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 log::{debug, error, info};
use rspotify::model::Id;
use serde::de::DeserializeOwned;
use serde::Serialize;

use crate::config::Config;
use crate::config::{self, CACHE_VERSION};
use crate::events::EventManager;
use crate::model::album::Album;
use crate::model::artist::Artist;
use crate::model::playable::Playable;
use crate::model::playlist::Playlist;
use crate::model::show::Show;
use crate::model::track::Track;
use crate::spotify::Spotify;

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>>>,
    pub shows: Arc<RwLock<Vec<Show>>>,
    pub is_done: Arc<RwLock<bool>>,
    pub user_id: Option<String>,
    pub display_name: Option<String>,
    ev: EventManager,
    spotify: Spotify,
    pub cfg: Arc<Config>,
}

impl Library {
    pub fn new(ev: &EventManager, spotify: Spotify, cfg: Arc<Config>) -> Self {
        let current_user = spotify.api.current_user();
        let user_id = current_user.as_ref().map(|u| u.id.id().to_string());
        let display_name = current_user.as_ref().and_then(|u| u.display_name.clone());

        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())),
            shows: Arc::new(RwLock::new(Vec::new())),
            is_done: Arc::new(RwLock::new(false)),
            user_id,
            display_name,
            ev: ev.clone(),
            spotify,
            cfg,
        };

        library.update_library();
        library
    }

    pub fn playlists(&self) -> RwLockReadGuard<Vec<Playlist>> {
        self.playlists.read().expect("can't readlock playlists")
    }

    fn load_cache<T: DeserializeOwned>(&self, cache_path: PathBuf, store: Arc<RwLock<Vec<T>>>) {
        let saved_cache_version = self.cfg.state().cache_version;
        if saved_cache_version < CACHE_VERSION {
            debug!(
                "Cache version for {:?} has changed from {} to {}, ignoring cache",
                cache_path, saved_cache_version, CACHE_VERSION
            );
            return;
        }

        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 ({} items)",
                        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: &Playlist) -> bool {
        self.playlists()
            .iter()
            .find(|local| local.id == remote.id)
            .map(|local| local.snapshot_id != remote.snapshot_id)
            .unwrap_or(true)
    }

    fn append_or_update(&self, updated: &Playlist) -> usize {
        let mut store = self.playlists.write().expect("can't writelock playlists");
        for (index, 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(|i| i.id == id)
        };

        if let Some(position) = pos {
            if self.spotify.api.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: &[Playable]) {
        debug!("saving {} tracks to list {}", tracks.len(), id);
        self.spotify.api.overwrite_playlist(id, tracks);

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

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

    pub fn update_library(&self) {
        *self.is_done.write().unwrap() = false;

        let library = self.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(),
                    );
                })
            };

            let t_shows = {
                let library = library.clone();
                thread::spawn(move || {
                    library.fetch_shows();
                })
            };

            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();
            t_shows.join().unwrap();

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

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

    fn fetch_shows(&self) {
        debug!("loading shows");

        let mut saved_shows: Vec<Show> = Vec::new();
        let mut shows_result = self.spotify.api.get_saved_shows(0);

        while let Some(shows) = shows_result.as_ref() {
            saved_shows.extend(shows.items.iter().map(|show| (&show.show).into()));

            // load next batch if necessary
            shows_result = match shows.next {
                Some(_) => {
                    debug!("requesting shows again..");
                    self.spotify
                        .api
                        .get_saved_shows(shows.offset + shows.items.len() as u32)
                }
                None => None,
            }
        }

        *self.shows.write().unwrap() = saved_shows;
    }

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

        let lists_page = self.spotify.api.current_user_playlist();
        let mut lists_batch = Some(lists_page.items.read().unwrap().clone());
        while let Some(lists) = &lists_batch {
            for (index, remote) in lists.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.clone();
                    playlist.tracks = None;
                    playlist.load_tracks(self.spotify.clone());
                    self.append_or_update(&playlist);
                    // trigger redraw
                    self.ev.trigger();
                }
            }
            lists_batch = lists_page.next();
        }

        // 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<&str> = None;

        let mut i: u32 = 0;

        loop {
            let page = self.spotify.api.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.as_deref();
            } 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
                .api
                .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();
            albums.extend(page.items.iter().map(|a| a.into()));

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

        albums.sort_unstable_by_key(|album| {
            format!(
                "{}{}{}",
                album.artists[0].to_lowercase(),
                album.year,
                album.title.to_lowercase()
            )
        });

        *(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
                .api
                .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.as_ref().map(|id| id.to_string()) != 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 playlist_update(&self, updated: &Playlist) {
        {
            let mut playlists = self.playlists.write().expect("can't writelock playlists");
            if let Some(playlist) = playlists.iter_mut().find(|p| p.id == updated.id) {
                *playlist = updated.clone();
            }
        }
        self.save_cache(config::cache_path(CACHE_PLAYLISTS), self.playlists.clone());
    }

    pub fn is_saved_track(&self, track: &Playable) -> 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
                .api
                .current_user_saved_tracks_add(
                    tracks.iter().filter_map(|t| t.id.as_deref()).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
                .api
                .current_user_saved_tracks_delete(
                    tracks.iter().filter_map(|t| t.id.as_deref()).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
                .api
                .current_user_saved_albums_add(vec![album_id.as_str()])
                .is_none()
            {
                return;
            }
        }

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

                // resort list of albums
                store.sort_unstable_by_key(|a| format!("{}{}{}", a.artists[0], a.year, a.title));
            }
        }

        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
                .api
                .current_user_saved_albums_delete(vec![album_id.as_str()])
                .is_none()
            {
                return;
            }
        }

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

        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
                .api
                .user_follow_artists(vec![artist_id.as_str()])
                .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
                .api
                .user_unfollow_artists(vec![artist_id.as_str()])
                .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
            .api
            .user_playlist_follow_playlist(playlist.id.as_str())
            .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);
            }
        }

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

    pub fn is_saved_show(&self, show: &Show) -> bool {
        if !*self.is_done.read().unwrap() {
            return false;
        }

        let shows = self.shows.read().unwrap();
        shows.iter().any(|s| s.id == show.id)
    }

    pub fn save_show(&self, show: &Show) {
        if !*self.is_done.read().unwrap() {
            return;
        }

        if self.spotify.api.save_shows(vec![show.id.as_str()]) {
            {
                let mut store = self.shows.write().unwrap();
                if !store.iter().any(|s| s.id == show.id) {
                    store.insert(0, show.clone());
                }
            }
        }
    }

    pub fn unsave_show(&self, show: &Show) {
        if !*self.is_done.read().unwrap() {
            return;
        }

        if self.spotify.api.unsave_shows(vec![show.id.as_str()]) {
            {
                let mut store = self.shows.write().unwrap();
                *store = store.iter().filter(|s| s.id != show.id).cloned().collect();
            }
        }
    }

    pub fn trigger_redraw(&self) {
        self.ev.trigger();
    }
}