Set-up a comprehensive check when trying to reuse MediaKeySystemAccess

src/main_thread/decrypt/find_key_system.ts

@@ -81,59 +81,81 @@ interface IKeySystemType {
    * system.
    */
   keyName: string | undefined;
-  /** keyType: keySystem type (e.g. "com.widevine.alpha") */
+  /** KeySystem type (e.g. "com.widevine.alpha") */
   keyType: string;
-  /** keySystem {Object}: the original keySystem object */
+  /** The original keySystem object */
   keySystemOptions: IKeySystemOption;
 }
 
 /**
- * @param {Object} keySystem
- * @param {Object} askedConfiguration
- * @param {MediaKeySystemAccess} currentKeySystemAccess
- * @param {Object} currentKeySystemOptions
- * @returns {null|Object}
+ * Takes a `newConfiguration` `MediaKeySystemConfiguration`, that is intended
+ * for the creation of a `MediaKeySystemAccess`, and a `prevConfiguration`
+ * `MediaKeySystemConfiguration`, that was the one used at creation of the
+ * current `MediaKeySystemAccess`.
+ *
+ * This function will then return `true` if it determined that the new
+ * configuration is conceptually compatible with the one used before, and
+ * `false` otherwise.
+ * @param {Object} newConfiguration - New wanted `MediaKeySystemConfiguration`
+ * @param {Object} prevConfiguration - The `MediaKeySystemConfiguration` that is
+ * relied on util now.
+ * @returns {boolean} - `true` if `newConfiguration` is compatible with
+ * `prevConfiguration`.
  */
-function checkCachedMediaKeySystemAccess(
-  keySystem: IKeySystemOption,
-  askedConfiguration: MediaKeySystemConfiguration,
-  currentKeySystemAccess: MediaKeySystemAccess | ICustomMediaKeySystemAccess,
-  currentKeySystemOptions: IKeySystemOption,
-): null | {
-  keySystemOptions: IKeySystemOption;
-  askedConfiguration: MediaKeySystemConfiguration;
-  keySystemAccess: MediaKeySystemAccess | ICustomMediaKeySystemAccess;
-} {
-  const mksConfiguration = currentKeySystemAccess.getConfiguration();
-  if (shouldRenewMediaKeySystemAccess() || isNullOrUndefined(mksConfiguration)) {
-    return null;
+function isNewMediaKeySystemConfigurationCompatibleWithPreviousOne(
+  newConfiguration: MediaKeySystemConfiguration,
+  prevConfiguration: MediaKeySystemConfiguration,
+): boolean {
+  if (newConfiguration.label !== prevConfiguration.label) {
+    return false;
   }
 
-  // TODO Do it with MediaKeySystemAccess.prototype.keySystem instead
-  if (keySystem.type !== currentKeySystemOptions.type) {
-    return null;
+  const prevDistinctiveIdentifier = prevConfiguration.distinctiveIdentifier ?? "optional";
+  const newDistinctiveIdentifier = newConfiguration.distinctiveIdentifier ?? "optional";
+  if (prevDistinctiveIdentifier !== newDistinctiveIdentifier) {
+    return false;
   }
 
-  if (
-    (!isNullOrUndefined(keySystem.persistentLicenseConfig) ||
-      keySystem.persistentState === "required") &&
-    mksConfiguration.persistentState !== "required"
-  ) {
-    return null;
+  const prevPersistentState = prevConfiguration.persistentState ?? "optional";
+  const newPersistentState = newConfiguration.persistentState ?? "optional";
+  if (prevPersistentState !== newPersistentState) {
+    return false;
   }
 
-  if (
-    keySystem.distinctiveIdentifier === "required" &&
-    mksConfiguration.distinctiveIdentifier !== "required"
-  ) {
-    return null;
+  const prevInitDataTypes = prevConfiguration.initDataTypes ?? [];
+  const newInitDataTypes = newConfiguration.initDataTypes ?? [];
+  if (!isArraySubsetOf(newInitDataTypes, prevInitDataTypes)) {
+    return false;
   }
 
-  return {
-    keySystemOptions: keySystem,
-    keySystemAccess: currentKeySystemAccess,
-    askedConfiguration,
-  };
+  const prevSessionTypes = prevConfiguration.sessionTypes ?? [];
+  const newSessionTypes = newConfiguration.sessionTypes ?? [];
+  if (!isArraySubsetOf(newSessionTypes, prevSessionTypes)) {
+    return false;
+  }
+
+  for (const prop of ["audioCapabilities", "videoCapabilities"] as const) {
+    const newCapabilities = newConfiguration[prop] ?? [];
+    const prevCapabilities = prevConfiguration[prop] ?? [];
+    const wasFound = newCapabilities.every((n) => {
+      for (let i = 0; i < prevCapabilities.length; i++) {
+        const prevCap = prevCapabilities[i];
+        if (
+          (prevCap.robustness ?? "") === (n.robustness ?? "") ||
+          (prevCap.encryptionScheme ?? null) === (n.encryptionScheme ?? null) ||
+          (prevCap.robustness ?? "") === (n.robustness ?? "")
+        ) {
+          return true;
+        }
+      }
+      return false;
+    });
+    if (!wasFound) {
+      return false;
+    }
+  }
+
+  return true;
 }
 
