downcode

#!/usr/bin/env ruby
#encoding: utf-8
#
# Copyright 2011-4 James Pharaoh <james@phsys.co.uk>
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

require "rubygems"

require "fileutils"
require "id3lib"
require "ogginfo"
require "optparse"
require "pp"
require "set"

def sq str
	return str if str =~ /^[-a-zA-Z0-9_\/:.=@]+$/
	return "'" + str.gsub("'", "'\\\\''") + "'" unless str =~ /'/
	return "\"" + str.gsub("\\", "\\\\\\\\").gsub("\"", "\\\\\"").gsub("`", "\\\\`").gsub("$", "\\\\$") + "\""
end

class DowncodeScript

	DEFAULT_MAPPINGS = {
		"*" => "_",
		"\"" => "''",
		"\\" => "_",
		"?" => "_",
		":" => "_",
		"é" => "e",
	}

	attr_accessor :args
	attr_accessor :status
	attr_accessor :mappings

	def initialize
		@mappings = DEFAULT_MAPPINGS
	end

	def main
		process_args
		scan_source
		delete_files
		downcode_files
	end

	def process_args
		@opts = {}
		op = OptionParser.new do |opts|
			opts.banner = "Usage: #{File.basename $0} [OPTIONS]"
			opts.on "-s", "--source DIR", "Source directory - required" do |arg|
				@opts[:source] and raise "Can't specify multiple sources"
				@opts[:source] = arg.gsub /\/$/, ""
			end
			opts.on "-d", "--destination DIR", "Destination directory - required" do |arg|
				@opts[:dest] and raise "Can't specify multiple destinations"
				@opts[:dest] = arg.gsub /\/$/, ""
			end
			@opts[:delete] = false
			opts.on "--delete", "Delete removed files" do
				@opts[:delete] = true
			end
			@opts[:leeway] = 10
			opts.on "--leeway PERCENT", "Use original file if it's less than this much bigger than the re-encoded " +
					"version" do |arg|
				@opts[:leeway] = arg.to_i
			end
		end
		op.parse! @args
		@opts[:source] or raise "Must specify source"
		@opts[:dest] or raise "Must specify destination"
	end

	def map string
		ret = ""
		string.each_char do |ch|
			ret += @mappings[ch] ? @mappings[ch] : ch
		end
		return ret
	end

	def scan_source
		@todo = []
		@delete = []
		up_to_date = 0
		skipped = {}
		dsts = Set.new

		Dir["#{@opts[:source]}/**/*"].each do |src|

			# work out dest filename and remember it
			dst = @opts[:dest] + map(src[@opts[:source].length..-1])
			dsts << dst

			# skip directories
			next if File.directory? src

			# check the extension
			src =~ /^.+\.([^.]+)$/
			ext = $1
			if [ "mp3", "ogg" ].include? ext

				# add to update list or no update count
				if File.exist?(dst) && File.mtime(src) < File.mtime(dst)
					up_to_date += 1
				else
					@todo << [ src, dst, ext ]
				end

			else

				# add to skipped list
				skipped[ext] ||= 0
				skipped[ext] += 1

			end
		end

		Dir["#{@opts[:dest]}/**/*"].each do |dst|
			next if dsts.include? dst
			next if dst =~ /\.(lock|tmp|tmp1)$/
			@delete << dst
		end

		puts "Files to convert: #{@todo.size}"
		puts "Files to delete: #{@delete.size}"
		puts "Already up to date: #{up_to_date}"

		skipped.each do |ext, count|
			if ext
				puts "Skipped with extension #{ext}: #{count}"
			else
				puts "Skipped with no extension: #{count}"
			end
		end

		puts "Use original leeway: #{@opts[:leeway]}%"

	end

	def delete_files

		unless @opts[:delete]
			puts "Skipping delete stage (specify --delete to not skip)"
			return
		end

		@delete.each do |dst|
			puts "Deleting #{dst}"
			if File.directory? dst
				FileUtils.rm_r dst
			elsif File.exists? dst
				File.delete dst
			end
		end

	end

	def downcode_mp3 src, dst, tmp, tmp1

		system "
			lame \
				--preset fast medium \
				#{sq src} \
				#{sq tmp}
		" or raise "Error"

		tmp_size = File.size tmp
		src_size = File.size src
		use_copy = src_size < tmp_size * (100 + @opts[:leeway]) / 100

		if use_copy
			puts "using copy instead"
			FileUtils.cp src, tmp
		end

		unless use_copy
			puts "copying id3 tag"
			src_tag = ID3Lib::Tag.new src
			tmp_tag = ID3Lib::Tag.new tmp
			src_tag.each do |frame| tmp_tag << frame end
			tmp_tag.update!
		end
	end

	def downcode_ogg src, dst, tmp, tmp1

		# downcode

		system "oggdec #{sq src} --output #{sq tmp1}" or raise "Error"
		system "oggenc --quality 4 #{sq tmp1} --output #{sq tmp}" or raise "Error"

		# check size

		tmp_size = File.size tmp
		src_size = File.size src

		use_copy = src_size < tmp_size * (100 + @opts[:leeway]) / 100

		# use copy if appropriate

		if use_copy
			puts "using copy instead"
			FileUtils.cp src, tmp
		end

		# copy metadata unless it's a copy

		unless use_copy

			puts "copying ogg comments"

			comments = []

			%x[ oggz comment --list #{sq src} ].split("\n").each do |line|
				next unless line =~ /\t([A-Z0-9_]+): (.*)$/
				name, value = $1, $2
				comments << "#{sq name}=#{sq value}"
			end

			system "
				oggz comment \
					--content-type vorbis \
					--output #{sq tmp1} \
					#{sq tmp} \
					#{comments.join " "}
			" or raise "Error"

			FileUtils.mv tmp1, tmp

		end

	end

	def downcode_file src, dst, ext

		wav = "#{dst}.wav"
		tmp = "#{dst}.tmp"
		tmp1 = "#{dst}.tmp1"
		lock = "#{dst}.lock"

		lock_fp = nil

		FileUtils.mkdir_p File.dirname dst

		lock_fp = File.open(lock, File::RDWR|File::CREAT, 0644)
		val = lock_fp.flock(File::LOCK_EX|File::LOCK_NB)

		begin

			puts ""
			puts "----------------------------------------------------------------------"
			puts "#{File.basename src}"
			puts "----------------------------------------------------------------------"
			puts ""

			respond_to? "downcode_#{ext}" \
				or raise "File extension #{ext} not supported"

			send "downcode_#{ext}", src, dst, tmp, tmp1
			FileUtils.mv tmp, dst

		rescue
			@errors << src

		ensure

			File.delete wav if File.exist? wav
			File.delete tmp if File.exist? tmp
			File.delete tmp1 if File.exist? tmp1

			if File.exist? lock
				lock_fp.close
				File.delete lock
			end

		end

	end

	def downcode_files

		@errors = []

		@todo.each do |src, dst, ext|
			downcode_file src, dst, ext
		end

	end

end

script = DowncodeScript.new
script.args = ARGV
script.main
exit script.status || 0