use std::{
    num::NonZeroU32,
    sync::{Arc, RwLock},
};

use softbuffer::{Context, Surface};
use winit::{
    application::ApplicationHandler,
    dpi::{LogicalPosition, LogicalSize, PhysicalPosition},
    event::{ElementState, Ime, MouseButton, MouseScrollDelta, WindowEvent},
    event_loop::{ActiveEventLoop, EventLoopProxy},
    keyboard::{Key, ModifiersState, NamedKey},
    window::{Window, WindowAttributes, WindowId},
};

use crate::{
    activity::Activity,
    developer_tools::DeveloperToolsState,
    document::NamespaceState,
    geometry::Point,
    scene::{self, SceneLayout},
    software_renderer::SoftwareRenderer,
};

#[derive(Clone, Debug)]
pub enum AppEvent {
    RuntimeFailed { message: String },
    DocumentUpdated,
    ConsoleFailed { message: String, source: String },
}

pub struct TesseraApp {
    window: Option<Arc<Window>>,
    context: Option<Context<Arc<Window>>>,
    surface: Option<Surface<Arc<Window>, Arc<Window>>>,
    namespace: Arc<RwLock<NamespaceState>>,
    developer_tools: DeveloperToolsState,
    layout: SceneLayout,
    pointer: Point,
    modifiers: ModifiersState,
    activity: Activity,
    event_client: crate::events::Client,
    guest_pressed: Option<crate::events::Input>,
    guest_focus: Option<crate::events::Input>,
    guest_key: Option<(NamedKey, crate::events::Input)>,
    guest_keyboard: bool,
}

impl TesseraApp {
    pub fn new(
        namespace: Arc<RwLock<NamespaceState>>,
        activity: Activity,
        proxy: EventLoopProxy<AppEvent>,
    ) -> anyhow::Result<Self> {
        let event_client = crate::events::Client::new(proxy.clone())?;
        Ok(Self {
            window: None,
            context: None,
            surface: None,
            namespace,
            developer_tools: {
                let mut state = DeveloperToolsState::default();
                state.proxy = Some(proxy);
                state
            },
            layout: SceneLayout::default(),
            pointer: Point::default(),
            modifiers: ModifiersState::default(),
            activity,
            event_client,
            guest_pressed: None,
            guest_focus: None,
            guest_key: None,
            guest_keyboard: true,
        })
    }

    fn apply_window_commands(&self) {
        let Some(window) = &self.window else {
            return;
        };
        let Ok(mut namespace) = self.namespace.write() else {
            return;
        };
        let commands = std::mem::take(&mut namespace.window_commands);
        for envelope in commands {
            if envelope.session == 0
                || envelope.session != namespace.runtime_session
                || envelope.command.window != crate::window::MAIN_WINDOW
            {
                continue;
            }
            match envelope.command.action {
                crate::window::Action::Resize { width, height } => {
                    let _ = window.request_inner_size(LogicalSize::new(width, height));
                }
                crate::window::Action::SetTitle(title) => window.set_title(&title),
                crate::window::Action::Focus => window.focus_window(),
            }
        }
        drop(namespace);
        self.publish_viewport();
    }

    fn publish_viewport(&self) {
        let Some(window) = &self.window else {
            return;
        };
        let size = window.inner_size().to_logical::<f32>(window.scale_factor());
        if size.width <= 0.0
            || size.height <= 0.0
            || !size.width.is_finite()
            || !size.height.is_finite()
        {
            return;
        }
        if let Ok(mut namespace) = self.namespace.write() {
            namespace.viewport = Some(crate::layout::Size {
                width: size.width.min(crate::ui_bridge::MAX_DIMENSION as f32),
                height: size.height.min(crate::ui_bridge::MAX_DIMENSION as f32),
            });
        }
    }

    fn request_redraw(&self) {
        if let Some(window) = &self.window {
            window.request_redraw();
        }
    }

    fn toggle_developer_tools(&mut self) {
        if let Ok(namespace) = self.namespace.read() {
            self.developer_tools.toggle(&namespace.document);
        }
        self.guest_keyboard = !self.developer_tools.open;
        self.request_redraw();
    }

    fn document_updated(&mut self) {
        self.apply_window_commands();
        if let Ok(namespace) = self.namespace.read() {
            self.developer_tools.document_updated(&namespace.document);
            let frame = &namespace.document.frame;
            self.guest_focus =
                frame
                    .focus
                    .filter(|_| frame.fault.is_none())
                    .map(|mount| crate::events::Input {
                        session: frame.session,
                        layout_version: frame.layout_version,
                        mount,
                        kind: "focus".into(),
                        point: None,
                        press_point: None,
                    });
        }
        self.request_redraw();
    }

