// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

module presentation;

struct PresentationSessionInfo {
  string url;
  string id;
};

enum PresentationSessionState {
  CONNECTED,
  DISCONNECTED
};

enum PresentationErrorType {
  NO_AVAILABLE_SCREENS,
  SESSION_REQUEST_CANCELLED,
  NO_PRESENTATION_FOUND,
  UNKNOWN,
};

struct PresentationError {
  PresentationErrorType error_type;
  string message;
};

enum PresentationMessageType {
  TEXT,
  ARRAY_BUFFER,
};

struct SessionMessage {
  string presentation_url;
  string presentation_id;
  PresentationMessageType type;
  string? message;
  array<uint8>? data;
};

interface PresentationService {
  // Called when the frame sets or changes the default presentation URL or
  // presentation ID.
  SetDefaultPresentationURL(
      string default_presentation_url,
      string? default_presentation_id);

  // Sets the PresentationServiceClient.
  SetClient(PresentationServiceClient client);

  // Starts listening for screen availability for the current default
  // presentation URL. Availability results will be returned to the client
  // via PresentationServiceClient::OnScreenAvailabilityUpdated.
  ListenForScreenAvailability();

  // Stops listening for screen availability for the current default
  // default presentation URL. The client will stop receiving availability
  // updates.
  StopListeningForScreenAvailability();

  // Called when the renderer is ready to receive the browser initiated
  // session. If the default session is started by the embedder before this
  // call, the embedder may queue it and run the callback when the call is
  // performed.
  ListenForDefaultSessionStart()
      => (PresentationSessionInfo? defaultSessionInfo);

  // Called when startSession() is called by the frame. The result callback
  // will return a non-null and valid PresentationSessionInfo if starting the
  // session succeeded, or null with a PresentationError if starting the
  // session failed.
  // The presentation id is always returned along with the initialized
  // session on success.
  // If the UA identifies a matching session (same presentation url and id),
  // the user may choose this existing session and the page will join it
  // rather than get a new one. An empty presentation id means that the
  // UA will generate the presentation id.
  StartSession(string presentation_url, string? presentation_id)
      => (PresentationSessionInfo? sessionInfo, PresentationError? error);

  // Called when joinSession() is called by the frame. The result callback
  // works the same as for the method above. JoinSession will join a known
  // session (i.e. when the page navigates or the user opens another tab)
  // silently and without user action.
  JoinSession(string presentation_url, string? presentation_id)
      => (PresentationSessionInfo? sessionInfo, PresentationError? error);

  // Called when send() is called by the frame. The true in the
  // result callback notifies that the service is ready for next message.
  // The false in the result callback notifies the renderer to stop sending
  // the send requests and invalidate all pending requests. This occurs
  // for eg., when frame is deleted or navigated away.
  SendSessionMessage(SessionMessage message_request) => (bool success);
  
  // Called when closeSession() is called by the frame.
  CloseSession(string presentation_url, string presentation_id);

  // Called when the frame is ready to process the next state change. Returns
  // the last session state if it’s changed since the last time the callback
  // was called. Might cause the event fired with the initial state change.
  ListenForSessionStateChange()
      => (PresentationSessionInfo sessionInfo,
          PresentationSessionState newState);

  // Called when the frame is ready to process the next batch of messages.
  // When the callback carries null messages, there is an error
  // at the presentation service side.
  ListenForSessionMessages()
      => (array<SessionMessage>? messages);
};

interface PresentationServiceClient {
  OnScreenAvailabilityUpdated(bool available);
};