MM-22845: Added support for permalink previews. (#17796)

* MM-22845: Added support for permalink previews.

* MM-22845: Adds license to new file.

* MM-22845: Adds endpoint to retrieve multiple posts by id.

* MM-22845: Fix for deleted post.

* MM-22845: Adds config setting for permalink previews.

* MM-22845: Adds API test for new endpoint.

* MM-22845: Fix typo.

* MM-22845: Tests that post create or updated via App get the previewed_post prop.

* MM-22845: Tests for matching permalinks.

* MM-22845: Adds PreparePostForClient test for permalink previews.

* MM-22845: Embeds entire post in permalink metadata.

* MM-22845: Filter WS message payload of created and edited post based on permissions.

* MM-22845: Runs app layer generator.

* MM-22845: Lint check fix.

* MM-22845: Adds feature flag.

* MM-22845: Clones WS message.

* MM-22845: Removes knowledge of permalink from LinkMetadata table. Removes knowledge of user id from post embedding methods in favour of a 'sanitize' method/step.

* MM-22845: Handle nil post metadata.

* MM-22845: Switch to cloning post.

* MM-22845: Removes unused code.

* MM-22845: Refactor.

* MM-22845: Reverts whitespace change.

* MM-22845: Removes unnecessary code.

* MM-22845: Removes unnecessary function.

* MM-22845: Warn but don't error if permalinked referenced post or channel is not found.

* MM-22845: Fix for clone method.

* MM-22845: Fix for clone method.

* MM-22845: Updates translations.

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

model/config.go

@@ -303,6 +303,7 @@ type ServiceSettings struct {
 	GoogleDeveloperKey                                *string  `access:"site_posts,write_restrictable,cloud_restrictable"`
 	DEPRECATED_DO_NOT_USE_EnableOnlyAdminIntegrations *bool    `json:"EnableOnlyAdminIntegrations" mapstructure:"EnableOnlyAdminIntegrations"` // Deprecated: do not use
 	EnableLinkPreviews                                *bool    `access:"site_posts"`
+	EnablePermalinkPreviews                           *bool    `access:"site_posts"`
 	RestrictLinkPreviews                              *string  `access:"site_posts"`
 	EnableTesting                                     *bool    `access:"environment_developer,write_restrictable,cloud_restrictable"`
 	EnableDeveloper                                   *bool    `access:"environment_developer,write_restrictable,cloud_restrictable"`
@@ -413,6 +414,10 @@ func (s *ServiceSettings) SetDefaults(isUpdate bool) {
 		s.EnableLinkPreviews = NewBool(true)
 	}
 
+	if s.EnablePermalinkPreviews == nil {
+		s.EnablePermalinkPreviews = NewBool(true)
+	}
+
 	if s.RestrictLinkPreviews == nil {
 		s.RestrictLinkPreviews = NewString("")
 	}

model/feature_flags.go

@@ -36,6 +36,8 @@ type FeatureFlags struct {
 	// Enable timed dnd support for user status
 	TimedDND bool
 
+	PermalinkPreviews bool
+
 	// Enable the Global Header
 	GlobalHeader bool
 
@@ -54,6 +56,7 @@ func (f *FeatureFlags) SetDefaults() {
 	f.PluginApps = ""
 	f.PluginFocalboard = ""
 	f.TimedDND = false
+	f.PermalinkPreviews = true
 	f.GlobalHeader = false
 	f.InviteMembersButton = "none"
 }

model/message_export.go

@@ -3,6 +3,8 @@
 
 package model
 
+import "encoding/json"
+
 type MessageExport struct {
 	TeamId          *string
 	TeamName        *string
@@ -34,3 +36,15 @@ type MessageExportCursor struct {
 	LastPostUpdateAt int64
 	LastPostId       string
 }
+
+// PreviewID returns the value of the post's previewed_post prop, if present, or an empty string.
+func (m *MessageExport) PreviewID() string {
+	var previewID string
+	props := map[string]interface{}{}
+	if m.PostProps != nil && json.Unmarshal([]byte(*m.PostProps), &props) == nil {
+		if val, ok := props[PostPropsPreviewedPost]; ok {
+			previewID = val.(string)
+		}
+	}
+	return previewID
+}

model/permalink.go

@@ -0,0 +1,34 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+import "encoding/json"
+
+type Permalink struct {
+	PreviewPost *PreviewPost `json:"preview_post"`
+}
+
+type PreviewPost struct {
+	PostID             string `json:"post_id"`
+	Post               *Post  `json:"post"`
+	TeamName           string `json:"team_name"`
+	ChannelDisplayName string `json:"channel_display_name"`
+}
+
+func NewPreviewPost(post *Post, team *Team, channel *Channel) *PreviewPost {
+	if post == nil {
+		return nil
+	}
+	return &PreviewPost{
+		PostID:             post.Id,
+		Post:               post,
+		TeamName:           team.Name,
+		ChannelDisplayName: channel.DisplayName,
+	}
+}
+
+func (o *Permalink) ToJson() string {
+	b, _ := json.Marshal(o)
+	return string(b)
+}

model/post.go

@@ -67,6 +67,8 @@ const (
 
 	PostPropsMentionHighlightDisabled = "mentionHighlightDisabled"
 	PostPropsGroupHighlightDisabled   = "disable_group_highlight"
+
+	PostPropsPreviewedPost = "previewed_post"
 )
 
 type Post struct {
@@ -749,3 +751,14 @@ func (o *Post) ToNilIfInvalid() *Post {
 	}
 	return o
 }
+
+func (o *Post) GetPreviewPost() *PreviewPost {
+	for _, embed := range o.Metadata.Embeds {
+		if embed.Type == PostEmbedPermalink {
+			if previewPost, ok := embed.Data.(*PreviewPost); ok {
+				return previewPost
+			}
+		}
+	}
+	return nil
+}

model/post_embed.go

@@ -8,6 +8,7 @@ const (
 	PostEmbedMessageAttachment PostEmbedType = "message_attachment"
 	PostEmbedOpengraph         PostEmbedType = "opengraph"
 	PostEmbedLink              PostEmbedType = "link"
+	PostEmbedPermalink         PostEmbedType = "permalink"
 )
 
 type PostEmbedType string

model/post_list.go

@@ -25,6 +25,23 @@ func NewPostList() *PostList {
 	}
 }
 
+func (o *PostList) Clone() *PostList {
+	orderCopy := make([]string, len(o.Order))
+	postsCopy := make(map[string]*Post)
+	for i, v := range o.Order {
+		orderCopy[i] = v
+	}
+	for k, v := range o.Posts {
+		postsCopy[k] = v.Clone()
+	}
+	return &PostList{
+		Order:      orderCopy,
+		Posts:      postsCopy,
+		NextPostId: o.NextPostId,
+		PrevPostId: o.PrevPostId,
+	}
+}
+
 func (o *PostList) ToSlice() []*Post {
 	var posts []*Post