use std::cmp::min;

use xcb::{
    x::{
        ChangeWindowAttributes, ConfigWindow, ConfigureNotifyEvent, ConfigureRequestEvent,
        ConfigureWindow, Cw, DestroyNotifyEvent, Drawable, EventMask, GetGeometry,
        GetWindowAttributes, MapRequestEvent, MapWindow, SendEvent, SendEventDest,
        UnmapNotifyEvent, UnmapWindow, Window,
    },
    xinerama::{self, ScreenInfo},
    BaseEvent, Connection, Extension, Xid,
};

use crate::{error::*, WM};
const BORDER_WIDTH: u16 = 3;

impl WM<'_> {
    /// Update the client state's recorded monitors and monitor sizes
    /// Returns true if any values changed, meaning windows should be re-tiled.
    pub(crate) fn update_geometry(&mut self) -> Result<bool> {
        let mut dirty = false;
        if self
            .conn
            .active_extensions()
            .any(|e| e == Extension::Xinerama)
        {
            let reply = self
                .conn
                .wait_for_reply(self.conn.send_request(&xinerama::QueryScreens {}))?;

            // Monitor removed, move its clients away
            if reply.screen_info().len() > self.clients.monitor_count() {
                dirty = true;
                self.clients.truncate_screens(reply.screen_info().len());
            }

            // Update screen info & add new client lists if needed
            for (i, monitor) in reply.screen_info().iter().enumerate() {
                dirty |= self.clients.set_monitor_geometry(i, (*monitor).into());
            }
        } else {
            // Only one screen
            if self.clients.monitor_count() > 1 {
                dirty = true;
                self.clients.truncate_screens(1);
            }

            // TODO: it looks like this won't actually update when the screen size changes?
            let setup = self.conn.get_setup();
            let screen = setup
                .roots()
                .nth(self.screen_num as usize)
                .ok_or(Error::NoSuchScreen)?;

            dirty |= self.clients.set_monitor_geometry(
                0,
                MonitorGeometry {
                    x_org: 0,
                    y_org: 0,
                    width: screen.width_in_pixels(),
                    height: screen.height_in_pixels(),
                },
            );
        }

        Ok(dirty)
    }

    /// Update our monitor geometry if the root window is reconfigured
    pub(crate) fn handle_configure_notify(&mut self, e: ConfigureNotifyEvent) -> Result<()> {
        if e.window() == self.root && self.update_geometry()? {
            self.clients.rearrange(self.conn);
            self.conn.flush()?;
        }
        Ok(())
    }

    /// Handle a configure request, by checking it's valid and performing it if so
    pub(crate) fn handle_configure_request(&mut self, e: ConfigureRequestEvent) -> Result<()> {
        if let Some(c) = self.clients.find_client_mut(e.window()) {
            // TODO: Allow changing some properties:
            //   - Border width
            //   - Size and position if floating
            c.configure_notify(self.conn);
            self.conn.flush()?;
        } else {
            // Configure it as requested, and sort the rest when we actually map the window
            self.conn
                .check_request(self.conn.send_request_checked(&ConfigureWindow {
                    window: e.window(),
                    value_list: &[
                        ConfigWindow::X(e.x().into()),
                        ConfigWindow::Y(e.y().into()),
                        ConfigWindow::Width(e.width().into()),
                        ConfigWindow::Height(e.height().into()),
                        ConfigWindow::BorderWidth(e.border_width().into()),
                        ConfigWindow::StackMode(e.stack_mode()),
                    ],
                }))?
        }

        Ok(())
    }

    /// Handle a destroyed window, removing it from the client list and rearranging.
    pub(crate) fn handle_destroy_notify(&mut self, e: DestroyNotifyEvent) -> Result<()> {
        if self.clients.remove_client(e.window()).is_some() {
            self.clients.rearrange(self.conn);
            self.conn.flush()?;
        }

        Ok(())
    }

    /// Map a window on request, starting to manage it if needed.
    pub(crate) fn handle_map_request(&mut self, e: MapRequestEvent) -> Result<()> {
        // Ignore already managed windows
        if self.clients.find_client_mut(e.window()).is_some() {
            return Ok(());
        }

        let attrs = self.conn.wait_for_reply(
            self.conn
                .send_request(&GetWindowAttributes { window: e.window() }),
        )?;
        if attrs.override_redirect() {
            return Ok(());
        }

