
		if err != nil {
			return err
		}

		iu.IsMentioned = true
		if has {
			_, err = e.Id(iu.ID).AllCols().Update(iu)
		} else {
			_, err = e.Insert(iu)
		}
		if err != nil {
			return err
		}
	}
	return nil
}

//    _____  .__.__                   __
//   /     \ |__|  |   ____   _______/  |_  ____   ____   ____
//  /  \ /  \|  |  | _/ __ \ /  ___/\   __\/  _ \ /    \_/ __ \
// /    Y    \  |  |_\  ___/ \___ \  |  | (  <_> )   |  \  ___/
// \____|__  /__|____/\___  >____  > |__|  \____/|___|  /\___  >
//         \/             \/     \/                   \/     \/

// Milestone represents a milestone of repository.
type Milestone struct {
	ID              int64 `xorm:"pk autoincr"`
	RepoID          int64 `xorm:"INDEX"`
	Name            string
	Content         string `xorm:"TEXT"`
	RenderedContent string `xorm:"-"`
	IsClosed        bool
	NumIssues       int
	NumClosedIssues int
	NumOpenIssues   int  `xorm:"-"`
	Completeness    int  // Percentage(1-100).
	IsOverDue       bool `xorm:"-"`

	DeadlineString string    `xorm:"-"`
	Deadline       time.Time `xorm:"-"`
	DeadlineUnix   int64
	ClosedDate     time.Time `xorm:"-"`
	ClosedDateUnix int64
}

func (m *Milestone) BeforeInsert() {
	m.DeadlineUnix = m.Deadline.Unix()
}

func (m *Milestone) BeforeUpdate() {
	if m.NumIssues > 0 {
		m.Completeness = m.NumClosedIssues * 100 / m.NumIssues
	} else {
		m.Completeness = 0
	}

	m.DeadlineUnix = m.Deadline.Unix()
	m.ClosedDateUnix = m.ClosedDate.Unix()
}

func (m *Milestone) AfterSet(colName string, _ xorm.Cell) {
	switch colName {
	case "num_closed_issues":
		m.NumOpenIssues = m.NumIssues - m.NumClosedIssues

	case "deadline_unix":
		m.Deadline = time.Unix(m.DeadlineUnix, 0).Local()
		if m.Deadline.Year() == 9999 {
			return
		}

		m.DeadlineString = m.Deadline.Format("2006-01-02")
		if time.Now().Local().After(m.Deadline) {
			m.IsOverDue = true
		}

	case "closed_date_unix":
		m.ClosedDate = time.Unix(m.ClosedDateUnix, 0).Local()
	}
}

// State returns string representation of milestone status.
func (m *Milestone) State() api.StateType {
	if m.IsClosed {
		return api.STATE_CLOSED
	}
	return api.STATE_OPEN
}

func (m *Milestone) APIFormat() *api.Milestone {
	apiMilestone := &api.Milestone{
		ID:           m.ID,
		State:        m.State(),
		Title:        m.Name,
		Description:  m.Content,
		OpenIssues:   m.NumOpenIssues,
		ClosedIssues: m.NumClosedIssues,
	}
	if m.IsClosed {
		apiMilestone.Closed = &m.ClosedDate
	}
	if m.Deadline.Year() < 9999 {
		apiMilestone.Deadline = &m.Deadline
	}
	return apiMilestone
}

// NewMilestone creates new milestone of repository.
func NewMilestone(m *Milestone) (err error) {
	sess := x.NewSession()
	defer sessionRelease(sess)
	if err = sess.Begin(); err != nil {
		return err
	}

	if _, err = sess.Insert(m); err != nil {
		return err
	}

	if _, err = sess.Exec("UPDATE `repository` SET num_milestones = num_milestones + 1 WHERE id = ?", m.RepoID); err != nil {
		return err
	}
	return sess.Commit()
}

func getMilestoneByRepoID(e Engine, repoID, id int64) (*Milestone, error) {
	m := &Milestone{
		ID:     id,
		RepoID: repoID,
	}
	has, err := e.Get(m)
	if err != nil {
		return nil, err
	} else if !has {
		return nil, ErrMilestoneNotExist{id, repoID}
	}
	return m, nil
}

