Add plain-text post previews

I opted to do this by making a new markdown renderer that only outputs
plain text, no HTML. This feels a lot more sane to me than trying to
strip HTML out of already-parsed stuff. The tradeoff right now is that
some content just doesn't show up at all, notably bbcode content. I
doubt anyone will care.

src/config/config.go.example

@@ -1,16 +1,23 @@
 package config
 
+import (
+	"github.com/jackc/pgx/v4"
+	"github.com/rs/zerolog"
+)
+
 var Config = HMNConfig{
-	Env:     Dev,
-	Addr:    ":9001",
-	BaseUrl: "http://handmade.local:9001",
-	LogLevel: zerolog.TraceLevel,
+	Env:         Dev,
+	Addr:        ":9001",
+	PrivateAddr: ":9002",
+	BaseUrl:     "http://handmade.local:9001",
+	LogLevel:    zerolog.TraceLevel,
 	Postgres: PostgresConfig{
 		User:     "hmn",
 		Password: "password",
 		Hostname: "handmade.local",
 		Port:     5454,
 		DbName:   "hmn",
+		LogLevel: pgx.LogLevelTrace,
 		MinConn:  2, // Keep these low for dev, high for production
 		MaxConn:  2,
 	},

src/parsing/parsing.go

@@ -9,37 +9,23 @@ import (
 	"github.com/yuin/goldmark/util"
 )
 
-var previewMarkdown = goldmark.New(
-	goldmark.WithExtensions(
-		extension.GFM,
-		highlightExtension,
-		SpoilerExtension{},
-		EmbedExtension{
-			Preview: true,
-		},
-		MathjaxExtension{},
-		BBCodeExtension{
-			Preview: true,
-		},
-	),
-)
-var realMarkdown = goldmark.New(
-	goldmark.WithExtensions(
-		extension.GFM,
-		highlightExtension,
-		SpoilerExtension{},
-		EmbedExtension{},
-		MathjaxExtension{},
-		BBCodeExtension{},
-	),
+// Used for rendering real-time previews of post content.
+var PreviewMarkdown = goldmark.New(
+	goldmark.WithExtensions(makeGoldmarkExtensions(true)...),
 )
 
-func ParsePostInput(source string, preview bool) string {
-	md := realMarkdown
-	if preview {
-		md = previewMarkdown
-	}
+// Used for generating the final HTML for a post.
+var RealMarkdown = goldmark.New(
+	goldmark.WithExtensions(makeGoldmarkExtensions(false)...),
+)
 
+// Used for generating plain-text previews of posts.
+var PlaintextMarkdown = goldmark.New(
+	goldmark.WithExtensions(makeGoldmarkExtensions(false)...),
+	goldmark.WithRenderer(plaintextRenderer{}),
+)
+
+func ParsePostInput(source string, md goldmark.Markdown) string {
 	var buf bytes.Buffer
 	if err := md.Convert([]byte(source), &buf); err != nil {
 		panic(err)
@@ -48,6 +34,21 @@ func ParsePostInput(source string, preview bool) string {
 	return buf.String()
 }
 
+func makeGoldmarkExtensions(preview bool) []goldmark.Extender {
+	return []goldmark.Extender{
+		extension.GFM,
+		highlightExtension,
+		SpoilerExtension{},
+		EmbedExtension{
+			Preview: preview,
+		},
+		MathjaxExtension{},
+		BBCodeExtension{
+			Preview: preview,
+		},
+	}
+}
+
 var highlightExtension = highlighting.NewHighlighting(
 	highlighting.WithFormatOptions(HMNChromaOptions...),
 	highlighting.WithWrapperRenderer(func(w util.BufWriter, context highlighting.CodeBlockContext, entering bool) {

