class Roda
  module RodaPlugins
    # The assets plugin adds support for rendering your CSS and javascript
    # asset files on the fly in development, and compiling them
    # to a single, compressed file in production.
    #
    # This uses the render plugin for rendering the assets, and the render
    # plugin uses tilt internally, so you can use any template engine
    # supported by tilt for you assets.  Tilt ships with support for
    # the following asset template engines, assuming the necessary libaries
    # are installed:
    #
    # css :: Less, Sass, Scss
    # js :: CoffeeScript
    #
    # == Usage
    #
    # When loading the plugin, use the :css and :js options
    # to set the source file(s) to use for CSS and javascript assets:
    #
    #   plugin :assets, :css => 'some_file.scss', :js => 'some_file.coffee'
    #
    # This will look for the following files:
    #
    #   assets/css/some_file.scss
    #   assets/js/some_file.coffee
    #
    # If you want to change the paths where asset files are stored, see the
    # Options section below.
    #
    # === Serving
    #
    # In your routes, call the r.assets method to add a route to your assets,
    # which will make your app serve the rendered assets:
    #
    #   route do |r|
    #     r.assets
    #   end
    #
    # You should generally call +r.assets+ inside the route block itself, and not
    # under any branches of the routing tree.
    #
    # === Views
    #
    # In your layout view, use the assets method to add links to your CSS and
    # javascript assets:
    #
    #   <%= assets(:css) %>
    #   <%= assets(:js) %>
    #
    # You can add attributes to the tags by using an options hash:
    #
    #   <%= assets(:css, :media => 'print') %>
    #
    # == Asset Groups
    #
    # The asset plugin supports groups for the cases where you have different
    # css/js files for your front end and back end.  To use asset groups, you
    # pass a hash for the :css and/or :js options:
    #
    #   plugin :assets, :css => {:frontend => 'some_frontend_file.scss',
    #                            :backend => 'some_backend_file.scss'}
    #
    # This expects the following directory structure for your assets:
    #
    #   assets/css/frontend/some_frontend_file.scss
    #   assets/css/backend/some_backend_file.scss
    #
    # If you want do not want to force that directory structure when using
    # asset groups, you can use the <tt>:group_subdirs => false</tt> option.
    #
    # In your view code use an array argument in your call to assets:
    #
    #   <%= assets([:css, :frontend]) %>
    #
    # === Nesting
    #
    # Asset groups also supporting nesting, though that should only be needed
    # in fairly large applications.  You can use a nested hash when loading
    # the plugin:
    #
    #   plugin :assets,
    #     :css => {:frontend => {:dashboard => 'some_frontend_file.scss'}}
    #
    # and an extra entry per nesting level when creating the tags.
    #
    #   <%= assets([:css, :frontend, :dashboard]) %>
    #
    # == Caching
    #
    # The assets plugin uses the caching plugin internally, and will set the
    # Last-Modified header to the modified timestamp of the asset source file
    # when rendering the asset.
    #
    # If you have assets that include other asset files, such as using @import
    # in a sass file, you need to specify the dependencies for your assets so
    # that the assets plugin will correctly pick up changes.  You can do this
    # using the :dependencies option to the plugin, which takes a hash where
    # the keys are paths to asset files, and values are arrays of paths to
    # dependencies of those asset files:
    #
    #   app.plugin :assets,
    #     :dependencies=>{'assets/css/bootstrap.scss'=>Dir['assets/css/bootstrap/' '**/*.scss']}
    #
    # == Asset Compilation
    #
    # In production, you are generally going to want to compile your assets
    # into a single file, with you can do by calling compile_assets after
    # loading the plugin:
    #
    #   plugin :assets, :css => 'some_file.scss', :js => 'some_file.coffee'
    #   compile_assets
    #
    # After calling compile_assets, calls to assets in your views will default
    # to a using a single link each to your CSS and javascript compiled asset
    # files.  By default the compiled files are written to the public directory,
    # so that they can be served by the webserver.
    #
    # === Asset Compression
    #
    # If you have the yuicompressor gem installed and working, it will be used
    # automatically to compress your javascript and css assets.  Otherwise,
    # the assets will just be concatenated together and not compressed during
    # compilation.
    #
    # === With Asset Groups
    #
    # When using asset groups, a separate compiled file will be produced per
    # asset group.
    #
    # === Unique Asset Names
    #
    # When compiling assets, a unique name is given to each asset file, using the
    # a SHA1 hash of the content of the file.  This is done so that clients do
    # not attempt to use cached versions of the assets if the asset has changed.
    #
    # === Serving
    #
    # If you call +r.assets+ when compiling assets, will serve the compiled asset
    # files.  However, it is recommended to have the main webserver (e.g. nginx)
