From 9945ab061dc4faa0858655ffce099f828de9431c Mon Sep 17 00:00:00 2001
From: Ben Visness <bvisness@gmail.com>
Date: Fri, 30 Jul 2021 17:32:19 -0500
Subject: [PATCH] Add blog post editing

---
 src/hmnurl/urls.go                            |  36 +-
 src/rawdata/scss/_content.scss                |   4 +-
 src/rawdata/scss/_core.scss                   |  12 +-
 src/rawdata/scss/_editor.scss                 |  43 +--
 src/rawdata/scss/_forum.scss                  |   4 +-
 .../scss/tachyons/scss/_variables.scss        |   1 +
 src/templates/src/editor.html                 |  13 +-
 src/templates/src/editorpreviews.js           |  33 ++
 src/templates/templates.go                    |  23 +-
 src/website/blogs.go                          |  92 ++++-
 src/website/forums.go                         | 317 ++++--------------
 src/website/landing.go                        |   6 +-
 src/website/post_helper.go                    |   2 +-
 src/website/routes.go                         |   8 +
 src/website/threads_and_posts_helper.go       | 221 +++++++++++-
 15 files changed, 465 insertions(+), 350 deletions(-)
 create mode 100644 src/templates/src/editorpreviews.js

diff --git a/src/hmnurl/urls.go b/src/hmnurl/urls.go
index 3876cd48..1e223eb3 100644
--- a/src/hmnurl/urls.go
+++ b/src/hmnurl/urls.go
@@ -414,17 +414,17 @@ func BuildBlog(projectSlug string, page int) string {
 	return ProjectUrl(path, nil, projectSlug)
 }
 
-var RegexBlogThread = regexp.MustCompile(`^/blog/p/(?P<threadid>\d+)(-([^/]+))?(/(?P<page>\d+))?$`)
+var RegexBlogThread = regexp.MustCompile(`^/blog/p/(?P<threadid>\d+)(-([^/]+))?$`)
 
-func BuildBlogThread(projectSlug string, threadId int, title string, page int) string {
+func BuildBlogThread(projectSlug string, threadId int, title string) string {
 	defer CatchPanic()
-	builder := buildBlogThreadPath(threadId, title, page)
+	builder := buildBlogThreadPath(threadId, title)
 	return ProjectUrl(builder.String(), nil, projectSlug)
 }
 
-func BuildBlogThreadWithPostHash(projectSlug string, threadId int, title string, page int, postId int) string {
+func BuildBlogThreadWithPostHash(projectSlug string, threadId int, title string, postId int) string {
 	defer CatchPanic()
-	builder := buildBlogThreadPath(threadId, title, page)
+	builder := buildBlogThreadPath(threadId, title)
 	return ProjectUrlWithFragment(builder.String(), nil, projectSlug, strconv.Itoa(postId))
 }
 
@@ -463,15 +463,6 @@ func BuildBlogPostReply(projectSlug string, threadId int, postId int) string {
 	return ProjectUrl(builder.String(), nil, projectSlug)
 }
 
-var RegexBlogPostQuote = regexp.MustCompile(`^/blog/p/(?P<threadid>\d+)/e/(?P<postid>\d+)/quote$`)
-
-func BuildBlogPostQuote(projectSlug string, threadId int, postId int) string {
-	defer CatchPanic()
-	builder := buildBlogPostPath(threadId, postId)
-	builder.WriteString("/quote")
-	return ProjectUrl(builder.String(), nil, projectSlug)
-}
-
 /*
 * Library
  */
@@ -525,6 +516,13 @@ func BuildProjectCSS(color string) string {
 	return Url("/assets/project.css", []Q{{"color", color}})
 }
 
+var RegexEditorPreviewsJS = regexp.MustCompile("^/assets/editorpreviews.js$")
+
+func BuildEditorPreviewsJS() string {
+	defer CatchPanic()
+	return Url("/assets/editorpreviews.js", nil)
+}
+
 // NOTE(asaf): No Regex or tests for remote assets, since we don't parse it ourselves
 func BuildS3Asset(s3key string) string {
 	defer CatchPanic()
@@ -665,11 +663,7 @@ func buildForumPostPath(subforums []string, threadId int, postId int) *strings.B
 	return builder
 }
 
-func buildBlogThreadPath(threadId int, title string, page int) *strings.Builder {
-	if page < 1 {
-		panic(oops.New(nil, "Invalid blog thread page (%d), must be >= 1", page))
-	}
-
+func buildBlogThreadPath(threadId int, title string) *strings.Builder {
 	if threadId < 1 {
 		panic(oops.New(nil, "Invalid blog thread ID (%d), must be >= 1", threadId))
 	}
@@ -682,10 +676,6 @@ func buildBlogThreadPath(threadId int, title string, page int) *strings.Builder
 		builder.WriteRune('-')
 		builder.WriteString(PathSafeTitle(title))
 	}
-	if page > 1 {
-		builder.WriteRune('/')
-		builder.WriteString(strconv.Itoa(page))
-	}
 
 	return &builder
 }
diff --git a/src/rawdata/scss/_content.scss b/src/rawdata/scss/_content.scss
index 175555c3..b23eb050 100644
--- a/src/rawdata/scss/_content.scss
+++ b/src/rawdata/scss/_content.scss
@@ -7,7 +7,7 @@
 }
 
 .monospace {
-  font-family: "Fira Mono", monospace;
+  font-family: $monospace-fonts;
   background-color: rgba(0, 0, 0, 0.1);
   padding: 0.2em 0 0.05em;
   border-radius: 3px;
@@ -52,7 +52,7 @@
 }
 
 pre {
-  font-family: "Fira Mono", monospace;
+  font-family: $monospace-fonts;
 }
 
 .hmn-code {
diff --git a/src/rawdata/scss/_core.scss b/src/rawdata/scss/_core.scss
index 8b0b5d81..4b687931 100644
--- a/src/rawdata/scss/_core.scss
+++ b/src/rawdata/scss/_core.scss
@@ -136,8 +136,14 @@ hr  {
   max-width: 300px;
 }
 
+$monospace-fonts: "Fira Mono", monospace;
+
+.mono {
+  font-family: $monospace-fonts;
+}
+
 article code {
-  font-family: "Fira Mono", monospace;
+  font-family: $monospace-fonts;
 }
 
 .big { font-size:120%; }
@@ -318,6 +324,10 @@ article code {
   min-height: $height-5;
 }
 
