use std::collections::HashMap;
use std::time::Duration;

use tokio::{
    sync::RwLock,
    sync::oneshot::{self, Sender},
};
use sqlx::SqlitePool;
use tauri::{
    Manager,
    async_runtime as rt,
};

use crate::credentials::{
    Session,
    BaseCredentials,
    SessionCredentials,
};
use crate::{config, config::AppConfig};
use crate::ipc::{self, Approval};
use crate::errors::*;
use crate::shortcuts;


#[derive(Debug)]
struct Visibility {
    leases: usize,
    original: Option<bool>,
}

impl Visibility {
    fn new() -> Self {
        Visibility { leases: 0, original: None }
    }

    fn acquire(&mut self, delay_ms: u64) -> Result<VisibilityLease, WindowError> {
        let app = crate::app::APP.get().unwrap();
        let window = app.get_window("main")
            .ok_or(WindowError::NoMainWindow)?;

        self.leases += 1;
        // `original` represents the visibility of the window before any leases were acquired
        // None means we don't know, Some(false) means it was previously hidden,
        // Some(true) means it was previously visible
        if self.original.is_none() {
            let is_visible = window.is_visible()?;
            self.original = Some(is_visible);
        }

        let state = app.state::<AppState>();
        if matches!(self.original, Some(true)) && state.desktop_is_gnome {
            // Gnome has a really annoying "focus-stealing prevention" behavior means we
            // can't just pop up when the window is already visible, so to work around it
            // we hide and then immediately unhide the window
            window.hide()?;
        }
        window.show()?;
        window.set_focus()?;

        let (tx, rx) = oneshot::channel();
        let lease = VisibilityLease { notify: tx };

        let delay = Duration::from_millis(delay_ms);
        let handle = app.app_handle();
        rt::spawn(async move {
            // We don't care if it's an error; lease being dropped should be handled identically
            let _ = rx.await;
            tokio::time::sleep(delay).await;
            // we can't use `self` here because we would have to move it into the async block
            let state = handle.state::<AppState>();
            let mut visibility = state.visibility.write().await;
            visibility.leases -= 1;
            if visibility.leases == 0 {
                if let Some(false) = visibility.original {
                    window.hide().error_print();
                }
                visibility.original = None;
            }
        });

        Ok(lease)
    }
}

pub struct VisibilityLease {
    notify: Sender<()>,
}

impl VisibilityLease {
    pub fn release(self) {
        rt::spawn(async move {
            if let Err(_) = self.notify.send(()) {
                eprintln!("Error releasing visibility lease")
            }
        });
    }
}


#[derive(Debug)]
pub struct AppState {
    pub config: RwLock<AppConfig>,
    pub session: RwLock<Session>,
    pub request_count: RwLock<u64>,
    pub waiting_requests: RwLock<HashMap<u64, Sender<Approval>>>,
    pub pending_terminal_request: RwLock<bool>,
    // these are never modified and so don't need to be wrapped in RwLocks
    pub setup_errors: Vec<String>,
    pub desktop_is_gnome: bool,
    pool: sqlx::SqlitePool,
    visibility: RwLock<Visibility>,
}

impl AppState {
    pub fn new(
        config: AppConfig,
        session: Session,
        pool: SqlitePool,
        setup_errors: Vec<String>,
        desktop_is_gnome: bool,
    ) -> AppState {
        AppState {
            config: RwLock::new(config),
            session: RwLock::new(session),
            request_count: RwLock::new(0),
            waiting_requests: RwLock::new(HashMap::new()),
            pending_terminal_request: RwLock::new(false),
            setup_errors,
            desktop_is_gnome,
            pool,
            visibility: RwLock::new(Visibility::new()),
        }
    }

    pub async fn new_creds(&self, base_creds: BaseCredentials, passphrase: &str) -> Result<(), UnlockError> {
        let locked = base_creds.encrypt(passphrase)?;
        // do this first so that if it fails we don't save bad credentials
        self.new_session(base_creds).await?;
        locked.save(&self.pool).await?;

        Ok(())
    }

    pub async fn update_config(&self, new_config: AppConfig) -> Result<(), SetupError> {
        let mut live_config = self.config.write().await;
        
        // update autostart if necessary
        if new_config.start_on_login != live_config.start_on_login {
            config::set_auto_launch(new_config.start_on_login)?;
        }

        // re-register hotkeys if necessary
        if new_config.hotkeys.show_window != live_config.hotkeys.show_window
            || new_config.hotkeys.launch_terminal != live_config.hotkeys.launch_terminal
        {
            shortcuts::register_hotkeys(&new_config.hotkeys)?;
        }

        new_config.save(&self.pool).await?;
        *live_config = new_config;
        Ok(())
    }

    pub async fn register_request(&self, sender: Sender<Approval>) -> u64 {
        let count = {
            let mut c = self.request_count.write().await;
            *c += 1;
            c
        };

        let mut waiting_requests = self.waiting_requests.write().await;
        waiting_requests.insert(*count, sender); // `count` is the request id
        *count
    }

    pub async fn unregister_request(&self, id: u64) {
        let mut waiting_requests = self.waiting_requests.write().await;
        waiting_requests.remove(&id);
    }

    pub async fn acquire_visibility_lease(&self, delay: u64) -> Result<VisibilityLease, WindowError> {
        let mut visibility = self.visibility.write().await;
        visibility.acquire(delay)
    }

    pub async fn send_response(&self, response: ipc::RequestResponse) -> Result<(), SendResponseError> {
        if let Approval::Approved = response.approval {
            let mut session = self.session.write().await;
            session.renew_if_expired().await?;
        }

        let mut waiting_requests = self.waiting_requests.write().await;
        waiting_requests
            .remove(&response.id)
            .ok_or(SendResponseError::NotFound)?
            .send(response.approval)
            .map_err(|_| SendResponseError::Abandoned)
    }

    pub async fn unlock(&self, passphrase: &str) -> Result<(), UnlockError> {
        let base_creds = match *self.session.read().await {
            Session::Empty => {return Err(UnlockError::NoCredentials);},
            Session::Unlocked{..} => {return Err(UnlockError::NotLocked);},
            Session::Locked(ref locked) => locked.decrypt(passphrase)?,
        };
        // Read lock is dropped here, so this doesn't deadlock
        self.new_session(base_creds).await?;

        Ok(())
    }

    pub async fn is_unlocked(&self) -> bool {
        let session = self.session.read().await;
        matches!(*session, Session::Unlocked{..})
    }

    pub async fn base_creds_cloned(&self) -> Result<BaseCredentials, GetCredentialsError> {
        let app_session = self.session.read().await;
        let (base, _session) = app_session.try_get()?;
        Ok(base.clone())
    }

    pub async fn session_creds_cloned(&self) -> Result<SessionCredentials, GetCredentialsError> {
        let app_session = self.session.read().await;
        let (_bsae, session) = app_session.try_get()?;
        Ok(session.clone())
    }

    async fn new_session(&self, base: BaseCredentials) -> Result<(), GetSessionError> {
        let session = SessionCredentials::from_base(&base).await?;
        let mut app_session = self.session.write().await;
        *app_session = Session::Unlocked {base, session};
        Ok(())
    }

    pub async fn register_terminal_request(&self) -> Result<(), ()> {
        let mut req = self.pending_terminal_request.write().await;
        if *req {
            // if a request is already pending, we can't register a new one
            Err(())
        }
        else {
            *req = true;
            Ok(())
        }
    }

    pub async fn unregister_terminal_request(&self) {
        let mut req = self.pending_terminal_request.write().await;
        *req = false;
    }
}