From 7de332c2bb5cddf6591b93b16e536b845ea7ab76 Mon Sep 17 00:00:00 2001
From: Simon Ser <contact@emersion.fr>
Date: Tue, 25 Feb 2020 18:16:26 +0100
Subject: [PATCH] plugins/viewtext: linkify plaintext messages

---
 go.mod                     |  1 +
 go.sum                     |  2 +
 plugins/viewtext/viewer.go | 99 ++++++++++++++++++++++++++++++++------
 3 files changed, 87 insertions(+), 15 deletions(-)

diff --git a/go.mod b/go.mod
index 2dc7ba1..3035f2e 100644
--- a/go.mod
+++ b/go.mod
@@ -21,6 +21,7 @@ require (
 	github.com/mattn/go-isatty v0.0.12 // indirect
 	github.com/microcosm-cc/bluemonday v1.0.2
 	github.com/yuin/gopher-lua v0.0.0-20191220021717-ab39c6098bdb
+	gitlab.com/golang-commonmark/linkify v0.0.0-20191026162114-a0c2df6c8f82
 	golang.org/x/crypto v0.0.0-20200210222208-86ce3cb69678 // indirect
 	golang.org/x/net v0.0.0-20200202094626-16171245cfb2
 	golang.org/x/sys v0.0.0-20200212091648-12a6c2dcc1e4 // indirect
diff --git a/go.sum b/go.sum
index 67a10ac..50b1faa 100644
--- a/go.sum
+++ b/go.sum
@@ -67,6 +67,8 @@ github.com/valyala/fasttemplate v1.1.0/go.mod h1:UQGH1tvbgY+Nz5t2n7tXsz52dQxojPU
 github.com/yuin/gopher-lua v0.0.0-20190206043414-8bfc7677f583/go.mod h1:gqRgreBUhTSL0GeU64rtZ3Uq3wtjOa/TB2YfrtkCbVQ=
 github.com/yuin/gopher-lua v0.0.0-20191220021717-ab39c6098bdb h1:ZkM6LRnq40pR1Ox0hTHlnpkcOTuFIDQpZ1IN8rKKhX0=
 github.com/yuin/gopher-lua v0.0.0-20191220021717-ab39c6098bdb/go.mod h1:gqRgreBUhTSL0GeU64rtZ3Uq3wtjOa/TB2YfrtkCbVQ=
+gitlab.com/golang-commonmark/linkify v0.0.0-20191026162114-a0c2df6c8f82 h1:oYrL81N608MLZhma3ruL8qTM4xcpYECGut8KSxRY59g=
+gitlab.com/golang-commonmark/linkify v0.0.0-20191026162114-a0c2df6c8f82/go.mod h1:Gn+LZmCrhPECMD3SOKlE+BOHwhOYD9j7WT9NUtkCrC8=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20191227163750-53104e6ec876/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/crypto v0.0.0-20200210222208-86ce3cb69678 h1:wCWoJcFExDgyYx2m2hpHgwz8W3+FPdfldvIgzqDIhyg=
diff --git a/plugins/viewtext/viewer.go b/plugins/viewtext/viewer.go
index cca38a8..9a91f08 100644
--- a/plugins/viewtext/viewer.go
+++ b/plugins/viewtext/viewer.go
@@ -1,21 +1,55 @@
 package koushinviewtext
 
 import (
-	"bytes"
+	"bufio"
 	"fmt"
 	"html/template"
-	"io/ioutil"
+	"net/url"
 	"strings"
 
 	"git.sr.ht/~emersion/koushin"
 	koushinbase "git.sr.ht/~emersion/koushin/plugins/base"
 	"github.com/emersion/go-message"
+	"gitlab.com/golang-commonmark/linkify"
 )
 
 // TODO: dim quotes and "On xxx, xxx wrote:" lines
-// TODO: turn URLs into links
 
-const tpl = `<pre>{{.}}</pre>`
+const (
+	tplStr     = `<pre>{{range .}}{{.}}{{end}}</pre>`
+	linkTplStr = `<a href="{{.Href}}" target="_blank" rel="nofollow noopener">{{.Text}}</a>`
+)
+
+var tpl *template.Template
+
+func init() {
+	tpl = template.Must(template.New("view-text.html").Parse(tplStr))
+	template.Must(tpl.New("view-text-link.html").Parse(linkTplStr))
+}
+
+type linkRenderData struct {
+	Href string
+	Text string
+}
+
+var allowedSchemes = map[string]bool{
+	"http":   true,
+	"https":  true,
+	"mailto": true,
+	"ftp":    true,
+	"sftp":   true,
+	"ftps":   true,
+	"tel":    true,
+}
+
+func executeTemplate(name string, data interface{}) (template.HTML, error) {
+	var sb strings.Builder
+	err := tpl.ExecuteTemplate(&sb, name, data)
+	if err != nil {
+		return "", err
+	}
+	return template.HTML(sb.String()), nil
+}
 
 type viewer struct{}
 
@@ -28,20 +62,55 @@ func (viewer) ViewMessagePart(ctx *koushin.Context, msg *koushinbase.IMAPMessage
 		return nil, koushinbase.ErrViewUnsupported
 	}
 
-	body, err := ioutil.ReadAll(part.Body)
-	if err != nil {
+	var tokens []interface{}
+	scanner := bufio.NewScanner(part.Body)
+	for scanner.Scan() {
+		l := scanner.Text()
+
+		i := 0
+		for _, link := range linkify.Links(l) {
+			href := l[link.Start:link.End]
+			if link.Scheme == "" {
+				href = "https://" + href
+			} else if !strings.HasPrefix(href, link.Scheme) {
+				href = link.Scheme + href
+			}
+
+			u, err := url.Parse(href)
+			if err != nil {
+				continue
+			}
+
+			if !allowedSchemes[u.Scheme] {
+				continue
+			}
+
+			// TODO: redirect mailto links to the composer
+
+			if i < link.Start {
+				tokens = append(tokens, l[i:link.Start])
+			}
+			tok, err := executeTemplate("view-text-link.html", linkRenderData{
+				Href: href,
+				Text: l[link.Start:link.End],
+			})
+			if err != nil {
+				return nil, err
+			}
+			tokens = append(tokens, tok)
+			i = link.End
+		}
+		if i < len(l) {
+			tokens = append(tokens, l[i:])
+		}
+
+		tokens = append(tokens, "\n")
+	}
+	if err := scanner.Err(); err != nil {
 		return nil, fmt.Errorf("failed to read part body: %v", err)
 	}
 
-	t := template.Must(template.New("view-text.html").Parse(tpl))
-
-	var buf bytes.Buffer
-	err = t.Execute(&buf, string(body))
-	if err != nil {
-		return nil, err
-	}
-
-	return template.HTML(buf.String()), nil
+	return executeTemplate("view-text.html", tokens)
 }
 
 func init() {