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Transfer protocol specification

General notes

Variables

Elements like {ID} represents variables that will be replaced at runtime.

Examples

URL : /music/{ID}/ needs a song ID to be valid.

REST

For convenience, all endpoints must comply to the REST convention. More information is available on Wikipedia.

In short, RESTful services build their URL this way :

/{OBJET_TYPE}/{ID}

And the HTTP method define the action to be done.

PUT (Create) : Create a new instance

GET (Read) : Fetch information

POST (Update) : Update an existing instance

DELETE (Delete) : Delete an existing instance

Examples

GET /music/ will return all songs GET /music/{ID} will return one song according to the given ID POST /music/{ID} will update the given instance with the payload that is sent along.

Notes

Since this application is about getting information and sending commands, we should only use GET and POST on a limited set of URLs.

Extra data

In the case you want to implemented extra stuff, you can add an extra-data parameter to your input or your output, so you can add data without polluting the standardized dataset.

If you use it, you should use an application key to identify your application so our extra-data won't be mixed up. You can see an implementation of this principle down below.

Input format

Most of the time, the client won't need to send anything to the server.

POST (HTTP headers)
----
extra-data : {
    key: '{APPLICATION_KEY}',
    ...
}

This format will be used to illustrate a HTTP call and its payload. Everything below ------ should be its form data.

Output format

All returned output will be under this format :

    <response>
        <data>
            ...
        </data>
        <extra-data>
            <key>{APPLICATION_KEY}</key>
            ...
        </extra-data>
    </response>

The <data> tag is used to return main data (i.e, song list, etc.) and the <extra-data> tag is used to return extra information that your client and server will understand in the case you want to implement extra functionnality that might not be supported by other clients.

Serialization format

By default, the exchange format will be xml since the information returned by vlcj is already in this format.

Status code

All successful call will result in a HTTP 200 for the response status code. If a resource is unavailable or doesn't exist (i.e, fetching a song with the wrong id, or trying to play a song that doesn't exist), the server should answer with a HTTP 404. For other errors, the server should return a HTTP 500. You can return extra data about the error in the extra-data part of your response if you want, but the HTTP status should be enough to identify what type of error you are facing (maybe not HTTP 500, but it could be anything and you should check your server, it should not happen).

You must handle all response other than HTTP 200 as an error to prevent your client from crashing.

Model representation

Music

A song is represented by an id, the title and the artist

Example

    <song>
        <id>1</id>
        <title>Foo</title>
        <artist>Bar</artist>
    </song>

HTTP Endpoints

Here are all HTTP endpoints needed to communicate with the server with the complete details.

Music

Listing songs

URL : /music/

HTTP Method : GET

Expected input

None

Expected output

The expected output should be a list of MP3 metadata that is given by vlcj.

Example
    <response>
        <data>
            <songs>
                <song>
                    {MUSIC MODEL REPRESENTATION}
                </song>
                <song>
                    ...
                </song>
                ...
            </songs>
        </data>
        <extra-data>
            ...
        </extra-data>
    </response>

Get one song

URL : /music/{ID}/

HTTP Method : GET

Expected input

None, all parameters are in the URL

Expected output

The expected output should be the representation of one song has given by vlcj.

Example
    <response>
        <data>
            <song>
                {MUSIC MODEL REPRESENTATION}
            </song>
        </data>
        <extra-data>
            ...
        </extra-data>
    </response>

Video

We do not support videos.

Player

The player is more a controller than a model, but it will look like a REST endpoint too. This spec won't specify the behavior your server is supposed to have. For example, if you choose that playing a media clears the playlist, that's your choice. Another team could choose to just jump to the song in the current playlist if found in it.

Get the player status

URL : /player/

HTTP Method : GET

Expected input

None

Expected output

This should be the current song or video that is playing plus information about time left and what is the next item in the playlist if any. It should be empty if not playing.

Example
    <response>
        <data>
            <song>
                ...
            </song>
            OR NOTHING
            <play-info>
                <media-length>HH:MM:SS</media-length> // length of the media being played
                <play-time>HH:MM:SS</play-time> // what part the player is reading
                <next-media>
                    <type>MUSIC</type>
                    <id>{ID}</id>
                </next-media>
            </play-info>
        </data>
        <extra-data>
            ...
        </extra-data>
    </response>
Notes

You could poll this endpoint periodically to synchronize your player with the server. For example, if you want to display a seek bar and you want it to be in sync, just fetch the play-time and adjust your seek bar in consequence, but don't forget to take response time in account. It should be different when we will read the actual stream because it should provide a set of accurate information about that.

Play a media

URL : /player/

HTTP Method : POST

Expected input

The expected input must contain the action to execute (play), the type, and the id of the media to be played.

Example
POST
----
action: play
type: music
id: 1
play-time: 0:00
Expected output

None.

Notes

To seek to a specific time, play-time can be used to specify the desired time. When not defined, it should defaulted to 0:00 on the server.

Stop the player

URL : /player/

HTTP Method : POST

Expected input

The expected input must contain the action to execute (stop).

Expected output

None.

Play previous/next media

URL : /player/

HTTP Method : POST

Expected input

The expected input must contain the action to execute (previous / next).

Example
POST
----
action: next
Expected output

None.

Playlist

A playlist can contain different type of media.

Get the playlist

URL : /playlist/

HTTP Method : GET

Expected input

None.

Expected output

A list of media that is currently in the playlist.

Example
    <response>
        <data>
            <songs>
                <song>
                    {MUSIC MODEL REPRESENTATION}
                </song>
                ...
            </songs>
        </data>
        <extra-data>
            ...
        </extra-data>
    </response>

Add a media to the playlist

URL : /playlist/

HTTP Method : POST

Expected input

The expected input must contain the type, and the id of the media to be played.

Example
POST
----
id: 1
Expected output

None.

Remove a media from the playlist

URL : /playlist/{INDEX}/

HTTP Method : DELETE

Expected input

The expected input must contain the type, and the id of the media to be deleted.

Example
DELETE /playlist/1/ # to delete an element at the index 0

DELETE /playlist/ # to delete all element
Expected output

None.

Streaming

We only support music streaming using MP3.

Stream a media

URL : /player/

HTTP Method : POST

Expected input

The expected input must contain the type, and the id of the media to be streamed.

Example
POST
----
action: stream
type: music
id: 1
Expected output

None.

Notes

To control (play, stop, next, previous) the stream, you can use the same actions defined earlier. By default, the stream should be configured to play on the port 8888 (eg. 127.0.0.1:8888). If the parameter id is empty, it should, if playing, stream the current song.