Spike: Can we serve content directly from Publishing API?

.gitignore

@@ -14,6 +14,7 @@
 /coverage
 /spec/reports
 spec/examples.txt
+.byebug_history
 
 # Ignore the generated pact
 spec/pacts/publishing_api-content_store.json

Gemfile.lock

@@ -81,13 +81,13 @@ GEM
     ast (2.4.2)
     awesome_print (1.9.2)
     aws-eventstream (1.3.0)
-    aws-partitions (1.873.0)
-    aws-sdk-core (3.190.1)
+    aws-partitions (1.878.0)
+    aws-sdk-core (3.190.2)
       aws-eventstream (~> 1, >= 1.3.0)
       aws-partitions (~> 1, >= 1.651.0)
       aws-sigv4 (~> 1.8)
       jmespath (~> 1, >= 1.6.1)
-    aws-sdk-kms (1.75.0)
+    aws-sdk-kms (1.76.0)
       aws-sdk-core (~> 3, >= 3.188.0)
       aws-sigv4 (~> 1.1)
     aws-sdk-s3 (1.142.0)
@@ -101,7 +101,8 @@ GEM
     bindex (0.8.1)
     bootsnap (1.17.0)
       msgpack (~> 1.2)
-    brakeman (6.1.0)
+    brakeman (6.1.1)
+      racc
     brpoplpush-redis_script (0.1.3)
       concurrent-ruby (~> 1.0, >= 1.0.5)
       redis (>= 1.0, < 6)
@@ -137,7 +138,7 @@ GEM
     diff-lcs (1.5.0)
     dig_rb (1.0.1)
     docile (1.4.0)
-    domain_name (0.6.20231109)
+    domain_name (0.6.20240107)
     drb (2.2.0)
       ruby2_keywords
     erubi (1.12.0)
@@ -148,14 +149,14 @@ GEM
     factory_bot_rails (6.4.3)
       factory_bot (~> 6.4)
       railties (>= 5.0.0)
-    faraday (2.7.10)
-      faraday-net_http (>= 2.0, < 3.1)
-      ruby2_keywords (>= 0.0.4)
-    faraday-net_http (3.0.2)
-    ffi (1.15.5)
+    faraday (2.9.0)
+      faraday-net_http (>= 2.0, < 3.2)
+    faraday-net_http (3.1.0)
+      net-http
+    ffi (1.16.3)
     find_a_port (1.0.1)
     fuzzy_match (2.1.0)
-    gds-api-adapters (92.0.0)
+    gds-api-adapters (92.1.0)
       addressable
       link_header
       null_logger
@@ -171,10 +172,10 @@ GEM
       warden-oauth2 (~> 0.0.1)
     globalid (1.2.1)
       activesupport (>= 6.1)
-    google-protobuf (3.25.1)
-    google-protobuf (3.25.1-aarch64-linux)
-    google-protobuf (3.25.1-arm64-darwin)
-    google-protobuf (3.25.1-x86_64-linux)
+    google-protobuf (3.25.2)
+    google-protobuf (3.25.2-aarch64-linux)
+    google-protobuf (3.25.2-arm64-darwin)
+    google-protobuf (3.25.2-x86_64-linux)
     googleapis-common-protos-types (1.11.0)
       google-protobuf (~> 3.18)
     govspeak (8.3.2)
@@ -203,7 +204,7 @@ GEM
     govuk_personalisation (0.15.0)
       plek (>= 1.9.0)
       rails (>= 6, < 8)
-    govuk_publishing_components (37.0.0)
+    govuk_publishing_components (37.2.1)
       govuk_app_config
       govuk_personalisation (>= 0.7.0)
       kramdown
@@ -224,7 +225,7 @@ GEM
       capybara (>= 3.36)
       puma
       selenium-webdriver (>= 4.0)
-    hashdiff (1.0.1)
+    hashdiff (1.1.0)
     hashie (5.0.0)
     htmlentities (4.3.4)
     http-accept (1.7.0)