    # serve the compiled files, instead of relying on the application.
    #
    # Assuming you are using compiled assets in production mode that are served
    # by the webserver, you can remove the serving of them by the application:
    #
    #   route do |r|
    #     r.assets unless ENV['RACK_ENV'] == 'production'
    #   end
    #
    # If you do have the application serve the compiled assets, it will use the
    # Last-Modified header to make sure that clients do not redownload compiled
    # assets that haven't changed.
    #
    # === Asset Precompilation
    #
    # If you want to precompile your assets, so they do not need to be compiled
    # every time you boot the application, you can provide a :precompiled option
    # when loading the plugin.  The value of this option should be the filename
    # where the compiled asset metadata is stored.  
    #
    # If the compiled assset metadata file does not exist when the assets plugin
    # is loaded, the plugin will run in non-compiled mode.  However, when you call
    # compile_assets, it will write the compiled asset metadata file after
    # compiling the assets.
    #
    # If the compiled asset metadata file already exists when the assets plugin
    # is loaded, the plugin will read the file to get the compiled asset metadata,
    # and it will run in compiled mode, assuming that the compiled asset files
    # already exist.
    #
    # ==== On Heroku
    #
    # Heroku supports precompiling the assets when using Roda.  You just need to
    # add an assets:precompile task, similar to this:
    #
    #   namespace :assets do
    #     desc "Precompile the assets"
    #     task :precompile do
    #       require './app'
    #       App.compile_assets
    #     end
    #   end
    #
    # == Plugin Options
    #
    # :add_suffix :: Whether to append a .css or .js extension to asset routes in non-compiled mode
    #                (default: false)
    # :compiled_css_dir :: Directory name in which to store the compiled css file,
    #                      inside :compiled_path (default: nil)
    # :compiled_css_route :: Route under :prefix for compiled css assets (default: :compiled_css_dir)
    # :compiled_js_dir :: Directory name in which to store the compiled javascript file,
    #                     inside :compiled_path (default: nil)
    # :compiled_js_route :: Route under :prefix for compiled javscript assets (default: :compiled_js_dir)
    # :compiled_name :: Compiled file name prefix (default: 'app')
    # :compiled_path:: Path inside public folder in which compiled files are stored (default: :prefix)
    # :concat_only :: Whether to just concatenate instead of concatentating
    #                 and compressing files (default: false)
    # :css_dir :: Directory name containing your css source, inside :path (default: 'css')
    # :css_headers :: A hash of additional headers for your rendered css files
    # :css_opts :: Template options to pass to the render plugin (via :template_opts) when rendering css assets
    # :css_route :: Route under :prefix for css assets (default: :css_dir)
    # :dependencies :: A hash of dependencies for your asset files.  Keys should be paths to asset files,
    #                  values should be arrays of paths your asset files depends on.  This is used to
    #                  detect changes in your asset files.
    # :group_subdirs :: Whether a hash used in :css and :js options requires the assets for the
    #                   related group are contained in a subdirectory with the same name (default: true)
    # :headers :: A hash of additional headers for both js and css rendered files
    # :js_dir :: Directory name containing your javascript source, inside :path (default: 'js')
    # :js_headers :: A hash of additional headers for your rendered javascript files
    # :js_opts :: Template options to pass to the render plugin (via :template_opts) when rendering javascript assets
    # :js_route :: Route under :prefix for javascript assets (default: :js_dir)
    # :path :: Path to your asset source directory (default: 'assets')
    # :prefix :: Prefix for assets path in your URL/routes (default: 'assets')
    # :precompiled :: Path to the compiled asset metadata file.  If the file exists, will use compiled
    #                 mode using the metadata in the file.  If the file does not exist, will use
    #                 non-compiled mode, but will write the metadata to the file if compile_assets is called.
    # :public :: Path to your public folder, in which compiled files are placed (default: 'public')
    module Assets
      DEFAULTS = {
        :compiled_name    => 'app'.freeze,
        :js_dir           => 'js'.freeze,
        :css_dir          => 'css'.freeze,
        :path             => 'assets'.freeze,
        :prefix           => 'assets'.freeze,
        :public           => 'public'.freeze,
        :concat_only      => false,
        :compiled         => false,
        :add_suffix       => false,
        :group_subdirs    => true,
        :compiled_css_dir => nil,
        :compiled_js_dir  => nil,
      }.freeze
      JS_END = "\"></script>".freeze
      CSS_END = "\" />".freeze
      SPACE = ' '.freeze
      DOT = '.'.freeze
      SLASH = '/'.freeze
      NEWLINE = "\n".freeze
      EMPTY_STRING = ''.freeze
      JS_SUFFIX = '.js'.freeze
      CSS_SUFFIX = '.css'.freeze

