From e7bf5bd59fc0a43172b6ab5b338e1d60bd4b3bbb Mon Sep 17 00:00:00 2001
From: Tulir Asokan <tulir@maunium.net>
Date: Sat, 14 Apr 2018 00:34:25 +0300
Subject: Add basic HTML rendering (ref #16)

---
 ui/messages/htmlparser.go | 136 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 136 insertions(+)
 create mode 100644 ui/messages/htmlparser.go

(limited to 'ui/messages/htmlparser.go')

diff --git a/ui/messages/htmlparser.go b/ui/messages/htmlparser.go
new file mode 100644
index 0000000..0475e7a
--- /dev/null
+++ b/ui/messages/htmlparser.go
@@ -0,0 +1,136 @@
+// gomuks - A terminal Matrix client written in Go.
+// Copyright (C) 2018 Tulir Asokan
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU 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 General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package messages
+
+import (
+	"strings"
+
+	"golang.org/x/net/html"
+	"maunium.net/go/gomatrix"
+	"maunium.net/go/gomuks/debug"
+	"maunium.net/go/gomuks/ui/messages/tstring"
+	"maunium.net/go/tcell"
+)
+
+// TagArray is a reversed queue for remembering what HTML tags are open.
+type TagArray []string
+
+// Pushb converts the given byte array into a string and calls Push().
+func (ta *TagArray) Pushb(tag []byte) {
+	ta.Push(string(tag))
+}
+
+// Popb converts the given byte array into a string and calls Pop().
+func (ta *TagArray) Popb(tag []byte) {
+	ta.Pop(string(tag))
+}
+
+// Hasb converts the given byte array into a string and calls Has().
+func (ta *TagArray) Hasb(tag []byte) {
+	ta.Has(string(tag))
+}
+
+// HasAfterb converts the given byte array into a string and calls HasAfter().
+func (ta *TagArray) HasAfterb(tag []byte, after int) {
+	ta.HasAfter(string(tag), after)
+}
+
+// Push adds the given tag to the array.
+func (ta *TagArray) Push(tag string) {
+	*ta = append(*ta, "")
+	copy((*ta)[1:], *ta)
+	(*ta)[0] = tag
+}
+
+// Pop removes the given tag from the array.
+func (ta *TagArray) Pop(tag string) {
+	if (*ta)[0] == tag {
+		// This is the default case and is lighter than append(), so we handle it separately.
+		*ta = (*ta)[1:]
+	} else if index := ta.Has(tag); index != -1 {
+		*ta = append((*ta)[:index], (*ta)[index+1:]...)
+	}
+}
+
+// Has returns the first index where the given tag is, or -1 if it's not in the list.
+func (ta *TagArray) Has(tag string) int {
+	return ta.HasAfter(tag, -1)
+}
+
+// HasAfter returns the first index after the given index where the given tag is,
+// or -1 if the given tag is not on the list after the given index.
+func (ta *TagArray) HasAfter(tag string, after int) int {
+	for i := after + 1; i < len(*ta); i++ {
+		if (*ta)[i] == tag {
+			return i
+		}
+	}
+	return -1
+}
+
+// ParseHTMLMessage parses a HTML-formatted Matrix event into a UIMessage.
+func ParseHTMLMessage(evt *gomatrix.Event) tstring.TString {
+	//textData, _ := evt.Content["body"].(string)
+	htmlData, _ := evt.Content["formatted_body"].(string)
+
+	z := html.NewTokenizer(strings.NewReader(htmlData))
+	text := tstring.NewTString("")
+
+	openTags := &TagArray{}
+
+Loop:
+	for {
+		tt := z.Next()
+		switch tt {
+		case html.ErrorToken:
+			break Loop
+		case html.TextToken:
+			style := tcell.StyleDefault
+			for _, tag := range *openTags {
+				switch tag {
+				case "b", "strong":
+					style = style.Bold(true)
+				case "i", "em":
+					style = style.Italic(true)
+				case "s", "del":
+					style = style.Strikethrough(true)
+				case "u", "ins":
+					style = style.Underline(true)
+				}
+			}
+			text = text.AppendStyle(string(z.Text()), style)
+		case html.SelfClosingTagToken, html.StartTagToken:
+			tagb, _ := z.TagName()
+			tag := string(tagb)
+			switch tag {
+			case "br":
+				debug.Print("BR found")
+				debug.Print(text.String())
+				text = text.Append("\n")
+			default:
+				if tt == html.StartTagToken {
+					openTags.Push(tag)
+				}
+			}
+		case html.EndTagToken:
+			tagb, _ := z.TagName()
+			openTags.Popb(tagb)
+		}
+	}
+
+	return text
+}
-- 
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