use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::sync::{Arc, Mutex};
use std::time::{Duration, Instant};
use tauri::{AppHandle, Emitter, State};
use x11rb::atom_manager;
use x11rb::connection::Connection;
use x11rb::protocol::xproto::{
    AtomEnum, ChangeWindowAttributesAux, ClientMessageEvent, ConfigureWindowAux,
    ConnectionExt as XprotoConnectionExt, EventMask, StackMode,
};
use x11rb::protocol::Event;
use x11rb::rust_connection::RustConnection;

atom_manager! {
    pub Atoms: AtomsCookie {
        _NET_CLIENT_LIST,
        _NET_WM_PID,
        _NET_WM_NAME,
        _XEMBED,
        _XEMBED_INFO,
        WM_PROTOCOLS,
        WM_DELETE_WINDOW,
        UTF8_STRING,
    }
}

// XEmbed protocol message opcodes (subset).
const XEMBED_EMBEDDED_NOTIFY: u32 = 0;

#[derive(Clone)]
struct X11Conn {
    conn: Arc<RustConnection>,
    atoms: Atoms,
    root: u32,
}

#[allow(dead_code)]
#[derive(Debug, Clone)]
pub struct AppInfo {
    pub xid: u32,
    pub pid: u32,
    pub command: String,
}

pub struct X11State {
    conn: Mutex<Option<X11Conn>>,
    tauri_xid: Mutex<Option<u32>>,
    windows: Arc<Mutex<HashMap<u32, AppInfo>>>,
}

impl X11State {
    pub fn new() -> Self {
        Self {
            conn: Mutex::new(None),
            tauri_xid: Mutex::new(None),
            windows: Arc::new(Mutex::new(HashMap::new())),
        }
    }

    fn ensure_conn(&self, app: &AppHandle) -> Result<X11Conn, String> {
        let mut guard = self.conn.lock().unwrap();
        if let Some(c) = guard.as_ref() {
            return Ok(c.clone());
        }
        let (raw, screen_num) = RustConnection::connect(None).map_err(|e| e.to_string())?;
        let conn = Arc::new(raw);
        let atoms = Atoms::new(&*conn)
            .map_err(|e| e.to_string())?
            .reply()
            .map_err(|e| e.to_string())?;
        let root = conn.setup().roots[screen_num].root;

        let conn_t = conn.clone();
        let windows_t = self.windows.clone();
        let app_t = app.clone();
        std::thread::spawn(move || event_loop(conn_t, windows_t, app_t));

        let c = X11Conn { conn, atoms, root };
        *guard = Some(c.clone());
        Ok(c)
    }

    fn ensure_xid(
        &self,
        app: &AppHandle,
        window: &tauri::WebviewWindow,
    ) -> Result<u32, String> {
        let mut guard = self.tauri_xid.lock().unwrap();
        if let Some(xid) = *guard {
            return Ok(xid);
        }
        let xid = fetch_tauri_xid(app, window.clone())?;
        *guard = Some(xid);
        Ok(xid)
    }
}

fn fetch_tauri_xid(app: &AppHandle, window: tauri::WebviewWindow) -> Result<u32, String> {
    use std::sync::mpsc;
    let (tx, rx) = mpsc::sync_channel(1);
    app.run_on_main_thread(move || {
        let result: Result<u32, String> = (|| {
            use gtk::prelude::*;
            let gtk_win = window.gtk_window().map_err(|e| e.to_string())?;
            let gdk_win = gtk_win.window().ok_or_else(|| "no GDK window yet".to_string())?;
            let x11: gdkx11::X11Window = gdk_win.downcast().map_err(|_| {
                "Tauri's window is not an X11 window — likely running on Wayland. \
                 GDK_BACKEND=x11 should force X11; check that XWayland is installed \
                 (apt install xwayland) and restart the app."
                    .to_string()
            })?;
            Ok(x11.xid() as u32)
        })();
        let _ = tx.send(result);
    })
    .map_err(|e| e.to_string())?;
    rx.recv().map_err(|e| e.to_string())?
}

fn event_loop(
    conn: Arc<RustConnection>,
    windows: Arc<Mutex<HashMap<u32, AppInfo>>>,
    app: AppHandle,
) {
    loop {
        match conn.wait_for_event() {
            Ok(Event::DestroyNotify(e)) => {
                let removed = windows.lock().unwrap().remove(&e.window);
                if removed.is_some() {
                    let _ = app.emit("app:destroyed", e.window);
                }
            }
            Ok(_) => {}
            Err(_) => break,
        }
    }
}

