require 'erb'
require 'rubygems/dependency_installer'

module Bundler
  class Installer < Environment
    class << self
      attr_accessor :post_install_messages
    end

    # Begins the installation process for Bundler.
    # For more information see the #run method on this class.
    def self.install(root, definition, options = {})
      installer = new(root, definition)
      installer.run(options)
      installer
    end

    # Runs the install procedures for a specific Gemfile.
    #
    # Firstly, this method will check to see if Bundler.bundle_path exists
    # and if not then will create it. This is usually the location of gems
    # on the system, be it RVM or at a system path.
    #
    # Secondly, it checks if Bundler has been configured to be "frozen"
    # Frozen ensures that the Gemfile and the Gemfile.lock file are matching.
    # This stops a situation where a developer may update the Gemfile but may not run
    # `bundle install`, which leads to the Gemfile.lock file not being correctly updated.
    # If this file is not correctly updated then any other developer running
    # `bundle install` will potentially not install the correct gems.
    #
    # Thirdly, Bundler checks if there are any dependencies specified in the Gemfile using
    # Bundler::Environment#dependencies. If there are no dependencies specified then
    # Bundler returns a warning message stating so and this method returns.
    #
    # Fourthly, Bundler checks if the default lockfile (Gemfile.lock) exists, and if so
    # then proceeds to set up a defintion based on the default gemfile (Gemfile) and the
    # default lock file (Gemfile.lock). However, this is not the case if the platform is different
    # to that which is specified in Gemfile.lock, or if there are any missing specs for the gems.
    #
    # Fifthly, Bundler resolves the dependencies either through a cache of gems or by remote.
    # This then leads into the gems being installed, along with stubs for their executables,
    # but only if the --binstubs option has been passed or Bundler.options[:bin] has been set
    # earlier.
    #
    # Sixthly, a new Gemfile.lock is created from the installed gems to ensure that the next time
    # that a user runs `bundle install` they will receive any updates from this process.
    #
    # Finally: TODO add documentation for how the standalone process works.
    def run(options)
      # Create the BUNDLE_PATH directory
      begin
        Bundler.bundle_path.mkpath unless Bundler.bundle_path.exist?
      rescue Errno::EEXIST
        raise PathError, "Could not install to path `#{Bundler.settings[:path]}` " +
          "because of an invalid symlink. Remove the symlink so the directory can be created."
      end

      if Bundler.settings[:frozen]
        @definition.ensure_equivalent_gemfile_and_lockfile(options[:deployment])
      end

      if dependencies.empty?
        Bundler.ui.warn "The Gemfile specifies no dependencies"
        lock
        return
      end

      if Bundler.default_lockfile.exist? && !options["update"]
        begin
          tmpdef = Definition.build(Bundler.default_gemfile, Bundler.default_lockfile, nil)
          local = true unless tmpdef.new_platform? || tmpdef.missing_specs.any?
        rescue BundlerError
        end
      end

      # Since we are installing, we can resolve the definition
      # using remote specs
      unless local
        options["local"] ?
          @definition.resolve_with_cache! :
          @definition.resolve_remotely!
      end

      # Must install gems in the order that the resolver provides
      # as dependencies might actually affect the installation of
      # the gem.
      Installer.post_install_messages = {}
      specs.each do |spec|
        install_gem_from_spec(spec, options[:standalone])
      end

      lock
      generate_standalone(options[:standalone]) if options[:standalone]
    end

  private

    def install_gem_from_spec(spec, standalone = false)
      # Download the gem to get the spec, because some specs that are returned
      # by rubygems.org are broken and wrong.
      Bundler::Fetcher.fetch(spec) if spec.source.is_a?(Bundler::Source::Rubygems)

      # Fetch the build settings, if there are any
      settings = Bundler.settings["build.#{spec.name}"]
      Bundler.rubygems.with_build_args [settings] do
        spec.source.install(spec)
        Bundler.ui.debug "from #{spec.loaded_from} "
      end

      # newline comes after installing, some gems say "with native extensions"
      Bundler.ui.info ""
      if Bundler.settings[:bin]
        standalone ? generate_standalone_bundler_executable_stubs(spec) : generate_bundler_executable_stubs(spec)
      end

      FileUtils.rm_rf(Bundler.tmp)
    rescue Exception => e
      # install hook failed
      raise e if e.is_a?(Bundler::InstallHookError)

      # other failure, likely a native extension build failure
      Bundler.ui.info ""
      Bundler.ui.warn "#{e.class}: #{e.message}"
      msg = "An error occurred while installing #{spec.name} (#{spec.version}),"
      msg << " and Bundler cannot continue.\nMake sure that `gem install"
      msg << " #{spec.name} -v '#{spec.version}'` succeeds before bundling."
      Bundler.ui.debug e.backtrace.join("\n")
      raise Bundler::InstallError, msg
    end

    def generate_bundler_executable_stubs(spec)
      # double-assignment to avoid warnings about variables that will be used by ERB
      bin_path = bin_path = Bundler.bin_path
      template = template = File.read(File.expand_path('../templates/Executable', __FILE__))
      relative_gemfile_path = relative_gemfile_path = Bundler.default_gemfile.relative_path_from(bin_path)
      ruby_command = ruby_command = Thor::Util.ruby_command

      spec.executables.each do |executable|
        next if executable == "bundle"
        File.open "#{bin_path}/#{executable}", 'w', 0755 do |f|
          f.puts ERB.new(template, nil, '-').result(binding)
        end
      end
    end

    def generate_standalone_bundler_executable_stubs(spec)
      # double-assignment to avoid warnings about variables that will be used by ERB
      bin_path = Bundler.bin_path
      template = File.read(File.expand_path('../templates/Executable.standalone', __FILE__))
      ruby_command = ruby_command = Thor::Util.ruby_command

      spec.executables.each do |executable|
        next if executable == "bundle"
        standalone_path = standalone_path = Pathname(Bundler.settings[:path]).expand_path.relative_path_from(bin_path)
        executable_path = executable_path = Pathname(spec.full_gem_path).join(spec.bindir, executable).relative_path_from(bin_path)
        File.open "#{bin_path}/#{executable}", 'w', 0755 do |f|
          f.puts ERB.new(template, nil, '-').result(binding)
        end
      end
    end

    def generate_standalone(groups)
      standalone_path = Bundler.settings[:path]
      bundler_path = File.join(standalone_path, "bundler")
      FileUtils.mkdir_p(bundler_path)

      paths = []

      if groups.empty?
        specs = Bundler.definition.requested_specs
      else
        specs = Bundler.definition.specs_for groups.map { |g| g.to_sym }
      end

      specs.each do |spec|
        next if spec.name == "bundler"

        spec.require_paths.each do |path|
          full_path = File.join(spec.full_gem_path, path)
          paths << Pathname.new(full_path).relative_path_from(Bundler.root.join(bundler_path))
        end
      end


      File.open File.join(bundler_path, "setup.rb"), "w" do |file|
        file.puts "path = File.expand_path('..', __FILE__)"
        paths.each do |path|
          file.puts %{$:.unshift File.expand_path("\#{path}/#{path}")}
        end
      end
    end
  end
end