feat: extend conditional_get with Prism and ConditionalGet

lib/prism/conditional_get.rb

@@ -0,0 +1,75 @@
+module Prism
+  # HTTP conditional GET support (ETag / Last-Modified), mixed into
+  # Controller alongside Renderable. Requires the host to provide
+  # `headers`, `request` and `halt` (all supplied by Renderable).
+  module ConditionalGet
+    # Sets ETag/Last-Modified and halts with 304 if the client's cached
+    # copy is still fresh. Returns nil (via halt) when it short-circuits.
+    def fresh_when(etag: nil, last_modified: nil, weak: true)
+      set_conditional_headers(etag: etag, last_modified: last_modified, weak: weak)
+      halt(412, '') if precondition_failed?
+      halt(304, '') if request_fresh?
+    end
+
+    # Sets ETag/Last-Modified and returns whether the response is stale
+    # (i.e. whether the caller should still render). Halts with 304 itself
+    # when the client's copy is fresh, so callers can write
+    # `render(...) if stale?(etag: post)`.
+    def stale?(etag: nil, last_modified: nil, weak: true)
+      set_conditional_headers(etag: etag, last_modified: last_modified, weak: weak)
+      halt(412, '') if precondition_failed?
+      fresh = request_fresh?
+      halt(304, '') if fresh
+      !fresh
+    end
+
+    private
+
+    # If-Match/If-Unmodified-Since guard writes against the lost-update
+    # problem: unlike If-None-Match/If-Modified-Since (which ask "may I
+    # skip re-sending this?"), these ask "does the client's copy still
+    # match what's on the server?" and abort the request with 412 when it
+    # does not, regardless of HTTP method.
+    def precondition_failed?
+      match = request.headers['If-Match']
+      unmodified_since = request.headers['If-Unmodified-Since']
+      return false if match.nil? && unmodified_since.nil?
+
+      match_ok = match.nil? || etag_matches?(match)
+      unmodified_ok = unmodified_since.nil? || not_modified_since?(unmodified_since)
+      !(match_ok && unmodified_ok)
+    end
+
+    def set_conditional_headers(etag:, last_modified:, weak:)
+      if etag
+        digest = Digest::SHA1.hexdigest(etag.to_s)
+        headers['ETag'] = weak ? %(W/"#{digest}") : %("#{digest}")
+      end
+      headers['Last-Modified'] = last_modified.utc.httpdate if last_modified
+    end
+
+    def request_fresh?
+      none_match = request.headers['If-None-Match']
+      modified_since = request.headers['If-Modified-Since']
+      return false if none_match.nil? && modified_since.nil?
+
+      etag_fresh = none_match.nil? || etag_matches?(none_match)
+      time_fresh = modified_since.nil? || not_modified_since?(modified_since)
+      etag_fresh && time_fresh
+    end
+
+    def etag_matches?(header_value)
+      current = headers['ETag']
+      return false unless current
+      header_value.split(',').map(&:strip).any? { |candidate| candidate == '*' || candidate == current }
+    end
+
+    def not_modified_since?(header_value)
+      current = headers['Last-Modified']
+      return false unless current
+      Time.httpdate(header_value) >= Time.httpdate(current)
+    rescue ArgumentError
+      false
+    end
+  end
+end

lib/prism/controller.rb

@@ -1,22 +1,48 @@
 module Prism
   class Controller
     include Renderable
+    include ConditionalGet
 
     class << self
+      # Combines this controller's own filters with everything declared on
+      # its ancestors, ancestors first, so a shared ApplicationController can
+      # declare `protect_from_forgery`/`before_action :require_authentication`
+      # once and have every subclass run it - the same way `layout`/
+      # `views_root` already fall back to the superclass.
       def before_actions
-        @before_actions ||= []
+        own = @before_actions ||= []
+        superclass.respond_to?(:before_actions) ? superclass.before_actions + own : own
       end
 