+.minh-6 {
+  min-height: $height-6;
+}
+
 .fira {
   font-family: "Fira Sans", sans-serif;
 }
diff --git a/src/rawdata/scss/_editor.scss b/src/rawdata/scss/_editor.scss
index d1c1e5b8..b6ab5bcd 100644
--- a/src/rawdata/scss/_editor.scss
+++ b/src/rawdata/scss/_editor.scss
@@ -1,3 +1,4 @@
+// TODO: Old and wrong and bad
 .toolbar {
   @include usevar('background-color', 'editor-toolbar-background');
   @include usevar('border-color', 'editor-toolbar-border-color');
@@ -35,44 +36,10 @@
   }
 }
 
-.editor {
-  .toolbar {
-    width:95%;
-    margin:10px auto;
-
-    select {
-      font-size:10pt;
-      border:0px;
-
-      &:hover {
-        border:0px;
-      }
-
-      &:focus{
-        border:0px;
-      }
-    }
-
-    #bold {
-      font-weight: bold;
-    }
-
-    #italic {
-      font-style: italic;
-    }
-
-    #underline {
-      text-decoration: underline;
-    }
-
-    #monospace {
-      font-family: monospace;
-    }
-
-    #url {
-      text-decoration: underline;
-      font-style: italic;
-    }
+@media #{$breakpoint-not-small} {
+  #preview-container {
+    max-height: calc(100vh - 20rem);
+    overflow: auto;
   }
 }
 
diff --git a/src/rawdata/scss/_forum.scss b/src/rawdata/scss/_forum.scss
index 14daab4a..e5ccc72e 100644
--- a/src/rawdata/scss/_forum.scss
+++ b/src/rawdata/scss/_forum.scss
@@ -131,7 +131,7 @@
 }
 
 .codeblocktable {
-  font-family: "Fira Mono", monospace;
+  font-family: $monospace-fonts;
   font-size:14px;
   overflow:auto;
   line-height:1.5em;
@@ -406,7 +406,7 @@ li.post-entry {
 
     border-width: 1px;
     border-radius: 2px;
-    font-family: "Fira Mono", monospace;
+    font-family: $monospace-fonts;
     width:49%;
     box-sizing:border-box;
     padding: 4px;
diff --git a/src/rawdata/scss/tachyons/scss/_variables.scss b/src/rawdata/scss/tachyons/scss/_variables.scss
index f3cad387..d4ee6c50 100644
--- a/src/rawdata/scss/tachyons/scss/_variables.scss
+++ b/src/rawdata/scss/tachyons/scss/_variables.scss
@@ -36,6 +36,7 @@ $height-2: 2rem !default;
 $height-3: 4rem !default;
 $height-4: 8rem !default;
 $height-5: 16rem !default;
+$height-6: 32rem !default;
 $width-1: 1rem !default;
 $width-2: 2rem !default;
 $width-3: 4rem !default;
diff --git a/src/templates/src/editor.html b/src/templates/src/editor.html
index 2ef0e33b..6acb6496 100644
--- a/src/templates/src/editor.html
+++ b/src/templates/src/editor.html
@@ -1,13 +1,14 @@
 {{ template "base.html" . }}
 
 {{ define "extrahead" }}
+    {{/* TODO: These are no longer useful? */}}
     <link rel="stylesheet" href="{{ static "editor.css" }}" />
     <script src="{{ static "util.js" }}"></script>
     <script src="{{ static "editor.js" }}"></script>
 
     <script src="{{ static "go_wasm_exec.js" }}"></script>
     <script>
-        const previewWorker = new Worker('{{ static "js/editorpreviews.js" }}');
+        const previewWorker = new Worker('/assets/editorpreviews.js');
     </script>
 
     <style>
@@ -19,15 +20,15 @@
 
 {{ define "content" }}
 <div class="content-block ph3 ph0-ns">
-    {{ if .Title }}
+    {{ if not .CanEditTitle }}
         <h2>{{ .Title }}</h2>
     {{ end }}
     <div class="flex flex-column flex-row-ns">
         <form id="form" action="{{ .SubmitUrl }}" method="post" class="flex-fair-ns">
             {{ csrftoken .Session }}
 
-            {{ if not (or .PostReplyingTo .IsEditing) }}
-                <input id="title" class="b w-100 mb1" name="title" type="text" placeholder="Post title..."/>
+            {{ if .CanEditTitle }}
+                <input id="title" class="b w-100 mb1" name="title" type="text" placeholder="Post title..." value="{{ .Title }}" />
             {{ end }}
             {{/* TODO: Reintroduce the toolbar in a way that makes sense for Markdown */}}
             {{/*
@@ -51,7 +52,7 @@
                 <input type="button" id="youtube" value="youtube" />
             </div>
             */}}
-            <textarea id="editor" class="w-100 h5 minh-5" name="body">{{ if .IsEditing }}{{ .EditInitialContents }}{{ end }}</textarea>
+            <textarea id="editor" class="w-100 h6 minh-6 pa2 mono lh-copy" name="body">{{ .EditInitialContents }}</textarea>
 
             <div class="flex flex-row-reverse justify-start mt2">
                 <input type="submit" class="button ml2" name="submit" value="{{ .SubmitLabel }}" />
@@ -99,7 +100,7 @@
             {% endif %}
             */}}
         </form>
-        <div class="post post-preview mv3 mathjax flex-fair-ns mv0-ns ml3-ns">
+        <div id="preview-container" class="post post-preview mv3 mathjax flex-fair-ns mv0-ns ml3-ns overflow-auto">
             <div id="preview" class="body contents"></div>
         </div>
     </div>
diff --git a/src/templates/src/editorpreviews.js b/src/templates/src/editorpreviews.js
new file mode 100644
index 00000000..8ed71dcc
--- /dev/null
+++ b/src/templates/src/editorpreviews.js
@@ -0,0 +1,33 @@
+importScripts('/public/go_wasm_exec.js');
+
+/*
+NOTE(ben): The structure here is a little funny but allows for some debouncing. Any postMessages
+that got queued up can run all at once, then it can process the latest one.
+ */
+
+let ready = false;
+let inputData = null;
+
+onmessage = ({ data }) => {
+    inputData = data;
+    setTimeout(doPreview, 0);
+}
+
+const go = new Go();
+WebAssembly.instantiateStreaming(fetch('/public/parsing.wasm'), go.importObject)
+    .then(result => {
+        go.run(result.instance); // don't await this; we want it to be continuously running
+        ready = true;
+        setTimeout(doPreview, 0);
+    });
+
+const doPreview = () => {
+    if (!ready || inputData === null) {
+        return;
+    }
+
+    const result = parseMarkdown(inputData);
+    inputData = null;
+
+    postMessage(result);
+}
diff --git a/src/templates/templates.go b/src/templates/templates.go
index 294c40e7..9efde09a 100644
--- a/src/templates/templates.go
+++ b/src/templates/templates.go
@@ -30,7 +30,7 @@ func Init() {
 
 	files, _ := templateFs.ReadDir("src")
 	for _, f := range files {
-		if strings.HasSuffix(f.Name(), ".html") {
+		if hasSuffix(f.Name(), ".html") {
 			t := template.New(f.Name())
 			t = t.Funcs(sprig.FuncMap())
 			t = t.Funcs(HMNTemplateFuncs)
@@ -40,17 +40,7 @@ func Init() {
 			}
 