      # Load the render and caching plugins plugins, since the assets plugin
      # depends on them.
      def self.load_dependencies(app, _opts = nil)
        app.plugin :render
        app.plugin :caching
      end

      # Setup the options for the plugin.  See the Assets module RDoc
      # for a description of the supported options.
      def self.configure(app, opts = {})
        if app.assets_opts
          prev_opts = app.assets_opts[:orig_opts]
          orig_opts = app.assets_opts[:orig_opts].merge(opts)
          [:headers, :css_headers, :js_headers, :css_opts, :js_opts, :dependencies].each do |s|
            if prev_opts[s]
              if opts[s]
                orig_opts[s] = prev_opts[s].merge(opts[s])
              else
                orig_opts[s] = prev_opts[s].dup
              end
            end
          end
          app.opts[:assets] = orig_opts.dup
          app.opts[:assets][:orig_opts] = orig_opts
        else
          app.opts[:assets] = opts.dup
          app.opts[:assets][:orig_opts] = opts
        end
        opts = app.opts[:assets]

        # Combine multiple values into a path, ignoring trailing slashes
        j = lambda do |*v|
          opts.values_at(*v).
            reject{|s| s.to_s.empty?}.
            map{|s| s.chomp('/')}.
            join('/').freeze
        end

        # Same as j, but add a trailing slash if not empty
        sj = lambda do |*v|
          s = j.call(*v)
          s.empty? ? s : (s + '/').freeze
        end

        if opts[:precompiled] && !opts[:compiled] && ::File.exist?(opts[:precompiled])
          require 'json'
          opts[:compiled] = ::JSON.parse(::File.read(opts[:precompiled]))
        end

        DEFAULTS.each do |k, v|
          opts[k] = v unless opts.has_key?(k)
        end

        [
         [:compiled_path, :prefix],
         [:js_route, :js_dir],
         [:css_route, :css_dir],
         [:compiled_js_route, :compiled_js_dir],
         [:compiled_css_route, :compiled_css_dir]
        ].each do |k, v|
          opts[k]  = opts[v] unless opts.has_key?(k)
        end

        [:css_headers, :js_headers, :css_opts, :js_opts, :dependencies].each do |s|
          opts[s] ||= {} 
        end

        if headers = opts[:headers]
          opts[:css_headers] = headers.merge(opts[:css_headers])
          opts[:js_headers]  = headers.merge(opts[:js_headers])
        end
        opts[:css_headers]['Content-Type'] ||= "text/css; charset=UTF-8".freeze
        opts[:js_headers]['Content-Type']  ||= "application/javascript; charset=UTF-8".freeze

        [:css_headers, :js_headers, :css_opts, :js_opts, :dependencies].each do |s|
          opts[s].freeze
        end
        [:headers, :css, :js].each do |s|
          opts[s].freeze if opts[s]
        end

        # Used for reading/writing files
        opts[:js_path]           = sj.call(:path, :js_dir)
        opts[:css_path]          = sj.call(:path, :css_dir)
        opts[:compiled_js_path]  = j.call(:public, :compiled_path, :compiled_js_dir, :compiled_name)
        opts[:compiled_css_path] = j.call(:public, :compiled_path, :compiled_css_dir, :compiled_name)

        # Used for URLs/routes
        opts[:js_prefix]           = sj.call(:prefix, :js_route)
        opts[:css_prefix]          = sj.call(:prefix, :css_route)
        opts[:compiled_js_prefix]  = j.call(:prefix, :compiled_js_route, :compiled_name)
        opts[:compiled_css_prefix] = j.call(:prefix, :compiled_css_route, :compiled_name)
        opts[:js_suffix]           = opts[:add_suffix] ? JS_SUFFIX : EMPTY_STRING
        opts[:css_suffix]          = opts[:add_suffix] ? CSS_SUFFIX : EMPTY_STRING

        opts.freeze
      end

      module ClassMethods
        # Return the assets options for this class.
        def assets_opts
          opts[:assets]
        end