       def after_actions
-        @after_actions ||= []
+        own = @after_actions ||= []
+        superclass.respond_to?(:after_actions) ? superclass.after_actions + own : own
+      end
+
+      # Own handlers first (most recently declared first, like Rails'
+      # reverse-declaration-order matching), then the superclass's - so an
+      # ApplicationController-wide `rescue_from StandardError` never shadows
+      # a more specific handler a subclass declares for itself.
+      def rescue_handlers
+        own = (@rescue_handlers ||= []).reverse
+        superclass.respond_to?(:rescue_handlers) ? own + superclass.rescue_handlers : own
+      end
+
+      def rescue_from(*exception_classes, with: nil, &block)
+        raise ArgumentError, 'rescue_from needs with: or a block' unless with || block
+        exception_classes.each { |klass| (@rescue_handlers ||= []) << { klass: klass, with: with, block: block } }
       end
 
       def before_action(*names, only: nil, except: nil, &block)
-        register_filter(before_actions, names, only, except, block)
+        register_filter(@before_actions ||= [], names, only, except, block)
       end
 
       def after_action(*names, only: nil, except: nil, &block)
-        register_filter(after_actions, names, only, except, block)
+        register_filter(@after_actions ||= [], names, only, except, block)
+      end
+
+      def protect_from_forgery(only: nil, except: nil)
+        before_action(:verify_authenticity_token!, only: only, except: except)
       end
 
       def layout(name = :missing)
@@ -29,8 +55,11 @@ module Prism
         @views_root || superclass_views_root || 'app/views'
       end
 
+      # "posts" for PostsController, "admin/posts" for Admin::PostsController
+      # (keeps the full module path so namespaced views live under
+      # app/views/admin/posts/, matching Rails' convention).
       def controller_path
-        Inflector.underscore(name.to_s.split('::').last.sub(/Controller\z/, ''))
+        Inflector.underscore(name.to_s.sub(/Controller\z/, ''))
       end
 
       private
@@ -61,8 +90,12 @@ module Prism
 
     def process
       catch(:halt) do
+        begin
           run_before_actions
           finalize_body(send(@action_name))
+        rescue StandardError => e
+          handle_exception(e)
+        end
       end
       catch(:halt) { run_after_actions }
       finalize_flash
@@ -82,9 +115,40 @@ module Prism
       view_resolver.render_collection(partial_path(name), collection, locals: locals, as: as)
     end
 
+    # Rails-style content negotiation: `respond_to { |f| f.html { render }; f.json { json(x) } }`.
+    # Renders 406 when the negotiated format (see Request#format) has no matching block.
+    def respond_to
+      responder = Responder.new
+      yield responder
+      format = request.format
+      responder.respond(format)
+    rescue Responder::UnknownFormat
+      halt(406, "Not Acceptable: #{format}")
+    end
+
     private
 
+    UnsafeMethods = %w[POST PUT PATCH DELETE].freeze
+
+    def verify_authenticity_token!
+      return unless UnsafeMethods.include?(@request.request_method)
+      token = params['authenticity_token'] || @request.headers['X-Csrf-Token']
+      halt(422, 'invalid authenticity token') unless csrf.valid_token?(token)
+    end
+
+    # Finds the most specific registered `rescue_from` handler (`is_a?`
+    # against the raised exception) and runs it - the handler is expected
+    # to finish the response itself (`halt`/`render`/`redirect`), the same
+    # contract Rails' rescue_from has. Re-raises when nothing matches, so
+    # an unhandled exception still reaches the application-level fallback.
+    def handle_exception(exception)
+      handler = self.class.rescue_handlers.find { |candidate| exception.is_a?(candidate[:klass]) }
+      raise exception unless handler
+      handler[:block] ? instance_exec(exception, &handler[:block]) : send(handler[:with], exception)
+    end
+
     def finalize_body(result)
+      return if @response.streaming?
       return unless @response.body.empty?
       @response.body = [result.to_s] if result.is_a?(String)
     end
@@ -94,7 +158,7 @@ module Prism
     end
 
     def view_resolver
-      @view_resolver ||= View.new(self.class.views_root)
+      @view_resolver ||= View.new(self.class.views_root, helpers: self)
     end
 
     def run_before_actions