        // Start managing, and map window
        self.manage(self.conn, e.window());

        self.conn.flush()?;

        Ok(())
    }

    /// Handle a window being unmapped by updating its client state, or stop managing it.
    pub(crate) fn handle_unmap_notify(&mut self, e: UnmapNotifyEvent) -> Result<()> {
        if self.clients.find_client_mut(e.window()).is_some() {
            if e.is_from_send_event() {
                // TODO: set client state to withdrawn
            } else {
                self.clients.remove_client(e.window());
                self.clients.rearrange(self.conn);
                // TODO: 'disown' the window - unmange(c, 0)
            }
        }

        Ok(())
    }

    /// Start managing the given window, adding it to the client list and ensuring its configuration is valid.
    /// This function sends multiple requests without checking them, so conn.flush() should be called after.
    fn manage(&mut self, conn: &Connection, window: Window) {
        // TODO: inherit from parent if window is transient
        let mon = self.clients.focused_mon();

        let Ok(geom) = conn.wait_for_reply(conn.send_request(&GetGeometry {
            drawable: Drawable::Window(window),
        })) else {
            return; // window stopped existing, so we can't manage it
        };

        self.unfocus();

        // TODO: inserting at index 0 is why dwm uses linked lists, maybe this can be improved
        self.clients.mons[mon].clients.insert(
            0,
            Client {
                window,
                x: 0,
                y: 0,
                width: 0,
                height: 0,
                border_width: BORDER_WIDTH,
                mapped: false,
            },
        );

        // TODO: Clamp window size to monitor

        let c = &mut self.clients.mons[mon].clients[0];

        c.set_geom(
            conn,
            geom.x(),
            geom.y(),
            geom.width(),
            geom.height(),
            BORDER_WIDTH,
        );
        c.set_border(conn, self.colours.border_normal());
        c.ensure_mapped(conn);

        // TODO: updatewindowtype
        // TODO: updatesizehints
        // TODO: updatewmhints

        // XSelectInput(dpy, w, EnterWindowMask|FocusChangeMask|PropertyChangeMask|StructureNotifyMask);
        c.select_input(
            conn,
            EventMask::ENTER_WINDOW
                | EventMask::FOCUS_CHANGE
                | EventMask::PROPERTY_CHANGE
                | EventMask::STRUCTURE_NOTIFY,
        );
        // TODO: grabbuttons
        // TODO: add to NetClientList
        // TODO: XMoveResizeWindow(dpy, c->win, c->x + 2 * sw, c->y, c->w, c->h); /* some windows require this */
        // TODO: setclientstate(c, NormalState);

        self.refocus(mon, 0);
        self.clients.rearrange_monitor(conn, mon);
    }
}

/// Holds state related to the window manager's clients
/// This contains a list of clients per monitor, alongside info on that monitor's screen size.
pub struct ClientState {
    /// The current arranging function.
    /// This function is expected to ensure that all clients are the correct size, reconfigure them if needed, and map/unmap as needed.
    arrange: &'static dyn Fn(&mut MonitorInfo, &Connection),
    mons: Vec<MonitorInfo>,

    focused: (usize, usize),
}

impl Default for ClientState {
    fn default() -> Self {
        Self {
            arrange: &tile,
            focused: (0, 0),
            mons: vec![],
        }
    }
}

impl std::fmt::Debug for ClientState {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("ClientState")
            .field("focused", &self.focused)
            .field("mons", &self.mons)
            .finish()
    }
}

/// Info stored for a single monitor
#[derive(Debug)]
pub struct MonitorInfo {
    /// Clients attached to that monitor
    clients: Vec<Client>,

