1 files changed, 118 insertions, 0 deletions
diff --git a/js/loader/ImportMap.h b/js/loader/ImportMap.h
new file mode 100644
index 0000000000..d304a52856
--- /dev/null
+++ b/js/loader/ImportMap.h
@@ -0,0 +1,118 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef js_loader_ImportMap_h
+#define js_loader_ImportMap_h
+
+#include <functional>
+#include <map>
+
+#include "js/SourceText.h"
+#include "mozilla/AlreadyAddRefed.h"
+#include "mozilla/Logging.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/UniquePtr.h"
+#include "nsStringFwd.h"
+#include "nsTArray.h"
+#include "ResolveResult.h"
+
+struct JSContext;
+class nsIScriptElement;
+class nsIURI;
+
+namespace JS::loader {
+class LoadedScript;
+class ScriptLoaderInterface;
+class ScriptLoadRequest;
+
+/**
+ * A helper class to report warning to ScriptLoaderInterface.
+ */
+class ReportWarningHelper {
+ public:
+  ReportWarningHelper(ScriptLoaderInterface* aLoader,
+                      ScriptLoadRequest* aRequest)
+      : mLoader(aLoader), mRequest(aRequest) {}
+
+  void Report(const char* aMessageName,
+              const nsTArray<nsString>& aParams = nsTArray<nsString>()) const;
+
+ private:
+  RefPtr<ScriptLoaderInterface> mLoader;
+  ScriptLoadRequest* mRequest;
+};
+
+// Specifier map from import maps.
+// https://html.spec.whatwg.org/multipage/webappapis.html#module-specifier-map
+using SpecifierMap =
+    std::map<nsString, nsCOMPtr<nsIURI>, std::greater<nsString>>;
+
+// Scope map from import maps.
+// https://html.spec.whatwg.org/multipage/webappapis.html#concept-import-map-scopes
+using ScopeMap = std::map<nsCString, mozilla::UniquePtr<SpecifierMap>,
+                          std::greater<nsCString>>;
+
+/**
+ * Implementation of Import maps.
+ * https://html.spec.whatwg.org/multipage/webappapis.html#import-maps
+ */
+class ImportMap {
+ public:
+  ImportMap(mozilla::UniquePtr<SpecifierMap> aImports,
+            mozilla::UniquePtr<ScopeMap> aScopes)
+      : mImports(std::move(aImports)), mScopes(std::move(aScopes)) {}
+
+  /**
+   * Parse the JSON string from the Import map script.
+   * This function will throw a TypeError if there's any invalid key or value in
+   * the JSON text according to the spec.
+   *
+   * https://html.spec.whatwg.org/multipage/webappapis.html#parse-an-import-map-string
+   */
+  static mozilla::UniquePtr<ImportMap> ParseString(
+      JSContext* aCx, JS::SourceText<char16_t>& aInput, nsIURI* aBaseURL,
+      const ReportWarningHelper& aWarning);
+
+  /**
+   * This implements "Resolve a module specifier" algorithm defined in the
+   * Import maps spec.
+   *
+   * See
+   * https://html.spec.whatwg.org/multipage/webappapis.html#resolve-a-module-specifier
+   *
+   * Impl note: According to the spec, if the specifier cannot be resolved, this
+   * method will throw a TypeError(Step 13). But the tricky part is when
+   * creating a module script,
+   * see
+   * https://html.spec.whatwg.org/multipage/webappapis.html#validate-requested-module-specifiers
+   * If the resolving failed, it shall catch the exception and set to the
+   * script's parse error.
+   * For implementation we return a ResolveResult here, and the callers will
+   * need to convert the result to a TypeError if it fails.
+   */
+  static ResolveResult ResolveModuleSpecifier(ImportMap* aImportMap,
+                                              ScriptLoaderInterface* aLoader,
+                                              LoadedScript* aScript,
+                                              const nsAString& aSpecifier);
+
+  // Logging
+  static mozilla::LazyLogModule gImportMapLog;
+
+ private:
+  /**
+   * https://html.spec.whatwg.org/multipage/webappapis.html#import-map-processing-model
+   *
+   * Formally, an import map is a struct with two items:
+   * 1. imports, a module specifier map, and
+   * 2. scopes, an ordered map of URLs to module specifier maps.
+   */
+  mozilla::UniquePtr<SpecifierMap> mImports;
+  mozilla::UniquePtr<ScopeMap> mScopes;
+};
+
+}  // namespace JS::loader
+
+#endif  // js_loader_ImportMap_h