Go to Comment endpoint + notification fixes

* Add endpoint /go/comment?id= that finds the right page that a comment
  can be seen on for the current user and redirects there.
* Resolves issues with link discrepancies in comment notifications, if
  the recipient sees different page numbers depending on blocklist
  status.
* Supports copyable permalinks to any comment on the site reliably.

pkg/controller/comment/goto_comment.go

@@ -0,0 +1,75 @@
+package comment
+
+import (
+	"fmt"
+	"net/http"
+	"strconv"
+
+	"code.nonshy.com/nonshy/website/pkg/config"
+	"code.nonshy.com/nonshy/website/pkg/models"
+	"code.nonshy.com/nonshy/website/pkg/session"
+	"code.nonshy.com/nonshy/website/pkg/templates"
+)
+
+// GoToComment finds the correct link to view a comment.
+func GoToComment() http.HandlerFunc {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		// Query params.
+		var (
+			commentID uint64
+		)
+
+		// Parse the ID param.
+		if idStr := r.FormValue("id"); idStr == "" {
+			session.FlashError(w, r, "Comment ID required.")
+			templates.Redirect(w, "/")
+			return
+		} else {
+			if idInt, err := strconv.Atoi(idStr); err != nil {
+				session.FlashError(w, r, "Comment ID invalid.")
+				templates.Redirect(w, "/")
+				return
+			} else {
+				commentID = uint64(idInt)
+			}
+		}
+
+		// Get the current user.
+		currentUser, err := session.CurrentUser(r)
+		if err != nil {
+			session.FlashError(w, r, "Couldn't get current user: %s", err)
+			templates.Redirect(w, "/")
+			return
+		}
+
+		// Locate this comment.
+		comment, err := models.GetComment(commentID)
+		if err != nil {
+			session.FlashError(w, r, "Couldn't find that comment: %s", err)
+			templates.Redirect(w, "/")
+			return
+		}
+
+		// Where is this comment at?
+		switch comment.TableName {
+		case "threads":
+			// A forum thread, find what page it is on.
+			page, err := models.FindPageByComment(currentUser, comment, config.PageSizeThreadList)
+			if err != nil {
+				session.FlashError(w, r, "Couldn't find that comment, but bringing you to the forum thread instead.")
+				page = 1
+			}
+
+			templates.Redirect(w, fmt.Sprintf("/forum/thread/%d?page=%d#p%d", comment.TableID, page, comment.ID))
+			return
+		case "photos":
+			// A photo comment thread, easy: only one page.
+			templates.Redirect(w, fmt.Sprintf("/photo/view?id=%d#p%d", comment.TableID, comment.ID))
+			return
+		default:
+			session.FlashError(w, r, "Unknown type of comment.")
+		}
+
+		templates.Redirect(w, "/")
+	})
+}

pkg/controller/comment/post_comment.go

@@ -177,7 +177,7 @@ func PostComment() http.HandlerFunc {
 							TableName: comment.TableName,
 							TableID:   comment.TableID,
 							Message:   message,
-							Link:      fmt.Sprintf("%s#p%d", fromURL, comment.ID),
+							Link:      fmt.Sprintf("/go/comment?id=%d", comment.ID),
 						}
 						if err := models.CreateNotification(notif); err != nil {
 							log.Error("Couldn't create Comment notification: %s", err)
@@ -201,7 +201,7 @@ func PostComment() http.HandlerFunc {
 							TableName: comment.TableName,
 							TableID:   comment.TableID,
 							Message:   message,
-							Link:      fromURL,
+							Link:      fmt.Sprintf("/go/comment?id=%d", comment.ID),
 						}
 						if err := models.CreateNotification(notif); err != nil {
 							log.Error("Couldn't create Comment notification for subscriber %d: %s", userID, err)

pkg/models/comment.go

@@ -1,6 +1,8 @@
 package models
 
 import (
+	"errors"
+	"math"
 	"strings"
 	"time"
 
@@ -108,6 +110,50 @@ func PaginateComments(user *User, tableName string, tableID uint64, pager *Pagin
 	return cs, result.Error
 }
 
