use std::collections::HashMap;
use std::iter::Iterator;
use std::ops::Deref;
use std::path::PathBuf;
use std::sync::{Arc, RwLock, RwLockReadGuard};
use std::thread;

use rspotify::spotify::model::playlist::SimplifiedPlaylist;
use serde::de::DeserializeOwned;
use serde::Serialize;

use album::Album;
use artist::Artist;
use config;
use events::EventManager;
use playlist::Playlist;
use spotify::Spotify;
use track::Track;

const CACHE_TRACKS: &str = "tracks.db";
const CACHE_ALBUMS: &str = "albums.db";
const CACHE_ARTISTS: &str = "artists.db";
const CACHE_PLAYLISTS: &str = "playlists.db";

#[derive(Clone)]
pub struct Library {
    pub tracks: Arc<RwLock<Vec<Track>>>,
    pub albums: Arc<RwLock<Vec<Album>>>,
    pub artists: Arc<RwLock<Vec<Artist>>>,
    pub playlists: Arc<RwLock<Vec<Playlist>>>,
    is_done: Arc<RwLock<bool>>,
    user_id: Option<String>,
    ev: EventManager,
    spotify: Arc<Spotify>,
    pub use_nerdfont: bool,
}

impl Library {
    pub fn new(ev: &EventManager, spotify: Arc<Spotify>, use_nerdfont: bool) -> Self {
        let user_id = spotify.current_user().map(|u| u.id);

        let library = Self {
            tracks: Arc::new(RwLock::new(Vec::new())),
            albums: Arc::new(RwLock::new(Vec::new())),
            artists: Arc::new(RwLock::new(Vec::new())),
            playlists: Arc::new(RwLock::new(Vec::new())),
            is_done: Arc::new(RwLock::new(false)),
            user_id,
            ev: ev.clone(),
            spotify,
            use_nerdfont,
        };

        {
            let library = library.clone();
            thread::spawn(move || {
                let t_tracks = {
                    let library = library.clone();
                    thread::spawn(move || {
                        library
                            .load_cache(config::cache_path(CACHE_TRACKS), library.tracks.clone());
                        library.fetch_tracks();
                        library
                            .save_cache(config::cache_path(CACHE_TRACKS), library.tracks.clone());
                    })
                };

                let t_albums = {
                    let library = library.clone();
                    thread::spawn(move || {
                        library
                            .load_cache(config::cache_path(CACHE_ALBUMS), library.albums.clone());
                        library.fetch_albums();
                        library
                            .save_cache(config::cache_path(CACHE_ALBUMS), library.albums.clone());
                    })
                };

                let t_artists = {
                    let library = library.clone();
                    thread::spawn(move || {
                        library
                            .load_cache(config::cache_path(CACHE_ARTISTS), library.artists.clone());
                        library.fetch_artists();
                    })
                };

                let t_playlists = {
                    let library = library.clone();
                    thread::spawn(move || {
                        library.load_cache(
                            config::cache_path(CACHE_PLAYLISTS),
                            library.playlists.clone(),
                        );
                        library.fetch_playlists();
                        library.save_cache(
                            config::cache_path(CACHE_PLAYLISTS),
                            library.playlists.clone(),
                        );
                    })
                };

                t_tracks.join().unwrap();
                t_artists.join().unwrap();

                library.populate_artists();
                library.save_cache(config::cache_path(CACHE_ARTISTS), library.artists.clone());

                t_albums.join().unwrap();
                t_playlists.join().unwrap();

                let mut is_done = library.is_done.write().unwrap();
                *is_done = true;

                library.ev.trigger();
            });
        }

        library
    }

    pub fn items(&self) -> RwLockReadGuard<Vec<Playlist>> {
        self.playlists
            .read()
            .expect("could not readlock listview content")
    }

    fn load_cache<T: DeserializeOwned>(&self, cache_path: PathBuf, store: Arc<RwLock<Vec<T>>>) {
        if let Ok(contents) = std::fs::read_to_string(&cache_path) {
            debug!("loading cache from {}", cache_path.display());
            let parsed: Result<Vec<T>, _> = serde_json::from_str(&contents);
            match parsed {
                Ok(cache) => {
                    debug!(
                        "cache from {} loaded ({} lists)",
                        cache_path.display(),
                        cache.len()
                    );
                    let mut store = store.write().expect("can't writelock store");
                    store.clear();
                    store.extend(cache);

