use crate::scripting::guiwin::GuiWin;
use crate::termwindow::TermWindowNotif;
use crate::TermWindow;
use ::window::*;
use anyhow::{Context, Error};
pub use config::FrontEndSelection;
use mux::client::ClientId;
use mux::window::WindowId as MuxWindowId;
use mux::{Mux, MuxNotification};
use promise::{Future, Promise};
use std::cell::RefCell;
use std::collections::{BTreeMap, HashSet};
use std::rc::Rc;
use std::sync::Arc;
use wezterm_term::{Alert, ClipboardSelection};
use wezterm_toast_notification::*;

pub struct GuiFrontEnd {
    connection: Rc<Connection>,
    switching_workspaces: RefCell<bool>,
    spawned_mux_window: RefCell<HashSet<MuxWindowId>>,
    known_windows: RefCell<BTreeMap<Window, MuxWindowId>>,
    client_id: Arc<ClientId>,
}

impl Drop for GuiFrontEnd {
    fn drop(&mut self) {
        ::window::shutdown();
    }
}

impl GuiFrontEnd {
    pub fn try_new() -> anyhow::Result<Rc<GuiFrontEnd>> {
        let connection = Connection::init()?;
        connection.set_event_handler(Self::app_event_handler);

        let mux = Mux::get();
        let client_id = mux.active_identity().expect("to have set my own id");

        let front_end = Rc::new(GuiFrontEnd {
            connection,
            switching_workspaces: RefCell::new(false),
            spawned_mux_window: RefCell::new(HashSet::new()),
            known_windows: RefCell::new(BTreeMap::new()),
            client_id: client_id.clone(),
        });

        mux.subscribe(move |n| {
            match n {
                MuxNotification::WindowWorkspaceChanged(_)
                | MuxNotification::ActiveWorkspaceChanged(_)
                | MuxNotification::WindowCreated(_)
                | MuxNotification::WindowRemoved(_) => {
                    promise::spawn::spawn_into_main_thread(async move {
                        let fe = crate::frontend::front_end();
                        if !fe.is_switching_workspace() {
                            fe.reconcile_workspace();
                        }
                    })
                    .detach();
                }
                MuxNotification::TabAddedToWindow { .. } => {}
                MuxNotification::PaneRemoved(_) => {}
                MuxNotification::WindowInvalidated(_) => {}
                MuxNotification::PaneOutput(_) => {}
                MuxNotification::PaneAdded(_) => {}
                MuxNotification::Alert {
                    pane_id: _,
                    alert:
                        Alert::ToastNotification {
                            title,
                            body,
                            focus: _,
                        },
                } => {
                    let message = if title.is_none() { "" } else { &body };
                    let title = title.as_ref().unwrap_or(&body);
                    // FIXME: if notification.focus is true, we should do
                    // something here to arrange to focus pane_id when the
                    // notification is clicked
                    persistent_toast_notification(title, message);
                }
                MuxNotification::Alert {
                    pane_id: _,
                    alert: Alert::Bell,
                } => {
                    // Handled via TermWindowNotif; NOP it here.
                }
                MuxNotification::Alert {
                    pane_id: _,
                    alert:
                        Alert::OutputSinceFocusLost
                        | Alert::PaletteChanged
                        | Alert::CurrentWorkingDirectoryChanged
                        | Alert::WindowTitleChanged(_)
                        | Alert::TabTitleChanged(_)
                        | Alert::IconTitleChanged(_)
                        | Alert::SetUserVar { .. },
                } => {}
                MuxNotification::Empty => {
                    promise::spawn::spawn_into_main_thread(async move {
                        if mux::activity::Activity::count() == 0 {
                            log::trace!("Mux is now empty, terminate gui");
                            Connection::get().unwrap().terminate_message_loop();
                        }
                    })
                    .detach();
                }
                MuxNotification::SaveToDownloads { name, data } => {
                    if !config::configuration().allow_download_protocols {
                        log::error!(
                            "Ignoring download request for {:?}, \
                                 as allow_download_protocols=false",
                            name
                        );
                    } else if let Err(err) = crate::download::save_to_downloads(name, &*data) {
                        log::error!("save_to_downloads: {:#}", err);
                    }
                }
                MuxNotification::AssignClipboard {
                    pane_id,
                    selection,
                    clipboard,
                } => {
                    promise::spawn::spawn_into_main_thread(async move {
                        let fe = crate::frontend::front_end();
                        log::trace!(
                            "set clipboard in pane {} {:?} {:?}",
                            pane_id,
                            selection,
                            clipboard
                        );
                        if let Some(window) = fe.known_windows.borrow().keys().next() {
                            window.set_clipboard(
                                match selection {
                                    ClipboardSelection::Clipboard => Clipboard::Clipboard,
                                    ClipboardSelection::PrimarySelection => {
                                        Clipboard::PrimarySelection
                                    }
                                },
                                clipboard.unwrap_or_else(String::new),
                            );
                        } else {
                            log::error!("Cannot assign clipboard as there are no windows");
                        };
                    })
                    .detach();
                }
            }
            true
        });
        // Re-evaluate the config so that folks that are using
        // `wezterm.gui.get_appearance()` can have that take effect
        // before any windows are created
        config::reload();

