require 'rubygems/command'
require 'rubygems/local_remote_options'
require 'rubygems/version_option'

class Gem::Commands::DependencyCommand < Gem::Command

  include Gem::LocalRemoteOptions
  include Gem::VersionOption

  def initialize
    super 'dependency',
          'Show the dependencies of an installed gem',
          :version => Gem::Requirement.default, :domain => :local

    add_version_option
    add_platform_option
    add_prerelease_option

    add_option('-R', '--[no-]reverse-dependencies',
               'Include reverse dependencies in the output') do
      |value, options|
      options[:reverse_dependencies] = value
    end

    add_option('-p', '--pipe',
               "Pipe Format (name --version ver)") do |value, options|
      options[:pipe_format] = value
    end

    add_local_remote_options
  end

  def arguments # :nodoc:
    "GEMNAME       name of gem to show dependencies for"
  end

  def defaults_str # :nodoc:
    "--local --version '#{Gem::Requirement.default}' --no-reverse-dependencies"
  end

  def description # :nodoc:
    <<-EOF
The dependency commands lists which other gems a given gem depends on.  For
local gems only the reverse dependencies can be shown (which gems depend on
the named gem).

The dependency list can be displayed in a format suitable for piping for
use with other commands.
    EOF
  end

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

  def fetch_remote_specs dependency # :nodoc:
    fetcher = Gem::SpecFetcher.fetcher

    ss, = fetcher.spec_for_dependency dependency

    ss.map { |spec, _| spec }
  end

  def fetch_specs dependency # :nodoc:
    specs = []

    specs.concat dependency.matching_specs     if local?
    specs.concat fetch_remote_specs dependency if remote?

    ensure_specs specs

    specs.uniq.sort
  end

  def gem_dependency args, version, prerelease # :nodoc:
    args << '' if args.empty?

    pattern = if args.length == 1 and args.first =~ /\A\/(.*)\/(i)?\z/m then
                flags = $2 ? Regexp::IGNORECASE : nil
                Regexp.new $1, flags
              else
                /\A#{Regexp.union(*args)}/
              end

    dependency = Gem::Deprecate.skip_during {
      Gem::Dependency.new pattern, version
    }

    dependency.prerelease = prerelease

    dependency
  end

  def display_pipe specs # :nodoc:
    specs.each do |spec|
      unless spec.dependencies.empty? then
        spec.dependencies.sort_by { |dep| dep.name }.each do |dep|
          say "#{dep.name} --version '#{dep.requirement}'"
        end
      end
    end
  end

  def display_readable specs, reverse # :nodoc:
    response = ''

    specs.each do |spec|
      response << print_dependencies(spec)
      unless reverse[spec.full_name].empty? then
        response << "  Used by\n"
        reverse[spec.full_name].each do |sp, dep|
          response << "    #{sp} (#{dep})\n"
        end
      end
      response << "\n"
    end

    say response
  end

  def execute
    ensure_local_only_reverse_dependencies

    dependency =
      gem_dependency options[:args], options[:version], options[:prerelease]

    specs = fetch_specs dependency

    reverse = reverse_dependencies specs

    if options[:pipe_format] then
      display_pipe specs
    else
      display_readable specs, reverse
    end
  end

  def ensure_local_only_reverse_dependencies # :nodoc:
    if options[:reverse_dependencies] and remote? and not local? then
      alert_error 'Only reverse dependencies for local gems are supported.'
      terminate_interaction 1
    end
  end

  def ensure_specs specs # :nodoc:
    return unless specs.empty?

    patterns = options[:args].join ','
    say "No gems found matching #{patterns} (#{options[:version]})" if
      Gem.configuration.verbose

    terminate_interaction 1
  end

  def print_dependencies(spec, level = 0) # :nodoc:
    response = ''
    response << '  ' * level + "Gem #{spec.full_name}\n"
    unless spec.dependencies.empty? then
      spec.dependencies.sort_by { |dep| dep.name }.each do |dep|
        response << '  ' * level + "  #{dep}\n"
      end
    end
    response
  end

  def remote_specs dependency # :nodoc:
    fetcher = Gem::SpecFetcher.fetcher

    ss, _ = fetcher.spec_for_dependency dependency

    ss.map { |s,o| s }
  end

  def reverse_dependencies specs # :nodoc:
    reverse = Hash.new { |h, k| h[k] = [] }

    return reverse unless options[:reverse_dependencies]

    specs.each do |spec|
      reverse[spec.full_name] = find_reverse_dependencies spec
    end

    reverse
  end

  ##
  # Returns an Array of [specification, dep] that are satisfied by +spec+.

  def find_reverse_dependencies spec # :nodoc:
    result = []

    Gem::Specification.each do |sp|
      sp.dependencies.each do |dep|
        dep = Gem::Dependency.new(*dep) unless Gem::Dependency === dep

        if spec.name == dep.name and
           dep.requirement.satisfied_by?(spec.version) then
          result << [sp.full_name, dep]
        end
      end
    end

    result
  end

end