#!/usr/bin/env ruby

require 'yaml'
require 'uri'
require 'net/http'
require 'openssl'
require 'rubygems/version'
require 'fspath'

# Fetch and compare latest tool/library versions
class Livecheck
  # Commands
  class Cli
    VERSION_REGEXP = /^([A-Z]+)_VER *:= *(.*)$/

    def initialize(args)
      @update = args.delete('--update')
      abort '--update is the only supported option' unless args.empty?
    end

    def run
      dump_changes

      return unless @update
      return unless livechecks.any?(&:changed?)

      update_changelog
      update_makefile
    end

  private

    def dump_changes
      livechecks.each do |lc|
        next unless lc.changed?
        puts "#{lc.name_n_latest_version} (current: #{lc.current_version})"
      end
    end

    def update_changelog
      changelog = FSPath('CHANGELOG.markdown')
      lines = changelog.readlines
      lines.insert(4, "\n") if lines[4] =~ /^## /
      lines.insert(4, changelog_entry)
      write(changelog, lines.join(''))
    end

    def update_makefile
      content = makefile.read.gsub(VERSION_REGEXP) do
        livecheck = livechecks_by_name[Regexp.last_match[1].downcase]
        "#{livecheck.name.upcase}_VER := #{livecheck.latest_version}"
      end
      write(makefile, content)
    end

    def makefile
      FSPath('Makefile')
    end

    def livechecks
      @livechecks ||= makefile.read.scan(VERSION_REGEXP).map do |name, version|
        Livecheck.new(name.downcase, version)
      end
    end

    def livechecks_by_name
      @livechecks_by_name ||= Hash[livechecks.map{ |lc| [lc.name, lc] }]
    end

    def changelog_entry
      github_user = `git config github.user`.strip
      changed = livechecks.select(&:changed?)
      %W[
        *
        #{to_sentence(changed.map(&:name_n_latest_version))}
        [@#{github_user}](https://github.com/#{github_user})
      ].join(' ') + "\n"
    end

    def to_sentence(array)
      case array.length
      when 0 then ''
      when 1 then array[0].to_s
      else "#{array[0...-1].join(', ')} and #{array[-1]}"
      end
    end

    def write(path, data)
      path.temp_file(path.dirname) do |io|
        io.write data
        io.path.rename(path)
      end
      warn "Wrote #{path}"
    end
  end

  # Compare versions including libjpeg ones (9b <=> 9)
  class Version
    include Comparable

    attr_reader :string, :parsed
    alias_method :to_s, :string

    def initialize(string)
      @string = string
      @parsed = begin
        Gem::Version.new(string)
      rescue ArgumentError
        nil
      end
    end

    def <=>(other)
      if parsed && other.parsed
        parsed <=> other.parsed
      else
        string <=> other.string
      end
    end
  end

  CONFIG = YAML.load(DATA).freeze

  attr_reader :name, :current_version

  def initialize(name, current_version)
    @name = name
    @current_version = Version.new(current_version)
    @fetcher = Thread.new{ fetch_versions.last }
  end

  def latest_version
    @fetcher.value
  end

  def changed?
    latest_version != current_version
  end

  def name_n_latest_version
    "#{name} #{latest_version}"
  end

private

  def config
    CONFIG[name] || fail(ArgumentError, "Livecheck for #{name} not defined")
  end

  def get(url)
    uri = URI(url)
    http = Net::HTTP.new(uri.host, uri.port)
    http.use_ssl = (uri.scheme == 'https')
    http.request_get(uri.request_uri).body
  end

  def fetch_versions
    body = get(config['url'])

    version_regex = Regexp.new(config['regexp'])

    versions = body.scan(version_regex).map{ |match| Version.new(*match) }.sort
    fail "No versions found for #{name} in body:\n#{body}" if versions.empty?

    versions
  end
end

Livecheck::Cli.new(ARGV).run

__END__
advancecomp:
  url: https://github.com/amadvance/advancecomp/releases.atom
  regexp: /amadvance/advancecomp/releases/tag/v(\d+(?:\.\d+)*)
gifsicle:
  url: https://www.lcdf.org/gifsicle/
  regexp: gifsicle-(\d+(?:\.\d+)*)\.tar\.gz
jhead:
  url: http://www.sentex.net/~mwandel/jhead/
  regexp: jhead-(\d+(?:\.\d+)*)
jpegoptim:
  url: https://www.kokkonen.net/tjko/src/
  regexp: jpegoptim-(\d+(?:\.\d+)*)
jpegarchive:
  url: https://github.com/danielgtaylor/jpeg-archive/releases.atom
  regexp: <title>JPEG-Archive (\d+(?:\.\d+)*)</title>
libjpeg:
  url: http://www.ijg.org/files/
  regexp: jpegsrc.v(.*?).tar.gz
libmozjpeg:
  url: https://github.com/mozilla/mozjpeg/releases.atom
  regexp: <title>mozjpeg v(\d+(?:\.\d+)*)</title>
libpng:
  url: https://sourceforge.net/projects/libpng/rss?path=/libpng16
  regexp: /libpng\d*/(\d+(?:\.\d+)*)/
libz:
  url: https://sourceforge.net/projects/libpng/rss?path=/zlib
  regexp: /zlib/(\d+(?:\.\d+)*)/
optipng:
  url: https://sourceforge.net/projects/optipng/rss
  regexp: /OptiPNG/optipng-(\d+(?:\.\d+)*)/
pngcrush:
  url: https://sourceforge.net/projects/pmt/rss?path=/pngcrush
  regexp: /pngcrush/(\d+(?:\.\d+)*)/
pngquant:
  url: https://github.com/pornel/pngquant/releases.atom
  regexp: /pornel/pngquant/releases/tag/(\d+(?:\.\d+)*)