# frozen_string_literal: true

require_relative "text"
##
# A Source knows how to list and fetch gems from a RubyGems marshal index.
#
# There are other Source subclasses for installed gems, local gems, the
# Compact Index API and so-forth.

class Gem::Source
  include Comparable
  include Gem::Text

  FILES = { # :nodoc:
    released: "specs",
    latest: "latest_specs",
    prerelease: "prerelease_specs",
  }.freeze

  ##
  # The URI this source will fetch gems from.

  attr_reader :uri

  ##
  # Creates a new Source which will use the index located at +uri+.

  def initialize(uri)
    require_relative "uri"
    @uri = Gem::Uri.parse!(uri)
    @update_cache = nil
  end

  ##
  # Sources are ordered by installation preference.

  def <=>(other)
    case other
    when Gem::Source::Installed,
         Gem::Source::Local,
         Gem::Source::Lock,
         Gem::Source::SpecificFile,
         Gem::Source::Git,
         Gem::Source::Vendor then
      -1
    when Gem::Source then
      unless @uri
        return 0 unless other.uri
        return 1
      end

      return -1 unless other.uri

      # Returning 1 here ensures that when sorting a list of sources, the
      # original ordering of sources supplied by the user is preserved.
      return 1 unless @uri.to_s == other.uri.to_s

      0
    end
  end

  def ==(other) # :nodoc:
    self.class === other && @uri == other.uri
  end

  alias_method :eql?, :== # :nodoc:

  ##
  # Returns a Set that can fetch specifications from this source.
  #
  # The set will optionally fetch prereleases if requested.
  #
  def dependency_resolver_set(prerelease = false)
    new_dependency_resolver_set.tap {|set| set.prerelease = prerelease }
  end

  def hash # :nodoc:
    @uri.hash
  end

  ##
  # Returns the local directory to write +uri+ to.

  def cache_dir(uri)
    # Correct for windows paths
    escaped_path = uri.path.sub(%r{^/([a-z]):/}i, '/\\1-/')

    File.join Gem.spec_cache_dir, "#{uri.host}%#{uri.port}", File.dirname(escaped_path)
  end

  ##
  # Returns true when it is possible and safe to update the cache directory.

  def update_cache?
    return @update_cache unless @update_cache.nil?
    @update_cache =
      begin
        File.stat(Gem.user_home).uid == Process.uid
      rescue Errno::ENOENT
        false
      end
  end

  ##
  # Fetches a specification for the given Gem::NameTuple.

  def fetch_spec(name_tuple)
    fetcher = Gem::RemoteFetcher.fetcher

    spec_file_name = name_tuple.spec_name

    # The name tuple comes from a remote index and is not otherwise
    # validated, so refuse anything that would escape the spec cache
    # directory when used as a path component.
    if File.basename(spec_file_name) != spec_file_name
      raise Gem::Exception, "malformed spec name: #{spec_file_name.inspect}"
    end

    source_uri = enforce_trailing_slash(uri) + "#{Gem::MARSHAL_SPEC_DIR}#{spec_file_name}"

    cache_dir = cache_dir source_uri

    local_spec = File.join cache_dir, spec_file_name

    if File.exist? local_spec
      spec = Gem.read_binary local_spec
      Gem.load_safe_marshal
      spec = begin
               Gem::SafeMarshal.safe_load(spec)
             rescue StandardError
               nil
             end
      return spec if spec
    end

    source_uri.path << ".rz"

    spec = fetcher.fetch_path source_uri
    spec = Gem::Util.inflate spec

    if update_cache?
      require "fileutils"
      FileUtils.mkdir_p cache_dir

      File.open local_spec, "wb" do |io|
        io.write spec
      end
    end

    Gem.load_safe_marshal
    # TODO: Investigate setting Gem::Specification#loaded_from to a URI
    Gem::SafeMarshal.safe_load spec
  end

  ##
  # Loads +type+ kind of specs fetching from +@uri+ if the on-disk cache is
  # out of date.
  #
  # +type+ is one of the following:
  #
  # :released   => Return the list of all released specs
  # :latest     => Return the list of only the highest version of each gem
  # :prerelease => Return the list of all prerelease only specs
  #
  # The compact index is used when the source provides it, falling back
  # to the Marshal spec indexes.

  def load_specs(type)
    load_compact_index_specs(type) || load_marshal_specs(type)
  end

  ##
  # The compact index client for this source, caching under
  # Gem.spec_cache_dir. Also used by Gem::Resolver::APISet.

  def compact_index_client # :nodoc:
    @compact_index_client ||= begin
      require_relative "compact_index_client"

      index_uri = compact_index_uri

      Gem::CompactIndexClient.new(compact_index_cache_dir(index_uri),
        Gem::CompactIndexClient::HTTPFetcher.new(index_uri))
    end
  end

  ##
  # The publish time of gem +name+ at +version+ for +platform+, when this
  # source provides it through the compact index created_at metadata.
  # Returns nil when the source, the gem or the version has no known
  # publish time.

  def created_at(name, version, platform = Gem::Platform::RUBY)
    return unless %w[http https].include?(uri.scheme)

