# iPX for iOS

ipx's page in an app, with the audio played by the phone rather than the page: it plays on with
the screen locked, and the lock screen, Control Center, headphones and a car over Bluetooth or USB
drive it. Everything you see is the page, as on the home screen; the app adds the player behind it.

## Build it

On a Mac with Xcode:

```sh
brew install xcodegen
cd ios && xcodegen generate && open iPX.xcodeproj
```

Set your team under Signing & Capabilities, pick your phone, and run. The project is generated
from `project.yml`, so `.xcodeproj` is not in git: edit the yml. Nothing on Tower can build it.

A free personal team works, but a build on it expires after seven days and is reinstalled from
Xcode. A paid account ($99 a year) makes that a year and adds TestFlight. Playing with the screen
locked is a plist key (`UIBackgroundModes: audio`), not an entitlement, so it works on either.
CarPlay's own dashboard app does not: Apple grants `com.apple.developer.carplay-audio` on request.

## Which server

The first launch asks, with `https://ipodderx.sdf1.net` filled in; a bare host gets `https://`.
Shake the phone to change it. Plain `http://` only on your own network
(`http://192.168.1.130:8099`), which is all `NSAllowsLocalNetworking` allows. Sign in on the page
that follows, through Cloudflare Access or ipx's own form; the cookies that leaves are what the
player uses (`CookieBridge`). `-ipx.server <url>` as a launch argument overrides it for a run.

## Player token

The player normally rides on the web view's cookie, which ends with Cloudflare Access's session.
To make it outlast that, shake the phone, choose Player Token and enter an ipx API token (the
page's Settings, API tokens) and the address to send it to, `https://ipxapi.sdf1.net`. The token is
kept in the keychain (`Credentials.swift`). The player's audio, positions, read flags, artwork and
the unread badge go to that address with `Authorization: Bearer`; the page still signs in as it
did, at the server address. Without a token the player sends only the cookie, as before.

`ipxapi.sdf1.net` is the tunnel's route to the same ipx-web as `ipodderx.sdf1.net`, with no Access
application in front, which would turn a bearer header away. Cloudflare's firewall (a custom rule
on the `sdf1.net` zone) blocks every request to it except a bearer-token one for `/api/feeds`,
`/api/me`, `/api/art`, `/api/entries/*` and `/media/*`; ipx still checks the token.

## How it hangs together

| | |
|---|---|
| `Sources/App.swift` | the app and its one scene |
| `Sources/WebViewController.swift` | the `WKWebView`, the server question, a page that will not load |
| `Sources/Bridge.swift` | the messages to and from `web/src/native.ts` |
| `Sources/Playback.swift` | `AVPlayer`, the audio session, now playing, the remote commands, saving positions |
| `Sources/CookieBridge.swift` | the web view's cookies into `HTTPCookieStorage.shared`, for the player |
| `Sources/Server.swift` | which server |

## The messages

The page's half is `web/src/native.ts`, and `node tests/native-bridge.ts` holds it to these. A
change to them is a change to both halves in one commit, and the page has to be deployed before
an app that needs it.

Page to app, on `webkit.messageHandlers.ipx`:

| | |
|---|---|
| `{t:"ready", version, rate, volume}` | the bridge is in |
| `{t:"load", url, enc, feedId, guid, title, feedTitle, artwork, position, duration, rate, volume}` | the element's `src` was set to an audio file |
| `{t:"play"}` `{t:"pause"}` `{t:"stop"}` | |
| `{t:"seek", to}` `{t:"rate", v}` `{t:"volume", v}` | |
| `{t:"position", url}` | save where we are; a path, not a time, since a page frozen in the background holds an old one |

App to page, as `window.ipxNative.on(...)`:

| | |
|---|---|
| `{t:"time", cur, dur}` | `timeupdate` |
| `{t:"meta", dur}` | `loadedmetadata`: the page seeks to where you left off |
| `{t:"state", playing}` | `play` or `pause` |
| `{t:"ended"}` | |
| `{t:"error", message}` | the page says so |

The app writes the position (every ten seconds and on pause) and marks an item read at 90%, from
its own clock, so both happen while the page is frozen. Video stays in the page.

## Not yet

* Episodes kept on the device (#412) are the page's service worker's, which a `WKWebView` does
  not run without App-Bound Domains; the app plays them from the server.
* Without the player token the cookie is the only credential: when Cloudflare Access's expires
  mid-drive, playback stops with "Sign in again", and opening the app signs in.
* CarPlay's dashboard app needs Apple's entitlement first; then it is a second scene over the same
  `Playback`.