# Android Auto Media Specification

## Purpose

PluriWave MUST expose a browsable station tree and play-by-media-id interface to Android Auto (projected) via the existing `PluriWaveAudioHandler` (`audio_service` MediaBrowserService/MediaSession), so a driver can browse and play stations from the car head unit without rebuilding the audio pipeline.

## Requirements

### Requirement: Android Auto Discovery Declaration

The app MUST declare itself as a media app to Android Auto so the car head unit discovers it.

#### Scenario: Android Auto scans installed apps

- GIVEN PluriWave is installed on the phone
- WHEN Android Auto scans installed apps for car-app support
- THEN it finds `res/xml/automotive_app_desc.xml` declaring `<uses name="media"/>`
- AND the `AndroidManifest.xml` `<application>` block declares `<meta-data android:name="com.google.android.gms.car.application" android:resource="@xml/automotive_app_desc"/>`
- AND PluriWave appears in the car's media app list

### Requirement: Browsable Media Tree

`getChildren` MUST return a browsable tree rooted at `AudioService.browsableRootId`, organized into non-playable folders (Favoritos, Todas las emisoras, Mis emisoras) containing playable station items. Playable station items SHOULD carry an audio-quality subtitle when known.
(Previously: no subtitle requirement; folders and playable items were otherwise unchanged.)

#### Scenario: Car requests the root

- GIVEN the car head unit connects and requests the root (`AudioService.browsableRootId`)
- WHEN `getChildren` is called with the root id
- THEN it returns three folder `MediaItem`s (Favoritos, Todas las emisoras, Mis emisoras), each with `playable: false`

#### Scenario: Car requests a folder with no stations

- GIVEN the user has zero favorite stations
- WHEN `getChildren` is called with the Favoritos folder id
- THEN it returns an empty list, not an error

#### Scenario: Browse requested before app state is loaded

- GIVEN the audio handler starts cold and station/favorites Provider state has not finished loading
- WHEN `getChildren` is called (root or any folder)
- THEN it returns a valid, possibly empty, list without throwing and without blocking or crashing the service

#### Scenario: Station has known codec and bitrate

- GIVEN a station's `Emisora.codec` and `Emisora.bitrate` are both known (non-null)
- WHEN it is mapped to a playable `MediaItem`
- THEN `displaySubtitle` SHALL contain a human-readable quality hint combining bitrate and codec (e.g. "128 kbps · MP3")

#### Scenario: Station has unknown codec or bitrate

- GIVEN a station's `Emisora.codec` or `Emisora.bitrate` (or both) is null/unknown
- WHEN it is mapped to a playable `MediaItem`
- THEN `displaySubtitle` SHALL omit the quality hint gracefully (no subtitle, or a subtitle with no quality fragment)
- AND the subtitle MUST NOT render literal placeholder text such as "null kbps" or "null · null"

### Requirement: Playable Item Metadata

Every playable `MediaItem` (station) MUST include a non-empty `title` and a loadable `artUri`. Stations without a logo MUST fall back to on-brand artwork, and stations whose logo URL cannot actually be loaded MUST degrade to the same on-brand fallback instead of rendering broken or blank art. The fallback MUST be visually consistent with the phone UI's per-station rotation rather than a generic launcher-icon copy.
(Previously: fallback only covered a null/empty favicon and pointed at a bundled default-artwork asset that read as a copy of the launcher icon.)

#### Scenario: Station has a valid, reachable remote logo

- GIVEN a station has a remote logo URL that resolves to a loadable image
- WHEN it is mapped to a `MediaItem`
- THEN `title` is the station name and `artUri` is the station's logo URL

#### Scenario: Station has no logo (Case A)

- GIVEN a station has no logo (`favicon` is null or empty)
- WHEN it is mapped to a `MediaItem`
- THEN `artUri` is set to one of the on-brand `station_art_*` fallback assets instead of being empty or null

#### Scenario: Station's logo URL is present but unreachable (Case B)

- GIVEN a station has a non-empty `favicon` URL that cannot be loaded (dead link, unreachable host, or non-image response)
- WHEN it is mapped to (or resolved as) a `MediaItem` in the Android Auto browse tree
- THEN the system SHALL show the same on-brand fallback art used for Case A instead of broken or blank art
- AND the car head unit MUST NOT display an empty, broken-image, or indefinitely-loading art tile for that station

#### Scenario: Fallback art matches phone-UI per-station selection

- GIVEN a station falls back to on-brand art (Case A or Case B)
- WHEN the fallback asset is chosen for that station
- THEN the selected asset MUST be one of the same 4 rotating assets used by the phone UI (`station_art_aurora`, `station_art_cosmic`, `station_art_pulse`, `station_art_nova`)
- AND the same station MUST deterministically resolve to the same asset on both the phone UI and Android Auto (per-station selection parity), not a random or session-varying choice

#### Scenario: Fallback art is on-brand, not the launcher icon

- GIVEN a station requires fallback art (Case A or Case B)
- WHEN its `artUri` is resolved
- THEN it MUST NOT point at a byte-for-byte copy of the app launcher icon
- AND it MUST point at one of the 4 on-brand `station_art_*` assets

### Requirement: Media Item Resolution by ID

`getMediaItem` MUST resolve a single station id to its full `MediaItem`, returning `null` for unknown ids instead of throwing.

#### Scenario: Known station id

- GIVEN a valid station id that exists in current state
- WHEN `getMediaItem(id)` is called
- THEN it returns the corresponding `MediaItem` with `title` and `artUri` populated

#### Scenario: Unknown station id

- GIVEN an id that does not match any known station or folder
- WHEN `getMediaItem(id)` is called
- THEN it returns `null` without throwing

### Requirement: Play by Media ID Reuses Existing Playback Path

`playFromMediaId` MUST resolve the id to an `Emisora` and invoke the existing internal `playMediaItem` path; it MUST NOT duplicate playback or reconnection logic.

#### Scenario: User selects a station in the car

- GIVEN the user taps a playable station item on the car head unit
- WHEN `playFromMediaId(id)` is called
- THEN the id is resolved to an `Emisora` via the existing resolution logic (`_emisoraDesdeMediaItem`)
- AND playback starts through the existing `playMediaItem` internal path
- AND no separate or duplicated playback logic is executed

#### Scenario: Unknown or stale media id

- GIVEN `playFromMediaId` is called with an id that no longer resolves to a known station
- WHEN resolution fails
- THEN playback does not start and no unhandled exception propagates from the handler

### Requirement: Playback State Synchronization

Play/pause/stop state changes MUST remain synchronized between the car head unit and the phone UI, regardless of which side initiated the change.

#### Scenario: User pauses from the car

- GIVEN a station is playing and projected to the car
- WHEN the user pauses from the car head unit
- THEN the phone UI reflects the paused state via the shared `MediaSession`/`PlaybackState`

#### Scenario: User pauses from the phone

- GIVEN a station is playing and projected to the car
- WHEN the user pauses from the phone UI
- THEN the car head unit reflects the paused state via the same shared session