#[derive(Deserialize)]
pub struct LaunchOpts {
    pub command: String,
}

#[derive(Serialize, Clone)]
pub struct LaunchedApp {
    pub xid: u32,
    pub title: String,
}

#[tauri::command]
pub async fn app_launch(
    app: AppHandle,
    state: State<'_, X11State>,
    window: tauri::WebviewWindow,
    opts: LaunchOpts,
) -> Result<LaunchedApp, String> {
    let c = state.ensure_conn(&app)?;
    let parent_xid = state.ensure_xid(&app, &window)?;

    let parts = shell_words::split(&opts.command).map_err(|e| e.to_string())?;
    if parts.is_empty() {
        return Err("empty command".into());
    }
    let (program, args) = parts.split_first().unwrap();
    let child = std::process::Command::new(program)
        .args(args)
        .stdin(std::process::Stdio::null())
        .spawn()
        .map_err(|e| format!("spawn failed: {}", e))?;
    let root_pid = child.id();
    // Detach: we don't wait() — Tauri exiting will SIGHUP it via the X11 parent.
    std::mem::forget(child);

    let client_xid = wait_for_window_by_pid(&c, root_pid, Duration::from_secs(20))
        .ok_or_else(|| "could not find window for launched process".to_string())?;

    embed_window(&c, client_xid, parent_xid)?;

    let title = read_window_title(&c, client_xid).unwrap_or_else(|| opts.command.clone());

    state.windows.lock().unwrap().insert(
        client_xid,
        AppInfo {
            xid: client_xid,
            pid: root_pid,
            command: opts.command.clone(),
        },
    );

    Ok(LaunchedApp { xid: client_xid, title })
}

#[tauri::command]
pub fn app_set_geometry(
    app: AppHandle,
    state: State<'_, X11State>,
    window: tauri::WebviewWindow,
    xid: u32,
    x: f64,
    y: f64,
    width: f64,
    height: f64,
) -> Result<(), String> {
    let c = state.ensure_conn(&app)?;
    let sf = window.scale_factor().map_err(|e| e.to_string())?;
    let outer = window.outer_position().map_err(|e| e.to_string())?;
    let inner = window.inner_position().map_err(|e| e.to_string())?;
    let off_x = inner.x - outer.x;
    let off_y = inner.y - outer.y;
    let phys_x = (x * sf).round() as i32 + off_x;
    let phys_y = (y * sf).round() as i32 + off_y;
    let phys_w = ((width * sf).round() as i32).max(1) as u32;
    let phys_h = ((height * sf).round() as i32).max(1) as u32;
    c.conn
        .configure_window(
            xid,
            &ConfigureWindowAux::new()
                .x(phys_x)
                .y(phys_y)
                .width(phys_w)
                .height(phys_h)
                .stack_mode(StackMode::ABOVE),
        )
        .map_err(|e| e.to_string())?;
    c.conn.flush().map_err(|e| e.to_string())?;
    Ok(())
}

#[tauri::command]
pub fn app_set_visible(
    app: AppHandle,
    state: State<'_, X11State>,
    xid: u32,
    visible: bool,
) -> Result<(), String> {
    let c = state.ensure_conn(&app)?;
    if visible {
        c.conn.map_window(xid).map_err(|e| e.to_string())?;
    } else {
        c.conn.unmap_window(xid).map_err(|e| e.to_string())?;
    }
    c.conn.flush().map_err(|e| e.to_string())?;
    Ok(())
}

#[tauri::command]
pub fn app_set_all_visible(
    app: AppHandle,
    state: State<'_, X11State>,
    visible: bool,
) -> Result<(), String> {
    let c = state.ensure_conn(&app)?;
    let xids: Vec<u32> = state.windows.lock().unwrap().keys().copied().collect();
    for xid in xids {
        if visible {
            let _ = c.conn.map_window(xid);
        } else {
            let _ = c.conn.unmap_window(xid);
        }
    }
    let _ = c.conn.flush();
    Ok(())
}

#[tauri::command]
pub fn app_close(app: AppHandle, state: State<'_, X11State>, xid: u32) -> Result<(), String> {
    let c = state.ensure_conn(&app)?;
    let event = ClientMessageEvent::new(
        32,
        xid,
        c.atoms.WM_PROTOCOLS,
        [c.atoms.WM_DELETE_WINDOW, 0, 0, 0, 0],
    );
    let _ = c.conn.send_event(false, xid, EventMask::NO_EVENT, event);
    c.conn.flush().map_err(|e| e.to_string())?;
    state.windows.lock().unwrap().remove(&xid);
    Ok(())
}

fn embed_window(c: &X11Conn, client_xid: u32, parent_xid: u32) -> Result<(), String> {
    // Listen for destroy / property changes on the embedded window.
    c.conn
        .change_window_attributes(
            client_xid,
            &ChangeWindowAttributesAux::new()
                .event_mask(EventMask::STRUCTURE_NOTIFY | EventMask::PROPERTY_CHANGE),
        )
        .map_err(|e| e.to_string())?;

