Support API reference URLs from the old site

Old site index is committed instead of fetched as that site is going to
be replaced with this one, so we expect not to be able to fetch it in the
future.

Tested with:
 - /manual/en/class.hack.vectortv.php
 - /manual/en/hack.vectortv.clear.php
 - /manual/en/function.hack.hh.asio.curl-exec.php

Author: fredemmott

bin/build.php

@@ -9,6 +9,8 @@ function hhvm_to_yaml(): void {
   (new GuidesIndexBuildStep())->buildAll();
   (new APIIndexBuildStep())->buildAll();
 
+  (new APILegacyRedirectsBuildStep())->buildAll();
+
   (new StaticResourceMapBuildStep())->buildAll();
 
   (new MergedMarkdownBuildStep())->buildAll();

legacy-docs-site-index.json

@@ -0,0 +1,113 @@
+<?hh // strict
+
+namespace HHVM\UserDocumentation;
+
+final class APILegacyRedirectsBuildStep extends BuildStep {
+  use CodegenBuildStep;
+
+  /*  curl http://docs.hhvm.com/manual/en/search-index.json \
+   *    > legacy-docs-site-index.json
+   *
+   * This file is committed instead of fetched as we expect that site to
+   * be taken down soon.
+   */
+  const string LEGACY_INDEX = LocalConfig::ROOT.'/legacy-docs-site-index.json';
+
+  public function buildAll(): void {
+    Log::i("\nAPILegacyRedirectsBuild");
+    $this->createIndex();
+  }
+
+  private function createIndex(
+  ): void {
+    $index = $this->generateIndexData();
+
+    $code = $this->writeCode(
+      'APILegacyRedirectData.hhi',
+      $index,
+    );
+    file_put_contents(
+      BuildPaths::APIDOCS_LEGACY_REDIRECTS,
+      $code,
+    );
+  }
+
+  private function generateIndexData(): array<string, string> {
+    $old_index = json_decode(file_get_contents(self::LEGACY_INDEX));
+    $old_classes = [];
+    $old_methods = [];
+    $old_functions = [];
+
+    Log::v("\nProcessing old site index");
+    foreach ($old_index as $entry) {
+      Log::v('.');
+      list ($name, $id, $type) = $entry;
+
+      $name = html_entity_decode($name);
+
+      if ($type === 'phpdoc:classref') {
+        $name = explode('<', $name)[0]; // remove generics
+        $old_classes[$name] = $id;
+        continue;
+      }
+      if ($type !== 'refentry') {
+        continue;
+      }
+      $parts = (new Vector(explode('::', $name)))
+        ->map($x ==> explode('<', $x)[0]);
+
+      if (count($parts) === 1) {
+        $old_functions[$parts[0]] = $id;
+        continue;
+      }
+
+      invariant(
+        count($parts) === 2,
+        "Definition %s has %d parts",
+        $name,
+        count($parts),
+      );
+
+      $old_methods[implode('::', $parts)] = $id;
+    }
+
+    Log::v("\nCross-referencing with current site index");
+
+    $old_ids_to_new_urls = [];
+
+    $classes = (Map {})
+      ->setAll(APIIndex::getClassIndex(APIDefinitionType::CLASS_DEF))
+      ->setAll(APIIndex::getClassIndex(APIDefinitionType::INTERFACE_DEF))
+      ->setAll(APIIndex::getClassIndex(APIDefinitionType::TRAIT_DEF));
+
+    foreach ($classes as $class) {
+      Log::v('.');
+      $old_id = idx($old_classes, $class['name']);
+
+      if ($old_id) {
+        $old_ids_to_new_urls[$old_id] =
+          URLBuilder::getPathForClass($class);
+      }
+
+      foreach ($class['methods'] as $method) {
+        $name = $class['name'].'::'.$method['name'];
+        $old_id = idx($old_methods, $class['name'].'::'.$method['name']);
+        if ($old_id) {
+          $old_ids_to_new_urls[$old_id] =
+            URLBuilder::getPathForMethod($method);
+        }
+      }
+    }
+
+    foreach (APIIndex::getFunctionIndex() as $function) {
+      Log::v('.');
+      $old_id = idx($old_functions, $function['name']);
+      if ($old_id) {
+        $old_ids_to_new_urls[$old_id] =
+          URLBuilder::getPathForFunction($function);
+      } 
+    }
+
+    return $old_ids_to_new_urls;
+  }
+}

src/build/APILegacyRedirectsBuildStep.php

@@ -10,6 +10,8 @@
   const string APIDOCS_MARKDOWN = LocalConfig::BUILD_DIR.'/api-markdown';
   const string APIDOCS_HTML = LocalConfig::BUILD_DIR.'/api-html';
   const string APIDOCS_INDEX = LocalConfig::BUILD_DIR.'/api-index.php';
+  const string APIDOCS_LEGACY_REDIRECTS
+    = LocalConfig::BUILD_DIR.'/api-legacy-redirects.php';
   const string APIDOCS_NAV_DATA = LocalConfig::BUILD_DIR.'/api-nav.js';
 
   const string GUIDES_MARKDOWN = LocalConfig::ROOT.'/guides';

src/build/BuildPaths.php

@@ -0,0 +1,10 @@
+<?hh // decl
+
+namespace HHVM\UserDocumentation;
+
+final class APILegacyRedirectData {
+  public static function getIndex(
+  ): array<string, string> {
+    /* CODEGEN GOES HERE */
+  }
+}

src/codegen-hhi/APILegacyRedirectData.hhi

@@ -0,0 +1,17 @@
+<?hh // strict
+
+use HHVM\UserDocumentation\BuildPaths;
+use HHVM\UserDocumentation\APILegacyRedirectData;
+
+require_once(BuildPaths::APIDOCS_LEGACY_REDIRECTS);
+
+final class APILegacyRedirectController extends WebController {
+  public async function respond(): Awaitable<void> {
+    $id = $this->getRequiredStringParam('legacy_id');
+    $url = idx(APILegacyRedirectData::getIndex(), $id);
+    if ($url) {
+      throw new RedirectException($url);
+    }
+    throw new HTTPNotFoundException();
+  }
+}

src/site/APILegacyRedirectController.php

@@ -21,6 +21,9 @@ private function getRoutes(
         => RedirectToGuideFirstPageController::class,
       '/{product:(?:hack|hhvm)}/{guide}/{page}'
         => GuidePageController::class,
+      '/manual/en/{legacy_id}.php'
+        => APILegacyRedirectController::class,
+
       '/__content'
         => WebPageContentController::class,
       '/s/{checksum}{file:/.+}'