+// FindPageByComment finds out what page a comment ID exists on for the current user, taking into
+// account their block lists and comment visibility.
+//
+// Note: the comments are assumed ordered by created_at asc.
+func FindPageByComment(user *User, comment *Comment, pageSize int) (int, error) {
+	var (
+		allCommentIDs  []uint64
+		blockedUserIDs = BlockedUserIDs(user)
+		wheres         = []string{}
+		placeholders   = []interface{}{}
+	)
+
+	// Get the complete set of comment IDs that this comment is on a thread of.
+	wheres = append(wheres, "table_name = ? AND table_id = ?")
+	placeholders = append(placeholders, comment.TableName, comment.TableID)
+
+	if len(blockedUserIDs) > 0 {
+		wheres = append(wheres, "user_id NOT IN ?")
+		placeholders = append(placeholders, blockedUserIDs)
+	}
+
+	result := DB.Table(
+		"comments",
+	).Select(
+		"id",
+	).Where(
+		strings.Join(wheres, " AND "),
+		placeholders...,
+	).Order("created_at asc").Scan(&allCommentIDs)
+	if result.Error != nil {
+		return 0, result.Error
+	}
+
+	// Scan the comment thread to find it.
+	for i, cid := range allCommentIDs {
+		if cid == comment.ID {
+			var page = int(math.Ceil(float64(i) / float64(pageSize)))
+			return page, nil
+		}
+	}
+
+	return -1, errors.New("comment not visible to current user")
+}
+
 // ListComments returns a complete set of comments without paging.
 func ListComments(user *User, tableName string, tableID uint64) ([]*Comment, error) {
 	var (

pkg/router/router.go

@@ -112,6 +112,9 @@ func New() http.Handler {
 	mux.Handle("/v1/barertc/report", barertc.Report())
 	mux.Handle("/v1/barertc/profile", barertc.Profile())
 
+	// Redirect endpoints.
+	mux.Handle("/go/comment", middleware.LoginRequired(comment.GoToComment()))
+
 	// Static files.
 	mux.Handle("/static/", http.StripPrefix("/static/", http.FileServer(http.Dir(config.StaticPath))))
 

web/templates/forum/newest.html

@@ -105,7 +105,7 @@
 
                         <div class="columns is-multiline is-gapless mb-0">
                             <div class="column is-narrow">
-                                <a href="/forum/thread/{{.ThreadID}}?page=-1" class="has-text-grey">
+                                <a href="/go/comment?id={{.Comment.ID}}" class="has-text-grey">
                                     <h2 class="is-size-5 py-0 is-italic has-text-grey">
                                         <span class="icon"><i class="fa fa-reply"></i></span>
                                         Comment added by
@@ -131,7 +131,7 @@
 
                         </div>
 
-                        <a href="/forum/thread/{{.ThreadID}}?page=-1" class="has-text-dark">
+                        <a href="/go/comment?id={{.Comment.ID}}" class="has-text-dark">
                             {{TrimEllipses .Comment.Message 256}}
                         </a>
 

web/templates/forum/thread.html

@@ -298,6 +298,15 @@
                         </a>
                     </div>
                     {{end}}
+
+                    <!-- Copy link to clipboard -->
+                    <div class="column is-narrow">
+                        <a href="/go/comment?id={{.ID}}" onclick="navigator.clipboard.writeText(this.href); window.location='#p{{.ID}}'; return false"
+                            class="has-text-dark"
+                            title="Copy link to clipboard">
+                            <span class="icon"><i class="fa fa-paragraph"></i></span>
+                        </a>
+                    </div>
                 </div>
 
                 {{if $Root.CurrentUser.IsAdmin}}

web/templates/photo/permalink.html

@@ -289,6 +289,15 @@
                                             </a>
                                         </div>
                                         {{end}}
+
+                                        <!-- Copy link to clipboard -->
+                                        <div class="column is-narrow">
+                                            <a href="/go/comment?id={{.ID}}" onclick="navigator.clipboard.writeText(this.href); window.location='#p{{.ID}}'; return false"
+                                                class="has-text-dark"
+                                                title="Copy link to clipboard">
+                                                <span class="icon"><i class="fa fa-paragraph"></i></span>
+                                            </a>
+                                        </div>
                                     </div>
                                 </div>
                             </div>