class Gem::Commands::UnpackCommand

def arguments # :nodoc:
  "GEMNAME       name of gem to unpack"
end

def defaults_str # :nodoc:
  "--version '#{Gem::Requirement.default}'"
end

def description
  <<-EOF
e unpack command allows you to examine the contents of a gem or modify
em to help diagnose a bug.
u can add the contents of the unpacked gem to the load path using the
BYLIB environment variable or -I:
$ gem unpack my_gem
Unpacked gem: '.../my_gem-1.0'
[edit my_gem-1.0/lib/my_gem.rb]
$ ruby -Imy_gem-1.0/lib -S other_program
u can repackage an unpacked gem using the build command.  See the build
mmand help for an example.
  EOF
end

def execute
  security_policy = options[:security_policy]
  get_all_gem_names.each do |name|
    dependency = Gem::Dependency.new name, options[:version]
    path = get_path dependency
    unless path
      alert_error "Gem '#{name}' not installed nor fetchable."
      next
    end
    if @options[:spec]
      spec, metadata = Gem::Package.raw_spec(path, security_policy)
      if metadata.nil?
        alert_error "--spec is unsupported on '#{name}' (old format gem)"
        next
      end
      spec_file = File.basename spec.spec_file
      FileUtils.mkdir_p @options[:target] if @options[:target]
      destination = if @options[:target]
        File.join @options[:target], spec_file
      else
        spec_file
      end
      File.open destination, "w" do |io|
        io.write metadata
      end
    else
      basename = File.basename path, ".gem"
      target_dir = File.expand_path basename, options[:target]
      package = Gem::Package.new path, security_policy
      package.extract_files target_dir
      say "Unpacked gem: '#{target_dir}'"
    end
  end
end

def find_in_cache(filename)
  Gem.path.each do |path|
    this_path = File.join(path, "cache", filename)
    return this_path if File.exist? this_path
  end
  nil
end

def get_path(dependency)
  return dependency.name if /\.gem$/i.match?(dependency.name)
  specs = dependency.matching_specs
  selected = specs.max_by(&:version)
  return Gem::RemoteFetcher.fetcher.download_to_cache(dependency) unless
    selected
  return unless /^#{selected.name}$/i.match?(dependency.name)
  # We expect to find (basename).gem in the 'cache' directory.  Furthermore,
  # the name match must be exact (ignoring case).
  path = find_in_cache File.basename selected.cache_file
  return Gem::RemoteFetcher.fetcher.download_to_cache(dependency) unless path
  path
end

def initialize
  require "fileutils"
  super "unpack", "Unpack an installed gem to the current directory",
        version: Gem::Requirement.default,
        target: Dir.pwd
  add_option("--target=DIR",
             "target directory for unpacking") do |value, options|
    options[:target] = value
  end
  add_option("--spec", "unpack the gem specification") do |_value, options|
    options[:spec] = true
  end
  add_security_option
  add_version_option
end

def usage # :nodoc:
  "#{program_name} GEMNAME"
end