//! Desktop notifications for the other players' card plays.
//!
//! Move notifications are opt-in (the bell in the game HUD), fire only
//! while the game page is in the background, and only for games the viewer
//! is seated in. They are delivered through the service worker —
//! page-context notifications are rejected on some platforms (Android in
//! particular) — with a page-context fallback when no worker is active.
//!
//! The interesting logic is split into pure functions ([`last_play`],
//! [`opponent_play`], [`message`]) so it is unit-testable on the host;
//! everything else talks to the browser.
use std::cell::{Cell, RefCell};
use std::rc::Rc;

use wasm_bindgen::JsCast;
use wasm_bindgen_futures::{spawn_local, JsFuture};

use crate::model::{card_label, is_briscola, is_chiamata, GameView};

/// localStorage key holding whether the user wants move notifications.
const ENABLED_KEY: &str = "tavolo.notify.moves";

/// The most recent card played, in a form comparable across snapshots.
#[derive(Debug, Clone, PartialEq)]
pub struct LastPlay {
    pub seat: usize,
    pub card: String,
}

/// The browser's notification permission.
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum Permission {
    Default,
    Granted,
    Denied,
    /// The browser has no Notification API at all.
    Unsupported,
}

/// Whether the user has opted into move notifications. The preference is
/// global (all games) and per device; browsers without `localStorage`
/// (rare) just never remember it.
pub fn enabled() -> bool {
    storage()
        .and_then(|s| s.get_item(ENABLED_KEY).ok().flatten())
        .as_deref()
        == Some("1")
}

/// Persist the opt-in state.
pub fn set_enabled(on: bool) {
    if let Some(storage) = storage() {
        let _ = if on {
            storage.set_item(ENABLED_KEY, "1")
        } else {
            storage.remove_item(ENABLED_KEY)
        };
    }
}

fn storage() -> Option<web_sys::Storage> {
    web_sys::window()?.local_storage().ok().flatten()
}

fn has_notification_api() -> bool {
    js_sys::Reflect::get(&js_sys::global(), &wasm_bindgen::JsValue::from_str("Notification"))
        .map(|value| !value.is_undefined())
        .unwrap_or(false)
}

/// The browser's current notification permission.
pub fn permission() -> Permission {
    if !has_notification_api() {
        return Permission::Unsupported;
    }
    match web_sys::Notification::permission() {
        web_sys::NotificationPermission::Granted => Permission::Granted,
        web_sys::NotificationPermission::Denied => Permission::Denied,
        _ => Permission::Default,
    }
}

/// Ask the browser for the notification permission.
///
/// Must be called from a user gesture (a click): Chrome rejects
/// permission prompts without one. Returns the resulting permission.
pub async fn request_permission() -> Permission {
    if !has_notification_api() {
        return Permission::Unsupported;
    }
    match web_sys::Notification::request_permission() {
        Ok(promise) => {
            let _ = JsFuture::from(promise).await;
            // Re-read the permission: the promise resolves to the same
            // enum, but re-reading also covers browsers that settled it
            // through their own UI.
            permission()
        }
        Err(_) => permission(),
    }
}

/// Whether the page is not in the foreground: the tab is hidden, or its
/// window lost focus. Notifications are only useful — and only shown —
/// when the viewer cannot see the table.
pub fn page_in_background() -> bool {
    let Some(window) = web_sys::window() else {
        // No window object: headless contexts cannot show notifications
        // anyway; treat the page as visible and stay quiet.
        return false;
    };
    let Some(document) = window.document() else {
        return false;
    };
    document.hidden() || !document.has_focus().unwrap_or(true)
}

/// The viewer's seat, or `None` for spectators. The viewer is the only
/// player whose hand is present in the snapshot.
pub fn viewer_seat(game: &GameView) -> Option<usize> {
    if game.spectator {
        return None;
    }
    game.players
        .iter()
        .find(|p| p.hand.is_some())
        .map(|p| p.seat)
}

/// The most recent card played in the snapshot, across all game families:
///
/// - scopone and scopa report every play in `last_move`;
/// - briscola and briscola chiamata don't: a play either extends `trick`
///   or, when it completes the trick, moves `trick` into `last_trick` —
///   in both cases the latest play is the last card of the trick.
pub fn last_play(game: &GameView) -> Option<LastPlay> {
    if let Some(mv) = &game.last_move {
        return Some(LastPlay { seat: mv.seat, card: mv.card.clone() });
    }
    if let Some(card) = game.trick.last() {
        return Some(LastPlay { seat: card.seat, card: card.card.clone() });
    }
    game.last_trick
        .as_ref()
        .and_then(|trick| trick.cards.last())
        .map(|card| LastPlay { seat: card.seat, card: card.card.clone() })
}

/// The play to announce between two snapshots.
///
/// `primed` is false for the first snapshot after a (re)connection: the
/// snapshot is a resync, not a play, and only establishes the baseline.
/// Only plays by *other* seats are reported; the viewer's own plays (and
/// the server's auto-plays for them) are already visible.
pub fn opponent_play(primed: bool, prev: Option<&LastPlay>, next: &GameView) -> Option<LastPlay> {
    let cur = last_play(next)?;
    if !primed || Some(&cur) == prev {
        return None;
    }
    // Spectators (and snapshots without a visible hand) have no seat to
    // compare against: stay quiet rather than announce every play.
    let seat = viewer_seat(next)?;
    if cur.seat == seat {
        return None;
    }
    Some(cur)
}