                    // force refresh of UI (if visible)
                    self.ev.trigger();
                }
                Err(e) => {
                    error!("can't parse cache: {}", e);
                }
            }
        }
    }

    fn save_cache<T: Serialize>(&self, cache_path: PathBuf, store: Arc<RwLock<Vec<T>>>) {
        match serde_json::to_string(&store.deref()) {
            Ok(contents) => std::fs::write(cache_path, contents).unwrap(),
            Err(e) => error!("could not write cache: {:?}", e),
        }
    }

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

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

    pub fn delete_playlist(&self, id: &str) {
        if !*self.is_done.read().unwrap() {
            return;
        }

        let pos = {
            let store = self.playlists.read().expect("can't readlock playlists");
            store.iter().position(|ref i| i.id == id)
        };

        if let Some(position) = pos {
            if self.spotify.delete_playlist(id) {
                {
                    let mut store = self.playlists.write().expect("can't writelock playlists");
                    store.remove(position);
                }
                self.save_cache(config::cache_path(CACHE_PLAYLISTS), self.playlists.clone());
            }
        }
    }

    pub fn overwrite_playlist(&self, id: &str, tracks: &[Track]) {
        debug!("saving {} tracks to {}", tracks.len(), id);
        self.spotify.overwrite_playlist(id, &tracks);

        self.update_playlists();
    }

    pub fn save_playlist(&self, name: &str, tracks: &[Track]) {
        debug!("saving {} tracks to new list {}", tracks.len(), name);
        match self.spotify.create_playlist(name, None, None) {
            Some(id) => self.overwrite_playlist(&id, &tracks),
            None => error!("could not create new playlist.."),
        }
    }

    pub fn update_playlists(&self) {
        self.fetch_playlists();
        self.save_cache(config::cache_path(CACHE_PLAYLISTS), self.playlists.clone());
    }

    fn fetch_playlists(&self) {
        debug!("loading playlists");
        let mut stale_lists = self.playlists.read().unwrap().clone();
        let mut list_order = Vec::new();

        let mut lists_result = self.spotify.current_user_playlist(50, 0);
        while let Some(ref lists) = lists_result.clone() {
            for (index, remote) in lists.items.iter().enumerate() {
                list_order.push(remote.id.clone());

                // remove from stale playlists so we won't prune it later on
                if let Some(index) = stale_lists.iter().position(|x| x.id == remote.id) {
                    stale_lists.remove(index);
                }

                if self.needs_download(remote) {
                    info!("updating playlist {} (index: {})", remote.name, index);
                    let mut playlist: Playlist = remote.into();
                    playlist.load_tracks(self.spotify.clone());
                    self.append_or_update(&playlist);
                    // trigger redraw
                    self.ev.trigger();
                }
            }

            // 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)
                }
                None => None,
            }
        }

        // remove stale playlists
        for stale in stale_lists {
            let index = self
                .playlists
                .read()
                .unwrap()
                .iter()
                .position(|x| x.id == stale.id);
            if let Some(index) = index {
                debug!("removing stale list: {:?}", stale.name);
                self.playlists.write().unwrap().remove(index);
            }
        }

        // sort by remote order
        self.playlists.write().unwrap().sort_by(|a, b| {
            let a_index = list_order.iter().position(|x| x == &a.id);
            let b_index = list_order.iter().position(|x| x == &b.id);
            a_index.cmp(&b_index)
        });

