use std::collections::{HashMap, HashSet};
use std::sync::LazyLock;
use std::sync::Arc;
use std::future::Future;
use std::pin::Pin;
use std::time::*;

use super::cache::AsyncCache;
use super::deserialize::{GetRecentTracks, GetUserInfo, Track, User};

use reqwest::{Client, StatusCode};
use dotenv::var;
use tokio::sync::RwLock;
use handlebars::{Handlebars, handlebars_helper};
use duration_str as ds;

static INTERNAL_THEMES: &[(&'static str, &'static str)] = &[("plain", include_str!("themes/plain.hbs"))];

pub static STATE: LazyLock<Arc<State>> = LazyLock::new(|| {
    State::new()
});

fn user_getter(username: &String) -> Pin<Box<(dyn Future<Output = Result<Arc<(User, Track)>, (StatusCode, &'static str)>> + Send + Sync)>> {
    let username = urlencoding::encode(username.as_ref()).to_string();
    Box::pin(async move {
        let userreq = STATE.http.get(format!("https://ws.audioscrobbler.com/2.0/?method=user.getInfo&format=json&user={username}&api_key={}", STATE.lastfm_api_key))
            .send().await
            .map_err(|e| {log::error!("Failed to get info for user `{username}`: {e}"); (StatusCode::SERVICE_UNAVAILABLE, "Couldn't connect to last.fm!")})?;
        if userreq.status() == StatusCode::NOT_FOUND { return Err((StatusCode::NOT_FOUND, "User does not exist!")); }

        let userinfo = userreq.json::<GetUserInfo>().await
            .map_err(|e| {log::error!("Couldn't parse user.getInfo for `{username}`: {e}"); (StatusCode::INTERNAL_SERVER_ERROR, "Couldn't parse user.getInfo!")})?.user;

        let tracksreq = STATE.http.get(format!("https://ws.audioscrobbler.com/2.0/?method=user.getRecentTracks&format=json&extended=1&limit=1&user={username}&api_key={}", STATE.lastfm_api_key))
            .send().await
            .map_err(|e| {log::error!("Failed to get tracks for user `{username}`: {e}"); (StatusCode::SERVICE_UNAVAILABLE, "Couldn't connect to last.fm!")})?;
        if tracksreq.status() == StatusCode::NOT_FOUND { return Err((StatusCode::NOT_FOUND, "User does not exist!")); }
        if tracksreq.status() == StatusCode::FORBIDDEN { return Err((StatusCode::FORBIDDEN, "You need to unprivate your song history!")); }

        let tracksinfo = tracksreq.json::<GetRecentTracks>().await
            .map_err(|e| {log::error!("Couldn't parse user.getRecentTracks for `{username}`: {e}"); (StatusCode::INTERNAL_SERVER_ERROR, "Couldn't parse user.getRecentTracks!")})?
            .recenttracks.track.into_iter().nth(0).ok_or((StatusCode::UNPROCESSABLE_ENTITY, "You need to listen to some songs first!"))?;

        Ok(Arc::new((userinfo, tracksinfo)))
    })
}

fn font_getter(fontname: &String) -> Pin<Box<(dyn Future<Output = Result<Arc<str>, (StatusCode, &'static str)>> + Send + Sync)>> {
  let fontname = urlencoding::encode(fontname.as_ref()).to_string();
  Box::pin(async move {
    let Some(google_api_key) = STATE.google_api_key.clone()
    else {
      unreachable!();
    };

    let fontreq = STATE.http.get(format!("https://www.googleapis.com/webfonts/v1/webfonts?key={}&family={fontname}", google_api_key))
      .send().await
      .map_err(|e| {log::error!("Failed to get info for font `{fontname}`: {e}"); (StatusCode::SERVICE_UNAVAILABLE, "Couldn't connect to Google Fonts!")})?;
    if fontreq.status() == StatusCode::NOT_FOUND { return Err((StatusCode::NOT_FOUND, "Font does not exist!")); }
    if fontreq.status() == StatusCode::FORBIDDEN {
      log::error!("Invalid Google API key in config!");
      return Err((StatusCode::SERVICE_UNAVAILABLE, "This instance is not configured to support Google Fonts properly, please use a different font."));
    }

    let cssreq = STATE.http.get(format!("https://fonts.googleapis.com/css2?family={fontname}"))
      .send().await
      .map_err(|e| {log::error!("Failed to get CSS for font `{fontname}`: {e}"); (StatusCode::SERVICE_UNAVAILABLE, "Couldn't download font CSS!")})?;

    Ok(cssreq.text().await.unwrap().into())
  })
}

type UserGetter = fn(&String) -> Pin<Box<(dyn Future<Output = Result<Arc<(User, Track)>, (StatusCode, &'static str)>> + Send + Sync)>>;
type UserCache = Arc<RwLock<AsyncCache<String, Arc<(User, Track)>, UserGetter>>>;
type FontGetter = fn(&String) -> Pin<Box<(dyn Future<Output = Result<Arc<str>, (StatusCode, &'static str)>> + Send + Sync)>>;
type FontCache = Arc<RwLock<AsyncCache<String, Arc<str>, FontGetter>>>;
#[derive(Debug)]
enum Whitelist {
    Exclusive{cache: UserCache, whitelist: HashSet<String>},
    Open{default_cache: UserCache, whitelist_cache: UserCache, whitelist: HashSet<String>}
}
#[derive(Debug)]
pub struct State {
    lastfm_api_key: Arc<str>,
    google_api_key: Option<Arc<str>>,
    whitelist: Whitelist,
    port: u16,

