Mail assignee when issue/pull request is assigned (#8546)

* Send email to assigned user

* Only send mail if enabled

* Mail also when assigned through API

* Need to refactor functions from models to issue service

* Refer to issue index rather than ID

* Disable email notifications completly at initalization if global disable

* Check of user enbled mail shall be in mail notification function only

* Initialize notifications from routers init function.

* Use the assigned comment when sending assigned mail

* Refactor so that assignees always added as separate step when new issue/pr.

* Check error from AddAssignees

* Check if user can be assiged to issue or pull request

* Missing return

* Refactor of CanBeAssigned check.

CanBeAssigned shall have same check as UI.

* Clarify function names (toggle rather than update/change), and clean up.

* Fix review comments.

* Flash error if assignees was not added when creating issue/pr

* Generate error if assignee users doesn't exist

services/issue/issue.go

@@ -9,12 +9,13 @@ import (
 
 	"code.gitea.io/gitea/models"
 	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/notification"
 	api "code.gitea.io/gitea/modules/structs"
 )
 
 // NewIssue creates new issue with labels for repository.
-func NewIssue(repo *models.Repository, issue *models.Issue, labelIDs []int64, assigneeIDs []int64, uuids []string) error {
-	if err := models.NewIssue(repo, issue, labelIDs, assigneeIDs, uuids); err != nil {
+func NewIssue(repo *models.Repository, issue *models.Issue, labelIDs []int64, uuids []string) error {
+	if err := models.NewIssue(repo, issue, labelIDs, uuids); err != nil {
 		return err
 	}
 
@@ -96,3 +97,104 @@ func ChangeTitle(issue *models.Issue, doer *models.User, title string) (err erro
 
 	return nil
 }
+
+// UpdateAssignees is a helper function to add or delete one or multiple issue assignee(s)
+// Deleting is done the GitHub way (quote from their api documentation):
+// https://developer.github.com/v3/issues/#edit-an-issue
+// "assignees" (array): Logins for Users to assign to this issue.
+// Pass one or more user logins to replace the set of assignees on this Issue.
+// Send an empty array ([]) to clear all assignees from the Issue.
+func UpdateAssignees(issue *models.Issue, oneAssignee string, multipleAssignees []string, doer *models.User) (err error) {
+	var allNewAssignees []*models.User
+
+	// Keep the old assignee thingy for compatibility reasons
+	if oneAssignee != "" {
+		// Prevent double adding assignees
+		var isDouble bool
+		for _, assignee := range multipleAssignees {
+			if assignee == oneAssignee {
+				isDouble = true
+				break
+			}
+		}
+
+		if !isDouble {
+			multipleAssignees = append(multipleAssignees, oneAssignee)
+		}
+	}
+
+	// Loop through all assignees to add them
+	for _, assigneeName := range multipleAssignees {
+		assignee, err := models.GetUserByName(assigneeName)
+		if err != nil {
+			return err
+		}
+
+		allNewAssignees = append(allNewAssignees, assignee)
+	}
+
+	// Delete all old assignees not passed
+	if err = models.DeleteNotPassedAssignee(issue, doer, allNewAssignees); err != nil {
+		return err
+	}
+
+	// Add all new assignees
+	// Update the assignee. The function will check if the user exists, is already
+	// assigned (which he shouldn't as we deleted all assignees before) and
+	// has access to the repo.
+	for _, assignee := range allNewAssignees {
+		// Extra method to prevent double adding (which would result in removing)
+		err = AddAssigneeIfNotAssigned(issue, doer, assignee.ID)
+		if err != nil {
+			return err
+		}
+	}
+
+	return
+}
+
+// AddAssigneeIfNotAssigned adds an assignee only if he isn't already assigned to the issue.
+// Also checks for access of assigned user
+func AddAssigneeIfNotAssigned(issue *models.Issue, doer *models.User, assigneeID int64) (err error) {
+	assignee, err := models.GetUserByID(assigneeID)
+	if err != nil {
+		return err
+	}
+
+	// Check if the user is already assigned
+	isAssigned, err := models.IsUserAssignedToIssue(issue, assignee)
+	if err != nil {
+		return err
+	}
+	if isAssigned {
+		// nothing to to
+		return nil
+	}
+
+	valid, err := models.CanBeAssigned(assignee, issue.Repo, issue.IsPull)
+	if err != nil {
+		return err
+	}
+	if !valid {
+		return models.ErrUserDoesNotHaveAccessToRepo{UserID: assigneeID, RepoName: issue.Repo.Name}
+	}
+
+	removed, comment, err := issue.ToggleAssignee(doer, assigneeID)
+	if err != nil {
+		return err
+	}
+
+	notification.NotifyIssueChangeAssignee(doer, issue, assignee, removed, comment)
+
+	return nil
+}
+
+// AddAssignees adds a list of assignes (from IDs) to an issue
+func AddAssignees(issue *models.Issue, doer *models.User, assigneeIDs []int64) (err error) {
+	for _, assigneeID := range assigneeIDs {
+		if err = AddAssigneeIfNotAssigned(issue, doer, assigneeID); err != nil {
+			return err
+		}
+	}
+	return nil
+}