 			Templates[f.Name()] = t
-		} else if strings.HasSuffix(f.Name(), ".css") {
-			t := template.New(f.Name())
-			t = t.Funcs(sprig.FuncMap())
-			t = t.Funcs(HMNTemplateFuncs)
-			t, err := t.ParseFS(templateFs, "src/"+f.Name())
-			if err != nil {
-				logging.Fatal().Str("filename", f.Name()).Err(err).Msg("failed to parse template")
-			}
-
-			Templates[f.Name()] = t
-		} else if strings.HasSuffix(f.Name(), ".xml") {
+		} else if hasSuffix(f.Name(), ".css", ".js", ".xml") {
 			t := template.New(f.Name())
 			t = t.Funcs(sprig.FuncMap())
 			t = t.Funcs(HMNTemplateFuncs)
@@ -64,6 +54,15 @@ func Init() {
 	}
 }
 
+func hasSuffix(s string, suffixes ...string) bool {
+	for _, suffix := range suffixes {
+		if strings.HasSuffix(s, suffix) {
+			return true
+		}
+	}
+	return false
+}
+
 func names(ts []*template.Template) []string {
 	result := make([]string, len(ts))
 	for i, t := range ts {
diff --git a/src/website/blogs.go b/src/website/blogs.go
index d6099144..7d0f2fba 100644
--- a/src/website/blogs.go
+++ b/src/website/blogs.go
@@ -1,11 +1,14 @@
 package website
 
 import (
+	"fmt"
 	"net/http"
 	"strconv"
 
 	"git.handmade.network/hmn/hmn/src/db"
 	"git.handmade.network/hmn/hmn/src/hmnurl"
+	"git.handmade.network/hmn/hmn/src/models"
+	"git.handmade.network/hmn/hmn/src/oops"
 	"git.handmade.network/hmn/hmn/src/templates"
 )
 
@@ -35,11 +38,11 @@ func BlogThread(c *RequestContext) ResponseData {
 	for _, p := range posts {
 		post := templates.PostToTemplate(&p.Post, p.Author, c.Theme)
 		post.AddContentVersion(p.CurrentVersion, p.Editor)
-		addBlogUrlsToPost(&post, c.CurrentProject.Slug, p.Thread.ID, p.Post.ID)
+		addBlogUrlsToPost(&post, c.CurrentProject.Slug, &p.Thread, p.Post.ID)
 
 		if p.ReplyPost != nil {
 			reply := templates.PostToTemplate(p.ReplyPost, p.ReplyAuthor, c.Theme)
-			addBlogUrlsToPost(&reply, c.CurrentProject.Slug, p.Thread.ID, p.Post.ID)
+			addBlogUrlsToPost(&reply, c.CurrentProject.Slug, &p.Thread, p.Post.ID)
 			post.ReplyPost = &reply
 		}
 
@@ -67,10 +70,83 @@ func BlogPostRedirectToThread(c *RequestContext) ResponseData {
 
 	thread := FetchThread(c.Context(), c.Conn, cd.ThreadID)
 
-	threadUrl := hmnurl.BuildBlogThread(c.CurrentProject.Slug, cd.ThreadID, thread.Title, 1)
+	threadUrl := hmnurl.BuildBlogThread(c.CurrentProject.Slug, cd.ThreadID, thread.Title)
 	return c.Redirect(threadUrl, http.StatusFound)
 }
 
+func BlogPostEdit(c *RequestContext) ResponseData {
+	cd, ok := getCommonBlogData(c)
+	if !ok {
+		return FourOhFour(c)
+	}
+
+	if !UserCanEditPost(c.Context(), c.Conn, *c.CurrentUser, cd.PostID) {
+		return FourOhFour(c)
+	}
+
+	postData := FetchPostAndStuff(c.Context(), c.Conn, cd.ThreadID, cd.PostID)
+
+	baseData := getBaseData(c)
+	if postData.Thread.FirstID == postData.Post.ID {
+		baseData.Title = fmt.Sprintf("Editing \"%s\" | %s", postData.Thread.Title, c.CurrentProject.Name)
+	} else {
+		baseData.Title = fmt.Sprintf("Editing Post | %s", c.CurrentProject.Name)
+	}
+	baseData.MathjaxEnabled = true
+	// TODO(ben): Set breadcrumbs
+
+	editData := getEditorDataForEdit(baseData, postData)
+	editData.SubmitUrl = hmnurl.BuildBlogPostEdit(c.CurrentProject.Slug, cd.ThreadID, cd.PostID)
+	editData.SubmitLabel = "Submit Edited Post"
+	if postData.Thread.FirstID != postData.Post.ID {
+		editData.SubmitLabel = "Submit Edited Comment"
+	}
+
+	var res ResponseData
+	res.MustWriteTemplate("editor.html", editData, c.Perf)
+	return res
+}
+
+func BlogPostEditSubmit(c *RequestContext) ResponseData {
+	cd, ok := getCommonBlogData(c)
+	if !ok {
+		return FourOhFour(c)
+	}
+
+	if !UserCanEditPost(c.Context(), c.Conn, *c.CurrentUser, cd.PostID) {
+		return FourOhFour(c)
+	}
+
+	tx, err := c.Conn.Begin(c.Context())
+	if err != nil {
+		panic(err)
+	}
+	defer tx.Rollback(c.Context())
+
+	postData := FetchPostAndStuff(c.Context(), tx, cd.ThreadID, cd.PostID)
+
+	c.Req.ParseForm()
+	title := c.Req.Form.Get("title")
+	unparsed := c.Req.Form.Get("body")
+	editReason := c.Req.Form.Get("editreason")
+	if title != "" && postData.Thread.FirstID != postData.Post.ID {
+		return RejectRequest(c, "You can only edit the title by editing the first post.")
+	}
+	if unparsed == "" {
+		return RejectRequest(c, "You must provide a post body.")
+	}
+
+	CreatePostVersion(c.Context(), tx, postData.Post.ID, unparsed, c.Req.Host, editReason, &c.CurrentUser.ID)
+
+	err = tx.Commit(c.Context())
+	if err != nil {
+		return ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to edit blog post"))
+	}
+
+	postUrl := hmnurl.BuildBlogThreadWithPostHash(c.CurrentProject.Slug, cd.ThreadID, postData.Thread.Title, cd.PostID)
+	return c.Redirect(postUrl, http.StatusSeeOther)
+}
+
 type commonBlogData struct {
 	c *RequestContext
 