        // And build the initial menu bar.
        // TODO: arrange for this to happen on config reload.
        crate::commands::CommandDef::recreate_menubar(&config::configuration());

        Ok(front_end)
    }

    fn app_event_handler(event: ApplicationEvent) {
        log::trace!("Got app event {event:?}");
        match event {
            ApplicationEvent::OpenCommandScript(file_name) => {
                promise::spawn::spawn(async move {
                    use config::keyassignment::SpawnTabDomain;
                    use wezterm_term::TerminalSize;

                    // We send the script to execute to the shell on stdin, rather than ask the
                    // shell to execute it directly, so that we start the shell and read in the
                    // user's rc files before running the script.  Without this, wezterm on macOS
                    // is launched with a default and very anemic path, and that is frustrating for
                    // users.

                    let mux = Mux::get();
                    let window_id = None;
                    let pane_id = None;
                    let cmd = None;
                    let cwd = None;
                    let workspace = mux.active_workspace();

                    match mux
                        .spawn_tab_or_window(
                            window_id,
                            SpawnTabDomain::DomainName("local".to_string()),
                            cmd,
                            cwd,
                            TerminalSize::default(),
                            pane_id,
                            workspace,
                        )
                        .await
                    {
                        Ok((_tab, pane, _window_id)) => {
                            log::trace!("Spawned {file_name} as pane_id {}", pane.pane_id());
                            let mut writer = pane.writer();
                            write!(writer, "{} ; exit\n", shlex::quote(&file_name)).ok();
                        }
                        Err(err) => {
                            log::error!("Failed to spawn {file_name}: {err:#?}");
                        }
                    };
                })
                .detach();
            }
            ApplicationEvent::PerformKeyAssignment(action) => {
                // We should only get here when there are no windows open
                // and the user picks an action from the menubar.
                // This is not currently possible, but could be in the
                // future.
                log::info!("perform: {action:?}");
            }
        }
    }

    pub fn run_forever(&self) -> anyhow::Result<()> {
        self.connection
            .run_message_loop()
            .context("running message loop")
    }

    pub fn reconcile_workspace(&self) -> Future<()> {
        let mut promise = Promise::new();
        let mux = Mux::get();
        let workspace = mux.active_workspace_for_client(&self.client_id);

        if mux.is_workspace_empty(&workspace) {
            // We don't want to silently kill off things that might
            // be running in other workspaces, so let's pick one
            // and activate it
            if self.is_switching_workspace() {
                promise.ok(());
                return promise.get_future().unwrap();
            }
            for workspace in mux.iter_workspaces() {
                if !mux.is_workspace_empty(&workspace) {
                    mux.set_active_workspace_for_client(&self.client_id, &workspace);
                    log::debug!("using {} instead, as it is not empty", workspace);
                    break;
                }
            }
        }

        let workspace = mux.active_workspace_for_client(&self.client_id);
        log::debug!("workspace is {}, fixup windows", workspace);

        let mut mux_windows = mux.iter_windows_in_workspace(&workspace);

        // First, repurpose existing windows.
        // Note that both iter_windows_in_workspace and self.known_windows have a
        // deterministic iteration order, so switching back and forth should result
        // in a consistent mux <-> gui window mapping.
        let known_windows = std::mem::take(&mut *self.known_windows.borrow_mut());
        let mut windows = BTreeMap::new();
        let mut unused = BTreeMap::new();

        for (window, window_id) in known_windows.into_iter() {
            if let Some(idx) = mux_windows.iter().position(|&id| id == window_id) {
                // it already points to the desired mux window
                windows.insert(window, window_id);
                mux_windows.remove(idx);
            } else {
                unused.insert(window, window_id);
            }
        }

        let mut mux_windows = mux_windows.into_iter();

        for (window, old_id) in unused.into_iter() {
            if let Some(mux_window_id) = mux_windows.next() {
                window.notify(TermWindowNotif::SwitchToMuxWindow(mux_window_id));
                windows.insert(window, mux_window_id);
            } else {
                // We have more windows than are in the new workspace;
                // we no longer need this one!
                window.close();
                front_end().spawned_mux_window.borrow_mut().remove(&old_id);
            }
        }

        log::trace!("reconcile: windows -> {:?}", windows);
        *self.known_windows.borrow_mut() = windows;

        let future = promise.get_future().unwrap();

