Add before hooks for Pages

README.md

@@ -41,6 +41,11 @@ require "css"
 class ArticlesPage < Crumble::Page
   layout ToHtml::Layout
 
+  before do
+    # Return `true` to continue, `false` for 400, or an Int32 HTTP status code.
+    ctx.request.headers["X-Auth"]? == "1" ? true : 401
+  end
+
   view do
     css_class ArticleListBox
 
@@ -79,6 +84,31 @@ end
 
 - Pass a class to `view(SomeView)` if you prefer a reusable component.
 - `layout SomeLayout` can reference an existing layout class, which is just something with a `#to_html(io : IO)` method that yields; when omitted, the view renders bare.
+- Use `before { ... }` to short-circuit with `false` (400) or an `Int32` status code.
+
+#### Path matching
+
+Pages can declare URL parameters and nested segments with path-matching macros:
+
+```crystal
+class AccountPostDetailsPage < Crumble::Page
+  root_path "/accounts"
+  path_param account_id
+  path_param slug, /[a-z0-9-]+/
+  nested_path "posts"
+  nested_path "details"
+
+  view do
+    template do
+      page = ctx.handler.as(AccountPostDetailsPage)
+      p { "account_id=#{page.account_id} slug=#{page.slug}" }
+    end
+  end
+end
+
+AccountPostDetailsPage.uri_path(account_id: 123, slug: "hello-world")
+# => /accounts/123/hello-world/posts/details
+```
 
 ### Resources
 

spec/page/before_spec.cr

@@ -0,0 +1,56 @@
+require "../spec_helper"
+
+module Crumble::Page::BeforeSpec
+  class Parent < Crumble::Page
+    before do
+      ctx.request.headers["X-OK"]? == "1"
+    end
+  end
+
+  class DeniedPage < Parent
+    before do
+      true
+    end
+
+    before do
+      403
+    end
+  end
+
+  class AllowedPage < Parent
+    view do
+      template do
+        p { "Success!" }
+      end
+    end
+  end
+
+  describe "DeniedPage" do
+    it "halts when parent before returns false" do
+      ctx = Crumble::Server::TestRequestContext.new(resource: DeniedPage.uri_path)
+      DeniedPage.handle(ctx).should eq(true)
+      ctx.response.status_code.should eq(400)
+    end
+
+    it "halts with status code when a before returns an Int32" do
+      headers = HTTP::Headers{"X-OK" => "1"}
+      ctx = Crumble::Server::TestRequestContext.new(resource: DeniedPage.uri_path, headers: headers)
+      DeniedPage.handle(ctx).should eq(true)
+      ctx.response.status_code.should eq(403)
+    end
+  end
+
+  describe "AllowedPage" do
+    it "renders when before returns true" do
+      res = String.build do |io|
+        headers = HTTP::Headers{"X-OK" => "1"}
+        ctx = Crumble::Server::TestRequestContext.new(response_io: io, resource: AllowedPage.uri_path, headers: headers)
+        AllowedPage.handle(ctx).should eq(true)
+        ctx.response.status_code.should eq(200)
+        ctx.response.flush
+      end
+
+      res.should contain("Success!")
+    end
+  end
+end

src/page/page.cr

@@ -8,6 +8,21 @@ abstract class Crumble::Page
     "Page"
   end
 
+  macro before(&blk)
+    def _before : Bool | Int32
+      {% if @type.has_method?("_before") %}
+        {% if @type.methods.map(&.name).includes?("_before") %}
+          prev = previous_def
+        {% else %}
+          prev = super
+        {% end %}
+        return prev unless prev == true
+      {% end %}
+
+      {{blk.body}}
+    end
+  end
+
   macro view(klass = nil, &blk)
     {% raise "Pass a view class or a block, not both" if klass && blk %}
     {% unless klass || blk %}{% raise "Provide a view class or block" %}{% end %}
@@ -66,6 +81,16 @@ abstract class Crumble::Page
     return false unless ctx.request.method == "GET"
 
     instance = new(ctx)
+    if instance.responds_to? :_before
+      ret_val = instance._before
+      if ret_val == false
+        ctx.response.status = :bad_request
+        return true
+      elsif ret_val.is_a?(Int32)
+        ctx.response.status_code = ret_val
+        return true
+      end
+    end
     instance.call
     true
   end