@@ -236,9 +237,9 @@ GEM
     i18n (1.14.1)
       concurrent-ruby (~> 1.0)
     io-console (0.7.1)
-    irb (1.11.0)
+    irb (1.11.1)
       rdoc
-      reline (>= 0.3.8)
+      reline (>= 0.4.2)
     jmespath (1.6.2)
     json (2.7.1)
     json-schema (4.1.1)
@@ -266,7 +267,7 @@ GEM
       net-smtp
     marcel (1.0.2)
     matrix (0.4.2)
-    mime-types (3.5.1)
+    mime-types (3.5.2)
       mime-types-data (~> 3.2015)
     mime-types-data (3.2023.1205)
     mini_mime (1.1.5)
@@ -275,14 +276,16 @@ GEM
     msgpack (1.7.2)
     multi_xml (0.6.0)
     mutex_m (0.2.0)
-    net-imap (0.4.8)
+    net-http (0.4.1)
+      uri
+    net-imap (0.4.9.1)
       date
       net-protocol
     net-pop (0.1.2)
       net-protocol
     net-protocol (0.2.2)
       timeout
-    net-smtp (0.4.0)
+    net-smtp (0.4.0.1)
       net-protocol
     netrc (0.11.0)
     nio4r (2.7.0)
@@ -305,7 +308,7 @@ GEM
       version_gem (~> 1.1)
     oj (3.16.3)
       bigdecimal (>= 3.0)
-    omniauth (2.1.1)
+    omniauth (2.1.2)
       hashie (>= 3.4.6)
       rack (>= 2.2.3)
       rack-protection
@@ -535,13 +538,13 @@ GEM
       term-ansicolor (~> 1.7)
       thor (>= 0.20, < 2.0)
     parallel (1.24.0)
-    parser (3.2.2.4)
+    parser (3.3.0.2)
       ast (~> 2.4.1)
       racc
     parslet (2.0.0)
     pg (1.5.4)
     plek (5.0.0)
-    prometheus_exporter (2.0.8)
+    prometheus_exporter (2.1.0)
       webrick
     psych (5.1.2)
       stringio
@@ -550,7 +553,8 @@ GEM
       nio4r (~> 2.0)
     racc (1.7.3)
     rack (2.2.8)
-    rack-protection (3.1.0)
+    rack-protection (3.2.0)
+      base64 (>= 0.1.0)
       rack (~> 2.2, >= 2.2.4)
     rack-proxy (0.7.7)
       rack
@@ -601,8 +605,8 @@ GEM
     redis (4.8.1)
     redis-namespace (1.11.0)
       redis (>= 4)
-    regexp_parser (2.8.3)
-    reline (0.4.1)
+    regexp_parser (2.9.0)
+    reline (0.4.2)
       io-console (~> 0.5)
     request_store (1.5.1)
       rack (>= 1.4)
@@ -648,10 +652,10 @@ GEM
       unicode-display_width (>= 2.4.0, < 3.0)
     rubocop-ast (1.30.0)
       parser (>= 3.2.1.0)
-    rubocop-capybara (2.19.0)
+    rubocop-capybara (2.20.0)
+      rubocop (~> 1.41)
+    rubocop-factory_bot (2.25.1)
       rubocop (~> 1.41)
-    rubocop-factory_bot (2.24.0)
-      rubocop (~> 1.33)
     rubocop-govuk (4.13.0)
       rubocop (= 1.59.0)
       rubocop-ast (= 1.30.0)
@@ -687,7 +691,7 @@ GEM
     sentry-sidekiq (5.16.1)
       sentry-ruby (~> 5.16.1)
       sidekiq (>= 3.0)
-    set (1.0.3)
+    set (1.1.0)
     sidekiq (6.5.12)
       connection_pool (>= 2.2.5, < 3)
       rack (~> 2.0)
@@ -731,6 +735,7 @@ GEM
     tzinfo (2.0.6)
       concurrent-ruby (~> 1.0)
     unicode-display_width (2.5.0)
+    uri (0.13.0)
     version_gem (1.1.3)
     warden (1.2.9)
       rack (>= 2.0.9)