        // then spawn any new windows that are needed
        promise::spawn::spawn(async move {
            while let Some(mux_window_id) = mux_windows.next() {
                if front_end().has_mux_window(mux_window_id)
                    || front_end()
                        .spawned_mux_window
                        .borrow()
                        .contains(&mux_window_id)
                {
                    continue;
                }
                front_end()
                    .spawned_mux_window
                    .borrow_mut()
                    .insert(mux_window_id);
                log::trace!("Creating TermWindow for mux_window_id={}", mux_window_id);
                if let Err(err) = TermWindow::new_window(mux_window_id).await {
                    log::error!("Failed to create window: {:#}", err);
                    let mux = Mux::get();
                    mux.kill_window(mux_window_id);
                    front_end()
                        .spawned_mux_window
                        .borrow_mut()
                        .remove(&mux_window_id);
                }
            }
            *front_end().switching_workspaces.borrow_mut() = false;
            promise.ok(());
        })
        .detach();
        future
    }

    fn has_mux_window(&self, mux_window_id: MuxWindowId) -> bool {
        for &mux_id in self.known_windows.borrow().values() {
            if mux_id == mux_window_id {
                return true;
            }
        }
        false
    }

    pub fn switch_workspace(&self, workspace: &str) {
        let mux = Mux::get();
        mux.set_active_workspace_for_client(&self.client_id, workspace);
        *self.switching_workspaces.borrow_mut() = false;
        self.reconcile_workspace();
    }

    pub fn record_known_window(&self, window: Window, mux_window_id: MuxWindowId) {
        self.known_windows
            .borrow_mut()
            .insert(window, mux_window_id);
        if !self.is_switching_workspace() {
            self.reconcile_workspace();
        }
    }

    pub fn forget_known_window(&self, window: &Window) {
        self.known_windows.borrow_mut().remove(window);
        if !self.is_switching_workspace() {
            self.reconcile_workspace();
        }
    }

    pub fn is_switching_workspace(&self) -> bool {
        *self.switching_workspaces.borrow()
    }

    pub fn gui_window_for_mux_window(&self, mux_window_id: MuxWindowId) -> Option<GuiWin> {
        let windows = self.known_windows.borrow();
        for (window, v) in windows.iter() {
            if *v == mux_window_id {
                return Some(GuiWin {
                    mux_window_id,
                    window: window.clone(),
                });
            }
        }
        None
    }
}

thread_local! {
    static FRONT_END: RefCell<Option<Rc<GuiFrontEnd>>> = RefCell::new(None);
}

pub fn try_front_end() -> Option<Rc<GuiFrontEnd>> {
    FRONT_END.with(|f| f.borrow().as_ref().map(Rc::clone))
}

pub fn front_end() -> Rc<GuiFrontEnd> {
    FRONT_END
        .with(|f| f.borrow().as_ref().map(Rc::clone))
        .expect("to be called on gui thread")
}

pub struct WorkspaceSwitcher {
    new_name: String,
}

impl WorkspaceSwitcher {
    pub fn new(new_name: &str) -> Self {
        *front_end().switching_workspaces.borrow_mut() = true;
        Self {
            new_name: new_name.to_string(),
        }
    }

    pub fn do_switch(self) {
        // Drop is invoked, which will complete the switch
    }
}

impl Drop for WorkspaceSwitcher {
    fn drop(&mut self) {
        front_end().switch_workspace(&self.new_name);
    }
}

pub fn shutdown() {
    FRONT_END.with(|f| drop(f.borrow_mut().take()));
}

pub fn try_new() -> Result<Rc<GuiFrontEnd>, Error> {
    let front_end = GuiFrontEnd::try_new()?;
    FRONT_END.with(|f| *f.borrow_mut() = Some(Rc::clone(&front_end)));
    Ok(front_end)
}