From ff7aa4eef39c8f887710ef0b779bc3163a5cc5c5 Mon Sep 17 00:00:00 2001
From: ayntgl <90600421+ayntgl@users.noreply.github.com>
Date: Fri, 1 Oct 2021 15:07:33 +0400
Subject: [PATCH] feat: implement discord-flavored markdown renderer (#66)

---
 go.mod      |  2 +-
 go.sum      |  4 ++--
 renderer.go | 20 ++++++++++++++++++--
 3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/go.mod b/go.mod
index 720f48a..7981881 100644
--- a/go.mod
+++ b/go.mod
@@ -7,6 +7,6 @@ require (
 	github.com/ayntgl/discordgo v0.23.3-0.20210920064905-b79d709bbafb
 	github.com/gdamore/tcell/v2 v2.4.1-0.20210905002822-f057f0a857a1
 	github.com/gen2brain/beeep v0.0.0-20210529141713-5586760f0cc1
-	github.com/rivo/tview v0.0.0-20210923051754-2cb20002bc4c
+	github.com/rivo/tview v0.0.0-20211001102648-5508f4b00266
 	github.com/zalando/go-keyring v0.1.1
 )
diff --git a/go.sum b/go.sum
index 77a2a21..4ea87b1 100644
--- a/go.sum
+++ b/go.sum
@@ -33,8 +33,8 @@ github.com/nu7hatch/gouuid v0.0.0-20131221200532-179d4d0c4d8d h1:VhgPp6v9qf9Agr/
 github.com/nu7hatch/gouuid v0.0.0-20131221200532-179d4d0c4d8d/go.mod h1:YUTz3bUH2ZwIWBy3CJBeOBEugqcmXREj14T+iG/4k4U=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/rivo/tview v0.0.0-20210923051754-2cb20002bc4c h1:ye4bWm8SafYmr0DADOKSfeVZ1Swzm9aLW+baCOcHDWE=
-github.com/rivo/tview v0.0.0-20210923051754-2cb20002bc4c/go.mod h1:WIfMkQNY+oq/mWwtsjOYHIZBuwthioY2srOmljJkTnk=
+github.com/rivo/tview v0.0.0-20211001102648-5508f4b00266 h1:UrmGSzDIp4gfkDuMLdXk1Tx4FjS8GTWrWJjHfnS6GmY=
+github.com/rivo/tview v0.0.0-20211001102648-5508f4b00266/go.mod h1:WIfMkQNY+oq/mWwtsjOYHIZBuwthioY2srOmljJkTnk=
 github.com/rivo/uniseg v0.2.0 h1:S1pD9weZBuJdFmowNwbpi7BJ8TNftyUImj/0WQi72jY=
 github.com/rivo/uniseg v0.2.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
 github.com/stretchr/objx v0.1.0 h1:4G4v2dO3VZwixGIRoQ5Lfboy6nUhCyYzaqnIAPPhYs4=
diff --git a/renderer.go b/renderer.go
index 2c1f82d..51b602c 100644
--- a/renderer.go
+++ b/renderer.go
@@ -2,11 +2,17 @@ package main
 
 import (
 	"fmt"
+	"regexp"
 	"strings"
 
 	"github.com/ayntgl/discordgo"
 )
 
+var boldRegex = regexp.MustCompile(`(?m)\*\*(.*?)\*\*`)
+var italicRegex = regexp.MustCompile(`(?m)\*(.*?)\*`)
+var underlineRegex = regexp.MustCompile(`(?m)__(.*?)__`)
+var strikeThroughRegex = regexp.MustCompile(`(?m)~~(.*?)~~`)
+
 func renderMessages(cID string) {
 	ms, err := session.ChannelMessages(cID, conf.GetMessagesLimit, "", "", "")
 	if err != nil {
@@ -39,7 +45,7 @@ func renderMessage(m *discordgo.Message) {
 
 			if rm.Content != "" {
 				rm.Content = parseMentions(rm.Content, rm.Mentions)
-				b.WriteString(rm.Content)
+				b.WriteString(parseMarkdown(rm.Content))
 			}
 
 			b.WriteString("[::-]\n")
@@ -50,7 +56,7 @@ func renderMessage(m *discordgo.Message) {
 		// (users mentioned in the message) and render the message content.
 		if m.Content != "" {
 			m.Content = parseMentions(m.Content, m.Mentions)
-			b.WriteString(m.Content)
+			b.WriteString(parseMarkdown(m.Content))
 		}
 		// If the edited timestamp of the message is not empty; it implies that
 		// the message has been edited, hence render the message with edited
@@ -120,3 +126,13 @@ func parseAuthor(b *strings.Builder, u *discordgo.User) {
 		b.WriteString("[#EB459E]BOT[-] ")
 	}
 }
+
+func parseMarkdown(md string) string {
+	var res string
+	res = boldRegex.ReplaceAllString(md, "[::b]$1[::-]")
+	res = italicRegex.ReplaceAllString(res, "[::i]$1[::-]")
+	res = underlineRegex.ReplaceAllString(res, "[::u]$1[::-]")
+	res = strikeThroughRegex.ReplaceAllString(res, "[::s]$1[::-]")
+
+	return res
+}