/// Track the notification baseline across game snapshots. The baseline
/// must be reset for every (re)connection; see [`opponent_play`].
#[derive(Clone)]
pub struct Baseline {
    prev: Rc<RefCell<Option<LastPlay>>>,
    primed: Rc<Cell<bool>>,
}

impl Baseline {
    pub fn new() -> Self {
        Baseline {
            prev: Rc::new(RefCell::new(None)),
            primed: Rc::new(Cell::new(false)),
        }
    }

    /// Forget the previous snapshot: the next one is a resync baseline.
    pub fn reset(&self) {
        *self.prev.borrow_mut() = None;
        self.primed.set(false);
    }

    /// Record `game` and return the opponent's play to notify about, if
    /// any. Must be called for every snapshot, whether or not the
    /// preference is on, so that enabling it mid-game never replays an
    /// old move.
    pub fn observe(&self, game: &GameView) -> Option<LastPlay> {
        let play = opponent_play(self.primed.get(), self.prev.borrow().as_ref(), game);
        *self.prev.borrow_mut() = last_play(game);
        self.primed.set(true);
        play
    }
}

/// The notification title and body for `play` in `game`.
pub fn message(game: &GameView, play: &LastPlay) -> (String, String) {
    let title = format!(
        "{} played {}",
        game.player_name_for_seat(play.seat),
        card_label(&play.card)
    );
    let mut parts = vec![if is_briscola(&game.game_type) || is_chiamata(&game.game_type) {
        format!("Deal {}", game.hand_number)
    } else {
        format!("Hand {}", game.hand_number)
    }];
    if game.your_turn == Some(true) {
        parts.push("Your turn".to_string());
    } else {
        parts.push(format!("{} to play", game.player_name_for_seat(game.turn)));
    }
    if let Some(mv) = &game.last_move {
        if mv.scopa {
            parts.push("Scopa!".to_string());
        }
        if mv.pigliatutto {
            parts.push("Asso pigliatutto!".to_string());
        }
    }
    (title, parts.join(" · "))
}

/// Show a desktop notification for `play`.
///
/// Best-effort: failures (no permission, no worker, platform rejection)
/// are silently ignored — the table itself is the source of truth.
pub fn notify_move(game: &GameView, play: &LastPlay) {
    let (title, body) = message(game, play);
    let url = format!("/game/{}", game.id);
    let tag = format!("tavolo-{}", game.id);
    spawn_local(async move {
        show(&title, &body, &tag, &url).await;
    });
}

/// Build the notification options shared by both delivery paths.
fn options(body: &str, tag: Option<&str>, url: &str) -> web_sys::NotificationOptions {
    let options = web_sys::NotificationOptions::new();
    options.set_body(body);
    options.set_icon("/assets/icons/icon-192.png");
    if let Some(tag) = tag {
        // renotify needs a tag; the tag replaces the previous move of the
        // same game instead of stacking one notification per play.
        options.set_tag(tag);
        options.set_renotify(true);
    }
    let data = js_sys::Object::new();
    let _ = js_sys::Reflect::set(
        &data,
        &wasm_bindgen::JsValue::from_str("url"),
        &wasm_bindgen::JsValue::from_str(url),
    );
    options.set_data(&data);
    options
}

async fn show(title: &str, body: &str, tag: &str, url: &str) {
    // Prefer the service worker registration: it is the only path that
    // works for installed PWAs on Android. `getRegistration` resolves
    // promptly (to `undefined` when nothing is registered), unlike
    // `ready`, which never settles without a worker.
    if let Some(window) = web_sys::window() {
        let container = window.navigator().service_worker();
        if let Ok(value) = JsFuture::from(container.get_registration()).await {
            if let Some(registration) = value.dyn_ref::<web_sys::ServiceWorkerRegistration>() {
                if let Ok(promise) =
                    registration.show_notification_with_options(title, &options(body, Some(tag), url))
                {
                    if JsFuture::from(promise).await.is_ok() {
                        return;
                    }
                }
            }
        }
    }
    let _ = web_sys::Notification::new_with_options(title, &options(body, None, url));
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::model::GameView;
    use serde_json::json;

    fn scopone_view(last_move: serde_json::Value, my_turn: bool) -> GameView {
        serde_json::from_value(json!({
            "id": "g1",
            "game_type": "scopone_scientifico",
            "phase": "playing",
            "hand_number": 2,
            "turn": 2,
            "your_turn": my_turn,
            "players": [
                {"sub": "alice", "name": "Alice", "seat": 0},
                {"sub": "bob", "name": "Bob", "seat": 1, "hand": ["01D", "02C"]},
                {"sub": "carol", "name": "Carol", "seat": 2},
                {"sub": "dave", "name": "Dave", "seat": 3},
            ],
            "last_move": last_move,
        }))
        .unwrap()
    }

    fn briscola_view(trick: Vec<serde_json::Value>, last_trick: serde_json::Value) -> GameView {
        serde_json::from_value(json!({
            "id": "g2",
            "game_type": "briscola",
            "phase": "playing",
            "hand_number": 1,
            "turn": 1,
            "your_turn": false,
            "players": [
                {"sub": "alice", "name": "Alice", "seat": 0, "hand": ["01D"]},
                {"sub": "bob", "name": "Bob", "seat": 1},
            ],
            "trick": trick,
            "last_trick": last_trick,
        }))
        .unwrap()
    }

    fn play(seat: usize, card: &str) -> LastPlay {
        LastPlay { seat, card: card.to_string() }
    }

