Merge downpour.com m4b files

downpour_merge.sh

#!/bin/bash
# Merges downpour.com m4b files into a single m4b file per book.

# Directions:
# download m4b files from downpour.com
# cd into the directory with "Book Title ...[File # of #].m4b
# run with no arguments

# Multiple books may all be downloaded into the same directory.
# Previously combined books may still exist in the same directory.
# The filenames from the web site do not need to be changed or cleaned up.
# (they may contain () [] " ' & ! etc)

# Extracts the cover art from "...[File 1 of #].m4b"
# Combines all m4b files and re-embeds the extracted cover image
# Outputs "Book Title.m4b"
# Optionally moves the source m4b files to orig/ or deletes them

# true = move original files to ./orig/
# false = delete original files
keep_src=false

abrt () { printf '%s: %s' "$0" "$@" >&2 ; exit 1 ; }

mp4art --version || abrt "Please install mp4art (https://github.com/enzo1982/mp4v2)"
m4b-tool --version || abrt "Please install m4b-tool (https://github.com/sandreas/m4b-tool)"

${keep_src} && { [[ -d orig ]] || mkdir orig || abrt "failed mkdir orig" ; }

for f in *File\ 1\ of\ *.m4b ;do
	title=${f%(*}
	title=${title% *}
	echo "\"$title\""

	# FIXME don't rely on globbing for sort order
	# FIXME don't proceed if any parts missing
	infiles=("${title}"\ \(*File\ *\ of\ *.m4b)
	outfile="${title}.m4b"
	[[ ${infiles[0]} =~ '[File 1 of 1].m4b' ]] && {
		mv -v "${infiles[0]}" "${outfile}"
		:
	} || {
		mp4art --extract "${infiles[0]}" || abrt "failed mp4art --extract"
		x=("${title}"*.art\[0\].jpg)
		cover=${x[0]}
		[[ -s ${cover} ]] || {
			cover=${title}.jpg
			printf 'No cover art found in "%s".\nPlease place "%s" in the current directory.\n' "${infiles[0]}" "${cover}"
			read -p "Then press Enter when ready: "
			[[ -s ${cover} ]] || abrt "Missing \"${cover}\""
		}

		m4b-tool merge --verbose --no-conversion --cover="${cover}" --output-file="${outfile}" -- "${infiles[@]}" || exit 1
		[[ -s ${outfile} ]] || abrt "Failed \"${outfile}\""

		rm "${cover}"
		${keep_src} && { mv -v "${infiles[@]}" orig ; : ; } || rm -v "${infiles[@]}"
	}

done