From 94423e4eeef1e3666f9c2a3817873c19cd30501d Mon Sep 17 00:00:00 2001
From: hensm <m@matt.tf>
Date: Mon, 3 May 2021 16:03:45 +0100
Subject: [PATCH] Remove outdated documentation

---
 IMPLEMENTATION.md | 142 +---------------------------------------------
 1 file changed, 1 insertion(+), 141 deletions(-)

diff --git a/IMPLEMENTATION.md b/IMPLEMENTATION.md
index f1f321d..85e6ff1 100644
--- a/IMPLEMENTATION.md
+++ b/IMPLEMENTATION.md
@@ -1,141 +1 @@
-# Extension Lifetime
-
-## StatusManager
-
-The StatusManager (`background/StatusManager.ts`) keeps a bridge instance active throughout the lifetime of the extension. It listens for `main:/serviceUp`, `main:/serviceDown` and `main:/receiverStatus` messages to keep track of and update a list of receiver devices that can be provided to other extension components. It also emits `serviceUp`, `serviceDown` and `statusUpdate` events containing relevant data.
-
-If the StatusManager unexpectedly loses its bridge connection, it will automatically reconnect with a 10-second interval.
-
-## Shim Initialization
-
-The `shim/content.ts` content script is registered for all pages. It creates an empty `window.chrome` object in the page context since some sites may expect it to exist. It also intercepts any `src` attribute changes on `<script>` elements where the cast API may be loaded directly from a `chrome-extension://` URL, then sets them to the regular cast API script URL.
-
-The background script registers a `webRequest.onBeforeRequest` listener that intercepts requests to Google’s Cast API library.
-
-When a request is intercepted, the `shim/contentBridge.ts` script is executed in the content script context. This facilitates any message passing across content/page script isolation (the shim itself is executed in the page context, both for convenience — since it interacts substantially with page scripts — and to avoid page scripts calling into extension contexts).
-
-Messages passed to the shim are custom events of type `__castMessage`. Messages passed back from the shim are custom events of type `__castMessageResponse`. Event listening and creation is handled by the `shim/eventMessageChannel.ts` module.
-
-The `shim/contentBridge.ts` script creates a message port connection (named `"shim"`) to the background script through which messages from the shim are forwarded. Messages are forwarded to the bridge and other parts of the extension via the background script.  
-
-The request is then redirected to the shim bundle (`shim/index.ts`) which creates the `window.chrome.cast` API object.
-
-The `shim:/initialized` message is sent to the shim and the `window.__onGCastApiAvailable` callback is called with the availability state (bridge availability/compatibility is passed as the message data).
-
-The cast API is now available to the web app.
-
-The web app calls `chrome.cast.initialize` with an `ApiConfig` object containing the Chromecast receiver app ID to use. The shim sends a `main:/shimInitialized` message to the background script. The bridge sends `main:/serviceUp` messages for any discovered devices with device info (address, port, label, etc…).
-
-### ShimManager
-
-The ShimManager (`background/ShimManager.ts`) handles initialization of shims and communication between them and a bridge instance. Once created, it listens for and passes status updates from the StatusManager directly to any registered shims via `shim:/serviceUp`/`shim:/serviceDown` messages.
-
-It provides a public `createShim` method which takes a `MessagePort` or `runtime.Port` port object as an input, but has different behavior depending on what type of port.
-
-If the passed content port object is of type `MessagePort`, the shim was initialized in the background context, since we can't have a `runtime.Port` that outputs to itself (and we need some sort of message channel to pass as an output to the API consumer).
-
-The `createShim` method passes off to the internal `createShimFromBackground` and `createShimFromContent` methods, which do mostly the same thing, except that content script context shims have extra checking for tab/frame IDs. The shim is registered, the bridge port is hooked up to the content port (and vice-versa with the other content message handling in internal method `handleContentMessage`).
-
-A `Shim` object is returned which contains the required `bridgePort` and `contentPort` and optionally `contentTabId` and `contentFrameId` if initialized with a content script context shim.