app/controllers/content_store/content_items_controller.rb

@@ -0,0 +1,35 @@
+class ContentStore::ContentItemsController < ApplicationController
+  skip_before_action :authenticate_user!
+
+  def show
+    @edition = find_content_item(content_store: params[:content_store], path: base_path)
+    raise_error(404, "Could not find a content item for #{base_path}") unless @edition
+    # NOTE: version here is @edition.user_facing_version, not Event.maximum(:id)
+    # as that is only for managing conflicts between publishing-api and content-store
+    #
+    @content_item = DownstreamPayload.new(@edition, @edition.user_facing_version, draft: draft?)
+    render json: @content_item.content_store_payload
+  end
+
+private
+
+  def find_content_item(content_store:, path:)
+    FindByPath.new(Edition.where(content_store:)).find(path)
+  end
+
+  def draft?
+    params[:content_store] == "draft"
+  end
+
+  def raise_error(code, message)
+    raise CommandError.new(
+      code:,
+      error_details: {
+        error: {
+          code:,
+          message:,
+        },
+      },
+    )
+  end
+end

app/models/find_by_path.rb

@@ -0,0 +1,79 @@
+class FindByPath
+  attr_reader :model_class
+
+  def initialize(model_class)
+    @model_class = model_class
+  end
+
+  def find(path)
+    exact_match = model_class.where(base_path: path).take(1).first
+    return exact_match if exact_match
+
+    matches = find_route_matches(path)
+
+    if matches.count.positive?
+      best_route_match(matches, path)
+    end
+  end
+
+private
+
+  def find_route_matches(path)
+    query = model_class
+      .where("routes  @> ?", json_path_element(path, "exact"))
+      # ANY will match any of the given array elements (similar to IN(), but for JSON arrays)
+      # the ARRAY [?]::jsonb[] is typecasting for PostgreSQL's JSON operators
+      .or(model_class.where("routes @> ANY (ARRAY [?]::jsonb[])", potential_prefix_json_matches(path)))
+
+    if model_class.attribute_names.include?("redirects")
+      query = query
+      .or(model_class.where("redirects  @> ?", json_path_element(path, "exact")))
+      .or(model_class.where("redirects @> ANY (ARRAY [?]::jsonb[])", potential_prefix_json_matches(path)))
+    end
+    query
+  end
+
+  # Given a path, will decompose the path into path prefixes, and
+  # return a JSON array element that can be matched against the
+  # routes or redirects array in the model_class
+  def potential_prefix_json_matches(path)
+    potential_prefixes(path).map { |p| json_path_element(p, "prefix") }
+  end
+
+  def json_path_element(path, type)
+    [{ path:, type: }].to_json
+  end
+
+  def best_route_match(matches, path)
+    exact_route_match(matches, path) || best_prefix_match(matches, path)
+  end
+
+  def potential_prefixes(path)
+    paths = path.split("/").reject(&:empty?)
+    (0...paths.size).map { |i| "/#{paths[0..i].join('/')}" }
+  end
+
+  def exact_route_match(matches, path)
+    matches.detect do |item|
+      routes_and_redirects(item).any? do |route|
+        route["path"] == path && route["type"] == "exact"
+      end
+    end
+  end
+
+  def best_prefix_match(matches, path)
+    prefixes = potential_prefixes(path)
+    sorted = matches.sort_by do |item|
+      best_match = routes_and_redirects(item)
+        .select { |route| route["type"] == "prefix" && prefixes.include?(route["path"]) }
+        .min_by { |route| -route["path"].length }
+
+      -best_match["path"].length
+    end
+    sorted.first
+  end
+
+  def routes_and_redirects(item)
+    item.routes + (item.respond_to?(:redirects) ? item.redirects : [])
+  end
+end

config/routes.rb

@@ -38,6 +38,10 @@ def content_id_constraint(request)
 
       get "/links/changes", to: "link_changes#index"
     end
+
+    namespace :content_store, path: "/content-store" do
+      get "/:content_store(/*base_path)", to: "content_items#show"
+    end
   end
 
   get "/healthcheck/live", to: proc { [200, {}, %w[OK]] }