        // trigger redraw
        self.ev.trigger();
    }

    fn fetch_artists(&self) {
        let mut artists: Vec<Artist> = Vec::new();
        let mut last: Option<String> = None;

        let mut i: u32 = 0;

        loop {
            let page = self.spotify.current_user_followed_artists(last);
            debug!("artists page: {}", i);
            i += 1;
            if page.is_none() {
                error!("Failed to fetch artists.");
                return;
            }
            let page = page.unwrap();

            artists.extend(page.items.iter().map(|fa| fa.into()));

            if page.next.is_some() {
                last = artists.last().unwrap().id.clone();
            } else {
                break;
            }
        }

        let mut store = self.artists.write().unwrap();

        for artist in artists.iter_mut() {
            let pos = store.iter().position(|a| a.id == artist.id);
            if let Some(i) = pos {
                store[i].is_followed = true;
                continue;
            }

            artist.is_followed = true;

            store.push(artist.clone());
        }
    }

    fn insert_artist(&self, id: &str, name: &str) {
        let mut artists = self.artists.write().unwrap();

        if !artists
            .iter()
            .any(|a| a.id.clone().unwrap_or_default() == id)
        {
            let mut artist = Artist::new(id.to_string(), name.to_string());
            artist.tracks = Some(Vec::new());
            artists.push(artist);
        }
    }

    fn fetch_albums(&self) {
        let mut albums: Vec<Album> = Vec::new();

        let mut i: u32 = 0;

        loop {
            let page = self.spotify.current_user_saved_albums(albums.len() as u32);
            debug!("albums page: {}", i);
            i += 1;
            if page.is_none() {
                error!("Failed to fetch albums.");
                return;
            }
            let page = page.unwrap();

            if page.offset == 0 {
                // If first page matches the first items in store and total is
                // identical, assume list is unchanged.

                let store = self.albums.read().unwrap();

                if page.total as usize == store.len()
                    && !page
                        .items
                        .iter()
                        .enumerate()
                        .any(|(i, a)| a.album.id != store[i].id.clone().unwrap_or_default())
                {
                    return;
                }
            }

            albums.extend(page.items.iter().map(|a| a.into()));

            if page.next.is_none() {
                break;
            }
        }

        *(self.albums.write().unwrap()) = albums;
    }

    fn fetch_tracks(&self) {
        let mut tracks: Vec<Track> = Vec::new();

        let mut i: u32 = 0;

        loop {
            let page = self.spotify.current_user_saved_tracks(tracks.len() as u32);

            debug!("tracks page: {}", i);
            i += 1;

            if page.is_none() {
                error!("Failed to fetch tracks.");
                return;
            }
            let page = page.unwrap();

            if page.offset == 0 {
                // If first page matches the first items in store and total is
                // identical, assume list is unchanged.

                let store = self.tracks.read().unwrap();

                if page.total as usize == store.len()
                    && !page
                        .items
                        .iter()
                        .enumerate()
                        .any(|(i, t)| t.track.id != store[i].id)
                {
                    return;
                }
            }

            tracks.extend(page.items.iter().map(|t| t.into()));

            if page.next.is_none() {
                break;
            }
        }

        *(self.tracks.write().unwrap()) = tracks;
    }

    fn populate_artists(&self) {
        // Remove old unfollowed artists
        {
            let mut artists = self.artists.write().unwrap();
            *artists = artists.iter().filter(|a| a.is_followed).cloned().collect();
        }

        // Add artists that aren't followed but have saved tracks
        {
            let tracks = self.tracks.read().unwrap();
            let mut track_artists: Vec<(&String, &String)> = tracks
                .iter()
                .flat_map(|t| t.artist_ids.iter().zip(t.artists.iter()))
                .collect();
            track_artists.dedup_by(|a, b| a.0 == b.0);

            for (id, name) in track_artists.iter() {
                self.insert_artist(id, name);
            }
        }

        let mut artists = self.artists.write().unwrap();
        let mut lookup: HashMap<String, Option<usize>> = HashMap::new();