-
-
-
-### Module
-
-The shim is designed to be injected into a running page or imported (via `shim/export.ts`) into another script. This is used for the built-in sender apps (media/mirroring) that run in the content script context.
-
-If the shim is injected into a page, `contentBridge.ts` is executed in the content script context and the main shim bundle (`shim/index.ts`) replaces the page-loaded cast API loader script.
-
-If the shim module is imported into another script, instead of setting the `window.__onGCastApiAvailable` callback, the module provides an `ensureInit` function which returns a promise. The consumer script must call this function and resolve the promise before calling any APIs (default export). The `ensureInit`-returned promise will resolve to a `MessagePort` object which can be used similarly to a WebExtension `runtime.Port`.
-
-````ts
-import cast, { ensureInit } from "./shim/export";
-
-ensureInit().then(backgroundPort => {
-    backgroundPort.postMessage({
-        subject: "bridge:/doSomething"
-    });
-
-    const sessionRequest = new cast.SessionRequest(
-            cast.media.DEFAULT_MEDIA_RECEIVER_APP_ID);
-    
-    // ...
-});
-````
-
-It creates a `MessageChannel` object where the `port1` property is a `MessagePort` used by the API consumer to communicate with the background script.
-
-Though the shim can only be imported into an extension context, hooking up message port communication is different depending on whether the it's a content script or background context.
-It determines this by checking the current URL protocol for `moz-extension:`, which is only true for the background script.
-
-The goal is for messages to be passed through the custom `MessageChannel` and routed appropriately, even if it's for a message that crosses no context boundaries (shim created and used in background context) where extension messaging cannot work.
-
-**Note: This could be needlessly complex, so PRs welcome for any kind of simplification here.**
-
-If in background context, the `ShimManager` is imported, initialized and the `port2` message port is passed to the `createShim` method which will setup the shim, pass messages from `port1` to the background script and pass messages from the background script back to `port1`. Incoming messages from `port1` are then passed over `shim/eventMessageChannel.ts` to the shim. Incoming messages from the shim over `shim/eventMessageChannel.ts` are posted to `port1`.
-
-If instead in a content script context, `shim/contentBridge.ts` is imported and with side-effects (background script still calls into ShimManager), it creates and exports a `backgroundPort`. The incoming messages on that port are posted to `port2` and the incoming messages on `port2` are posted to `backgroundPort`.
-
-<p align="center">
-    <img src="diagram_module.svg"
-         width="562"
-         vspace="10" hspace="10">
-</p>
-
-In either case, `port1` as part of a message channel to the background script is resolved as the result of the `ensureInit` promise as soon as the `shim:/initialized` message is passed to the shim.
-
-
-## User Interaction
-
-A user will trigger casting through the web app interface and the app calls `chrome.cast.requestSession`. The shim sends a `main:/selectReceiverBegin` message to the background script to open the receiver selector.
-
-The receiver selector is opened (popup browser window or native window depending on the receiver type). The receiver selector will handle user input and emit a `selected`, `cancelled`, or `error` event. Depending on the event, the background script will send a `shim:/selectReceiverEnd`, `shim:/selectReceiverCancelled` message to the shim. The `shim:/selectReceiverEnd` message contains info about the selected receiver and media type (`ReceiverSelection`).
-
-The shim then makes a connection to the selected receiver device and establishes the session.
-
-## Shim Implementation
-
-Cast SDK API calls are translated into Chromecast protocol messages and sent via `node-castv2`. Based on [@GPMDP/electron-chromecast](https://github.com/GPMDP/electron-chromecast), so there are many similarities. The shim and the bridge exchange messages to implement API methods which require communication with the receiver device.
-
-`Session` and `Media` objects have a counterpart object within the bridge. Some messages are routed directly to these objects. For `Session`, these are in the format `bridge:/session/impl_<methodName>`.