src/parsing/parsing_test.go

@@ -10,14 +10,14 @@ import (
 func TestMarkdown(t *testing.T) {
 	t.Run("fenced code blocks", func(t *testing.T) {
 		t.Run("multiple lines", func(t *testing.T) {
-			html := ParsePostInput("```\nmultiple lines\n\tof code\n```", false)
+			html := ParsePostInput("```\nmultiple lines\n\tof code\n```", RealMarkdown)
 			t.Log(html)
 			assert.Equal(t, 1, strings.Count(html, "<pre"))
 			assert.Contains(t, html, `class="hmn-code"`)
 			assert.Contains(t, html, "multiple lines\n\tof code")
 		})
 		t.Run("multiple lines with language", func(t *testing.T) {
-			html := ParsePostInput("```go\nfunc main() {\n\tfmt.Println(\"Hello, world!\")\n}\n```", false)
+			html := ParsePostInput("```go\nfunc main() {\n\tfmt.Println(\"Hello, world!\")\n}\n```", RealMarkdown)
 			t.Log(html)
 			assert.Equal(t, 1, strings.Count(html, "<pre"))
 			assert.Contains(t, html, `class="hmn-code"`)
@@ -30,7 +30,7 @@ func TestMarkdown(t *testing.T) {
 func TestBBCode(t *testing.T) {
 	t.Run("[code]", func(t *testing.T) {
 		t.Run("one line", func(t *testing.T) {
-			html := ParsePostInput("[code]Just some code, you know?[/code]", false)
+			html := ParsePostInput("[code]Just some code, you know?[/code]", RealMarkdown)
 			t.Log(html)
 			assert.Equal(t, 1, strings.Count(html, "<pre"))
 			assert.Contains(t, html, `class="hmn-code"`)
@@ -41,7 +41,7 @@ func TestBBCode(t *testing.T) {
 Multiline code
 	with an indent
 [/code]`
-			html := ParsePostInput(bbcode, false)
+			html := ParsePostInput(bbcode, RealMarkdown)
 			t.Log(html)
 			assert.Equal(t, 1, strings.Count(html, "<pre"))
 			assert.Contains(t, html, `class="hmn-code"`)
@@ -54,7 +54,7 @@ func main() {
 	fmt.Println("Hello, world!")
 }
 [/code]`
-			html := ParsePostInput(bbcode, false)
+			html := ParsePostInput(bbcode, RealMarkdown)
 			t.Log(html)
 			assert.Equal(t, 1, strings.Count(html, "<pre"))
 			assert.Contains(t, html, "Println")
@@ -114,4 +114,7 @@ func main() {
 [td]Body 1[/td] [td]Body 2[/td]
 [/tr]
 [/table]
+
+[youtube]https://www.youtube.com/watch?v=0J8G9qNT7gQ[/youtube]
+[youtube]https://youtu.be/0J8G9qNT7gQ[/youtube]
 `

src/parsing/renderer.go

@@ -0,0 +1,46 @@
+package parsing
+
+import (
+	"io"
+
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/renderer"
+)
+
+type plaintextRenderer struct{}
+
+var _ renderer.Renderer = plaintextRenderer{}
+
+func (r plaintextRenderer) Render(w io.Writer, source []byte, n ast.Node) error {
+	return ast.Walk(n, func(n ast.Node, entering bool) (ast.WalkStatus, error) {
+		if !entering {
+			return ast.WalkContinue, nil
+		}
+
+		switch n.Kind() {
+		case ast.KindText:
+			n := n.(*ast.Text)
+
+			_, err := w.Write(n.Text(source))
+			if err != nil {
+				return ast.WalkContinue, err
+			}
+
+			if n.SoftLineBreak() {
+				_, err := w.Write([]byte(" "))
+				if err != nil {
+					return ast.WalkContinue, err
+				}
+			}
+		case ast.KindParagraph:
+			_, err := w.Write([]byte(" "))
+			if err != nil {
+				return ast.WalkContinue, err
+			}
+		}
+
+		return ast.WalkContinue, nil
+	})
+}
+
+func (r plaintextRenderer) AddOptions(...renderer.Option) {}

src/parsing/wasm/parsingmain.go

@@ -8,7 +8,7 @@ import (
 
 func main() {
 	js.Global().Set("parseMarkdown", js.FuncOf(func(this js.Value, args []js.Value) interface{} {
-		return parsing.ParsePostInput(args[0].String(), true)
+		return parsing.ParsePostInput(args[0].String(), parsing.PreviewMarkdown)
 	}))
 
 	var done chan bool

src/templates/src/editor.html

@@ -8,9 +8,10 @@
     <script src="{{ static "go_wasm_exec.js" }}"></script>
     <script>
         const go = new Go();
-        WebAssembly.instantiateStreaming(fetch("{{ static "parsing.wasm" }}"), go.importObject).then(result => {
-            go.run(result.instance);
-        });
+        const goLoaded = WebAssembly.instantiateStreaming(fetch("{{ static "parsing.wasm" }}"), go.importObject)
+            .then(result => {
+                go.run(result.instance);
+            });
     </script>
 {{ end }}
 
@@ -110,6 +111,9 @@
         MathJax.typeset();
     }
 
+    goLoaded.then(() => {
+        updatePreview();
+    });
     tf.addEventListener('input', () => {
         updatePreview();
     });

src/website/forums.go

@@ -581,11 +581,17 @@ func ForumNewThreadSubmit(c *RequestContext) ResponseData {
 		sticky = true
 	}
 
-	parsed := parsing.ParsePostInput(unparsed, false)
+	parsed := parsing.ParsePostInput(unparsed, parsing.RealMarkdown)
 	now := time.Now()
-
 	ip := net.ParseIP(c.Req.RemoteAddr)
 
+	const previewMaxLength = 100
+	parsedPlaintext := parsing.ParsePostInput(unparsed, parsing.PlaintextMarkdown)
+	preview := parsedPlaintext
+	if len(preview) > previewMaxLength-1 {
+		preview = preview[:previewMaxLength-1] + "…"
+	}
+
 	// Create thread
 	var threadId int
 	err = tx.QueryRow(c.Context(),
@@ -615,7 +621,7 @@ func ForumNewThreadSubmit(c *RequestContext) ResponseData {
 		now,
 		currentCatId,
 		threadId,
-		"lol", // TODO: Actual previews
+		preview,
 		-1,
 		c.CurrentUser.ID,
 		models.CatKindForum,