        // Make sure only saved tracks are played when playing artists
        for artist in artists.iter_mut() {
            artist.tracks = Some(Vec::new());
        }

        artists.sort_unstable_by(|a, b| a.name.partial_cmp(&b.name).unwrap());

        // Add saved tracks to artists
        {
            let tracks = self.tracks.read().unwrap();
            for track in tracks.iter() {
                for artist_id in &track.artist_ids {
                    let index = if let Some(i) = lookup.get(artist_id).cloned() {
                        i
                    } else {
                        let i = artists
                            .iter()
                            .position(|a| &a.id.clone().unwrap_or_default() == artist_id);
                        lookup.insert(artist_id.clone(), i);
                        i
                    };

                    if let Some(i) = index {
                        let mut artist = artists.get_mut(i).unwrap();
                        if artist.tracks.is_none() {
                            artist.tracks = Some(Vec::new());
                        }

                        if let Some(tracks) = artist.tracks.as_mut() {
                            if tracks.iter().any(|t| t.id == track.id) {
                                continue;
                            }

                            tracks.push(track.clone());
                        }
                    }
                }
            }
        }
    }

    pub fn is_saved_track(&self, track: &Track) -> bool {
        if !*self.is_done.read().unwrap() {
            return false;
        }

        let tracks = self.tracks.read().unwrap();
        tracks.iter().any(|t| t.id == track.id)
    }

    pub fn save_tracks(&self, tracks: Vec<&Track>, api: bool) {
        if !*self.is_done.read().unwrap() {
            return;
        }

        if api
            && self
                .spotify
                .current_user_saved_tracks_add(
                    tracks
                        .iter()
                        .filter(|t| t.id.is_some())
                        .map(|t| t.id.clone().unwrap())
                        .collect(),
                )
                .is_none()
        {
            return;
        }

        {
            let mut store = self.tracks.write().unwrap();
            let mut i = 0;
            for track in tracks {
                if store.iter().any(|t| t.id == track.id) {
                    continue;
                }

                store.insert(i, track.clone());
                i += 1;
            }
        }

        self.populate_artists();

        self.save_cache(config::cache_path(CACHE_TRACKS), self.tracks.clone());
        self.save_cache(config::cache_path(CACHE_ARTISTS), self.artists.clone());
    }

    pub fn unsave_tracks(&self, tracks: Vec<&Track>, api: bool) {
        if !*self.is_done.read().unwrap() {
            return;
        }

        if api
            && self
                .spotify
                .current_user_saved_tracks_delete(
                    tracks
                        .iter()
                        .filter(|t| t.id.is_some())
                        .map(|t| t.id.clone().unwrap())
                        .collect(),
                )
                .is_none()
        {
            return;
        }

        {
            let mut store = self.tracks.write().unwrap();
            *store = store
                .iter()
                .filter(|t| !tracks.iter().any(|tt| t.id == tt.id))
                .cloned()
                .collect();
        }

        self.populate_artists();

        self.save_cache(config::cache_path(CACHE_TRACKS), self.tracks.clone());
        self.save_cache(config::cache_path(CACHE_ARTISTS), self.artists.clone());
    }

    pub fn is_saved_album(&self, album: &Album) -> bool {
        if !*self.is_done.read().unwrap() {
            return false;
        }

        let albums = self.albums.read().unwrap();
        albums.iter().any(|a| a.id == album.id)
    }

    pub fn save_album(&self, album: &mut Album) {
        if !*self.is_done.read().unwrap() {
            return;
        }

        if let Some(ref album_id) = album.id {
            if self
                .spotify
                .current_user_saved_albums_add(vec![album_id.clone()])
                .is_none()
            {
                return;
            }
        }

        album.load_tracks(self.spotify.clone());