@@ -145,9 +221,9 @@ func getCommonBlogData(c *RequestContext) (commonBlogData, bool) {
 	return res, true
 }
 
-func addBlogUrlsToPost(p *templates.Post, projectSlug string, threadId int, postId int) {
-	p.Url = hmnurl.BuildBlogPost(projectSlug, threadId, postId)
-	p.DeleteUrl = hmnurl.BuildBlogPostDelete(projectSlug, threadId, postId)
-	p.EditUrl = hmnurl.BuildBlogPostEdit(projectSlug, threadId, postId)
-	p.ReplyUrl = hmnurl.BuildBlogPostReply(projectSlug, threadId, postId)
+func addBlogUrlsToPost(p *templates.Post, projectSlug string, thread *models.Thread, postId int) {
+	p.Url = hmnurl.BuildBlogThreadWithPostHash(projectSlug, thread.ID, thread.Title, postId)
+	p.DeleteUrl = hmnurl.BuildBlogPostDelete(projectSlug, thread.ID, postId)
+	p.EditUrl = hmnurl.BuildBlogPostEdit(projectSlug, thread.ID, postId)
+	p.ReplyUrl = hmnurl.BuildBlogPostReply(projectSlug, thread.ID, postId)
 }
diff --git a/src/website/forums.go b/src/website/forums.go
index 707e5029..3ca9d880 100644
--- a/src/website/forums.go
+++ b/src/website/forums.go
@@ -1,11 +1,8 @@
 package website
 
 import (
-	"context"
-	"errors"
 	"fmt"
 	"math"
-	"net"
 	"net/http"
 	"strconv"
 	"strings"
@@ -15,10 +12,8 @@ import (
 	"git.handmade.network/hmn/hmn/src/hmnurl"
 	"git.handmade.network/hmn/hmn/src/models"
 	"git.handmade.network/hmn/hmn/src/oops"
-	"git.handmade.network/hmn/hmn/src/parsing"
 	"git.handmade.network/hmn/hmn/src/templates"
 	"git.handmade.network/hmn/hmn/src/utils"
-	"github.com/jackc/pgx/v4"
 )
 
 type forumData struct {
@@ -38,16 +33,44 @@ type forumSubforumData struct {
 	TotalThreads int
 }
 
+type editActionType string
+
 type editorData struct {
 	templates.BaseData
 	SubmitUrl   string
-	Title       string
 	SubmitLabel string
 
-	IsEditing           bool // false if new post, true if updating existing one
+	// The following are filled out automatically by the
+	// getEditorDataFor* functions.
+	Title               string
+	CanEditTitle        bool
+	IsEditing           bool
 	EditInitialContents string
+	PostReplyingTo      *templates.Post
+}
 
-	PostReplyingTo *templates.Post
+func getEditorDataForNew(baseData templates.BaseData, replyPost *templates.Post) editorData {
+	result := editorData{
+		BaseData:       baseData,
+		CanEditTitle:   replyPost == nil,
+		PostReplyingTo: replyPost,
+	}
+
+	if replyPost != nil {
+		result.Title = "Replying to post"
+	}
+
+	return result
+}
+
+func getEditorDataForEdit(baseData templates.BaseData, p postAndRelatedModels) editorData {
+	return editorData{
+		BaseData:            baseData,
+		Title:               p.Thread.Title,
+		CanEditTitle:        p.Thread.FirstID == p.Post.ID,
+		IsEditing:           true,
+		EditInitialContents: p.CurrentVersion.TextRaw,
+	}
 }
 
 func Forum(c *RequestContext) ResponseData {
@@ -590,12 +613,12 @@ func ForumNewThread(c *RequestContext) ResponseData {
 		return FourOhFour(c)
 	}
 
+	editData := getEditorDataForNew(baseData, nil)
+	editData.SubmitUrl = hmnurl.BuildForumNewThread(c.CurrentProject.Slug, cd.LineageBuilder.GetSubforumLineageSlugs(cd.SubforumID), true)
+	editData.SubmitLabel = "Post New Thread"
+
 	var res ResponseData
-	res.MustWriteTemplate("editor.html", editorData{
-		BaseData:    baseData,
-		SubmitUrl:   hmnurl.BuildForumNewThread(c.CurrentProject.Slug, cd.LineageBuilder.GetSubforumLineageSlugs(cd.SubforumID), true),
-		SubmitLabel: "Post New Thread",
-	}, c.Perf)
+	res.MustWriteTemplate("editor.html", editData, c.Perf)
 	return res
 }
 
@@ -642,23 +665,8 @@ func ForumNewThreadSubmit(c *RequestContext) ResponseData {
 		panic(oops.New(err, "failed to create thread"))
 	}
 
-	postId, _ := createNewForumPostAndVersion(c.Context(), tx, threadId, c.CurrentUser.ID, c.CurrentProject.ID, unparsed, c.Req.Host, nil)
-
-	// Update thread with post id
-	_, err = tx.Exec(c.Context(),
-		`
-		UPDATE handmade_thread
-		SET
-			first_id = $1,
-			last_id = $1
-		WHERE id = $2
-		`,
-		postId,
-		threadId,
-	)
-	if err != nil {
-		panic(oops.New(err, "failed to set thread post ids"))
-	}
+	// Create everything else
+	CreateNewPost(c.Context(), tx, c.CurrentProject.ID, threadId, models.ThreadTypeForumPost, c.CurrentUser.ID, nil, unparsed, c.Req.Host)
 
 	err = tx.Commit(c.Context())
 	if err != nil {
@@ -685,15 +693,12 @@ func ForumPostReply(c *RequestContext) ResponseData {
 	templatePost := templates.PostToTemplate(&postData.Post, postData.Author, c.Theme)
 	templatePost.AddContentVersion(postData.CurrentVersion, postData.Editor)
 
