# frozen-string-literal: true

require "tilt"

class Roda
  module RodaPlugins
    # The render plugin adds support for template rendering using the tilt
    # library.  Two methods are provided for template rendering, +view+
    # (which uses the layout) and +render+ (which does not).
    #
    #   plugin :render
    #
    #   route do |r|
    #     r.is 'foo' do
    #       view('foo') # renders views/foo.erb inside views/layout.erb
    #     end
    #
    #     r.is 'bar' do
    #       render('bar') # renders views/bar.erb
    #     end
    #   end
    #
    # The +render+ and +view+ methods just return strings, they do not have
    # side effects (unless the templates themselves have side effects).
    # As Roda uses the routing block return value as the body of the response,
    # in most cases you will call these methods as the last expression in a
    # routing block to have the response body be the result of the template
    # rendering.
    #
    # Because +render+ and +view+ just return strings, you can call them inside
    # templates (i.e. for subtemplates/partials), or multiple times in the
    # same route and combine the results together:
    #
    #   route do |r|
    #     r.is 'foo-bars' do
    #       @bars = Bar.where(:foo).map{|b| render(:bar, locals: {bar: b})}.join
    #       view('foo')
    #     end
    #   end
    #
    # You can provide options to the plugin method:
    #
    #   plugin :render, engine: 'haml', views: 'admin_views'
    #
    # = Plugin Options
    #
    # The following plugin options are supported:
    #
    # :allowed_paths :: Set the template paths to allow.  Attempts to render paths outside
    #                   of this directory will raise an error.  Defaults to the +:views+ directory.
    # :cache :: nil/false to disable template caching by default.  By default, caching
    #           is disabled by default if RACK_ENV is development.
    # :cache_class :: A class to use as the template cache instead of the default.
    # :check_paths :: Can be set to false to turn off template path checking.
    # :engine :: The tilt engine to use for rendering, also the default file extension for
    #            templates, defaults to 'erb'.
    # :escape :: Use Erubi as the ERB template engine, and enable escaping by default,
    #            which makes <tt><%= %></tt> escape output and  <tt><%== %></tt> not escape output.
    # :layout :: The base name of the layout file, defaults to 'layout'.  This can be provided as a hash
    #            with the :template or :inline options.
    # :layout_opts :: The options to use when rendering the layout, if different from the default options.
    # :template_opts :: The tilt options used when rendering all templates. defaults to:
    #                   <tt>{outvar: '@_out_buf', default_encoding: Encoding.default_external}</tt>.
    # :engine_opts :: The tilt options to use per template engine.  Keys are
    #                 engine strings, values are hashes of template options.
    # :views :: The directory holding the view files, defaults to the 'views' subdirectory of the
    #           application's :root option (the process's working directory by default).
    #
    # = Render/View Method Options
    #
    # Most of these options can be overridden at runtime by passing options
    # to the +view+ or +render+ methods:
    #
    #   view('foo', engine: 'html.erb')
    #   render('foo', views: 'admin_views')
    #
    # There are additional options to +view+ and +render+ that are
    # available at runtime:
    #
    # :cache :: Set to false to not cache this template, even when
    #           caching is on by default.  Set to true to force caching for
    #           this template, even when the default is to not cache (e.g.
    #           when using the :template_block option).
    # :cache_key :: Explicitly set the hash key to use when caching.
    # :content :: Only respected by +view+, provides the content to render
    #             inside the layout, instead of rendering a template to get
    #             the content.
    # :inline :: Use the value given as the template code, instead of looking
    #            for template code in a file.
    # :locals :: Hash of local variables to make available inside the template.
    # :path :: Use the value given as the full pathname for the file, instead
    #          of using the :views and :engine option in combination with the
    #          template name.
    # :scope :: The object in which context to evaluate the template.  By
    #           default, this is the Roda instance.
    # :template :: Provides the name of the template to use.  This allows you
    #              pass a single options hash to the render/view method, while
    #              still allowing you to specify the template name.
    # :template_block :: Pass this block when creating the underlying template,
    #                    ignored when using :inline.  Disables caching of the
    #                    template by default.
    # :template_class :: Provides the template class to use, inside of using
    #                    Tilt or <tt>Tilt[:engine]</tt>.
    #
    # Here's an example of using these options:
    #
    #   view(inline: '<%= @foo %>')
    #   render(path: '/path/to/template.erb')
    #
    # If you pass a hash as the first argument to +view+ or +render+, it should
    # have either +:template+, +:inline+, +:path+, or +:content+ (for +view+) as
    # one of the keys.
    #
    # = Speeding Up Template Rendering
    #
    # By default, determining the cache key to use for the template can be a lot
    # of work.  If you specify the +:cache_key+ option, you can save Roda from
    # having to do that work, which will make your application faster.  However,
    # if you do this, you need to make sure you choose a correct key.
    #
    # If your application uses a unique template per path, in that the same
    # path never uses more than one template, you can use the +view_options+ plugin
    # and do:
    #
    #   set_view_options cache_key: r.path_info
    #
    # at the top of your route block.  You can even do this if you do have paths
    # that use more than one template, as long as you specify +:cache_key+
    # specifically when rendering in those paths.
    #
    # If you use a single layout in your application, you can also make layout
    # rendering faster by specifying +:cache_key+ inside the +:layout_opts+
    # plugin option.
    module Render
      # Setup default rendering options.  See Render for details.
      def self.configure(app, opts=OPTS)
        if app.opts[:render]
          orig_cache = app.opts[:render][:cache]
          opts = app.opts[:render][:orig_opts].merge(opts)
        end
        app.opts[:render] = opts.dup
        app.opts[:render][:orig_opts] = opts

