[Proposal] Re-export config in v4 and synchronize main thread config and worker config

package.json

@@ -17,6 +17,11 @@
       "require": "./dist/commonjs/experimental/index.js",
       "default": "./dist/es2017/experimental/index.js"
     },
+    "./experimental/config": {
+      "import": "./dist/es2017/config.js",
+      "require": "./dist/commonjs/config.js",
+      "default": "./dist/es2017/config.js"
+    },
     "./experimental/features": {
       "import": "./dist/es2017/experimental/features/index.js",
       "require": "./dist/commonjs/experimental/features/index.js",

src/config.ts

@@ -9,13 +9,21 @@
 import type { IDefaultConfig } from "./default_config";
 import DEFAULT_CONFIG from "./default_config";
 import deepMerge from "./utils/deep_merge";
+import EventEmitter from "./utils/event_emitter";
 
-class ConfigHandler {
-  _config = DEFAULT_CONFIG;
+interface IConfigHandlerEvents {
+  update: Partial<IDefaultConfig>;
+}
+
+class ConfigHandler extends EventEmitter<IConfigHandlerEvents> {
+  public updated = false;
+  private _config = DEFAULT_CONFIG;
 
   update(config: Partial<IDefaultConfig>) {
     const newConfig = deepMerge(this._config, config);
     this._config = newConfig;
+    this.updated = true;
+    this.trigger("update", config);
   }
 
   getCurrent(): IDefaultConfig {

src/core/main/worker/worker_main.ts

@@ -401,6 +401,11 @@ export default function initializeWorkerMain() {
         break;
       }
 
+      case MainThreadMessageType.ConfigUpdate: {
+        config.update(msg.value);
+        break;
+      }
+
       default:
         assertUnreachable(msg);
     }

src/default_config.ts

@@ -1195,3 +1195,24 @@ const DEFAULT_CONFIG = {
 
 export type IDefaultConfig = typeof DEFAULT_CONFIG;
 export default DEFAULT_CONFIG;
+
+// NOTE Because the config may have to be serialized and shared between several
+// environments, we check here that some strict type is respected:
+//   - only a subset of types are authorized for now, just make it easier to
+//     reason about.
+//   - Needs to make sense in JSON: no `function`, no `Date`, no `undefined`...
+interface IGenericConfigData {
+  [key: string]:
+    | string
+    | number
+    | boolean
+    | number[]
+    | string[]
+    | Partial<Record<string, string[]>>
+    | IGenericConfigData;
+}
+
+function checkIsSerializable(_conf: IGenericConfigData): void {
+  // noop
+}
+checkIsSerializable(DEFAULT_CONFIG);

src/main_thread/api/public_api.ts

@@ -32,13 +32,15 @@ import getStartDate from "../../compat/get_start_date";
 import hasMseInWorker from "../../compat/has_mse_in_worker";
 import hasWorkerApi from "../../compat/has_worker_api";
 import isDebugModeEnabled from "../../compat/is_debug_mode_enabled";
+import config from "../../config";
 import type { ISegmentSinkMetrics } from "../../core/segment_sinks/segment_buffers_store";
 import type {
   IAdaptationChoice,
   IInbandEvent,
   IABRThrottlers,
   IBufferType,
 } from "../../core/types";
+import type { IDefaultConfig } from "../../default_config";
 import type { IErrorCode, IErrorType } from "../../errors";
 import { ErrorCodes, ErrorTypes, formatError, MediaError } from "../../errors";
 import WorkerInitializationError from "../../errors/worker_initialization_error";
@@ -573,6 +575,21 @@ class Player extends EventEmitter<IPublicAPIEvent> {
         },
         this._destroyCanceller.signal,
       );
+
+      const sendConfigUpdates = (updates: Partial<IDefaultConfig>) => {
+        if (this._priv_worker === null) {
+          return;
+        }
+        log.debug("---> Sending To Worker:", MainThreadMessageType.ConfigUpdate);
+        this._priv_worker.postMessage({
+          type: MainThreadMessageType.ConfigUpdate,
+          value: updates,
+        });
+      };
+      if (config.updated) {
+        sendConfigUpdates(config.getCurrent());
+      }
+      config.addEventListener("update", sendConfigUpdates, this._destroyCanceller.signal);
     });
   }
 

src/multithread_types.ts

@@ -14,6 +14,7 @@ import type {
   IRepresentationsChoice,
   ITrackSwitchingMode,
 } from "./core/types";
+import type { IDefaultConfig } from "./default_config";
 import type {
   ISerializedMediaError,
   ISerializedNetworkError,
@@ -158,6 +159,12 @@ export interface ILogLevelUpdateMessage {
   };
 }
 
+/** Message sent by the main thread to update the Worker's global config. */
+export interface IConfigUpdateMessage {
+  type: MainThreadMessageType.ConfigUpdate;
+  value: Partial<IDefaultConfig>;
+}
+
 /**
  * Message sent by the main thread when a new content should be "prepared".
  *
@@ -542,6 +549,7 @@ export const enum MainThreadMessageType {
   RemoveTextDataError = "remove-text-error",
   CodecSupportUpdate = "codec-support-update",
   ContentUrlsUpdate = "urls-update",
+  ConfigUpdate = "config-update",
   DecipherabilityStatusUpdate = "decipherability-update",
   LogLevelUpdate = "log-level-update",
   MediaSourceReadyStateChange = "media-source-ready-state-change",
@@ -560,6 +568,7 @@ export const enum MainThreadMessageType {
 export type IMainThreadMessage =
   | IInitMessage
   | ILogLevelUpdateMessage
+  | IConfigUpdateMessage
   | IPrepareContentMessage
   | IStopContentMessage
   | IStartPreparedContentMessage