    /// The monitor's geometry
    screen_info: MonitorGeometry,
}

impl MonitorInfo {
    fn clients_tiled_mut(&mut self) -> impl Iterator<Item = &mut Client> {
        // TODO: tag filtering, floating
        self.clients.iter_mut()
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct MonitorGeometry {
    pub x_org: i16,
    pub y_org: i16,
    pub width: u16,
    pub height: u16,
}

impl From<ScreenInfo> for MonitorGeometry {
    fn from(value: ScreenInfo) -> Self {
        Self {
            x_org: value.x_org,
            y_org: value.y_org,
            width: value.width,
            height: value.height,
        }
    }
}

impl ClientState {
    /// Set the new amount of screens, moving clients away if necessary
    pub fn truncate_screens(&mut self, new_size: usize) {
        // hack: double borrow stuff
        let mut moved_clients = vec![];
        for old in self.mons.drain(new_size - self.mons.len()..self.mons.len()) {
            moved_clients.extend(old.clients.into_iter());
        }
        self.mons[0].clients.extend(moved_clients);
    }

    /// Set the info for the given screen, resizing the monitor list if necessary.
    /// Returns true if the new info is different from the old one.
    pub fn set_monitor_geometry(&mut self, i: usize, info: MonitorGeometry) -> bool {
        while i >= self.mons.len() {
            self.mons.push(MonitorInfo::default())
        }
        let dirty = self.mons[i].screen_info != info;
        self.mons[i].screen_info = info;

        dirty
    }

    /// Get the amount of monitors this state is currently aware of
    pub fn monitor_count(&self) -> usize {
        self.mons.len()
    }

    /// Find the [`Client`] corresponding to the given window
    pub fn find_client_mut(&mut self, window: Window) -> Option<&mut Client> {
        self.mons
            .iter_mut()
            .flat_map(|mi| mi.clients.iter_mut())
            .find(|c| c.window == window)
    }

    /// Find the position of the client with the given window, returning (monitor, index)
    pub(crate) fn find_client_pos(&mut self, window: Window) -> Option<(usize, usize)> {
        for (pos_mon, mon) in self.mons.iter_mut().enumerate() {
            if let Some(pos) = mon.clients.iter().position(|c| c.window == window) {
                return Some((pos_mon, pos));
            }
        }
        None
    }

    /// Get a mutable reference to the currently focused client, if it exists.
    pub fn focused_mut(&mut self) -> Option<&mut Client> {
        self.client_mut(self.focused.0, self.focused.1)
    }

    /// Set the currently focused client, returning a mutable reference to it if the co-ordinates are valid.
    pub fn set_focused(&mut self, mut mon: usize, mut i: usize) -> Option<&mut Client> {
        if self.mons.is_empty() {
            return None;
        }

        if mon >= self.mons.len() {
            mon = self.mons.len() - 1;
        }

        if self.mons[mon].clients.is_empty() {
            return None;
        }

        if i >= self.mons[mon].clients.len() {
            i = self.mons[mon].clients.len() - 1;
        }

        self.focused = (mon, i);
        Some(&mut self.mons[mon].clients[i])
    }

    /// Get a mutable reference to the client at the given co-ordinates, if they are valid.
    pub fn client_mut(&mut self, mon: usize, i: usize) -> Option<&mut Client> {
        if mon < self.mons.len() && i < self.mons[mon].clients.len() {
            Some(&mut self.mons[mon].clients[i])
        } else {
            None
        }
    }

    /// Remove the client associated with the given window.
    /// This doesn't perform any of the associated X11 stuff
    pub fn remove_client(&mut self, window: Window) -> Option<Client> {
        let (mon, i) = self.find_client_pos(window)?;
        Some(self.mons[mon].clients.remove(i))
    }

    /// Rearrange all clients, reconfiguring them as needed.
    /// This function sends multiple requests without checking them, so conn.flush() should be called after.
    pub fn rearrange(&mut self, conn: &Connection) {
        for mon in 0..self.monitor_count() {
            self.rearrange_monitor(conn, mon);
        }
    }