    // Reparent into Tauri's X11 toplevel.
    c.conn
        .reparent_window(client_xid, parent_xid, 0, 0)
        .map_err(|e| e.to_string())?;

    c.conn.map_window(client_xid).map_err(|e| e.to_string())?;

    // Stack above the webview's GDK X11 surface (siblings under Tauri toplevel).
    c.conn
        .configure_window(
            client_xid,
            &ConfigureWindowAux::new().stack_mode(StackMode::ABOVE),
        )
        .map_err(|e| e.to_string())?;

    c.conn.flush().map_err(|e| e.to_string())?;

    // Inform the client it is now embedded (XEmbed protocol).
    let event = ClientMessageEvent::new(
        32,
        client_xid,
        c.atoms._XEMBED,
        [x11rb::CURRENT_TIME, XEMBED_EMBEDDED_NOTIFY, 0, parent_xid, 0],
    );
    let _ = c.conn.send_event(false, client_xid, EventMask::NO_EVENT, event);
    c.conn.flush().map_err(|e| e.to_string())?;

    Ok(())
}

fn wait_for_window_by_pid(c: &X11Conn, root_pid: u32, timeout: Duration) -> Option<u32> {
    let deadline = Instant::now() + timeout;
    while Instant::now() < deadline {
        let pids = collect_descendant_pids(root_pid);
        if let Some(xid) = find_window_for_pids(c, &pids) {
            return Some(xid);
        }
        std::thread::sleep(Duration::from_millis(150));
    }
    None
}

fn collect_descendant_pids(root: u32) -> Vec<u32> {
    let mut parents: HashMap<u32, u32> = HashMap::new();
    let Ok(entries) = std::fs::read_dir("/proc") else {
        return vec![root];
    };
    for entry in entries.flatten() {
        let name = entry.file_name();
        let Some(name_str) = name.to_str() else {
            continue;
        };
        let Ok(pid) = name_str.parse::<u32>() else {
            continue;
        };
        let stat_path = entry.path().join("stat");
        let Ok(stat) = std::fs::read_to_string(&stat_path) else {
            continue;
        };
        if let Some(rparen) = stat.rfind(')') {
            let rest = &stat[rparen + 1..];
            let fields: Vec<&str> = rest.split_whitespace().collect();
            if let Some(ppid_str) = fields.get(1) {
                if let Ok(ppid) = ppid_str.parse::<u32>() {
                    parents.insert(pid, ppid);
                }
            }
        }
    }
    let mut result = vec![root];
    let mut grew = true;
    while grew {
        grew = false;
        for (&pid, &ppid) in &parents {
            if result.contains(&ppid) && !result.contains(&pid) {
                result.push(pid);
                grew = true;
            }
        }
    }
    result
}

fn find_window_for_pids(c: &X11Conn, pids: &[u32]) -> Option<u32> {
    let reply = c
        .conn
        .get_property(false, c.root, c.atoms._NET_CLIENT_LIST, AtomEnum::WINDOW, 0, 1024)
        .ok()?
        .reply()
        .ok()?;
    let windows: Vec<u32> = reply.value32()?.collect();
    for xid in windows {
        if let Some(wpid) = read_window_pid(c, xid) {
            if pids.contains(&wpid) {
                return Some(xid);
            }
        }
    }
    None
}

fn read_window_pid(c: &X11Conn, xid: u32) -> Option<u32> {
    let reply = c
        .conn
        .get_property(false, xid, c.atoms._NET_WM_PID, AtomEnum::CARDINAL, 0, 1)
        .ok()?
        .reply()
        .ok()?;
    reply.value32().and_then(|mut it| it.next())
}

fn read_window_title(c: &X11Conn, xid: u32) -> Option<String> {
    let reply = c
        .conn
        .get_property(false, xid, c.atoms._NET_WM_NAME, c.atoms.UTF8_STRING, 0, 1024)
        .ok()?
        .reply()
        .ok()?;
    let s = String::from_utf8_lossy(&reply.value).to_string();
    if s.is_empty() {
        let r2 = c
            .conn
            .get_property(false, xid, AtomEnum::WM_NAME, AtomEnum::STRING, 0, 1024)
            .ok()?
            .reply()
            .ok()?;
        Some(String::from_utf8_lossy(&r2.value).to_string())
    } else {
        Some(s)
    }
}