From b2daf8e5d0d738fb0ec11b20bd992b29a42bc69f Mon Sep 17 00:00:00 2001
From: joshua stein <jcs@jcs.org>
Date: Sat, 27 May 2017 13:50:43 -0500
Subject: [PATCH] initial version

---
 id3chap.go | 119 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 119 insertions(+)
 create mode 100644 id3chap.go

diff --git a/id3chap.go b/id3chap.go
new file mode 100644
index 0000000..6a552ee
--- /dev/null
+++ b/id3chap.go
@@ -0,0 +1,119 @@
+//
+// id3chap
+// Copyright (c) 2017 joshua stein <jcs@jcs.org>
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions
+// are met:
+//
+// 1. Redistributions of source code must retain the above copyright
+//    notice, this list of conditions and the following disclaimer.
+// 2. Redistributions in binary form must reproduce the above copyright
+//    notice, this list of conditions and the following disclaimer in the
+//    documentation and/or other materials provided with the distribution.
+// 3. The name of the author may not be used to endorse or promote products
+//    derived from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+// IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+// OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+// IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+// NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+// THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+
+package main
+
+import (
+	"fmt"
+	id3 "github.com/jcs/id3-go"
+	id3v2 "github.com/jcs/id3-go/v2"
+	"os"
+	"strconv"
+)
+
+type Chapter struct {
+	element   string
+	startSecs uint32
+	endSecs   uint32
+	title     string
+}
+
+func usage() {
+	fmt.Printf("%s: <mp3 file> [<start seconds> <chapter label> ...]\n", os.Args[0])
+	os.Exit(1)
+}
+
+func main() {
+	if len(os.Args) < 4 {
+		usage()
+	}
+
+	fn := os.Args[1]
+	mp3, err := id3.Open(fn)
+	if err != nil {
+		fmt.Errorf("can't open %s: %s", fn, err)
+	}
+
+	chaps := make([]Chapter, 0)
+	tocchaps := make([]string, 0)
+
+	for x := 2; x < len(os.Args)-1; x += 2 {
+		if x+1 > len(os.Args)-2+1 {
+			usage()
+		}
+
+		startSecs, err := strconv.ParseUint(os.Args[x], 10, 32)
+		if err != nil {
+			fmt.Errorf("failed parsing seconds %#v: %v", os.Args[x], err)
+		}
+
+		element := fmt.Sprintf("chp%d", len(chaps))
+		tocchaps = append(tocchaps, element)
+
+		chap := Chapter{element, uint32(startSecs * 1000), 0, os.Args[x+1]}
+		chaps = append(chaps, chap)
+	}
+
+	// each chapter ends where the next one starts
+	for x := range chaps {
+		if x < len(chaps)-1 {
+			chaps[x].endSecs = chaps[x+1].startSecs
+		}
+	}
+
+	// and the last one ends when the file does
+	tlenf := mp3.Frame("TLEN")
+	if tlenf == nil {
+		fmt.Errorf("can't find TLEN frame, don't know total duration")
+	}
+	tlenft := tlenf.(*id3v2.TextFrame)
+	tlen, err := strconv.ParseUint(tlenft.Text(), 10, 32)
+	if err == nil {
+		fmt.Errorf("can't parse TLEN value %#v\n", tlenft.Text())
+	}
+
+	chaps[len(chaps)-1].endSecs = uint32(tlen)
+
+	// ready to modify the file, clear out what's there
+	mp3.DeleteFrames("CTOC")
+	mp3.DeleteFrames("CHAP")
+
+	// add each chapter
+	chapft := id3v2.V23FrameTypeMap["CHAP"]
+	for _, c := range chaps {
+		ch := id3v2.NewChapterFrame(chapft, c.element, c.startSecs, c.endSecs, 0, 0, true, c.title, "", "")
+		mp3.AddFrames(ch)
+	}
+
+	// build a new TOC referencing each chapter
+	ctocft := id3v2.V23FrameTypeMap["CTOC"]
+	toc := id3v2.NewTOCFrame(ctocft, "toc", true, true, tocchaps)
+	mp3.AddFrames(toc)
+
+	mp3.Close()
+}