// GetWebhookByRepoID returns the milestone in a repository.
func GetMilestoneByRepoID(repoID, id int64) (*Milestone, error) {
	return getMilestoneByRepoID(x, repoID, id)
}

// GetMilestonesByRepoID returns all milestones of a repository.
func GetMilestonesByRepoID(repoID int64) ([]*Milestone, error) {
	miles := make([]*Milestone, 0, 10)
	return miles, x.Where("repo_id = ?", repoID).Find(&miles)
}

// GetMilestones returns a list of milestones of given repository and status.
func GetMilestones(repoID int64, page int, isClosed bool) ([]*Milestone, error) {
	miles := make([]*Milestone, 0, setting.UI.IssuePagingNum)
	sess := x.Where("repo_id = ? AND is_closed = ?", repoID, isClosed)
	if page > 0 {
		sess = sess.Limit(setting.UI.IssuePagingNum, (page-1)*setting.UI.IssuePagingNum)
	}
	return miles, sess.Find(&miles)
}

func updateMilestone(e Engine, m *Milestone) error {
	_, err := e.Id(m.ID).AllCols().Update(m)
	return err
}

// UpdateMilestone updates information of given milestone.
func UpdateMilestone(m *Milestone) error {
	return updateMilestone(x, m)
}

func countRepoMilestones(e Engine, repoID int64) int64 {
	count, _ := e.Where("repo_id=?", repoID).Count(new(Milestone))
	return count
}

// CountRepoMilestones returns number of milestones in given repository.
func CountRepoMilestones(repoID int64) int64 {
	return countRepoMilestones(x, repoID)
}

func countRepoClosedMilestones(e Engine, repoID int64) int64 {
	closed, _ := e.Where("repo_id=? AND is_closed=?", repoID, true).Count(new(Milestone))
	return closed
}

// CountRepoClosedMilestones returns number of closed milestones in given repository.
func CountRepoClosedMilestones(repoID int64) int64 {
	return countRepoClosedMilestones(x, repoID)
}

// MilestoneStats returns number of open and closed milestones of given repository.
func MilestoneStats(repoID int64) (open int64, closed int64) {
	open, _ = x.Where("repo_id=? AND is_closed=?", repoID, false).Count(new(Milestone))
	return open, CountRepoClosedMilestones(repoID)
}

// ChangeMilestoneStatus changes the milestone open/closed status.
func ChangeMilestoneStatus(m *Milestone, isClosed bool) (err error) {
	repo, err := GetRepositoryByID(m.RepoID)
	if err != nil {
		return err
	}

	sess := x.NewSession()
	defer sessionRelease(sess)
	if err = sess.Begin(); err != nil {
		return err
	}

	m.IsClosed = isClosed
	if err = updateMilestone(sess, m); err != nil {
		return err
	}

	repo.NumMilestones = int(countRepoMilestones(sess, repo.ID))
	repo.NumClosedMilestones = int(countRepoClosedMilestones(sess, repo.ID))
	if _, err = sess.Id(repo.ID).AllCols().Update(repo); err != nil {
		return err
	}
	return sess.Commit()
}

func changeMilestoneIssueStats(e *xorm.Session, issue *Issue) error {
	if issue.MilestoneID == 0 {
		return nil
	}

	m, err := getMilestoneByRepoID(e, issue.RepoID, issue.MilestoneID)
	if err != nil {
		return err
	}

	if issue.IsClosed {
		m.NumOpenIssues--
		m.NumClosedIssues++
	} else {
		m.NumOpenIssues++
		m.NumClosedIssues--
	}

	return updateMilestone(e, m)
}

// ChangeMilestoneIssueStats updates the open/closed issues counter and progress
// for the milestone associated with the given issue.
func ChangeMilestoneIssueStats(issue *Issue) (err error) {
	sess := x.NewSession()
	defer sessionRelease(sess)
	if err = sess.Begin(); err != nil {
		return err
	}

