From 72fecd41f2b7441bc26c779575bbdfc19a407fe8 Mon Sep 17 00:00:00 2001
From: Clare Ming <cming@wikimedia.org>
Date: Tue, 14 Dec 2021 12:58:54 -0700
Subject: [PATCH] Add feature flag for sticky table of contents

- Add TOC feature requirement.
- Update data for SkinVector.
- Add TOC template.

Bug: T297610
Change-Id: I90bc5e21ba187ac9dd74d5e97763834795a0545b
---
 includes/Constants.php                      | 20 +++++++++++++++++
 includes/ServiceWiring.php                  | 24 +++++++++++++++++++++
 includes/SkinVector.php                     | 12 +++++++++++
 includes/templates/TableOfContents.mustache |  3 +++
 includes/templates/skin.mustache            |  3 +++
 skin.json                                   |  7 ++++++
 6 files changed, 69 insertions(+)
 create mode 100644 includes/templates/TableOfContents.mustache

diff --git a/includes/Constants.php b/includes/Constants.php
index bae1c63..cf62adb 100644
--- a/includes/Constants.php
+++ b/includes/Constants.php
@@ -296,6 +296,26 @@ final class Constants {
 	 */
 	public const FEATURE_LANGUAGE_ALERT_IN_SIDEBAR = 'LanguageAlertInSidebar';
 
+	/**
+	 * @var string
+	 */
+	public const REQUIREMENT_TABLE_OF_CONTENTS = 'TableOfContents';
+
+	/**
+	 * @var string
+	 */
+	public const CONFIG_TABLE_OF_CONTENTS = 'VectorTableOfContents';
+
+	/**
+	 * @var string
+	 */
+	public const QUERY_PARAM_TABLE_OF_CONTENTS = 'tableofcontents';
+
+	/**
+	 * @var string
+	 */
+	public const FEATURE_TABLE_OF_CONTENTS = 'TableOfContents';
+
 	/**
 	 * This class is for namespacing constants only. Forbid construction.
 	 * @throws FatalError
diff --git a/includes/ServiceWiring.php b/includes/ServiceWiring.php
index ab9e243..d1f95eb 100644
--- a/includes/ServiceWiring.php
+++ b/includes/ServiceWiring.php
@@ -191,6 +191,30 @@ return [
 			]
 		);
 
+		// Feature: T297610: Table of Contents
+		// ================================
+		$featureManager->registerRequirement(
+			new OverridableConfigRequirement(
+				$services->getMainConfig(),
+				$context->getUser(),
+				$context->getRequest(),
+				null,
+				Constants::CONFIG_TABLE_OF_CONTENTS,
+				Constants::REQUIREMENT_TABLE_OF_CONTENTS,
+				Constants::QUERY_PARAM_TABLE_OF_CONTENTS,
+				null
+			)
+		);
+
+		$featureManager->registerFeature(
+			Constants::FEATURE_TABLE_OF_CONTENTS,
+			[
+				Constants::REQUIREMENT_FULLY_INITIALISED,
+				Constants::REQUIREMENT_LATEST_SKIN_VERSION,
+				Constants::REQUIREMENT_TABLE_OF_CONTENTS
+			]
+		);
+
 		// Feature: Use Wvui Search
 		// ================================
 		$featureManager->registerRequirement(
diff --git a/includes/SkinVector.php b/includes/SkinVector.php
index 67b36bf..8a2be3e 100644
--- a/includes/SkinVector.php
+++ b/includes/SkinVector.php
@@ -461,6 +461,16 @@ class SkinVector extends SkinMustache {
 		return $featureManager->isFeatureEnabled( Constants::FEATURE_LANGUAGE_ALERT_IN_SIDEBAR );
 	}
 
+	/**
+	 * Determines if the Table of Contents should be visible.
+	 *
+	 * @return bool
+	 */
+	private function isTableOfContentsVisible(): bool {
+		$featureManager = VectorServices::getFeatureManager();
+		return $featureManager->isFeatureEnabled( Constants::FEATURE_TABLE_OF_CONTENTS );
+	}
+
 	/**
 	 * @inheritDoc
 	 */
@@ -498,6 +508,8 @@ class SkinVector extends SkinMustache {
 			'is-language-in-content-top' => $this->isLanguagesInContentAt( 'top' ),
 			'is-language-in-content-bottom' => $this->isLanguagesInContentAt( 'bottom' ),
 
+			'is-vector-table-of-contents-visible' => $this->isTableOfContentsVisible(),
+
 			'data-search-box' => $this->getSearchData(
 				$parentData['data-search-box'],
 				!$this->isLegacy(),
diff --git a/includes/templates/TableOfContents.mustache b/includes/templates/TableOfContents.mustache
new file mode 100644
index 0000000..3f5478c
--- /dev/null
+++ b/includes/templates/TableOfContents.mustache
@@ -0,0 +1,3 @@
+<div id="mw-panel-toc" class="mw-sidebar">
+	<!-- sticky TOC goes here -->
+</div>
diff --git a/includes/templates/skin.mustache b/includes/templates/skin.mustache
index 101c08a..e7e77a3 100644
--- a/includes/templates/skin.mustache
+++ b/includes/templates/skin.mustache
@@ -43,6 +43,9 @@
 	{{#sidebar-visible}}checked{{/sidebar-visible}}>
 
 {{>Header}}
+
+{{#is-vector-table-of-contents-visible}}{{>TableOfContents}}{{/is-vector-table-of-contents-visible}}
+
 <div class="mw-workspace-container">
 	{{>Navigation}}
 	<div class="mw-content-container">
diff --git a/skin.json b/skin.json
index d09128b..7e37621 100644
--- a/skin.json
+++ b/skin.json
@@ -420,6 +420,13 @@
 		"VectorDisableSidebarPersistence": {
 			"value": false,
 			"description": "@var boolean Temporary feature flag that disables saving the sidebar expanded/collapsed state as a user-preference (triggered via clicking the main menu icon). This is intended as a temporary kill-switch in the event that the DB is overloaded with writes to the user_options table."
+		},
+		"VectorTableOfContents": {
+			"value": {
+				"logged_in": false,
+				"logged_out": false
+			},
+			"description": "@var When `VectorTableOfContents` is enabled, the sticky table of contents is shown."
 		}
 	},
 	"ServiceWiringFiles": [