        # Compile options for the given asset type.  If no asset_type
        # is given, compile both the :css and :js asset types.  You
        # can specify an array of types (e.g. [:css, :frontend]) to
        # compile assets for the given asset group.
        def compile_assets(type=nil)
          require 'fileutils'

          unless assets_opts[:compiled]
            opts[:assets] = assets_opts.merge(:compiled => {})
          end

          if type == nil
            _compile_assets(:css)
            _compile_assets(:js)
          else
            _compile_assets(type)
          end

          if assets_opts[:precompiled]
            require 'json'
            ::FileUtils.mkdir_p(File.dirname(assets_opts[:precompiled]))
            ::File.open(assets_opts[:precompiled], 'wb'){|f| f.write(assets_opts[:compiled].to_json)}
          end

          assets_opts[:compiled]
        end

        private

        # Internals of compile_assets, handling recursive calls for loading
        # all asset groups under the given type.
        def _compile_assets(type)
          type, *dirs = type if type.is_a?(Array)
          dirs ||= []
          files = assets_opts[type]
          dirs.each{|d| files = files[d]}

          case files
          when Hash
            files.each_key{|dir| _compile_assets([type] + dirs + [dir])}
          else
            files = Array(files)
            compile_assets_files(files, type, dirs) unless files.empty?
          end
        end

        # Compile each array of files for the given type into a single
        # file.  Dirs should be an array of asset group names, if these
        # are files in an asset group.
        def compile_assets_files(files, type, dirs)
          dirs = nil if dirs && dirs.empty?
          o = assets_opts
          app = allocate

          content = files.map do |file|
            file = "#{dirs.join('/')}/#{file}" if dirs && o[:group_subdirs]
            file = "#{o[:"#{type}_path"]}#{file}"
            app.read_asset_file(file, type)
          end.join

          unless o[:concat_only]
            content = compress_asset(content, type)
          end

          suffix = ".#{dirs.join('.')}" if dirs
          key = "#{type}#{suffix}"
          unique_id = o[:compiled][key] = asset_digest(content)
          path = "#{o[:"compiled_#{type}_path"]}#{suffix}.#{unique_id}.#{type}"
          ::FileUtils.mkdir_p(File.dirname(path))
          ::File.open(path, 'wb'){|f| f.write(content)}
          nil
        end

        # Compress the given content for the given type using yuicompressor,
        # but handle cases where yuicompressor isn't installed or can't find
        # a java runtime.  This method can be overridden by the application
        # to use a different compressor.
        def compress_asset(content, type)
          require 'yuicompressor'
          # :nocov:
          content = YUICompressor.send("compress_#{type}", content, :munge => true)
          # :nocov:
        rescue LoadError, Errno::ENOENT
          # yuicompressor or java not available, just use concatenated, uncompressed output
          content
        end

        # Return a unique id for the given content.  By default, uses the
        # SHA1 hash of the content.  This method can be overridden to use
        # a different digest type or to return a static string if you don't
        # want to use a unique value.
        def asset_digest(content)
          require 'digest/sha1'
          Digest::SHA1.hexdigest(content)
        end
      end

      module InstanceMethods
        # Return a string containing html tags for the given asset type.
        # This will use a script tag for the :js type and a link tag for
        # the :css type.
        #
        # To return the tags for a specific asset group, use an array for
        # the type, such as [:css, :frontend].
        #
        # When the assets are not compiled, this will result in a separate
        # tag for each asset file.  When the assets are compiled, this will
        # result in a single tag to the compiled asset file.
        def assets(type, attrs = nil)
          o = self.class.assets_opts
          type, *dirs = type if type.is_a?(Array)
          stype = type.to_s

          attrs = if attrs
            ru = Rack::Utils
            attrs.map{|k,v| "#{k}=\"#{ru.escape_html(v.to_s)}\""}.join(SPACE)
          else
            EMPTY_STRING
          end

          if type == :js
            tag_start = "<script type=\"text/javascript\" #{attrs} src=\"/"
            tag_end = JS_END
          else
            tag_start = "<link rel=\"stylesheet\" #{attrs} href=\"/"
            tag_end = CSS_END
          end

