class Bundler::Resolver

def self.resolve(requirements, index, source_requirements = {})
  resolver = new(index, source_requirements)
  result = catch(:success) do
    resolver.resolve(requirements, {})
    output = resolver.errors.inject("") do |o, (conflict, (origin, requirement))|
      if origin
        o << "  Conflict on: #{conflict.inspect}:\n"
        o << "    * #{conflict} (#{origin.version}) activated by #{origin.required_by.first}\n"
        o << "    * #{requirement} required by #{requirement.required_by.first}\n"
      else
        o << "  #{requirement} not found in any of the sources\n"
        o << "      required by #{requirement.required_by.first}\n"
      end
      o << "    All possible versions of origin requirements conflict."
    end
    raise VersionConflict, "No compatible versions could be found for required dependencies:\n  #{output}"
    nil
  end
  if result
    # Order gems in order of dependencies. Every gem's dependency is at
    # a smaller index in the array.
    ordered = []
    result.values.each do |spec1|
      index = nil
      place = ordered.detect do |spec2|
        spec1.dependencies.any? { |d| d.name == spec2.name }
      end
      place ?
        ordered.insert(ordered.index(place), spec1) :
        ordered << spec1
    end
    ordered.reverse
  end
end