    @created_at_info ||= {}
    info = @created_at_info[name] ||= begin
      compact_index_client.fetch_info(name)
    rescue Gem::RemoteFetcher::FetchError, Gem::CompactIndexClient::Error
      []
    end

    platform = (platform || Gem::Platform::RUBY).to_s
    version = version.to_s

    row = info.find do |row_info|
      row_info[Gem::CompactIndexClient::INFO_VERSION] == version &&
        (row_info[Gem::CompactIndexClient::INFO_PLATFORM] || Gem::Platform::RUBY) == platform
    end
    return unless row

    value = row[Gem::CompactIndexClient::INFO_REQS].assoc("created_at")&.last&.first
    return unless value.is_a?(String)

    require "time"
    begin
      Time.iso8601(value)
    rescue ArgumentError
      nil
    end
  end

  ##
  # Downloads +spec+ and writes it to +dir+.  See also
  # Gem::RemoteFetcher#download.

  def download(spec, dir = Dir.pwd)
    fetcher = Gem::RemoteFetcher.fetcher
    fetcher.download spec, uri.to_s, dir
  end

  def pretty_print(q) # :nodoc:
    q.object_group(self) do
      q.group 2, "[Remote:", "]" do
        q.breakable
        q.text @uri.to_s

        if api = uri
          q.breakable
          q.text "API URI: "
          q.text api.to_s
        end
      end
    end
  end

  def typo_squatting?(host, distance_threshold = 4)
    return if @uri.host.nil?
    levenshtein_distance(@uri.host, host).between? 1, distance_threshold
  end

  private

  def load_marshal_specs(type)
    file       = FILES[type]
    fetcher    = Gem::RemoteFetcher.fetcher
    file_name  = "#{file}.#{Gem.marshal_version}"
    spec_path  = enforce_trailing_slash(uri) + "#{file_name}.gz"
    cache_dir  = cache_dir spec_path
    local_file = File.join(cache_dir, file_name)
    retried    = false

    if update_cache?
      require "fileutils"
      FileUtils.mkdir_p cache_dir
    end

    spec_dump = fetcher.cache_update_path spec_path, local_file, update_cache?

    Gem.load_safe_marshal
    begin
      Gem::NameTuple.from_list Gem::SafeMarshal.safe_load(spec_dump)
    rescue ArgumentError
      if update_cache? && !retried
        FileUtils.rm local_file
        retried = true
        retry
      else
        raise Gem::Exception.new("Invalid spec cache file in #{local_file}")
      end
    end
  end

  ##
  # Builds the name tuple list for +type+ from the compact index versions
  # file. Returns nil when the source does not provide a usable compact
  # index, so the caller can fall back to the Marshal spec indexes.

  def load_compact_index_specs(type)
    return unless %w[http https].include?(uri.scheme)

    versions = compact_index_versions
    return if versions.nil? || versions.empty?

    tuples = []

    versions.each_value do |rows|
      gem_tuples = rows.filter_map do |name, version_string, platform|
        next unless Gem::Version.correct?(version_string)

        version = Gem::Version.new(version_string)
        next if version.prerelease? != (type == :prerelease)

        Gem::NameTuple.new(name, version, platform || "ruby")
      end

      gem_tuples = max_versions_by_platform(gem_tuples) if type == :latest

      tuples.concat(gem_tuples)
    end

    tuples
  end

  def compact_index_versions
    @compact_index_versions ||= compact_index_client.versions
  rescue Gem::RemoteFetcher::FetchError, Gem::CompactIndexClient::Error
    @compact_index_versions = {}
    nil
  end

  def max_versions_by_platform(tuples)
    tuples.group_by(&:platform).map {|_, platform_tuples| platform_tuples.max_by(&:version) }
  end

  def compact_index_uri
    if uri.host == "rubygems.org"
      index_uri = uri.dup
      index_uri.host = "index.rubygems.org"
      index_uri
    else
      uri
    end
  end

  def compact_index_cache_dir(index_uri)
    if update_cache?
      # Correct for windows paths
      escaped_path = index_uri.path.sub(%r{^/([a-z]):/}i, '/\\1-/')

      File.join Gem.spec_cache_dir, "compact_index",
        "#{index_uri.host}%#{index_uri.port}", *escaped_path.split("/").reject(&:empty?)
    else
      require "tmpdir"
      require "fileutils"
      dir = Dir.mktmpdir "gem_compact_index"
      at_exit { FileUtils.rm_rf dir }
      dir
    end
  end

  def new_dependency_resolver_set
    return Gem::Resolver::IndexSet.new self if uri.scheme == "file"

    bundler_api_uri = enforce_trailing_slash(compact_index_uri) + "versions"

    begin
      fetcher = Gem::RemoteFetcher.fetcher
      response = fetcher.fetch_path bundler_api_uri, nil, true
    rescue Gem::RemoteFetcher::FetchError
      Gem::Resolver::IndexSet.new self
    else
      Gem::Resolver::APISet.new response.uri + "./info/"
    end
  end

  def enforce_trailing_slash(uri)
    uri.merge(uri.path.gsub(%r{/+$}, "") + "/")
  end
end

require_relative "source/git"
require_relative "source/installed"
require_relative "source/specific_file"
require_relative "source/local"
require_relative "source/lock"
require_relative "source/vendor"