-
-
-# Message Table (VERY OUTDATED)
-
-<!--<img src="diagram.png" width="866">-->
-
-| No. | Subject                                       | Origin     | Destination | Description |
-| --: | --------------------------------------------- | ---------- | ----------- | ----------- |
-|  1  | `shim:/initialized`                           | background | shim        | Sent once bridge has been created. |
-|  2  | `bridge:/initialize`                          | shim       | bridge      | Starts network discovery. |
-|  3  | `shim:/serviceUp`                             | bridge     | shim        | Sent once a receiver device has been found. |
-|  4  | `shim:/serviceDown`                           | bridge     | shim        | Sent once a receiver device has been lost. |
-|  5  | `main:/openPopup`                             | shim       | background  | Opens the receiver selection popup. |
-|  6  | `popup:/assignShim`                           | background | popup       | Provides popup with tab/frame ID for the opener shim so that it can make a direct connection. |
-|  7  | `shim:/popupReady`                            | popup      | shim        | Sent once popup is ready to receive data. |
-|  8  | `popup:/populateReceiverList`                 | shim       | popup       | Provides popup with current `state.receiverList`. |
-|  9  | `shim:/selectReceiver`                        | popup      | shim        | Sent once a receiver has been selected. |
-| 10  | `popup:/close`                                | shim       | popup       | Closes popup. |
-| 11  | `bridge:/session/initialize`                  | shim       | bridge      | Initializes cast session with receiver device. |
-| 12  | `bridge:/session/close`                       | shim       | bridge      | Closes cast session. |
-| 13  | `shim:/session/connected`                     | bridge     | shim        | Sent once cast session has connected. |
-| 14  | `shim:/session/updateStatus`                  | bridge     | shim        | Provides shim session with status updates. |
-| 15  | `bridge:/session/impl_addMessageListener`     | shim       | bridge      | Sends data to bridge for implementation of `Session#addMessageListener` method. |
-| 16  | `bridge:/session/impl_sendMessage`            | shim       | bridge      | Sends data to bridge for implementation of `Session#sendMessage` method. |
-| 17  | `bridge:/session/impl_setReceiverMuted`       | shim       | bridge      | Sends data to bridge for implementation of `Session#setReceiverMuted` method. |
-| 18  | `bridge:/session/impl_setReceiverVolumeLevel` | shim       | bridge      | Sends data to bridge for implementation of `Session#setReceiverVolumeLevel` method. |
-| 19  | `bridge:/session/impl_stop`                   | shim       | bridge      | Sends data to bridge for implementation of `Session#stop` method. |
-| 20  | `bridge:/media/initialize`                    | shim       | bridge      | Initializes bridge media message handler. |
-| 21  | `bridge:/media/sendMediaMessage`              | shim       | bridge      | Sends media message to receiver device. |
-| 22  | `shim:/session/impl_addMessageListener`       | shim       | popup       | Response from bridge->shim counterpart message. |
-| 23  | `shim:/session/impl_sendMessage`              | shim       | popup       | Response from bridge->shim counterpart message. |
-| 24  | `shim:/session/impl_setReceiverMuted`         | shim       | popup       | Response from bridge->shim counterpart message. |
-| 25  | `shim:/session/impl_setReceiverVolumeLevel`   | shim       | popup       | Response from bridge->shim counterpart message. |
-| 26  | `shim:/session/impl_stop`                     | shim       | popup       | Response from bridge->shim counterpart message. |
-| 27  | `shim:/media/sendMediaMessageResponse`        | shim       | popup       | Response from `sendMediaMessage`. Contains error status. |
-| 28  | `shim:/media/update`                          | shim       | popup       | Provides shim media with status updates. |
-| 29  | `bridge:/startHttpServer`                     | mediaCast  | bridge      | Starts HTTP server for serving local media to receiver device. |
-| 30  | `bridge:/stopHttpServer`                      | mediaCast  | bridge      | Stops HTTP server. |
-| 31  | `mediaCast:/httpServerStarted`                | bridge     | mediaCast   | Sent once HTTP server has started. |
-| 32  | `updater:/updateData`                         | options    | updater     | Sends initialization data to updater popup. |
-
+# WIP