class Gem::SpecFetcher

def self.fetcher
  @fetcher ||= new
end

def self.fetcher=(fetcher) # :nodoc:
  @fetcher = fetcher
end

def available_specs(type)
  errors = []
  list = {}
  @sources.each_source do |source|
    begin
      names = case type
              when :latest
                tuples_for source, :latest
              when :released
                tuples_for source, :released
              when :complete
                names =
                  tuples_for(source, :prerelease, true) +
                  tuples_for(source, :released)
                names.sort
              when :abs_latest
                names =
                  tuples_for(source, :prerelease, true) +
                  tuples_for(source, :latest)
                names.sort
              when :prerelease
                tuples_for(source, :prerelease)
              else
                raise Gem::Exception, "Unknown type - :#{type}"
              end
    rescue Gem::RemoteFetcher::FetchError => e
      errors << Gem::SourceFetchProblem.new(source, e)
    else
      list[source] = names
    end
  end
  [list, errors]
end

def detect(type=:complete)
  tuples = []
  list, _ = available_specs(type)
  list.each do |source, specs|
    specs.each do |tup|
      if yield(tup)
        tuples << [tup, source]
      end
    end
  end
  tuples
end

def initialize(sources = nil)
  @sources = sources || Gem.sources
  @update_cache =
    begin
      File.stat(Gem.user_home).uid == Process.uid
    rescue Errno::EACCES, Errno::ENOENT
      false
    end
  @specs = {}
  @latest_specs = {}
  @prerelease_specs = {}
  @caches = {
    :latest => @latest_specs,
    :prerelease => @prerelease_specs,
    :released => @specs,
  }
  @fetcher = Gem::RemoteFetcher.fetcher
end

def search_for_dependency(dependency, matching_platform=true)
  found = {}
  rejected_specs = {}
  list, errors = available_specs(dependency.identity)
  list.each do |source, specs|
    if dependency.name.is_a?(String) && specs.respond_to?(:bsearch)
      start_index = (0 ... specs.length).bsearch{|i| specs[i].name >= dependency.name }
      end_index   = (0 ... specs.length).bsearch{|i| specs[i].name > dependency.name }
      specs = specs[start_index ... end_index] if start_index && end_index
    end
    found[source] = specs.select do |tup|
      if dependency.match?(tup)
        if matching_platform and !Gem::Platform.match_gem?(tup.platform, tup.name)
          pm = (
            rejected_specs[dependency] ||= \
              Gem::PlatformMismatch.new(tup.name, tup.version))
          pm.add_platform tup.platform
          false
        else
          true
        end
      end
    end
  end
  errors += rejected_specs.values
  tuples = []
  found.each do |source, specs|
    specs.each do |s|
      tuples << [s, source]
    end
  end
  tuples = tuples.sort_by {|x| x[0] }
  return [tuples, errors]
end

def spec_for_dependency(dependency, matching_platform=true)
  tuples, errors = search_for_dependency(dependency, matching_platform)
  specs = []
  tuples.each do |tup, source|
    begin
      spec = source.fetch_spec(tup)
    rescue Gem::RemoteFetcher::FetchError => e
      errors << Gem::SourceFetchProblem.new(source, e)
    else
      specs << [spec, source]
    end
  end
  return [specs, errors]
end

def suggest_gems_from_name(gem_name, type = :latest, num_results = 5)
  gem_name        = gem_name.downcase.tr('_-', '')
  max             = gem_name.size / 2
  names           = available_specs(type).first.values.flatten(1)
  matches = names.map do |n|
    next unless n.match_platform?
    [n.name, 0] if n.name.downcase.tr('_-', '').include?(gem_name)
  end.compact
  if matches.length < num_results
    matches += names.map do |n|
      next unless n.match_platform?
      distance = levenshtein_distance gem_name, n.name.downcase.tr('_-', '')
      next if distance >= max
      return [n.name] if distance == 0
      [n.name, distance]
    end.compact
  end
  matches = if matches.empty? && type != :prerelease
              suggest_gems_from_name gem_name, :prerelease
            else
              matches.uniq.sort_by {|name, dist| dist }
            end
  matches.map {|name, dist| name }.uniq.first(num_results)
end

def tuples_for(source, type, gracefully_ignore=false) # :nodoc:
  @caches[type][source.uri] ||=
    source.load_specs(type).sort_by {|tup| tup.name }
rescue Gem::RemoteFetcher::FetchError
  raise unless gracefully_ignore
  []
end