    /// Rearrange a specific monitor
    /// This function sends multiple requests without checking them, so conn.flush() should be called after.
    fn rearrange_monitor(&mut self, conn: &Connection, mon: usize) {
        (self.arrange)(&mut self.mons[mon], conn);
    }

    fn focused_mon(&self) -> usize {
        self.focused.0
    }
}

/// Information about a single client / window
#[derive(Debug)]
pub struct Client {
    /// The corresponding X11 window
    window: Window,

    x: i16,
    y: i16,
    width: u16,
    height: u16,
    border_width: u16,
    mapped: bool,
}

impl Client {
    /// This function does not check for success, so conn.flush() should be called after.
    fn configure_notify(&self, conn: &Connection) {
        conn.send_request(&SendEvent {
            destination: SendEventDest::Window(self.window),
            event_mask: EventMask::STRUCTURE_NOTIFY,
            event: &ConfigureNotifyEvent::new(
                self.window,
                self.window,
                Window::none(),
                self.x,
                self.y,
                self.width,
                self.height,
                self.border_width,
                false,
            ),
            propagate: false,
        });
    }

    /// Set this client's geometry, also updating the X11 window if needed.
    fn set_geom(
        &mut self,
        conn: &Connection,
        x: i16,
        y: i16,
        width: u16,
        height: u16,
        border_width: u16,
    ) {
        if (x, y, width, height, border_width)
            == (self.x, self.y, self.width, self.height, self.border_width)
        {
            return;
        }

        self.x = x;
        self.y = y;
        self.width = width;
        self.height = height;
        self.border_width = border_width;

        conn.send_request(&ConfigureWindow {
            window: self.window,
            value_list: &[
                ConfigWindow::X(self.x.into()),
                ConfigWindow::Y(self.y.into()),
                ConfigWindow::Width(self.width.into()),
                ConfigWindow::Height(self.height.into()),
                ConfigWindow::BorderWidth(self.border_width.into()),
            ],
        });
    }

    /// Set the border of the X11 window to the given value.
    /// This sends a request but doesn't wait for the response.
    pub fn set_border(&self, conn: &Connection, colour: u32) {
        conn.send_request(&ChangeWindowAttributes {
            window: self.window(),
            value_list: &[Cw::BorderPixel(colour)],
        });
    }

    /// Ensure this client is currently mapped / visible
    pub fn ensure_mapped(&mut self, conn: &Connection) {
        if !self.mapped {
            conn.send_request(&MapWindow {
                window: self.window,
            });
            self.mapped = true;
        }
    }

    /// Ensure this client is currently unmapped / invisible
    pub fn ensure_unmapped(&mut self, conn: &Connection) {
        if self.mapped {
            conn.send_request(&UnmapWindow {
                window: self.window,
            });
            self.mapped = false;
        }
    }

    /// Get the associated window
    pub fn window(&self) -> Window {
        self.window
    }

    fn select_input(&self, conn: &Connection, event_mask: EventMask) {
        conn.send_request(&ChangeWindowAttributes {
            window: self.window(),
            value_list: &[Cw::EventMask(event_mask)],
        });
    }
}

impl Default for MonitorInfo {
    fn default() -> Self {
        Self {
            clients: vec![],
            screen_info: MonitorGeometry {
                x_org: 0,
                y_org: 0,
                width: 0,
                height: 0,
            },
        }
    }
}

fn tile(mon: &mut MonitorInfo, conn: &Connection) {
    if mon.clients.is_empty() {
        return;
    }

    let n = mon.clients_tiled_mut().count();
    let nmaster = 1;
    let mfact = 0.6;

    let MonitorGeometry {
        x_org,
        y_org,
        width: mon_width,
        height: mon_height,
    } = mon.screen_info;

    let main_width = if nmaster == 0 {
        0
    } else if n > nmaster {
        ((mon.screen_info.width as f64) * mfact) as u16
    } else {
        mon.screen_info.width
    };

    let (mut main_y, mut second_y) = (0, 0);
    for (i, c) in mon.clients_tiled_mut().enumerate() {
        if i < nmaster {
            let h = (mon_height - main_y) / (min(nmaster, n) - i) as u16;
            c.set_geom(
                conn,
                x_org,
                y_org + main_y as i16,
                main_width - (2 * c.border_width),
                h - (2 * c.border_width),
                c.border_width,
            );

            main_y += h;
        } else {
            let h = (mon_height - second_y) / (n - i) as u16;
            c.set_geom(
                conn,
                x_org + main_width as i16,
                y_org + second_y as i16,
                mon_width - main_width - (2 * c.border_width),
                h - (2 * c.border_width),
                c.border_width,
            );

            second_y += h;
        }

        c.ensure_mapped(conn);
    }
}