          # Create a tag for each individual file
          if compiled = o[:compiled]
            if dirs && !dirs.empty?
              key = dirs.join(DOT)
              ckey = "#{stype}.#{key}"
              if ukey = compiled[ckey]
                "#{tag_start}#{o[:"compiled_#{stype}_prefix"]}.#{key}.#{ukey}.#{stype}#{tag_end}"
              end
            elsif ukey = compiled[stype]
              "#{tag_start}#{o[:"compiled_#{stype}_prefix"]}.#{ukey}.#{stype}#{tag_end}"
            end
          else
            asset_dir = o[type]
            if dirs && !dirs.empty?
              dirs.each{|f| asset_dir = asset_dir[f]}
              prefix = "#{dirs.join(SLASH)}/" if o[:group_subdirs]
            end
            Array(asset_dir).map{|f| "#{tag_start}#{o[:"#{stype}_prefix"]}#{prefix}#{f}#{o[:"#{stype}_suffix"]}#{tag_end}"}.join(NEWLINE)
          end
        end

        # Render the asset with the given filename.  When assets are compiled,
        # or when the file is already of the given type (no rendering necessary),
        # this returns the contents of the compiled file.
        # When assets are not compiled and the file is not already of the correct,
        # this will render the asset using the render plugin.
        # In both cases, if the file has not been modified since the last request,
        # this will return a 304 response.
        def render_asset(file, type)
          o = self.class.assets_opts
          if o[:compiled]
            file = "#{o[:"compiled_#{type}_path"]}#{file}"
            check_asset_request(file, type, ::File.stat(file).mtime)
            ::File.read(file)
          else
            file = "#{o[:"#{type}_path"]}#{file}"
            check_asset_request(file, type, asset_last_modified(file))
            read_asset_file(file, type)
          end
        end

        # Return the content of the file if it is already of the correct type.
        # Otherwise, render the file using the render plugin.  +file+ should be
        # the relative path to the file from the current directory.
        def read_asset_file(file, type)
          if file.end_with?(".#{type}")
            ::File.read(file)
          else
            render_asset_file(file, :template_opts=>self.class.assets_opts[:"#{type}_opts"])
          end
        end

        private

        # Return when the file was last modified.  If the file depends on any
        # other files, check the modification times of all dependencies and
        # return the maximum.
        def asset_last_modified(file)
          if deps = self.class.assets_opts[:dependencies][file]
            ([file] + Array(deps)).map{|f| ::File.stat(f).mtime}.max
          else
            ::File.stat(file).mtime
          end
        end

        # If the asset hasn't been modified since the last request, return
        # a 304 response immediately.  Otherwise, add the appropriate
        # type-specific headers.
        def check_asset_request(file, type, mtime)
          @_request.last_modified(mtime)
          @_response.headers.merge!(self.class.assets_opts[:"#{type}_headers"])
        end

        # Render the given asset file using the render plugin, with the given options.
        # +file+ should be the relative path to the file from the current directory.
        def render_asset_file(file, options)
          render_template({:path => file}, options)
        end
      end

      module RequestClassMethods
        # An array of asset type strings and regexps for that type, for all asset types
        # handled.
        def assets_matchers
          @assets_matchers ||= [:css, :js].map do |t|
            [t.to_s.freeze, assets_regexp(t)].freeze if roda_class.assets_opts[t]
          end.compact.freeze
        end

        private

        # The regexp matcher to use for the given type.  This handles any asset groups
        # for the asset types.
        def assets_regexp(type)
          o = roda_class.assets_opts
          if compiled = o[:compiled]
            assets = compiled.select{|k,_| k =~ /\A#{type}/}.map do |k, md|
              "#{k.sub(/\A#{type}/, '')}.#{md}.#{type}"
            end
            /#{o[:"compiled_#{type}_prefix"]}(#{Regexp.union(assets)})/
          else
            assets = unnest_assets_hash(o[type])
            /#{o[:"#{type}_prefix"]}(#{Regexp.union(assets.uniq)})#{o[:"#{type}_suffix"]}/
          end
        end

        # Recursively unnested the given assets hash, returning a single array of asset
        # files for the given.
        def unnest_assets_hash(h)
          case h
          when Hash
            h.map do |k,v|
              assets = unnest_assets_hash(v)
              assets = assets.map{|x| "#{k}/#{x}"} if roda_class.assets_opts[:group_subdirs]
              assets
            end.flatten(1)
          else
            Array(h)
          end
        end
      end

      module RequestMethods
        # Render the matching asset if this is a GET request for a supported asset.
        def assets
          if is_get?
            self.class.assets_matchers.each do |type, matcher|
              is matcher do |file|
                scope.render_asset(file, type)
              end
            end
          end
        end
      end
    end

    register_plugin(:assets, Assets)
  end
end