//! Slot-number overlay on the desktop.
//!
//! Each captured slot gets a small wlr-layer-shell surface (top layer, anchored
//! at the slot's top-left). Clicking the overlay asks the daemon to make that
//! slot the new main.
//!
//! ## Safety
//!
//! Live Wayland rendering is **gated** behind `ENBOXER_ENABLE_OVERLAY=1`.
//! `cargo test`, `enboxer doctor`, and any code path that does not set the env
//! var returns a placeholder [`OverlayHandle`] and never connects to the
//! compositor. The user's Hyprland session is therefore never touched unless
//! they explicitly opt in.
//!
//! A working wlr-layer-shell client (buffer render + click IPC via
//! `zwlr_layer_shell_v1`) is a follow-up ticket; the geometry math and the
//! spawn / kill plan are real and tested here so the live render slots into a
//! known shape.

use crate::hypr::Client;

const OVERLAY_W: i32 = 96;
const OVERLAY_H: i32 = 96;

/// Geometry for one overlay surface.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct OverlayRect {
    pub x: i32,
    pub y: i32,
    pub w: i32,
    pub h: i32,
}

/// Pure: where the overlay should sit relative to a captured slot. Anchored to
/// the slot's top-left so the number is visible even when the slot window is
/// minimised or behind another surface.
pub fn overlay_rect(slot_x: i32, slot_y: i32, _slot_w: i32, _slot_h: i32) -> OverlayRect {
    OverlayRect {
        x: slot_x,
        y: slot_y,
        w: OVERLAY_W,
        h: OVERLAY_H,
    }
}

/// Pure: the IPC verb a click should send to the daemon to make `slot` the
/// new main. The live wlr-layer-shell surface writes
/// `enboxer ipc --sock <sock> <verb>` to the daemon's unix socket; the gating
/// stub logs the verb so the operator can confirm wiring by hand.
pub fn click_verb(slot: u32) -> String {
    format!("swap {slot}")
    // ponytail: keep the verb alone. `enboxer ipc --sock X swap N` is what
    // the user types too; calling enboxer here would re-exec ourselves.
}

/// True iff the user has opted in to live Wayland rendering.
pub fn live_enabled() -> bool {
    std::env::var("ENBOXER_ENABLE_OVERLAY")
        .map(|v| v == "1" || v.eq_ignore_ascii_case("true"))
        .unwrap_or(false)
}

/// One overlay per active slot. Cheap to clone; carries enough state for both
/// the stub and a future live surface.
#[derive(Debug, Clone)]
pub struct OverlayHandle {
    pub slot: u32,
    pub rect: OverlayRect,
}

impl OverlayHandle {
    /// Stub handle for non-live paths. Does not connect to Wayland.
    pub fn stub(slot: u32, rect: OverlayRect) -> Self {
        Self { slot, rect }
    }
}

/// Spawn one overlay for `client`. When `live_enabled()` is false, returns a
/// stub and never touches Wayland; otherwise it spawns a background thread
/// that connects to the compositor, creates a wlr-layer-shell surface for
/// this slot, draws the slot number into a shm-backed buffer, and posts
/// `swap <slot>` to the daemon unix socket on pointer button events.
///
/// `ipc_sock` is the daemon's listen socket — when the user clicks the
/// overlay we connect briefly, write one line, and disconnect. Pass the
/// same socket the daemon uses (`default_sock()`).
pub fn spawn(slot: u32, client: &Client) -> OverlayHandle {
    spawn_with_sock(slot, client, None)
}

/// Like [`spawn`] but lets the caller pass the IPC socket explicitly.
pub fn spawn_with_sock(
    slot: u32,
    client: &Client,
    ipc_sock: Option<std::path::PathBuf>,
) -> OverlayHandle {
    let rect = overlay_rect(client.at[0], client.at[1], client.size[0], client.size[1]);
    if !live_enabled() {
        tracing::debug!("overlay: stub for slot {slot} at {rect:?}");
        return OverlayHandle::stub(slot, rect);
    }
    let sock = ipc_sock.unwrap_or_else(crate::session::default_sock);
    match crate::wayland_layer::spawn(slot, rect, sock) {
        Ok(_) => OverlayHandle::stub(slot, rect),
        Err(e) => {
            tracing::warn!("overlay: live spawn failed for slot {slot}: {e}");
            OverlayHandle::stub(slot, rect)
        }
    }
}