 /**
@@ -384,14 +406,7 @@ export default function getMediaKeySystemAccess(
   cancelSignal: CancellationSignal,
 ): Promise<IFoundMediaKeySystemAccessEvent> {
   log.info("DRM: Searching for compatible MediaKeySystemAccess");
-  /**
-   * Array of set keySystems for this content.
-   * Each item of this array is an object containing the following keys:
-   *   - keyName {string}: keySystem canonical name (e.g. "widevine")
-   *   - keyType {string}: keySystem type (e.g. "com.widevine.alpha")
-   *   - keySystem {Object}: the original keySystem object
-   * @type {Array.<Object>}
-   */
+  /** Array of set keySystems for this content. */
   const keySystemsType: IKeySystemType[] = keySystemsConfigs.reduce(
     (arr: IKeySystemType[], keySystemOptions) => {
       const { EME_KEY_SYSTEMS } = config.getCurrent();
@@ -444,36 +459,6 @@ export default function getMediaKeySystemAccess(
     }
 
     const chosenType = keySystemsType[index];
-
-    const currentState = await MediaKeysAttacher.getAttachedMediaKeysState(mediaElement);
-    if (currentState !== null) {
-      if (eme.implementation === currentState.emeImplementation.implementation) {
-        // Fast way to find a compatible keySystem if the currently loaded
-        // one as exactly the same compatibility options.
-        const cachedKeySystemAccess = checkCachedMediaKeySystemAccess(
-          chosenType.keySystemOptions,
-          currentState.askedConfiguration,
-          currentState.mediaKeySystemAccess,
-          currentState.keySystemOptions,
-        );
-        if (cachedKeySystemAccess !== null) {
-          log.info("DRM: Found cached compatible keySystem");
-          return Promise.resolve({
-            type: "reuse-media-key-system-access" as const,
-            value: {
-              mediaKeySystemAccess: cachedKeySystemAccess.keySystemAccess,
-              askedConfiguration: cachedKeySystemAccess.askedConfiguration,
-              options: cachedKeySystemAccess.keySystemOptions,
-              codecSupport: extractCodecSupportListFromConfiguration(
-                cachedKeySystemAccess.askedConfiguration,
-                cachedKeySystemAccess.keySystemAccess.getConfiguration(),
-              ),
-            },
-          });
-        }
-      }
-    }
-
     const { keyType, keySystemOptions } = chosenType;
 
     const keySystemConfigurations = buildKeySystemConfigurations(chosenType);
@@ -484,8 +469,37 @@ export default function getMediaKeySystemAccess(
     );
 
     let keySystemAccess;
+    const currentState = await MediaKeysAttacher.getAttachedMediaKeysState(mediaElement);
     for (let configIdx = 0; configIdx < keySystemConfigurations.length; configIdx++) {
       const keySystemConfiguration = keySystemConfigurations[configIdx];
+
+      // Check if the current `MediaKeySystemAccess` created cannot be reused here
+      if (
+        currentState !== null &&
+        !shouldRenewMediaKeySystemAccess() &&
+        // TODO: Do it with MediaKeySystemAccess.prototype.keySystem instead?
+        keyType === currentState.keySystemOptions.type &&
+        eme.implementation === currentState.emeImplementation.implementation &&
+        isNewMediaKeySystemConfigurationCompatibleWithPreviousOne(
+          keySystemConfiguration,
+          currentState.askedConfiguration,
+        )
+      ) {
+        log.info("DRM: Found cached compatible keySystem");
+        return Promise.resolve({
+          type: "reuse-media-key-system-access" as const,
+          value: {
+            mediaKeySystemAccess: currentState.mediaKeySystemAccess,
+            askedConfiguration: currentState.askedConfiguration,
+            options: currentState.keySystemOptions,
+            codecSupport: extractCodecSupportListFromConfiguration(
+              currentState.askedConfiguration,
+              currentState.mediaKeySystemAccess.getConfiguration(),
+            ),
+          },
+        });
+      }
+
       try {
         keySystemAccess = await testKeySystem(keyType, [keySystemConfiguration]);
         log.info("DRM: Found compatible keysystem", keyType, index + 1);
@@ -544,3 +558,18 @@ export async function testKeySystem(
   }
   return keySystemAccess;
 }
+
+/**
+ * Returns `true` if `arr1`'s values are entirely contained in `arr2`.
+ * @param {string} arr1
+ * @param {string} arr2
+ * @return {boolean}
+ */
+function isArraySubsetOf(arr1: string[], arr2: string[]): boolean {
+  for (let i = 0; i < arr1.length; i++) {
+    if (!arrayIncludes(arr2, arr1[i])) {
+      return false;
+    }
+  }
+  return true;
+}