	if err = changeMilestoneIssueStats(sess, issue); err != nil {
		return err
	}

	return sess.Commit()
}

func changeMilestoneAssign(e *xorm.Session, issue *Issue, oldMilestoneID int64) error {
	if oldMilestoneID > 0 {
		m, err := getMilestoneByRepoID(e, issue.RepoID, oldMilestoneID)
		if err != nil {
			return err
		}

		m.NumIssues--
		if issue.IsClosed {
			m.NumClosedIssues--
		}

		if err = updateMilestone(e, m); err != nil {
			return err
		} else if _, err = e.Exec("UPDATE `issue_user` SET milestone_id = 0 WHERE issue_id = ?", issue.ID); err != nil {
			return err
		}
	}

	if issue.MilestoneID > 0 {
		m, err := getMilestoneByRepoID(e, issue.RepoID, issue.MilestoneID)
		if err != nil {
			return err
		}

		m.NumIssues++
		if issue.IsClosed {
			m.NumClosedIssues++
		}

		if err = updateMilestone(e, m); err != nil {
			return err
		} else if _, err = e.Exec("UPDATE `issue_user` SET milestone_id = ? WHERE issue_id = ?", m.ID, issue.ID); err != nil {
			return err
		}
	}

	return updateIssue(e, issue)
}

// ChangeMilestoneAssign changes assignment of milestone for issue.
func ChangeMilestoneAssign(issue *Issue, oldMilestoneID int64) (err error) {
	sess := x.NewSession()
	defer sess.Close()
	if err = sess.Begin(); err != nil {
		return err
	}

	if err = changeMilestoneAssign(sess, issue, oldMilestoneID); err != nil {
		return err
	}
	return sess.Commit()
}

// DeleteMilestoneByRepoID deletes a milestone from a repository.
func DeleteMilestoneByRepoID(repoID, id int64) error {
	m, err := GetMilestoneByRepoID(repoID, id)
	if err != nil {
		if IsErrMilestoneNotExist(err) {
			return nil
		}
		return err
	}

	repo, err := GetRepositoryByID(m.RepoID)
	if err != nil {
		return err
	}

	sess := x.NewSession()
	defer sessionRelease(sess)
	if err = sess.Begin(); err != nil {
		return err
	}

	if _, err = sess.Id(m.ID).Delete(new(Milestone)); err != nil {
		return err
	}

	repo.NumMilestones = int(countRepoMilestones(sess, repo.ID))
	repo.NumClosedMilestones = int(countRepoClosedMilestones(sess, repo.ID))
	if _, err = sess.Id(repo.ID).AllCols().Update(repo); err != nil {
		return err
	}

	if _, err = sess.Exec("UPDATE `issue` SET milestone_id = 0 WHERE milestone_id = ?", m.ID); err != nil {
		return err
	} else if _, err = sess.Exec("UPDATE `issue_user` SET milestone_id = 0 WHERE milestone_id = ?", m.ID); err != nil {
		return err
	}
	return sess.Commit()
}

// Attachment represent a attachment of issue/comment/release.
type Attachment struct {
	ID        int64  `xorm:"pk autoincr"`
	UUID      string `xorm:"uuid UNIQUE"`
	IssueID   int64  `xorm:"INDEX"`
	CommentID int64
	ReleaseID int64 `xorm:"INDEX"`
	Name      string

	Created     time.Time `xorm:"-"`
	CreatedUnix int64
}

func (a *Attachment) BeforeInsert() {
	a.CreatedUnix = time.Now().Unix()
}

func (a *Attachment) AfterSet(colName string, _ xorm.Cell) {
	switch colName {
	case "created_unix":
		a.Created = time.Unix(a.CreatedUnix, 0).Local()
	}
}

// AttachmentLocalPath returns where attachment is stored in local file system based on given UUID.
func AttachmentLocalPath(uuid string) string {
	return path.Join(setting.AttachmentPath, uuid[0:1], uuid[1:2], uuid)
}

// LocalPath returns where attachment is stored in local file system.
func (attach *Attachment) LocalPath() string {
	return AttachmentLocalPath(attach.UUID)
}

