#!/usr/bin/ruby

require 'rubygems/package'

module RubyGemsReq

  module Helpers

    # Keep only '!=' requirements.

    def self.conflicts(requirements)

      conflicts = requirements.select {|r| r.first == '!='}

    end

    # Converts Gem::Requirement into array of requirements strings compatible

    # with RPM .spec file.

    def self.requirement_versions_to_rpm(requirement)

      self.conflicts(requirement.requirements).map do |op, version|

        version == Gem::Version.new(0) ? "" : "= #{version}"

      end

    end

  end

  # Report conflicting gem dependencies including their version.

  def self.gem_depenencies(specification)

    specification.runtime_dependencies.each do |dependency|

      conflict_strings = Helpers::requirement_versions_to_rpm(dependency.requirement).map do |requirement|

        requirement_string = "rubygem(#{dependency.name}) #{requirement}"

      end

      if conflict_strings.length > 0

        conflict_string = conflict_strings.join(' with ')

        conflict_string.prepend('(').concat(')') if conflict_strings.length > 1

        puts conflict_string

      end

    end

  end

  # Reports all conflicts specified by all provided .gemspec files.

  def self.conflicts

    while filename = gets

      filename.strip!

      begin

        specification = Gem::Specification.load filename

        gem_depenencies(specification)

      rescue => e

        # Ignore all errors.

      end

    end

  end

end

if __FILE__ == $0

  RubyGemsReq::conflicts

end