module Gem
  class AvailableSet
    Tuple = Struct.new(:spec, :source)

    def initialize
      @set = []
      @sorted = nil
    end

    attr_reader :set

    def add(spec, source)
      @set << Tuple.new(spec, source)
      @sorted = nil
      self
    end

    def <<(o)
      case o
      when AvailableSet
        s = o.set
      when Array
        s = o.map do |sp,so|
          if !sp.kind_of?(Specification) or !so.kind_of?(Source)
            raise TypeError, "Array must be in [[spec, source], ...] form"
          end

          Tuple.new(sp,so)
        end
      else
        raise TypeError, "Must be an AvailableSet"
      end

      @set += s
      @sorted = nil

      self
    end

    def empty?
      @set.empty?
    end

    def all_specs
      @set.map { |t| t.spec }
    end

    def match_platform!
      @set.reject! { |t| !Gem::Platform.match(t.spec.platform) }
      @sorted = nil
      self
    end

    def sorted
      @sorted ||= @set.sort do |a,b|
        i = b.spec <=> a.spec
        i != 0 ? i : (a.source <=> b.source)
      end
    end

    def size
      @set.size
    end

    def source_for(spec)
      f = @set.find { |t| t.spec == spec }
      f.source
    end

    def pick_best!
      return self if empty?

      @set = [sorted.first]
      @sorted = nil
      self
    end

    def remove_installed!(dep)
      @set.reject! do |t|
        # already locally installed
        Gem::Specification.any? do |installed_spec|
          dep.name == installed_spec.name and
            dep.requirement.satisfied_by? installed_spec.version
        end
      end

      @sorted = nil
      self
    end

    def inject_into_list(dep_list)
      @set.each { |t| dep_list.add t.spec }
    end
  end
end