cmd/emaildecode: CLI to decode email body to plain text

The emaildecode accept file as input.
If the email header contains content-transfer-encoding with value
quoted-printable or base64, it will decode the message body and print it
to stdout as plain text.

2 files changed, 92 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
index 7faf3c6e..14402872 100644
--- a/.gitignore
+++ b/.gitignore
@@ -17,6 +17,7 @@
 *.zst
 /_bin/ansua
 /_bin/bcrypt
+/_bin/emaildecode
 /_bin/epoch
 /_bin/gofmtcomment
 /_bin/hexo
diff --git a/cmd/emaildecode/main.go b/cmd/emaildecode/main.go
new file mode 100644
index 00000000..970af753
--- /dev/null
+++ b/cmd/emaildecode/main.go
@@ -0,0 +1,91 @@
+// Copyright 2023, Shulhan <ms@kilabit.info>. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Program emaildecode convert the email body from quoted-printable to plain
+// text.
+// Usage,
+//
+//	emaildecode <file>
+//
+// The emaildecode accept single file as input, read its content, decode the
+// body based on Content-Transfer-Encoding, and then print each body to
+// standard output.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"os"
+
+	"git.sr.ht/~shulhan/pakakeh.go"
+	"git.sr.ht/~shulhan/pakakeh.go/lib/email"
+)
+
+var usage = `= emaildecode - CLI to decode email body
+
+== USAGE
+
+	emaildecode <COMMAND | FILE>
+
+List of accepted COMMANDS,
+
+	help - print the usage.
+
+FILE
+	The file that contains email to be decoded.
+
+== INFO
+
+Version: ` + pakakeh.Version + `
+Website: https://sr.ht/~shulhan/pakakeh.go/
+`
+
+const (
+	cmdHelp = `help`
+)
+
+func main() {
+	flag.Parse()
+
+	var fileInput = flag.Arg(0)
+	if len(fileInput) == 0 {
+		log.Fatalf(`missing file input`)
+	}
+
+	switch fileInput {
+	case cmdHelp:
+		fmt.Println(usage)
+		os.Exit(0)
+	}
+
+	var (
+		msg *email.Message
+		err error
+	)
+
+	msg, _, err = email.ParseFile(fileInput)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	var (
+		mime  *email.MIME
+		field *email.Field
+		x     int
+	)
+	for _, field = range msg.Header.Fields {
+		fmt.Printf(`%s: %s`, field.Name, field.Value)
+	}
+	for x, mime = range msg.Body.Parts {
+		fmt.Printf("\n-- mime #%d\n\n", x)
+		if mime.Header != nil {
+			for _, field = range mime.Header.Fields {
+				fmt.Printf(`%s: %s`, field.Name, field.Value)
+			}
+			fmt.Println(``)
+		}
+		fmt.Println(string(mime.Content))
+	}
+}