sdk/fidl/fuchsia.modular/component/component_context.fidl

// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

library fuchsia.modular;

using fuchsia.ledger;
using fuchsia.sys;

// Provided to all component instances in their respective initialization
// information by the framework. For example, a Module gets it from its
// ModuleContext and an Agent gets it from its AgentContext.
[Discoverable]
protocol ComponentContext {
    // Gets the Ledger associated with this component. This ledger instance is
    // unique to this component (nb. not the component instance) under this user.
    GetLedger(request<fuchsia.ledger.Ledger> request);

    // Used to start an agent in the user scope if it isn't already running, and
    // connect to it.
    ConnectToAgent(string url,
                   request<fuchsia.sys.ServiceProvider> incoming_services,
                   request<AgentController> controller);

    // Connects to an agent that provides the given |request.service_name|, and
    // then connects the given |request.channel| to that service.
    // |request.agent_controller| must be kept alive until the service is no
    // longer required.
    //
    // If an error is encountered, the |request.channel| will be closed with
    // a status code, such as:
    //   * ZX_ERR_NOT_FOUND -- if a |request.handler| agent URL is not
    //     specified, and an agent for the |request.service_name| is not found
    //   * ZX_ERR_PEER_CLOSED -- if |request.service_name| is not available from
    //     the agent (either specified or discovered)
    [Transitional]
    ConnectToAgentService(AgentServiceRequest request);

    // Used to create or delete a message queue or retrieve an existing queue
    // identified by |name|. |name| is local to the calling component instance.
    ObtainMessageQueue(string name, request<MessageQueue> queue);
    DeleteMessageQueue(string name);

    // Gets a MessageSender service that can be used to send a message to a queue
    // identified by |queue_token|. Token for a MessageQueue is obtained from its
    // GetToken() method. The token is unique within the scope of the user, i.e.
    // it can be used by other component instances than the one that created the
    // message queue.
    GetMessageSender(string queue_token, request<MessageSender> sender);

    // Gets the EntityResolver service, which can be used to resolve an entity
    // reference to an Entity interface.
    GetEntityResolver(request<EntityResolver> request);

    // Creates a new entity from |type_to_data| such that duplicate types are
    // overriden by subsequent entries.
    //
    // This is a useful way to represent small immutable entities without having
    // to provide the entity using an Agent. The types and data together must be
    // within 16KB in size.
    CreateEntityWithData(vector<TypeToDataEntry> type_to_data)
        -> (string? entity_reference);

    // Gets the package name of this component.
    //
    // TODO(vardhan): MI4-939. This information should likely be exposed by a
    // lower level (component-level, or application level). This information is
    // most meant for a component to identify itself automatically when publishing
    // metrics.
    GetPackageName() -> (string package_name);
};

// Used by ComponentContext.ConnectToAgentService
table AgentServiceRequest {
    // The name of the requested service.
    1: string service_name;

    // The channel that will be used to communicate with the requested service.
    2: handle<channel> channel;

    // The component URL of the Agent that is to provide the specified service.
    // If no handler is specified, the framework will perform resolution to
    // find an appropriate handler.
    3: fuchsia.sys.component_url handler;

    // The AgentController that keeps the agent alive.
    4: request<AgentController> agent_controller;
};

// Used by ComponentContext.CreateEntityWithData().
struct TypeToDataEntry {
    string type;
    string data;
};