-	var res ResponseData
-	res.MustWriteTemplate("editor.html", editorData{
-		BaseData:    baseData,
-		SubmitUrl:   hmnurl.BuildForumPostReply(c.CurrentProject.Slug, cd.LineageBuilder.GetSubforumLineageSlugs(cd.SubforumID), cd.ThreadID, cd.PostID),
-		SubmitLabel: "Submit Reply",
+	editData := getEditorDataForNew(baseData, &templatePost)
+	editData.SubmitUrl = hmnurl.BuildForumPostReply(c.CurrentProject.Slug, cd.LineageBuilder.GetSubforumLineageSlugs(cd.SubforumID), cd.ThreadID, cd.PostID)
+	editData.SubmitLabel = "Submit Reply"
 
-		Title:          "Replying to post",
-		PostReplyingTo: &templatePost,
-	}, c.Perf)
+	var res ResponseData
+	res.MustWriteTemplate("editor.html", editData, c.Perf)
 	return res
 }
 
@@ -711,10 +716,9 @@ func ForumPostReplySubmit(c *RequestContext) ResponseData {
 
 	c.Req.ParseForm()
 	// TODO(ben): Validation
-
 	unparsed := c.Req.Form.Get("body")
 
-	newPostId, _ := createNewForumPostAndVersion(c.Context(), tx, cd.ThreadID, c.CurrentUser.ID, c.CurrentProject.ID, unparsed, c.Req.Host, &cd.PostID)
+	newPostId, _ := CreateNewPost(c.Context(), tx, c.CurrentProject.ID, cd.ThreadID, models.ThreadTypeForumPost, c.CurrentUser.ID, &cd.PostID, unparsed, c.Req.Host)
 
 	err = tx.Commit(c.Context())
 	if err != nil {
@@ -731,30 +735,27 @@ func ForumPostEdit(c *RequestContext) ResponseData {
 		return FourOhFour(c)
 	}
 
-	if !cd.UserCanEditPost(c.Context(), c.Conn, *c.CurrentUser) {
+	if !UserCanEditPost(c.Context(), c.Conn, *c.CurrentUser, cd.PostID) {
 		return FourOhFour(c)
 	}
 
 	postData := FetchPostAndStuff(c.Context(), c.Conn, cd.ThreadID, cd.PostID)
 
 	baseData := getBaseData(c)
-	baseData.Title = fmt.Sprintf("Editing \"%s\" | %s", postData.Thread.Title, cd.SubforumTree[cd.SubforumID].Name)
+	if postData.Thread.FirstID == postData.Post.ID {
+		baseData.Title = fmt.Sprintf("Editing \"%s\" | %s", postData.Thread.Title, cd.SubforumTree[cd.SubforumID].Name)
+	} else {
+		baseData.Title = fmt.Sprintf("Editing Post | %s", cd.SubforumTree[cd.SubforumID].Name)
+	}
 	baseData.MathjaxEnabled = true
 	// TODO(ben): Set breadcrumbs
 
-	templatePost := templates.PostToTemplate(&postData.Post, postData.Author, c.Theme)
-	templatePost.AddContentVersion(postData.CurrentVersion, postData.Editor)
+	editData := getEditorDataForEdit(baseData, postData)
+	editData.SubmitUrl = hmnurl.BuildForumPostEdit(c.CurrentProject.Slug, cd.LineageBuilder.GetSubforumLineageSlugs(cd.SubforumID), cd.ThreadID, cd.PostID)
+	editData.SubmitLabel = "Submit Edited Post"
 
 	var res ResponseData
-	res.MustWriteTemplate("editor.html", editorData{
-		BaseData:    baseData,
-		SubmitUrl:   hmnurl.BuildForumPostEdit(c.CurrentProject.Slug, cd.LineageBuilder.GetSubforumLineageSlugs(cd.SubforumID), cd.ThreadID, cd.PostID),
-		Title:       postData.Thread.Title,
-		SubmitLabel: "Submit Edited Post",
-
-		IsEditing:           true,
-		EditInitialContents: postData.CurrentVersion.TextRaw,
-	}, c.Perf)
+	res.MustWriteTemplate("editor.html", editData, c.Perf)
 	return res
 }
 
@@ -764,7 +765,7 @@ func ForumPostEditSubmit(c *RequestContext) ResponseData {
 		return FourOhFour(c)
 	}
 
-	if !cd.UserCanEditPost(c.Context(), c.Conn, *c.CurrentUser) {
+	if !UserCanEditPost(c.Context(), c.Conn, *c.CurrentUser, cd.PostID) {
 		return FourOhFour(c)
 	}
 
@@ -779,7 +780,7 @@ func ForumPostEditSubmit(c *RequestContext) ResponseData {
 	unparsed := c.Req.Form.Get("body")
 	editReason := c.Req.Form.Get("editreason")
 
-	createForumPostVersion(c.Context(), tx, cd.PostID, unparsed, c.Req.Host, editReason, &c.CurrentUser.ID)
+	CreatePostVersion(c.Context(), tx, cd.PostID, unparsed, c.Req.Host, editReason, &c.CurrentUser.ID)
 
 	err = tx.Commit(c.Context())
 	if err != nil {
@@ -796,7 +797,7 @@ func ForumPostDelete(c *RequestContext) ResponseData {
 		return FourOhFour(c)
 	}
 
-	if !cd.UserCanEditPost(c.Context(), c.Conn, *c.CurrentUser) {
+	if !UserCanEditPost(c.Context(), c.Conn, *c.CurrentUser, cd.PostID) {
 		return FourOhFour(c)
 	}
 
@@ -831,7 +832,7 @@ func ForumPostDeleteSubmit(c *RequestContext) ResponseData {
 		return FourOhFour(c)
 	}
 
-	if !cd.UserCanEditPost(c.Context(), c.Conn, *c.CurrentUser) {
+	if !UserCanEditPost(c.Context(), c.Conn, *c.CurrentUser, cd.PostID) {
 		return FourOhFour(c)
 	}
 
@@ -841,208 +842,20 @@ func ForumPostDeleteSubmit(c *RequestContext) ResponseData {
 	}
 	defer tx.Rollback(c.Context())
 
