From e2854cac2f1923714b98fb6820742c2a0e4ec02a Mon Sep 17 00:00:00 2001
From: Bill Thiede <git@xinu.tv>
Date: Tue, 26 Dec 2017 12:33:33 -0800
Subject: [PATCH] Simple mbox parser.

---
 cmd/mbox2maildir/mbox2maildir.go      | 65 +++++++++++++++++++++++++++
 cmd/mbox2maildir/mbox2maildir_test.go | 51 +++++++++++++++++++++
 2 files changed, 116 insertions(+)
 create mode 100644 cmd/mbox2maildir/mbox2maildir.go
 create mode 100644 cmd/mbox2maildir/mbox2maildir_test.go

diff --git a/cmd/mbox2maildir/mbox2maildir.go b/cmd/mbox2maildir/mbox2maildir.go
new file mode 100644
index 0000000..ab558ba
--- /dev/null
+++ b/cmd/mbox2maildir/mbox2maildir.go
@@ -0,0 +1,65 @@
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"flag"
+	"io"
+	"os"
+
+	"github.com/golang/glog"
+)
+
+func writeMailderFile(b []byte) error { return nil }
+
+func parse(r io.Reader, writeMessage func(b []byte) error) error {
+	from := []byte("From ")
+	scanner := bufio.NewScanner(r)
+	buf := new(bytes.Buffer)
+	for scanner.Scan() {
+		b := scanner.Bytes()
+		if bytes.HasPrefix(b, from) {
+			// New message
+			if buf.Len() > 0 {
+				msg := buf.Bytes()
+				// Trim empty line from end of mbox message
+				msg = msg[:len(msg)-1]
+				if err := writeMessage(msg); err != nil {
+					return err
+				}
+			}
+			buf.Reset()
+		}
+		buf.Write(b)
+		buf.Write([]byte("\n"))
+	}
+	if buf.Len() > 0 {
+		if err := writeMessage(buf.Bytes()); err != nil {
+			return err
+		}
+	}
+	return scanner.Err()
+}
+
+func parseFile(p string) error {
+	r, err := os.Open(p)
+	if err != nil {
+		return err
+	}
+	defer r.Close()
+
+	if err := parse(r, writeMailderFile); err != nil {
+		return err
+	}
+
+	return nil
+}
+func main() {
+	flag.Parse()
+	defer glog.Flush()
+	for _, path := range flag.Args() {
+		if err := parseFile(path); err != nil {
+			glog.Errorf("Failed to parse %q: %v", err)
+		}
+	}
+}
diff --git a/cmd/mbox2maildir/mbox2maildir_test.go b/cmd/mbox2maildir/mbox2maildir_test.go
new file mode 100644
index 0000000..088a059
--- /dev/null
+++ b/cmd/mbox2maildir/mbox2maildir_test.go
@@ -0,0 +1,51 @@
+package main
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+)
+
+func TestParse(t *testing.T) {
+	const input = `From user1
+
+Body 1
+
+From user2
+
+Body 2 with From in it.
+
+From user3
+
+Body 3
+`
+	wants := []string{
+		`From user1
+
+Body 1
+`,
+		`From user2
+
+Body 2 with From in it.
+`,
+		`From user3
+
+Body 3
+`,
+	}
+	msgN := 0
+	testWriteMessage := func(got []byte) error {
+		want := wants[msgN]
+		if !bytes.Equal([]byte(want), got) {
+			t.Errorf("msg[%d] = %q, want %q", msgN, got, want)
+		}
+		msgN++
+		return nil
+	}
+	if err := parse(strings.NewReader(input), testWriteMessage); err != nil {
+		t.Errorf("parse() failed: %v", err)
+	}
+	if msgN != len(wants) {
+		t.Errorf("Parsed %d messages, expected %d", msgN, len(wants))
+	}
+}