        opts = app.opts[:render]
        opts[:engine] = (opts[:engine] || "erb").dup.freeze
        opts[:views] = app.expand_path(opts[:views]||"views").freeze
        opts[:allowed_paths] ||= [opts[:views]].freeze
        opts[:allowed_paths] = opts[:allowed_paths].map{|f| app.expand_path(f, nil)}.uniq.freeze
        opts[:check_paths] = true unless opts.has_key?(:check_paths)

        unless opts.has_key?(:explicit_cache)
          opts[:explicit_cache] = if opts.fetch(:cache, true)
            ENV['RACK_ENV'] == 'development'
          else
            true
          end
        end

        opts[:cache] = orig_cache || (opts[:cache_class] || RodaCache).new

        opts[:layout_opts] = (opts[:layout_opts] || {}).dup
        opts[:layout_opts][:_is_layout] = true
        if opts[:layout_opts][:views]
          opts[:layout_opts][:views] = app.expand_path(opts[:layout_opts][:views]).freeze
        end

        if layout = opts.fetch(:layout, true)
          opts[:layout] = true unless opts.has_key?(:layout)

          case layout
          when Hash
            opts[:layout_opts].merge!(layout)
          when true
            opts[:layout_opts][:template] ||= 'layout'
          else
            opts[:layout_opts][:template] = layout
          end
        end
        opts[:layout_opts].freeze

        template_opts = opts[:template_opts] = (opts[:template_opts] || {}).dup
        template_opts[:outvar] ||= '@_out_buf'
        unless template_opts.has_key?(:default_encoding)
          template_opts[:default_encoding] = Encoding.default_external
        end

        if opts[:escape]
          require 'tilt/erubi'
          template_opts[:escape] = true
        end
        template_opts.freeze

        engine_opts = opts[:engine_opts] = (opts[:engine_opts] || {}).dup
        engine_opts.to_a.each do |k,v|
          engine_opts[k] = v.dup.freeze
        end
        engine_opts.freeze

        opts.freeze
      end

      module ClassMethods
        # Copy the rendering options into the subclass, duping
        # them as necessary to prevent changes in the subclass
        # affecting the parent class.
        def inherited(subclass)
          super
          opts = subclass.opts[:render] = subclass.opts[:render].dup
          opts[:cache] = opts[:cache].dup
          opts.freeze
        end

        # Return the render options for this class.
        def render_opts
          opts[:render]
        end
      end

      module InstanceMethods
        # Render the given template. See Render for details.
        def render(template, opts = OPTS, &block)
          opts = render_template_opts(template, opts)
          retrieve_template(opts).render((opts[:scope]||self), (opts[:locals]||OPTS), &block)
        end

        # Return the render options for the instance's class.
        def render_opts
          self.class.render_opts
        end