-	isFirstPost, err := db.QueryBool(c.Context(), tx,
-		`
-		SELECT thread.first_id = $1
-		FROM
-			handmade_thread AS thread
-		WHERE
-			thread.id = $2
-		`,
-		cd.PostID,
-		cd.ThreadID,
-	)
-	if err != nil {
-		return ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to check if post was the first post in the thread"))
-	}
-
-	if isFirstPost {
-		// Just delete the whole thread and all its posts.
-		_, err = tx.Exec(c.Context(),
-			`
-			UPDATE handmade_thread
-			SET deleted = TRUE
-			WHERE id = $1
-			`,
-			cd.ThreadID,
-		)
-		_, err = tx.Exec(c.Context(),
-			`
-			UPDATE handmade_post
-			SET deleted = TRUE
-			WHERE thread_id = $1
-			`,
-			cd.ThreadID,
-		)
-
-		err = tx.Commit(c.Context())
-		if err != nil {
-			return ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to delete thread and posts when deleting the first post"))
-		}
-
-		forumUrl := hmnurl.BuildForum(c.CurrentProject.Slug, cd.LineageBuilder.GetSubforumLineageSlugs(cd.SubforumID), 1)
-		return c.Redirect(forumUrl, http.StatusSeeOther)
-	}
-
-	_, err = tx.Exec(c.Context(),
-		`
-		UPDATE handmade_post
-		SET deleted = TRUE
-		WHERE
-			id = $1
-		`,
-		cd.PostID,
-	)
-	if err != nil {
-		return ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to mark forum post as deleted"))
-	}
-
-	err = fixThreadPostIds(c.Context(), tx, cd.ThreadID)
-	if err != nil {
-		if errors.Is(err, errThreadEmpty) {
-			panic("it shouldn't be possible to delete the last remaining post in a thread, without it also being the first post in the thread and thus resulting in the whole thread getting deleted earlier")
-		} else {
-			return ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to fix up thread post ids"))
-		}
-	}
+	threadDeleted := DeletePost(c.Context(), tx, cd.ThreadID, cd.PostID)
 
 	err = tx.Commit(c.Context())
 	if err != nil {
 		return ErrorResponse(http.StatusInternalServerError, oops.New(err, "failed to delete post"))
 	}
 
-	threadUrl := hmnurl.BuildForumThread(c.CurrentProject.Slug, cd.LineageBuilder.GetSubforumLineageSlugs(cd.SubforumID), cd.ThreadID, "", 1) // TODO: Go to the last page of the thread? Or the post before the post we just deleted?
-	return c.Redirect(threadUrl, http.StatusSeeOther)
-}
-
-func createNewForumPostAndVersion(ctx context.Context, tx pgx.Tx, threadId, userId, projectId int, unparsedContent string, ipString string, replyId *int) (postId, versionId int) {
-	// Create post
-	err := tx.QueryRow(ctx,
-		`
-		INSERT INTO handmade_post (postdate, thread_id, thread_type, current_id, author_id, project_id, reply_id, preview)
-		VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
-		RETURNING id
-		`,
-		time.Now(),
-		threadId,
-		models.ThreadTypeForumPost,
-		-1,
-		userId,
-		projectId,
-		replyId,
-		"", // empty preview, will be updated later
-	).Scan(&postId)
-	if err != nil {
-		panic(oops.New(err, "failed to create post"))
+	if threadDeleted {
+		forumUrl := hmnurl.BuildForum(c.CurrentProject.Slug, cd.LineageBuilder.GetSubforumLineageSlugs(cd.SubforumID), 1)
+		return c.Redirect(forumUrl, http.StatusSeeOther)
+	} else {
+		threadUrl := hmnurl.BuildForumThread(c.CurrentProject.Slug, cd.LineageBuilder.GetSubforumLineageSlugs(cd.SubforumID), cd.ThreadID, "", 1) // TODO: Go to the last page of the thread? Or the post before the post we just deleted?
+		return c.Redirect(threadUrl, http.StatusSeeOther)
 	}
-
-	versionId = createForumPostVersion(ctx, tx, postId, unparsedContent, ipString, "", nil)
-
-	return
-}
-
-func createForumPostVersion(ctx context.Context, tx pgx.Tx, postId int, unparsedContent string, ipString string, editReason string, editorId *int) (versionId int) {
-	parsed := parsing.ParseMarkdown(unparsedContent, parsing.RealMarkdown)
-	ip := net.ParseIP(ipString)
-
-	const previewMaxLength = 100
-	parsedPlaintext := parsing.ParseMarkdown(unparsedContent, parsing.PlaintextMarkdown)
-	preview := parsedPlaintext
-	if len(preview) > previewMaxLength-1 {
-		preview = preview[:previewMaxLength-1] + "…"
-	}
-
-	// Create post version
-	err := tx.QueryRow(ctx,
-		`
-		INSERT INTO handmade_postversion (post_id, text_raw, text_parsed, ip, date, edit_reason, editor_id)
-		VALUES ($1, $2, $3, $4, $5, $6, $7)
-		RETURNING id
-		`,
-		postId,
-		unparsedContent,
-		parsed,
-		ip,
-		time.Now(),
-		editReason,
-		editorId,
-	).Scan(&versionId)
-	if err != nil {
-		panic(oops.New(err, "failed to create post version"))
-	}
-
-	// Update post with version id and preview
-	_, err = tx.Exec(ctx,
-		`
-		UPDATE handmade_post
-		SET current_id = $1, preview = $2
-		WHERE id = $3
-		`,
-		versionId,
-		preview,
-		postId,
-	)
-	if err != nil {
-		panic(oops.New(err, "failed to set current post version and preview"))
-	}
-
-	return
-}
-
-var errThreadEmpty = errors.New("thread contained no non-deleted posts")
-
-/*
-Ensures that the first_id and last_id on the thread are still good.
-
-Returns errThreadEmpty if the thread contains no visible posts any more.
-You should probably mark the thread as deleted in this case.
-*/
-func fixThreadPostIds(ctx context.Context, tx pgx.Tx, threadId int) error {
-	postsIter, err := db.Query(ctx, tx, models.Post{},
-		`
-		SELECT $columns
-		FROM handmade_post
-		WHERE
-			thread_id = $1
-			AND NOT deleted
-		`,
-		threadId,
-	)
-	if err != nil {
-		return oops.New(err, "failed to fetch posts when fixing up thread")
-	}
-
-	var firstPost, lastPost *models.Post
-	for _, ipost := range postsIter.ToSlice() {
-		post := ipost.(*models.Post)
-
-		if firstPost == nil || post.PostDate.Before(firstPost.PostDate) {
-			firstPost = post
-		}
-		if lastPost == nil || post.PostDate.After(lastPost.PostDate) {
-			lastPost = post
-		}
-	}
-
-	if firstPost == nil || lastPost == nil {
-		return errThreadEmpty
-	}
-
-	_, err = tx.Exec(ctx,
-		`
-		UPDATE handmade_thread
-		SET first_id = $1, last_id = $2
-		WHERE id = $3
-		`,
-		firstPost.ID,
-		lastPost.ID,
-		threadId,
-	)
-	if err != nil {
-		return oops.New(err, "failed to update thread first/last ids")
-	}
-
-	return nil
 }
 