// NewAttachment creates a new attachment object.
func NewAttachment(name string, buf []byte, file multipart.File) (_ *Attachment, err error) {
	attach := &Attachment{
		UUID: gouuid.NewV4().String(),
		Name: name,
	}

	localPath := attach.LocalPath()
	if err = os.MkdirAll(path.Dir(localPath), os.ModePerm); err != nil {
		return nil, fmt.Errorf("MkdirAll: %v", err)
	}

	fw, err := os.Create(localPath)
	if err != nil {
		return nil, fmt.Errorf("Create: %v", err)
	}
	defer fw.Close()

	if _, err = fw.Write(buf); err != nil {
		return nil, fmt.Errorf("Write: %v", err)
	} else if _, err = io.Copy(fw, file); err != nil {
		return nil, fmt.Errorf("Copy: %v", err)
	}

	if _, err := x.Insert(attach); err != nil {
		return nil, err
	}

	return attach, nil
}

func getAttachmentByUUID(e Engine, uuid string) (*Attachment, error) {
	attach := &Attachment{UUID: uuid}
	has, err := x.Get(attach)
	if err != nil {
		return nil, err
	} else if !has {
		return nil, ErrAttachmentNotExist{0, uuid}
	}
	return attach, nil
}

func getAttachmentsByUUIDs(e Engine, uuids []string) ([]*Attachment, error) {
	if len(uuids) == 0 {
		return []*Attachment{}, nil
	}

	// Silently drop invalid uuids.
	attachments := make([]*Attachment, 0, len(uuids))
	return attachments, e.In("uuid", uuids).Find(&attachments)
}

// GetAttachmentByUUID returns attachment by given UUID.
func GetAttachmentByUUID(uuid string) (*Attachment, error) {
	return getAttachmentByUUID(x, uuid)
}

func getAttachmentsByIssueID(e Engine, issueID int64) ([]*Attachment, error) {
	attachments := make([]*Attachment, 0, 10)
	return attachments, e.Where("issue_id = ? AND comment_id = 0", issueID).Find(&attachments)
}

// GetAttachmentsByIssueID returns all attachments of an issue.
func GetAttachmentsByIssueID(issueID int64) ([]*Attachment, error) {
	return getAttachmentsByIssueID(x, issueID)
}

func getAttachmentsByCommentID(e Engine, commentID int64) ([]*Attachment, error) {
	attachments := make([]*Attachment, 0, 10)
	return attachments, e.Where("comment_id=?", commentID).Find(&attachments)
}

// GetAttachmentsByCommentID returns all attachments if comment by given ID.
func GetAttachmentsByCommentID(commentID int64) ([]*Attachment, error) {
	return getAttachmentsByCommentID(x, commentID)
}

// DeleteAttachment deletes the given attachment and optionally the associated file.
func DeleteAttachment(a *Attachment, remove bool) error {
	_, err := DeleteAttachments([]*Attachment{a}, remove)
	return err
}

// DeleteAttachments deletes the given attachments and optionally the associated files.
func DeleteAttachments(attachments []*Attachment, remove bool) (int, error) {
	for i, a := range attachments {
		if remove {
			if err := os.Remove(a.LocalPath()); err != nil {
				return i, err
			}
		}

		if _, err := x.Delete(a); err != nil {
			return i, err
		}
	}

	return len(attachments), nil
}

// DeleteAttachmentsByIssue deletes all attachments associated with the given issue.
func DeleteAttachmentsByIssue(issueId int64, remove bool) (int, error) {
	attachments, err := GetAttachmentsByIssueID(issueId)

	if err != nil {
		return 0, err
	}

	return DeleteAttachments(attachments, remove)
}

// DeleteAttachmentsByComment deletes all attachments associated with the given comment.
func DeleteAttachmentsByComment(commentId int64, remove bool) (int, error) {
	attachments, err := GetAttachmentsByCommentID(commentId)

	if err != nil {
		return 0, err
	}

	return DeleteAttachments(attachments, remove)
}