Support formatting in rainbows

Fixes #119

3 files changed, 134 insertions, 12 deletions

diff --git a/ui/commands.go b/ui/commands.go
index 3d12eff..8cfe55d 100644
--- a/ui/commands.go
+++ b/ui/commands.go
@@ -22,6 +22,7 @@ import (
 	"io"
 	"math"
 	"os"
+	"regexp"
 	"runtime"
 	dbg "runtime/debug"
 	"runtime/pprof"
@@ -29,11 +30,12 @@ import (
 	"strconv"
 	"strings"
 	"time"
-	"unicode"
 
 	"github.com/lucasb-eyer/go-colorful"
+	"github.com/russross/blackfriday/v2"
 
 	"maunium.net/go/mautrix"
+	"maunium.net/go/mautrix/format"
 
 	"maunium.net/go/gomuks/debug"
 )
@@ -79,16 +81,23 @@ var rainbow = GradientTable{
 // TODO this command definitely belongs in a plugin once we have a plugin system.
 func makeRainbow(cmd *Command, msgtype mautrix.MessageType) {
 	text := strings.Join(cmd.Args, " ")
-	var html strings.Builder
-	for i, char := range text {
-		if unicode.IsSpace(char) {
-			html.WriteRune(char)
-			continue
-		}
-		color := rainbow.GetInterpolatedColorFor(float64(i) / float64(len(text))).Hex()
-		_, _ = fmt.Fprintf(&html, "<font data-mx-color=\"%[1]s\" color=\"%[1]s\">%[2]c</font>", color, char)
-	}
-	go cmd.Room.SendMessage(msgtype, html.String())
+
+	render := NewRainbowRenderer(blackfriday.NewHTMLRenderer(blackfriday.HTMLRendererParameters{
+		Flags: blackfriday.UseXHTML,
+	}))
+	htmlBodyBytes := blackfriday.Run([]byte(text), format.Extensions, blackfriday.WithRenderer(render))
+	htmlBody := strings.TrimRight(string(htmlBodyBytes), "\n")
+	htmlBody = format.AntiParagraphRegex.ReplaceAllString(htmlBody, "$1")
+	text = format.HTMLToText(htmlBody)
+
+	count := strings.Count(htmlBody, render.ColorID)
+	i := -1
+	htmlBody = regexp.MustCompile(render.ColorID).ReplaceAllStringFunc(htmlBody, func(match string) string {
+		i++
+		return rainbow.GetInterpolatedColorFor(float64(i) / float64(count)).Hex()
+	})
+
+	go cmd.Room.SendMessageHTML(msgtype, text, htmlBody)
 }
 
 func cmdRainbow(cmd *Command) {
diff --git a/ui/rainbow.go b/ui/rainbow.go
new file mode 100644
index 0000000..fca3cba
--- /dev/null
+++ b/ui/rainbow.go
@@ -0,0 +1,109 @@
+// gomuks - A terminal Matrix client written in Go.
+// Copyright (C) 2020 Tulir Asokan
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package ui
+
+import (
+	"bytes"
+	"fmt"
+	"html"
+	"io"
+	"math/rand"
+	"unicode"
+
+	"github.com/rivo/uniseg"
+	"github.com/russross/blackfriday/v2"
+)
+
+type RainbowRenderer struct {
+	*blackfriday.HTMLRenderer
+	sr *blackfriday.SPRenderer
+
+	ColorID string
+}
+
+func Rand(n int) (str string) {
+	b := make([]byte, n)
+	rand.Read(b)
+	str = fmt.Sprintf("%x", b)
+	return
+}
+
+func NewRainbowRenderer(html *blackfriday.HTMLRenderer) *RainbowRenderer {
+	return &RainbowRenderer{
+		HTMLRenderer: html,
+		sr:           blackfriday.NewSmartypantsRenderer(html.Flags),
+		ColorID:      Rand(16),
+	}
+}
+
+func (r *RainbowRenderer) RenderNode(w io.Writer, node *blackfriday.Node, entering bool) blackfriday.WalkStatus {
+	if node.Type == blackfriday.Text {
+		var buf bytes.Buffer
+		if r.Flags&blackfriday.Smartypants != 0 {
+			var tmp bytes.Buffer
+			escapeHTML(&tmp, node.Literal)
+			r.sr.Process(&buf, tmp.Bytes())
+		} else {
+			if node.Parent.Type == blackfriday.Link {
+				escLink(&buf, node.Literal)
+			} else {
+				escapeHTML(&buf, node.Literal)
+			}
+		}
+		graphemes := uniseg.NewGraphemes(buf.String())
+		buf.Reset()
+		for graphemes.Next() {
+			runes := graphemes.Runes()
+			if len(runes) == 1 && unicode.IsSpace(runes[0]) {
+				buf.WriteRune(runes[0])
+			}
+			_, _ = fmt.Fprintf(&buf, "<font color=\"%s\">%s</font>", r.ColorID, graphemes.Str())
+		}
+		_, _ = w.Write(buf.Bytes())
+		return blackfriday.GoToNext
+	}
+	return r.HTMLRenderer.RenderNode(w, node, entering)
+}
+
+// This stuff is copied directly from blackfriday
+var htmlEscaper = [256][]byte{
+	'&': []byte("&amp;"),
+	'<': []byte("&lt;"),
+	'>': []byte("&gt;"),
+	'"': []byte("&quot;"),
+}
+
+func escapeHTML(w io.Writer, s []byte) {
+	var start, end int
+	for end < len(s) {
+		escSeq := htmlEscaper[s[end]]
+		if escSeq != nil {
+			w.Write(s[start:end])
+			w.Write(escSeq)
+			start = end + 1
+		}
+		end++
+	}
+	if start < len(s) && end <= len(s) {
+		w.Write(s[start:end])
+	}
+}
+
+func escLink(w io.Writer, text []byte) {
+	unesc := html.UnescapeString(string(text))
+	escapeHTML(w, []byte(unesc))
+}
diff --git a/ui/room-view.go b/ui/room-view.go
index 3c4be8f..ef19c9d 100644
--- a/ui/room-view.go
+++ b/ui/room-view.go
@@ -622,6 +622,10 @@ func (view *RoomView) SendReaction(eventID string, reaction string) {
 }
 
 func (view *RoomView) SendMessage(msgtype mautrix.MessageType, text string) {
+	view.SendMessageHTML(msgtype, text, "")
+}
+
+func (view *RoomView) SendMessageHTML(msgtype mautrix.MessageType, text, html string) {
 	defer debug.Recover()
 	debug.Print("Sending message", msgtype, text, "to", view.Room.ID)
 	if !view.config.Preferences.DisableEmojis {
@@ -639,7 +643,7 @@ func (view *RoomView) SendMessage(msgtype mautrix.MessageType, text string) {
 			Event: view.replying,
 		}
 	}
-	evt := view.parent.matrix.PrepareMarkdownMessage(view.Room.ID, msgtype, text, rel)
+	evt := view.parent.matrix.PrepareMarkdownMessage(view.Room.ID, msgtype, text, html, rel)
 	msg := view.parseEvent(evt.SomewhatDangerousCopy())
 	view.content.AddMessage(msg, AppendMessage)
 	view.ClearAllContext()