use eventual::{Async, Future};
use protobuf;

use librespot_protocol as protocol;
use mercury::{MercuryRequest, MercuryMethod};
use util::{SpotifyId, FileId};
use session::Session;

pub trait MetadataTrait : Send + 'static {
    type Message: protobuf::MessageStatic;

    fn base_url() -> &'static str;
    fn parse(msg: &Self::Message) -> Self;
}

#[derive(Debug)]
pub struct Track {
    pub id: SpotifyId,
    pub name: String,
    pub album: SpotifyId,
    pub files: Vec<FileId>,
}

#[derive(Debug)]
pub struct Album {
    pub id: SpotifyId,
    pub name: String,
    pub artists: Vec<SpotifyId>,
    pub covers: Vec<FileId>
}

#[derive(Debug)]
pub struct Artist {
    pub id: SpotifyId,
    pub name: String,
}

pub type MetadataRef<T> = Future<T, ()>;
pub type TrackRef = MetadataRef<Track>;
pub type AlbumRef = MetadataRef<Album>;
pub type ArtistRef = MetadataRef<Artist>;

impl MetadataTrait for Track {
    type Message = protocol::metadata::Track;

    fn base_url() -> &'static str {
        "hm://metadata/3/track"
    }

    fn parse(msg: &Self::Message) -> Self {
        Track {
            id: SpotifyId::from_raw(msg.get_gid()),
            name: msg.get_name().to_owned(),
            album: SpotifyId::from_raw(msg.get_album().get_gid()),
            files: msg.get_file().iter()
                .map(|file| {
                    let mut dst = [0u8; 20];
                    dst.clone_from_slice(&file.get_file_id());
                    FileId(dst)
                })
                .collect(),
        }
    }
}

impl MetadataTrait for Album {
    type Message = protocol::metadata::Album;

    fn base_url() -> &'static str {
        "hm://metadata/3/album"
    }

    fn parse(msg: &Self::Message) -> Self {
        Album {
            id: SpotifyId::from_raw(msg.get_gid()),
            name: msg.get_name().to_owned(),
            artists: msg.get_artist().iter()
                .map(|a| SpotifyId::from_raw(a.get_gid()))
                .collect(),
            covers: msg.get_cover_group().get_image().iter()
                .map(|image| {
                    let mut dst = [0u8; 20];
                    dst.clone_from_slice(&image.get_file_id());
                    FileId(dst)
                })
                .collect(),
        }
    }
}


impl MetadataTrait for Artist {
    type Message = protocol::metadata::Artist;

    fn base_url() -> &'static str {
        "hm://metadata/3/artist"
    }

    fn parse(msg: &Self::Message) -> Self {
        Artist {
            id: SpotifyId::from_raw(msg.get_gid()),
            name: msg.get_name().to_owned(),
        }
    }
}

pub struct MetadataManager;

impl MetadataManager {
    pub fn new() -> MetadataManager {
        MetadataManager
    }

    pub fn get<T: MetadataTrait>(&mut self, session: &Session, id: SpotifyId)
      -> MetadataRef<T> {

        session.mercury(MercuryRequest {
            method: MercuryMethod::GET,
            uri: format!("{}/{}", T::base_url(), id.to_base16()),
            content_type: None,
            payload: Vec::new()
        }).and_then(|response| {
            let msg : T::Message = protobuf::parse_from_bytes(
                response.payload.first().unwrap()).unwrap();

            Ok(T::parse(&msg))
        })
    }
}