 type commonForumData struct {
diff --git a/src/website/landing.go b/src/website/landing.go
index 533ea439..1130b958 100644
--- a/src/website/landing.go
+++ b/src/website/landing.go
@@ -182,7 +182,7 @@ func Index(c *RequestContext) ResponseData {
 
 				landingPageProject.FeaturedPost = &LandingPageFeaturedPost{
 					Title:   projectPost.Thread.Title,
-					Url:     hmnurl.BuildBlogPost(proj.Slug, projectPost.Thread.ID, projectPost.Post.ID),
+					Url:     hmnurl.BuildBlogThread(proj.Slug, projectPost.Thread.ID, projectPost.Thread.Title),
 					User:    templates.UserToTemplate(&projectPost.User, c.Theme),
 					Date:    projectPost.Post.PostDate,
 					Unread:  !hasRead,
@@ -323,13 +323,13 @@ func Index(c *RequestContext) ResponseData {
 		FeedUrl:     hmnurl.BuildFeed(),
 		PodcastUrl:  hmnurl.BuildPodcast(models.HMNProjectSlug),
 		StreamsUrl:  hmnurl.BuildStreams(),
-		IRCUrl:      hmnurl.BuildBlogThread(models.HMNProjectSlug, 1138, "[Tutorial] Handmade Network IRC", 1),
+		IRCUrl:      hmnurl.BuildBlogThread(models.HMNProjectSlug, 1138, "[Tutorial] Handmade Network IRC"),
 		DiscordUrl:  "https://discord.gg/hxWxDee",
 		ShowUrl:     "https://handmadedev.show/",
 		ShowcaseUrl: hmnurl.BuildShowcase(),
 		NewsPost: LandingPageFeaturedPost{
 			Title:   newsPostResult.Thread.Title,
-			Url:     hmnurl.BuildBlogPost(models.HMNProjectSlug, newsPostResult.Thread.ID, newsPostResult.Post.ID),
+			Url:     hmnurl.BuildBlogThread(models.HMNProjectSlug, newsPostResult.Thread.ID, newsPostResult.Thread.Title),
 			User:    templates.UserToTemplate(&newsPostResult.User, c.Theme),
 			Date:    newsPostResult.Post.PostDate,
 			Unread:  true, // TODO
diff --git a/src/website/post_helper.go b/src/website/post_helper.go
index d1f7e8f2..52b27e5c 100644
--- a/src/website/post_helper.go
+++ b/src/website/post_helper.go
@@ -10,7 +10,7 @@ import (
 func UrlForGenericPost(thread *models.Thread, post *models.Post, lineageBuilder *models.SubforumLineageBuilder, projectSlug string) string {
 	switch post.ThreadType {
 	case models.ThreadTypeProjectArticle:
-		return hmnurl.BuildBlogPost(projectSlug, post.ThreadID, post.ID)
+		return hmnurl.BuildBlogThreadWithPostHash(projectSlug, post.ThreadID, thread.Title, post.ID)
 	case models.ThreadTypeForumPost:
 		return hmnurl.BuildForumPost(projectSlug, lineageBuilder.GetSubforumLineageSlugs(*thread.SubforumID), post.ThreadID, post.ID)
 	}
diff --git a/src/website/routes.go b/src/website/routes.go
index 25cc4388..85771126 100644
--- a/src/website/routes.go
+++ b/src/website/routes.go
@@ -168,6 +168,8 @@ func NewWebsiteRoutes(conn *pgxpool.Pool, perfCollector *perf.PerfCollector) htt
 
 	mainRoutes.GET(hmnurl.RegexBlogThread, BlogThread)
 	mainRoutes.GET(hmnurl.RegexBlogPost, BlogPostRedirectToThread)
+	mainRoutes.GET(hmnurl.RegexBlogPostEdit, BlogPostEdit)
+	mainRoutes.POST(hmnurl.RegexBlogPostEdit, BlogPostEditSubmit)
 
 	mainRoutes.GET(hmnurl.RegexPodcast, PodcastIndex)
 	mainRoutes.GET(hmnurl.RegexPodcastEdit, PodcastEdit)
@@ -180,6 +182,12 @@ func NewWebsiteRoutes(conn *pgxpool.Pool, perfCollector *perf.PerfCollector) htt
 	mainRoutes.GET(hmnurl.RegexPodcastRSS, PodcastRSS)
 
 	mainRoutes.GET(hmnurl.RegexProjectCSS, ProjectCSS)
+	mainRoutes.GET(hmnurl.RegexEditorPreviewsJS, func(c *RequestContext) ResponseData {
+		var res ResponseData
+		res.MustWriteTemplate("editorpreviews.js", nil, c.Perf)
+		res.Header().Add("Content-Type", "application/javascript")
+		return res
+	})
 
 	// Other
 	mainRoutes.AnyMethod(hmnurl.RegexCatchAll, FourOhFour)
diff --git a/src/website/threads_and_posts_helper.go b/src/website/threads_and_posts_helper.go
index 75bfc44c..49f622a4 100644
--- a/src/website/threads_and_posts_helper.go
+++ b/src/website/threads_and_posts_helper.go
@@ -4,10 +4,14 @@ import (
 	"context"
 	"errors"
 	"math"
+	"net"
+	"time"
 
 	"git.handmade.network/hmn/hmn/src/db"
 	"git.handmade.network/hmn/hmn/src/models"
 	"git.handmade.network/hmn/hmn/src/oops"
+	"git.handmade.network/hmn/hmn/src/parsing"
+	"github.com/jackc/pgx/v4"
 )
 
 type postAndRelatedModels struct {
@@ -187,7 +191,7 @@ func FetchThreadPostsAndStuff(
 	return thread, posts
 }
 