    #[test]
    fn last_play_reads_last_move() {
        let g = scopone_view(
            json!({"seat": 3, "name": "Dave", "card": "07D", "captured": []}),
            false,
        );
        assert_eq!(Some(play(3, "07D")), last_play(&g));
    }

    #[test]
    fn last_play_reads_the_trick_in_progress() {
        let g = briscola_view(
            vec![json!({"seat": 0, "card": "04C"}), json!({"seat": 1, "card": "02D"})],
            serde_json::Value::Null,
        );
        assert_eq!(Some(play(1, "02D")), last_play(&g));
    }

    #[test]
    fn last_play_reads_the_completed_trick() {
        // The trick-completing play empties `trick`; the newest card is
        // the last one of `last_trick.cards`.
        let g = briscola_view(
            vec![],
            json!({"winner": 1, "cards": [
                {"seat": 0, "card": "04C"},
                {"seat": 1, "card": "02D"},
            ]}),
        );
        assert_eq!(Some(play(1, "02D")), last_play(&g));
    }

    #[test]
    fn last_play_is_none_before_any_card() {
        let g = briscola_view(vec![], serde_json::Value::Null);
        assert_eq!(None, last_play(&g));
    }

    #[test]
    fn opponent_play_skips_the_first_snapshot() {
        let g = scopone_view(
            json!({"seat": 3, "name": "Dave", "card": "07D"}),
            false,
        );
        assert_eq!(None, opponent_play(false, None, &g));
    }

    #[test]
    fn opponent_play_skips_the_viewer_seat() {
        // Bob (seat 1) carries the hand: his own play is not announced.
        let g = scopone_view(
            json!({"seat": 1, "name": "Bob", "card": "07D"}),
            false,
        );
        assert_eq!(None, opponent_play(true, Some(&play(2, "03B")), &g));
    }

    #[test]
    fn opponent_play_reports_a_new_move_and_not_a_repeat() {
        let g = scopone_view(
            json!({"seat": 3, "name": "Dave", "card": "07D"}),
            false,
        );
        let prev = play(2, "03B");
        assert_eq!(Some(play(3, "07D")), opponent_play(true, Some(&prev), &g));
        assert_eq!(None, opponent_play(true, Some(&play(3, "07D")), &g));
    }

    #[test]
    fn opponent_play_stays_quiet_for_spectators() {
        let mut g = scopone_view(
            json!({"seat": 3, "name": "Dave", "card": "07D"}),
            false,
        );
        g.spectator = true;
        for player in &mut g.players {
            player.hand = None;
        }
        assert_eq!(None, opponent_play(true, Some(&play(2, "03B")), &g));
    }

    #[test]
    fn opponent_play_reports_after_a_hand_boundary() {
        // The new hand cleared `last_move`; the first play is still news.
        let g = scopone_view(
            json!({"seat": 0, "name": "Alice", "card": "01D"}),
            false,
        );
        assert_eq!(Some(play(0, "01D")), opponent_play(true, None, &g));
    }

    #[test]
    fn baseline_resets_per_connection() {
        let baseline = Baseline::new();
        let g = scopone_view(
            json!({"seat": 3, "name": "Dave", "card": "07D"}),
            false,
        );
        // First snapshot of the connection: baseline only.
        assert_eq!(None, baseline.observe(&g));
        // A new play by another seat is reported.
        let next = scopone_view(
            json!({"seat": 0, "name": "Alice", "card": "06C"}),
            false,
        );
        assert_eq!(Some(play(0, "06C")), baseline.observe(&next));
        // A reconnect resyncs to the same snapshot: no notification.
        baseline.reset();
        assert_eq!(None, baseline.observe(&next));
    }

    #[test]
    fn message_names_the_player_and_card() {
        let g = scopone_view(
            json!({"seat": 3, "name": "Dave", "card": "07D", "scopa": true}),
            true,
        );
        let (title, body) = message(&g, &play(3, "07D"));
        assert_eq!("Dave played 7 di denari", title);
        assert_eq!("Hand 2 · Your turn · Scopa!", body);
    }

    #[test]
    fn message_names_the_next_player_and_the_deal() {
        let mut g = briscola_view(vec![json!({"seat": 1, "card": "02D"})], serde_json::Value::Null);
        g.turn = 0;
        let (title, body) = message(&g, &play(1, "02D"));
        assert_eq!("Bob played 2 di denari", title);
        assert_eq!("Deal 1 · Alice to play", body);
    }
}