    handlebars: Handlebars<'static>,
    default_theme: Arc<str>,
    send_refresh_header: bool,
    http: Client,

    google_fonts_cache: FontCache,

    default_refresh: Duration,
    whitelist_refresh: Duration,
}

impl State {
    fn new() -> Arc<Self> {
        let duration_from_var = |v: &str, d: u64| -> Duration {var(v).map(|r| ds::parse(&r).expect("bad duration string")).unwrap_or_else(|_| Duration::from_secs(d))};
        let user_cache_from_duration = |d: Duration| -> UserCache {
            Arc::new(RwLock::new(AsyncCache::new(d, user_getter as UserGetter)))
        };
        let default_refresh = duration_from_var("LFME_DEFAULT_REFRESH", 300);
        let whitelist_refresh = duration_from_var("LFME_WHITELIST_REFRESH", 60);
        let default_cache = user_cache_from_duration(default_refresh);
        let whitelist_cache = user_cache_from_duration(whitelist_refresh);

        Arc::new(State {
            lastfm_api_key: var("LFME_LASTFM_API_KEY").expect("last.fm API key must be set").into(),
            port: var("LFME_PORT").map(|p| p.parse().expect("cannot parse as a port number")).unwrap_or(9999),
            send_refresh_header: !var("LFME_NO_REFRESH").map(|h| &h == "1").unwrap_or(false),
            http: Client::builder().https_only(true).user_agent(concat!(env!("CARGO_PKG_NAME"), "/", env!("CARGO_PKG_VERSION"))).build().unwrap(),

            handlebars: {
                let mut hb = Handlebars::new();

                handlebars_helper!(url_encode: |s: String| urlencoding::encode(&s));

                hb.register_helper("url-encode", Box::new(url_encode));

                for (key, fulltext) in INTERNAL_THEMES {
                    log::info!(target: "lfm::config::theme", "Registering internal theme `{key}`");
                    hb.register_template_string(key, fulltext).unwrap();
                }
                hb.set_dev_mode(var("LFME_THEME_DEV").map(|h| &h == "1").unwrap_or(false));

                if let Ok(themes_dir) = var("LFME_THEME_DIR") {
                    log::info!(target: "lfm::config::theme", "Registering theme dir `{themes_dir}`");
                    hb.register_templates_directory(&var("LFME_THEME_EXT").unwrap_or_else(|_| ".hbs".into()), themes_dir).unwrap();
                }

                hb
            },
            default_theme: var("LFME_THEME_DEFAULT").map(Into::into).unwrap_or_else(|_| "plain".into()),

            google_api_key: var("LFME_GOOGLE_API_KEY").map(Into::into).ok(),
            google_fonts_cache: Arc::new(RwLock::new(AsyncCache::new(Duration::from_secs(86400), font_getter as FontGetter))),

            whitelist: {
                let load_whitelist = || -> Option<HashSet<String>> {
                    var("LFME_WHITELIST").ok().map(
                        |w| w.split(",").map(|s| s.trim().to_string()).collect()
                    )
                };

                match var("LFME_WHITELIST_MODE").map(|m| m.to_ascii_lowercase()).unwrap_or_else(|_| "open".into()).as_str() {
                    "open" => {
                        Whitelist::Open{default_cache, whitelist_cache, whitelist: load_whitelist().unwrap_or_default()}
                    },
                    "exclusive" => {
                        Whitelist::Exclusive{cache: whitelist_cache, whitelist: load_whitelist().expect("LFME_WHITELIST not set, unable to serve anyone")}
                    },
                    m => {
                        panic!("Bad whitelist mode: `{m}`");
                    }
                }
            },
            default_refresh: default_refresh + Duration::from_secs(1),
            whitelist_refresh: whitelist_refresh + Duration::from_secs(1)
        })
    }

    pub fn port(&self) -> u16 { self.port }
    pub fn send_refresh_header(&self) -> bool { self.send_refresh_header }
    pub async fn get_fontinfo(&self, font: &String) -> Result<Arc<str>, (StatusCode, &'static str)> {
      self.google_fonts_cache.write().await.get_owned(font).await
    }
    pub fn has_google_api_key(&self) -> bool { self.google_api_key.is_some() }
    pub async fn get_userinfo(&self, user: &String) -> (Result<Arc<(User, Track)>, (StatusCode, &'static str)>, Duration) {
        match &self.whitelist {
            Whitelist::Open{default_cache, whitelist_cache, whitelist} => {
                if whitelist.contains(user) {
                    (whitelist_cache.write().await.get_owned(user).await, self.whitelist_refresh)
                }
                else {
                    (default_cache.write().await.get_owned(user).await, self.default_refresh)
                }
            },
            Whitelist::Exclusive{cache, whitelist} => {
                if whitelist.contains(user) {
                    (cache.write().await.get_owned(user).await, self.whitelist_refresh)
                }
                else { (Err((StatusCode::FORBIDDEN, "User not in whitelist!")), self.default_refresh) }
            }
        }
    }
    pub fn handlebars(&self) -> &Handlebars { &self.handlebars }
    pub fn default_theme(&self) -> Arc<str> { self.default_theme.clone() }
}