-func (cd *commonForumData) UserCanEditPost(ctx context.Context, connOrTx db.ConnOrTx, user models.User) bool {
+func UserCanEditPost(ctx context.Context, connOrTx db.ConnOrTx, user models.User, postId int) bool {
 	if user.IsStaff {
 		return true
 	}
@@ -204,7 +208,7 @@ func (cd *commonForumData) UserCanEditPost(ctx context.Context, connOrTx db.Conn
 			post.id = $1
 			AND NOT post.deleted
 		`,
-		cd.PostID,
+		postId,
 	)
 	if err != nil {
 		if errors.Is(err, db.ErrNoMatchingRows) {
@@ -217,3 +221,216 @@ func (cd *commonForumData) UserCanEditPost(ctx context.Context, connOrTx db.Conn
 
 	return result.AuthorID != nil && *result.AuthorID == user.ID
 }
+
+func CreateNewPost(
+	ctx context.Context,
+	tx pgx.Tx,
+	projectId int,
+	threadId int, threadType models.ThreadType,
+	userId int,
+	replyId *int,
+	unparsedContent string,
+	ipString string,
+) (postId, versionId int) {
+	// Create post
+	err := tx.QueryRow(ctx,
+		`
+		INSERT INTO handmade_post (postdate, thread_id, thread_type, current_id, author_id, project_id, reply_id, preview)
+		VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
+		RETURNING id
+		`,
+		time.Now(),
+		threadId,
+		models.ThreadTypeForumPost,
+		-1,
+		userId,
+		projectId,
+		replyId,
+		"", // empty preview, will be updated later
+	).Scan(&postId)
+	if err != nil {
+		panic(oops.New(err, "failed to create post"))
+	}
+
+	// Create and associate version
+	versionId = CreatePostVersion(ctx, tx, postId, unparsedContent, ipString, "", nil)
+
+	// Fix up thread
+	err = FixThreadPostIds(ctx, tx, threadId)
+	if err != nil {
+		panic(oops.New(err, "failed to fix up thread post IDs"))
+	}
+
+	return
+}
+
+func DeletePost(
+	ctx context.Context,
+	tx pgx.Tx,
+	threadId, postId int,
+) (threadDeleted bool) {
+	isFirstPost, err := db.QueryBool(ctx, tx,
+		`
+		SELECT thread.first_id = $1
+		FROM
+			handmade_thread AS thread
+		WHERE
+			thread.id = $2
+		`,
+		postId,
+		threadId,
+	)
+	if err != nil {
+		panic(oops.New(err, "failed to check if post was the first post in the thread"))
+	}
+
+	if isFirstPost {
+		// Just delete the whole thread and all its posts.
+		_, err = tx.Exec(ctx,
+			`
+			UPDATE handmade_thread
+			SET deleted = TRUE
+			WHERE id = $1
+			`,
+			threadId,
+		)
+		_, err = tx.Exec(ctx,
+			`
+			UPDATE handmade_post
+			SET deleted = TRUE
+			WHERE thread_id = $1
+			`,
+			threadId,
+		)
+
+		return true
+	}
+
+	_, err = tx.Exec(ctx,
+		`
+		UPDATE handmade_post
+		SET deleted = TRUE
+		WHERE
+			id = $1
+		`,
+		postId,
+	)
+	if err != nil {
+		panic(oops.New(err, "failed to mark forum post as deleted"))
+	}
+
+	err = FixThreadPostIds(ctx, tx, threadId)
+	if err != nil {
+		if errors.Is(err, errThreadEmpty) {
+			panic("it shouldn't be possible to delete the last remaining post in a thread, without it also being the first post in the thread and thus resulting in the whole thread getting deleted earlier")
+		} else {
+			panic(oops.New(err, "failed to fix up thread post ids"))
+		}
+	}
+
+	return false
+}
+
+func CreatePostVersion(ctx context.Context, tx pgx.Tx, postId int, unparsedContent string, ipString string, editReason string, editorId *int) (versionId int) {
+	parsed := parsing.ParseMarkdown(unparsedContent, parsing.RealMarkdown)
+	ip := net.ParseIP(ipString)
+
+	const previewMaxLength = 100
+	parsedPlaintext := parsing.ParseMarkdown(unparsedContent, parsing.PlaintextMarkdown)
+	preview := parsedPlaintext
+	if len(preview) > previewMaxLength-1 {
+		preview = preview[:previewMaxLength-1] + "…"
+	}
+
+	// Create post version
+	err := tx.QueryRow(ctx,
+		`
+		INSERT INTO handmade_postversion (post_id, text_raw, text_parsed, ip, date, edit_reason, editor_id)
+		VALUES ($1, $2, $3, $4, $5, $6, $7)
+		RETURNING id
+		`,
+		postId,
+		unparsedContent,
+		parsed,
+		ip,
+		time.Now(),
+		editReason,
+		editorId,
+	).Scan(&versionId)
+	if err != nil {
+		panic(oops.New(err, "failed to create post version"))
+	}
+
+	// Update post with version id and preview
+	_, err = tx.Exec(ctx,
+		`
+		UPDATE handmade_post
+		SET current_id = $1, preview = $2
+		WHERE id = $3
+		`,
+		versionId,
+		preview,
+		postId,
+	)
+	if err != nil {
+		panic(oops.New(err, "failed to set current post version and preview"))
+	}
+
+	return
+}
+
+var errThreadEmpty = errors.New("thread contained no non-deleted posts")
+
+/*
+Ensures that the first_id and last_id on the thread are still good.
+
+Returns errThreadEmpty if the thread contains no visible posts any more.
+You should probably mark the thread as deleted in this case.
+*/
+func FixThreadPostIds(ctx context.Context, tx pgx.Tx, threadId int) error {
+	postsIter, err := db.Query(ctx, tx, models.Post{},
+		`
+		SELECT $columns
+		FROM handmade_post
+		WHERE
+			thread_id = $1
+			AND NOT deleted
+		`,
+		threadId,
+	)
+	if err != nil {
+		return oops.New(err, "failed to fetch posts when fixing up thread")
+	}
+
+	var firstPost, lastPost *models.Post
+	for _, ipost := range postsIter.ToSlice() {
+		post := ipost.(*models.Post)
+
+		if firstPost == nil || post.PostDate.Before(firstPost.PostDate) {
+			firstPost = post
+		}
+		if lastPost == nil || post.PostDate.After(lastPost.PostDate) {
+			lastPost = post
+		}
+	}
+
+	if firstPost == nil || lastPost == nil {
+		return errThreadEmpty
+	}
+
+	_, err = tx.Exec(ctx,
+		`
+		UPDATE handmade_thread
+		SET first_id = $1, last_id = $2
+		WHERE id = $3
+		`,
+		firstPost.ID,
+		lastPost.ID,
+		threadId,
+	)
+	if err != nil {
+		return oops.New(err, "failed to update thread first/last ids")
+	}
+
+	return nil
+}