        {
            let mut store = self.albums.write().unwrap();
            if !store.iter().any(|a| a.id == album.id) {
                store.insert(0, album.clone());
            }
        }

        if let Some(tracks) = album.tracks.as_ref() {
            self.save_tracks(tracks.iter().collect(), false);
        }

        self.save_cache(config::cache_path(CACHE_ALBUMS), self.albums.clone());
    }

    pub fn unsave_album(&self, album: &mut Album) {
        if !*self.is_done.read().unwrap() {
            return;
        }

        if let Some(ref album_id) = album.id {
            if self
                .spotify
                .current_user_saved_albums_delete(vec![album_id.clone()])
                .is_none()
            {
                return;
            }
        }

        album.load_tracks(self.spotify.clone());

        {
            let mut store = self.albums.write().unwrap();
            *store = store.iter().filter(|a| a.id != album.id).cloned().collect();
        }

        if let Some(tracks) = album.tracks.as_ref() {
            self.unsave_tracks(tracks.iter().collect(), false);
        }

        self.save_cache(config::cache_path(CACHE_ALBUMS), self.albums.clone());
    }

    pub fn is_followed_artist(&self, artist: &Artist) -> bool {
        if !*self.is_done.read().unwrap() {
            return false;
        }

        let artists = self.artists.read().unwrap();
        artists.iter().any(|a| a.id == artist.id && a.is_followed)
    }

    pub fn follow_artist(&self, artist: &Artist) {
        if !*self.is_done.read().unwrap() {
            return;
        }

        if let Some(ref artist_id) = artist.id {
            if self
                .spotify
                .user_follow_artists(vec![artist_id.clone()])
                .is_none()
            {
                return;
            }
        }

        {
            let mut store = self.artists.write().unwrap();
            if let Some(i) = store.iter().position(|a| a.id == artist.id) {
                store[i].is_followed = true;
            } else {
                let mut artist = artist.clone();
                artist.is_followed = true;
                store.push(artist);
            }
        }

        self.populate_artists();

        self.save_cache(config::cache_path(CACHE_ARTISTS), self.artists.clone());
    }

    pub fn unfollow_artist(&self, artist: &Artist) {
        if !*self.is_done.read().unwrap() {
            return;
        }

        if let Some(ref artist_id) = artist.id {
            if self
                .spotify
                .user_unfollow_artists(vec![artist_id.clone()])
                .is_none()
            {
                return;
            }
        }

        {
            let mut store = self.artists.write().unwrap();
            if let Some(i) = store.iter().position(|a| a.id == artist.id) {
                store[i].is_followed = false;
            }
        }

        self.populate_artists();

        self.save_cache(config::cache_path(CACHE_ARTISTS), self.artists.clone());
    }

    pub fn is_saved_playlist(&self, playlist: &Playlist) -> bool {
        if !*self.is_done.read().unwrap() {
            return false;
        }

        let playlists = self.playlists.read().unwrap();
        playlists.iter().any(|p| p.id == playlist.id)
    }

    pub fn is_followed_playlist(&self, playlist: &Playlist) -> bool {
        self.user_id
            .as_ref()
            .map(|id| id != &playlist.owner_id)
            .unwrap_or(false)
    }

    pub fn follow_playlist(&self, playlist: &Playlist) {
        if !*self.is_done.read().unwrap() {
            return;
        }

        if self
            .spotify
            .user_playlist_follow_playlist(playlist.owner_id.clone(), playlist.id.clone())
            .is_none()
        {
            return;
        }

        let mut playlist = playlist.clone();
        playlist.load_tracks(self.spotify.clone());

        {
            let mut store = self.playlists.write().unwrap();
            if !store.iter().any(|p| p.id == playlist.id) {
                store.insert(0, playlist.clone());
            }
        }

        self.save_cache(config::cache_path(CACHE_PLAYLISTS), self.playlists.clone());
    }
}