        # Render the given template.  If there is a default layout
        # for the class, take the result of the template rendering
        # and render it inside the layout.  See Render for details.
        def view(template, opts=OPTS)
          opts = parse_template_opts(template, opts)
          content = opts[:content] || render_template(opts)

          if layout_opts  = view_layout_opts(opts)
            content = render_template(layout_opts){content}
          end

          content
        end

        private

        # Convert template options to single hash when rendering templates using render.
        def render_template_opts(template, opts)
          parse_template_opts(template, opts)
        end

        # Private alias for render.  Should be used by other plugins when they want to render a template
        # without a layout, as plugins can override render to use a layout.
        alias render_template render

        # If caching templates, attempt to retrieve the template from the cache.  Otherwise, just yield
        # to get the template.
        def cached_template(opts, &block)
          if (!render_opts[:explicit_cache] || opts[:cache]) && (key = opts[:cache_key])
            cache = render_opts[:cache]
            unless template = cache[key]
              template = cache[key] = yield
            end
            template
          else
            yield
          end
        end

        # Given the template name and options, set the template class, template path/content,
        # template block, and locals to use for the render in the passed options.
        def find_template(opts)
          render_opts = render_opts()
          engine_override = opts[:engine]
          engine = opts[:engine] ||= render_opts[:engine]
          if content = opts[:inline]
            path = opts[:path] = content
            template_class = opts[:template_class] ||= ::Tilt[engine]
            opts[:template_block] = Proc.new{content}
          else
            opts[:views] ||= render_opts[:views]
            path = opts[:path] ||= template_path(opts)
            template_class = opts[:template_class]
            opts[:template_class] ||= ::Tilt
          end

          if (cache = opts[:cache]).nil?
            cache = content || !opts[:template_block]
          end

          if cache
            template_block = opts[:template_block] unless content
            template_opts = opts[:template_opts]

            opts[:cache_key] ||= if template_class || engine_override || template_opts || template_block
              [path, template_class, engine_override, template_opts, template_block]
            else
              path
            end
          else
            opts.delete(:cache_key)
          end

          opts
        end

        # Return a single hash combining the template and opts arguments.
        def parse_template_opts(template, opts)
          opts = Hash[opts]
          if template.is_a?(Hash)
            opts.merge!(template)
          else
            opts[:template] = template
            opts
          end
        end

        # The default render options to use.  These set defaults that can be overridden by
        # providing a :layout_opts option to the view/render method.
        def render_layout_opts
          Hash[render_opts[:layout_opts]]
        end

        # Retrieve the Tilt::Template object for the given template and opts.
        def retrieve_template(opts)
          unless opts[:cache_key] && opts[:cache] != false
            found_template_opts = opts = find_template(opts)
          end
          cached_template(opts) do
            opts = found_template_opts || find_template(opts)
            template_opts = render_opts[:template_opts]
            if engine_opts = render_opts[:engine_opts][opts[:engine]]
              template_opts = Hash[template_opts].merge!(engine_opts)
            end
            if current_template_opts = opts[:template_opts]
              template_opts = Hash[template_opts].merge!(current_template_opts)
            end
            opts[:template_class].new(opts[:path], 1, template_opts, &opts[:template_block])
          end
        end

        # The name to use for the template.  By default, just converts the :template option to a string.
        def template_name(opts)
          opts[:template].to_s
        end

        # The template path for the given options.
        def template_path(opts)
          path = "#{opts[:views]}/#{template_name(opts)}.#{opts[:engine]}"
          if opts.fetch(:check_paths){render_opts[:check_paths]}
            full_path = self.class.expand_path(path)
            unless render_opts[:allowed_paths].any?{|f| full_path.start_with?(f)}
              raise RodaError, "attempt to render path not in allowed_paths: #{full_path} (allowed: #{render_opts[:allowed_paths].join(', ')})"
            end
          end
          path
        end

        # If a layout should be used, return a hash of options for
        # rendering the layout template.  If a layout should not be
        # used, return nil.
        def view_layout_opts(opts)
          if layout = opts.fetch(:layout, render_opts[:layout])
            layout_opts = render_layout_opts

            method_layout_opts = opts[:layout_opts]
            layout_opts.merge!(method_layout_opts) if method_layout_opts

            case layout
            when Hash
              layout_opts.merge!(layout)
            when true
              # use default layout
            else
              layout_opts[:template] = layout
            end

            layout_opts
          end
        end
      end
    end

    register_plugin(:render, Render)
  end
end