#!/usr/bin/env ruby

# BEGIN: Includes & Requires

require 'erb'
require 'json'
require 'net/http'
require 'English'
require 'rubygems/package'
require 'fileutils'
require 'optparse'

# END: Includes & Requires





# BEGIN: Overrides

class Dir
  def / (path)
    output_path = File.absolute_path(self.path) + '/' + path
    if File.directory? output_path
      Dir.new(output_path)
    else
      output_path
    end
  end
end

class String
  def / (other)
    self + '/' + other
  end
end

# END: Overrides



# BEGIN: Variables
URL_DOWNLOAD_BASE='https://dl.discordapp.net/apps/linux/{VERSION}/discord-{VERSION}.tar.gz'
DOWNLOAD_URL='https://discord.com/api/download/stable?platform=linux&format=tar.gz'

$CONFIG = Hash.new
$CONFIG[:icon_dir] = Dir.new(Dir.home) / '.local' / 'share' / 'icons'
File.mkdir($CONFIG[:icon_dir]) if not File.exist?($CONFIG[:icon_dir])
$CONFIG[:local_application_install_dir] = Dir.new(Dir.home) / '.local' / 'share' / 'applications'
File.mkdir($CONFIG[:local_application_install_dir]) if not File.exist?($CONFIG[:local_application_install_dir])
$CONFIG[:desktop_path] = Dir.new(Dir.home) / '.local' / 'share' / 'applications' / 'discord.desktop'
$CONFIG[:install_dir] = Dir.new(Dir.home) / '.opt'
File.mkdir($CONFIG[:install_dir]) if not File.exist?($CONFIG[:install_dir])
$CONFIG[:discord_path] = $CONFIG[:install_dir] / 'Discord'
$CONFIG[:desktop_file_path] = $CONFIG[:discord_path] / 'discord.desktop'
$CONFIG[:discord_version_file] = $CONFIG[:discord_path] / 'resources' / 'build_info.json'
$CONFIG[:action] = 'install'
$CONFIG[:keep_installer] = false
DISCORD_DESKTOP_CONTENTS=<<EOF
[Desktop Entry]
Name=Discord
StartupWMClass=discord
Comment=All-in-one voice and text chat for gamers that's free, secure, and works on both your desktop and phone.
GenericName=Internet Messenger
Exec=#{$CONFIG[:install_dir].path}/Discord/Discord
Icon=discord
Type=Application
Categories=Network;InstantMessaging;
Path=#{$CONFIG[:install_dir].path}/Discord
EOF
# END: Variables



# BEGIN: Handle CLI ARgs

OptionParser.new do |parser|
  parser.banner = "#{ File.basename($0) } [action]"
  parser.separator ""
  parser.separator "  Actions"
  parser.separator "------------------------------------------------------------------------"

  parser.on('-c', '--check', "Check and report installed & remote versions") do 
    $CONFIG[:action] = 'check'
  end

  parser.on('-i', '--install', "Check for & Install new version of discord (default)") do 
    $CONFIG[:action] = 'install'
  end

  parser.separator ""
  parser.separator "  General Flags"
  parser.separator "------------------------------------------------------------------------"
  parser.on('-h', '--help', "Show this help output") do 
    puts parser
    exit
  end
  parser.on('--keep', 'Keep discord tar.gz file (default: False)') do 
    $CONFIG[:keep_installer] = true
  end

end.parse!

# BEGIN: Handle CLI ARgs




# BEGIN: Helper Functions

def get_remote_version
  uri = URI(DOWNLOAD_URL)
  response = Net::HTTP.get(uri)
  if response =~ /discord-(?<version>\d+\.\d+\.\d+).tar.gz/
    Gem::Version.new($LAST_MATCH_INFO['version'])
  else
    raise "Failed to retrieve remote version"
  end
end

def get_local_version
  if File.exist? $CONFIG[:discord_version_file]
    data = JSON.load_file($CONFIG[:discord_version_file])
    Gem::Version.new(data['version'])
  else
    Gem::Version.new('0.0.0')
  end
end

def download_installer(version)
  uri = URI(URL_DOWNLOAD_BASE.gsub('{VERSION}', version.to_s))
  puts "download_installer: Downloading The discord #{version.to_s} tar.gz"
  file_contents = Net::HTTP.get(uri)
  output_file = "discord-#{version}.tar.gz"
  puts "download_installer: Output file will #{output_file}"
  $CONFIG[:install_dir].chdir do 
    File.open(output_file, 'wb') do |file|
      file.write(file_contents)
    end
  end
  puts "download_installer: tar.gz was downloaded"
end

def do_install(version)
  installer_file = "discord-#{version}.tar.gz"
  puts "do_install: Extracting new installer"
  $CONFIG[:install_dir].chdir do 
    File.open(installer_file, 'rb') do |file|
      Gem::Package.new("").extract_tar_gz(file, $CONFIG[:install_dir])
    end
  end

  if not $CONFIG[:keep_installer]
    puts "do_install: Removing new installer (#{installer_file})"
    File.unlink(installer_file)
  end
end

def update_desktop_file
  file_needs_updating = true
  puts "update_desktop_file: Checking if desktop entry needs updating"
  if File.exist?($CONFIG[:desktop_path])  
    puts "update_desktop_file: Desktop file exists, checking if it matches template"
    File.open($CONFIG[:desktop_path], 'r') do |file|
      if file.read() == DISCORD_DESKTOP_CONTENTS
        puts "update_desktop_file: Desktop file matches template. Not updating"
        file_needs_updating = false
      end
    end
  end

  if file_needs_updating
    File.open($CONFIG[:desktop_path], 'w') do |file|
      puts "update_desktop_file: Desktop File was written"
      file.write(DISCORD_DESKTOP_CONTENTS)
    end

    puts "update_desktop_file: Triggering desktop to install new desktop entry and refresh entries"
    %x[ desktop-file-install --dir=#{$CONFIG[:local_application_install_dir].path} #{$CONFIG[:desktop_path]} ]
  end
end

# END: Helper Functions



# BEGIN: Work

local_version = get_local_version
remote_version = get_remote_version

case $CONFIG[:action]
  when 'install'
    if local_version < remote_version
      puts "main: Installed Version will be updated"
      download_installer(remote_version)
      do_install(remote_version)
    elsif local_version == remote_version
      puts "main: Installed Version is up-to-date"
    else
      puts "main: What?"
    end
  when 'check'
    puts
    puts "  Report"
    puts "-------------------------------------"
    puts "  Remote Version: #{remote_version.to_s}"
    puts "   Local Version: #{local_version.to_s}"
    puts "  Needs Updating: #{(remote_version > local_version) ? "Yes" : "No"}"
end

# END: Work