// Copyright 2015-2018 Capital One Services, LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! # Message Broker
//! 
//! This module contains the message broker struct through which guest modules access
//! the currently bound `wascap:messaging` capability provider

use std::rc::Rc;
use super::SOURCE_GUEST;
use crate::HostRuntimeInterface;
use crate::Result;
use wascap_codec as codec;
use codec::AsCommand;
use codec::messaging::{PublishMessage, BrokerMessage};

const TARGET_MESSAGING: &'static str = "wascap:messaging";


/// Exposes message broker functionality to guest modules
pub struct MessageBroker {
   hri: Rc<&'static dyn HostRuntimeInterface>,
}

impl MessageBroker {
    pub(crate) fn new(hri: Rc<&'static dyn HostRuntimeInterface>) -> MessageBroker {
        MessageBroker {
            hri,
        }
    }

    /// Publishes a new message on the given subject with an optional reply-to
    pub fn publish(&self, subject: &str, reply_to: Option<&str>, payload: &[u8]) -> Result<()> {
        let cmd = PublishMessage {
            message: Some(BrokerMessage {
                subject: subject.to_string(),
                reply_to: reply_to.map_or("".to_string(), |r| r.to_string()),
                body: payload.to_vec(),                
            })
        }.as_command(SOURCE_GUEST, TARGET_MESSAGING);
        self.hri.do_host_call(&cmd).map(|_evt| ())
    }
}