/// Track one overlay per active slot. Pure: no Wayland touched.
#[derive(Debug, Default)]
pub struct OverlayHub {
    by_slot: std::collections::BTreeMap<u32, OverlayHandle>,
}

impl OverlayHub {
    pub fn new() -> Self {
        Self::default()
    }

    /// Pure: compute the spawn / kill diff between the current slot set and
    /// the desired one. Tests use this to verify routing shape without
    /// connecting to Wayland.
    pub fn plan(
        &self,
        slots: &[(u32, Client)],
    ) -> (Vec<OverlayHandle>, Vec<u32>) {
        let want: std::collections::BTreeMap<u32, &Client> =
            slots.iter().map(|(s, c)| (*s, c)).collect();
        let spawn_list: Vec<OverlayHandle> = want
            .iter()
            .filter(|(s, _)| !self.by_slot.contains_key(*s))
            .map(|(s, c)| spawn(*s, c))
            .collect();
        let kill: Vec<u32> = self
            .by_slot
            .keys()
            .filter(|s| !want.contains_key(s))
            .copied()
            .collect();
        (spawn_list, kill)
    }

    /// Apply the plan: drop killed slots, insert spawned ones, return the
    /// list of overlays the caller should actually open.
    pub fn sync(
        &mut self,
        slots: &[(u32, Client)],
    ) -> Vec<OverlayHandle> {
        let (to_spawn, kill) = self.plan(slots);
        for k in kill {
            self.by_slot.remove(&k);
        }
        for h in &to_spawn {
            self.by_slot.insert(h.slot, h.clone());
        }
        to_spawn
    }

    pub fn len(&self) -> usize {
        self.by_slot.len()
    }

    pub fn is_empty(&self) -> bool {
        self.by_slot.is_empty()
    }

    pub fn kill_all(&mut self) {
        self.by_slot.clear();
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    fn client(addr: &str, at: (i32, i32)) -> Client {
        Client {
            address: addr.into(),
            class: "wow".into(),
            title: addr.into(),
            pid: 1,
            at: [at.0, at.1],
            size: [800, 600],
            mapped: true,
            hidden: false,
            xwayland: true,
            focus_history_id: 0,
        }
    }

    #[test]
    fn overlay_rect_is_anchored_top_left() {
        let r = overlay_rect(1920, 200, 800, 600);
        assert_eq!(r.x, 1920);
        assert_eq!(r.y, 200);
        assert_eq!(r.w, OVERLAY_W);
        assert_eq!(r.h, OVERLAY_H);
    }

    #[test]
    fn click_verb_is_swap_with_slot_number() {
        assert_eq!(click_verb(3), "swap 3");
        assert_eq!(click_verb(1), "swap 1");
    }

    #[test]
    fn live_enabled_defaults_off_and_respects_env() {
        std::env::remove_var("ENBOXER_ENABLE_OVERLAY");
        assert!(!live_enabled());
        std::env::set_var("ENBOXER_ENABLE_OVERLAY", "1");
        assert!(live_enabled());
        std::env::set_var("ENBOXER_ENABLE_OVERLAY", "true");
        assert!(live_enabled());
        std::env::set_var("ENBOXER_ENABLE_OVERLAY", "yes");
        assert!(!live_enabled());
        std::env::remove_var("ENBOXER_ENABLE_OVERLAY");
    }

    #[test]
    fn spawn_returns_stub_when_live_disabled() {
        std::env::remove_var("ENBOXER_ENABLE_OVERLAY");
        let c = client("0xa", (100, 200));
        let h = spawn(2, &c);
        assert_eq!(h.slot, 2);
        assert_eq!(h.rect.x, 100);
        assert_eq!(h.rect.y, 200);
        assert!(!live_enabled());
    }

    #[test]
    fn plan_spawns_new_slots_and_kills_gone_ones() {
        let mut hub = OverlayHub::new();
        let s1 = vec![(1, client("0xa", (0, 0))), (2, client("0xb", (1000, 0)))];
        let spawned = hub.sync(&s1);
        assert_eq!(spawned.len(), 2);
        assert_eq!(hub.len(), 2);

        // slot 3 appears, slot 1 disappears
        let s2 = vec![(2, client("0xb", (1000, 0))), (3, client("0xc", (0, 1000)))];
        let spawned = hub.sync(&s2);
        assert_eq!(spawned.len(), 1);
        assert_eq!(spawned[0].slot, 3);
        assert_eq!(hub.len(), 2);
        assert!(hub.by_slot.contains_key(&2));
        assert!(hub.by_slot.contains_key(&3));
        assert!(!hub.by_slot.contains_key(&1));
    }

    #[test]
    fn kill_all_clears() {
        let mut hub = OverlayHub::new();
        hub.sync(&[(1, client("0xa", (0, 0)))]);
        assert!(!hub.is_empty());
        hub.kill_all();
        assert!(hub.is_empty());
    }
}