use std::iter::Iterator;
use std::ops::Deref;
use std::sync::{Arc, RwLock};

use rspotify::spotify::model::playlist::SimplifiedPlaylist;

use events::{Event, EventManager};
use spotify::Spotify;
use track::Track;

#[derive(Clone, Deserialize, Serialize)]
pub struct Playlist {
    pub meta: SimplifiedPlaylist,
    pub tracks: Vec<Track>,
}

pub enum PlaylistEvent {
    NewList(usize, Playlist),
}

#[derive(Default, Serialize, Deserialize)]
pub struct PlaylistStore {
    pub playlists: Vec<Playlist>,
}

#[derive(Clone)]
pub struct Playlists {
    pub store: Arc<RwLock<PlaylistStore>>,
    ev: EventManager,
    spotify: Arc<Spotify>,
}

impl Playlists {
    pub fn new(ev: &EventManager, spotify: &Arc<Spotify>) -> Playlists {
        Playlists {
            store: Arc::new(RwLock::new(PlaylistStore::default())),
            ev: ev.clone(),
            spotify: spotify.clone(),
        }
    }

    pub fn load_cache(&self) {
        let xdg_dirs = xdg::BaseDirectories::with_prefix("ncspot").unwrap();
        if let Ok(cache_path) = xdg_dirs.place_cache_file("playlists.db") {
            if let Ok(contents) = std::fs::read_to_string(&cache_path) {
                debug!(
                    "loading playlist cache from {}",
                    cache_path.to_str().unwrap()
                );
                let parsed: Result<PlaylistStore, _> = serde_json::from_str(&contents);
                if let Ok(cache) = parsed {
                    debug!("playlist cache loaded ({} lists)", cache.playlists.len());
                    let mut store = self.store.write().expect("can't writelock playlist store");
                    store.playlists.clear();
                    store.playlists.extend(cache.playlists);

                    // force refresh of UI (if visible)
                    self.ev.send(Event::ScreenChange("playlists".to_owned()));
                } else {
                    error!("playlist cache corrupted?");
                }
            }
        }
    }

    pub fn save_cache(&self) {
        let xdg_dirs = xdg::BaseDirectories::with_prefix("ncspot").unwrap();
        if let Ok(cache_path) = xdg_dirs.place_cache_file("playlists.db") {
            match serde_json::to_string(&self.store.deref()) {
                Ok(contents) => std::fs::write(cache_path, contents).unwrap(),
                Err(e) => error!("could not write playlist cache: {:?}", e),
            }
        }
    }

    fn process_playlist(list: &SimplifiedPlaylist, spotify: &Spotify) -> Playlist {
        debug!("got list: {}", list.name);
        let id = list.id.clone();

        let mut collected_tracks = Vec::new();

        let mut tracks_result = spotify.user_playlist_tracks(&id, 100, 0).ok();
        while let Some(ref tracks) = tracks_result.clone() {
            for listtrack in &tracks.items {
                collected_tracks.push(Track::new(&listtrack.track));
            }
            debug!("got {} tracks", tracks.items.len());

            // load next batch if necessary
            tracks_result = match tracks.next {
                Some(_) => {
                    debug!("requesting tracks again..");
                    spotify
                        .user_playlist_tracks(&id, 100, tracks.offset + tracks.items.len() as u32)
                        .ok()
                }
                None => None,
            }
        }
        Playlist {
            meta: list.clone(),
            tracks: collected_tracks,
        }
    }

    fn needs_download(&self, remote: &SimplifiedPlaylist) -> bool {
        for local in &self
            .store
            .read()
            .expect("can't readlock playlists")
            .playlists
        {
            if local.meta.id == remote.id {
                return local.meta.snapshot_id != remote.snapshot_id;
            }
        }
        true
    }

    fn append_or_update(&self, updated: &Playlist) -> usize {
        let mut store = self.store.write().expect("can't writelock playlists");
        for (index, mut local) in store.playlists.iter_mut().enumerate() {
            if local.meta.id == updated.meta.id {
                *local = updated.clone();
                return index;
            }
        }
        store.playlists.push(updated.clone());
        store.playlists.len() - 1
    }

    pub fn fetch_playlists(&self) {
        debug!("loading playlists");
        let mut lists_result = self.spotify.current_user_playlist(50, 0).ok();
        while let Some(ref lists) = lists_result.clone() {
            for remote in &lists.items {
                if self.needs_download(remote) {
                    info!("updating playlist {}", remote.name);
                    let playlist = Self::process_playlist(&remote, &self.spotify);
                    let index = self.append_or_update(&playlist);
                    self.ev.send(Event::Playlist(PlaylistEvent::NewList(
                        index,
                        playlist.clone(),
                    )));
                }
            }

            // load next batch if necessary
            lists_result = match lists.next {
                Some(_) => {
                    debug!("requesting playlists again..");
                    self.spotify
                        .current_user_playlist(50, lists.offset + lists.items.len() as u32)
                        .ok()
                }
                None => None,
            }
        }
    }
}