librespot/src/mercury.rs

use byteorder::{BigEndian, ByteOrder, ReadBytesExt, WriteBytesExt};
use protobuf::{self, Message};
use readall::ReadAllExt;
use std::collections::{HashMap, LinkedList};
use std::io::{Cursor, Read, Write};
use std::fmt;
use std::mem::replace;
use std::sync::mpsc;

use connection::Packet;
use librespot_protocol as protocol;
use subsystem::Subsystem;
use util::Either::{Left, Right};

#[derive(Debug, PartialEq, Eq)]
pub enum MercuryMethod {
    GET,
    SUB,
    UNSUB,
    SEND,
}

pub struct MercuryRequest {
    pub method: MercuryMethod,
    pub uri: String,
    pub content_type: Option<String>,
    pub callback: Option<MercuryCallback>,
    pub payload: Vec<Vec<u8>>
}

#[derive(Debug)]
pub struct MercuryResponse {
    pub uri: String,
    pub payload: LinkedList<Vec<u8>>
}

pub type MercuryCallback = mpsc::Sender<MercuryResponse>;

pub struct MercuryPending {
    parts: LinkedList<Vec<u8>>,
    partial: Option<Vec<u8>>,
    callback: Option<MercuryCallback>
}

pub struct MercuryManager {
    next_seq: u32,
    pending: HashMap<Vec<u8>, MercuryPending>,
    subscriptions: HashMap<String, MercuryCallback>,

    requests: mpsc::Receiver<MercuryRequest>,
    packet_tx: mpsc::Sender<Packet>,
    packet_rx: mpsc::Receiver<Packet>,
}

impl fmt::Display for MercuryMethod {
    fn fmt(&self, formatter: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        formatter.write_str(match *self {
            MercuryMethod::GET => "GET",
            MercuryMethod::SUB => "SUB",
            MercuryMethod::UNSUB => "UNSUB",
            MercuryMethod::SEND => "SEND"
        })
    }
}

impl MercuryManager {
    pub fn new(tx: mpsc::Sender<Packet>) -> (MercuryManager,
                                             mpsc::Sender<MercuryRequest>,
                                             mpsc::Sender<Packet>) {
        let (req_tx, req_rx) = mpsc::channel();
        let (pkt_tx, pkt_rx) = mpsc::channel();

        (MercuryManager {
            next_seq: 0,
            pending: HashMap::new(),
            subscriptions: HashMap::new(),

            requests: req_rx,
            packet_rx: pkt_rx,
            packet_tx: tx,
        }, req_tx, pkt_tx)
    }

    fn request(&mut self, req: MercuryRequest) {
        let mut seq = [0u8; 4];
        BigEndian::write_u32(&mut seq, self.next_seq);
        self.next_seq += 1;
        let data = self.encode_request(&seq, &req);

        let cmd = match req.method {
            MercuryMethod::SUB => 0xb3,
            MercuryMethod::UNSUB => 0xb4,
            _ => 0xb2,
        };

        self.packet_tx.send(Packet {
            cmd: cmd,
            data: data
        }).unwrap();

        if req.method != MercuryMethod::SUB {
            self.pending.insert(seq.to_vec(), MercuryPending{
                parts: LinkedList::new(),
                partial: None,
                callback: req.callback,
            });
        } else if let Some(cb) = req.callback {
            self.subscriptions.insert(req.uri, cb);
        }
    }

    fn parse_part(mut s: &mut Read) -> Vec<u8> {
        let size = s.read_u16::<BigEndian>().unwrap() as usize;
        let mut buffer = vec![0; size];
        s.read_all(&mut buffer).unwrap();

        buffer
    }

    fn complete_request(&mut self, cmd: u8, mut pending: MercuryPending) {
        let header_data = match pending.parts.pop_front() {
            Some(data) => data,
            None => panic!("No header part !")
        };

        let header : protocol::mercury::Header =
            protobuf::parse_from_bytes(&header_data).unwrap();

        let callback = if cmd == 0xb5 {
            self.subscriptions.get(header.get_uri())
        } else {
            pending.callback.as_ref()
        };

        if let Some(ref ch) = callback {
            ch.send(MercuryResponse{
                uri: header.get_uri().to_string(),
                payload: pending.parts
            }).unwrap();
        }
    }

    fn handle_packet(&mut self, cmd: u8, data: Vec<u8>) {
        let mut packet = Cursor::new(data);

        let seq = {
            let seq_length = packet.read_u16::<BigEndian>().unwrap() as usize;
            let mut seq = vec![0; seq_length];
            packet.read_all(&mut seq).unwrap();
            seq
        };
        let flags = packet.read_u8().unwrap();
        let count = packet.read_u16::<BigEndian>().unwrap() as usize;

        let mut pending = if let Some(pending) = self.pending.remove(&seq) {
            pending
        } else if cmd == 0xb5 {
            MercuryPending {
                parts: LinkedList::new(),
                partial: None,
                callback: None,
            }
        } else {
            println!("Ignore seq {:?} cmd {}", seq, cmd);
            return
        };

        for i in 0..count {
            let mut part = Self::parse_part(&mut packet);
            if let Some(mut data) = replace(&mut pending.partial, None) {
                data.append(&mut part);
                part = data;
            }

            if i == count - 1 && (flags == 2) {
                pending.partial = Some(part)
            } else {
                pending.parts.push_back(part);
            }
        }

        if flags == 0x1 {
            self.complete_request(cmd, pending);
        } else {
            self.pending.insert(seq, pending);
        }
    }

    fn encode_request(&self, seq: &[u8], req: &MercuryRequest) -> Vec<u8> {
        let mut packet = Vec::new();
        packet.write_u16::<BigEndian>(seq.len() as u16).unwrap();
        packet.write_all(seq).unwrap();
        packet.write_u8(1).unwrap(); // Flags: FINAL
        packet.write_u16::<BigEndian>(1 + req.payload.len() as u16).unwrap(); // Part count

        let mut header = protobuf_init!(protocol::mercury::Header::new(), {
            uri: req.uri.clone(),
            method: req.method.to_string(),
        });
        if let Some(ref content_type) = req.content_type {
            header.set_content_type(content_type.clone());
        }

        packet.write_u16::<BigEndian>(header.compute_size() as u16).unwrap();
        header.write_to_writer(&mut packet).unwrap();

        for p in &req.payload {
            packet.write_u16::<BigEndian>(p.len() as u16).unwrap();
            packet.write(&p).unwrap();
        }

        packet
    }
}

impl Subsystem for MercuryManager {
    fn run(mut self) {
        loop {
            match {
                let requests = &self.requests;
                let packets = &self.packet_rx;

                select!{
                    r = requests.recv() => {
                        Left(r.unwrap())
                    },
                    p = packets.recv() => {
                        Right(p.unwrap())
                    }
                }
            } {
                Left(req) => {
                    self.request(req);
                }
                Right(pkt) => {
                    self.handle_packet(pkt.cmd, pkt.data);
                }
            }

        }
    }
}