    fn handle_keyboard(&mut self, event: &winit::event::KeyEvent) {
        if self.guest_keyboard && self.handle_guest_key(event) {
            self.request_redraw();
            return;
        }
        if self.developer_tools.keyboard_control(
            event,
            self.modifiers.shift_key(),
            &self.layout.developer_tools,
            &self.activity,
        ) {
            self.request_redraw();
            return;
        }
        if event.state != ElementState::Pressed {
            return;
        }
        let is_f12 = matches!(event.logical_key, Key::Named(NamedKey::F12));
        let is_i =
            matches!(&event.logical_key, Key::Character(value) if value.eq_ignore_ascii_case("i"));
        let mac_shortcut = self.modifiers.super_key() && self.modifiers.alt_key() && is_i;
        let other_shortcut = self.modifiers.control_key() && self.modifiers.shift_key() && is_i;
        if is_f12 || mac_shortcut || other_shortcut {
            if !event.repeat {
                self.toggle_developer_tools();
            }
            return;
        }
        if !self.developer_tools.open || self.developer_tools.focus.is_none() {
            return;
        }
        let command = self.modifiers.super_key() || self.modifiers.control_key();
        if command && let Key::Character(value) = &event.logical_key {
            match value.to_lowercase().as_str() {
                "a" => self.developer_tools.selection = true,
                "v" => match crate::clipboard::read() {
                    Ok(value) => self.developer_tools.insert(&value),
                    Err(error) => self.developer_tools.input_error = format!("Clipboard: {error}"),
                },
                "c" | "x" => {
                    let selected = self.developer_tools.selected_text();
                    if !selected.is_empty() {
                        match crate::clipboard::write(&selected) {
                            Ok(()) if value.eq_ignore_ascii_case("x") => {
                                self.developer_tools.insert("")
                            }
                            Ok(()) => {}
                            Err(error) => {
                                self.developer_tools.input_error = format!("Clipboard: {error}")
                            }
                        }
                    }
                }
                _ => {}
            }
        } else if let Key::Named(key) = &event.logical_key {
            if !self.developer_tools.preedit.is_empty() {
                return;
            }
            self.developer_tools
                .key(key, self.modifiers.shift_key(), command);
        } else if !command
            && self.developer_tools.preedit.is_empty()
            && let Some(text) = &event.text
        {
            let text: String = text.chars().filter(|c| !c.is_control()).collect();
            self.developer_tools.insert(&text);
        }
        self.request_redraw();
    }

    fn guest_covered(&self, point: Point) -> bool {
        let panel = self.layout.developer_tools.panel;
        self.developer_tools.open
            && crate::geometry::Rect::new(
                panel.x - 6.0,
                panel.y - 6.0,
                panel.width + 12.0,
                panel.height + 12.0,
            )
            .contains(point)
    }

    fn guest_hit(&self) -> Option<crate::events::Input> {
        if self.guest_covered(self.pointer) {
            return None;
        }
        let current = self.namespace.read().ok()?;
        if current.viewport.is_some_and(|size| {
            self.pointer.x < 0.0
                || self.pointer.y < 0.0
                || self.pointer.x >= size.width
                || self.pointer.y >= size.height
        }) {
            return None;
        }
        let frame = &current.document.frame;
        if frame.session == 0 {
            return None;
        }
        let mount = frame.hit_test(self.pointer)?;
        Some(crate::events::Input {
            session: frame.session,
            layout_version: frame.layout_version,
            mount: mount.id,
            kind: "click".into(),
            point: Some([self.pointer.x, self.pointer.y]),
            press_point: Some([self.pointer.x, self.pointer.y]),
        })
    }

    fn send_guest(&mut self, event: crate::events::Input) {
        if !self.event_client.send(event) {
            self.developer_tools.input_error = "Native event queue is unavailable or full".into();
            self.developer_tools.open = true;
        }
    }

    fn handle_guest_key(&mut self, event: &winit::event::KeyEvent) -> bool {
        let Key::Named(key) = &event.logical_key else {
            return false;
        };
        if *key == NamedKey::Tab {
            if event.state == ElementState::Pressed && !event.repeat {
                let next = self.namespace.read().ok().and_then(|namespace| {
                    let frame = &namespace.document.frame;
                    if frame.session == 0 || frame.fault.is_some() {
                        return None;
                    }
                    let targets: Vec<_> = frame
                        .mounts
                        .iter()
                        .filter(|mount| mount.interactive)
                        .collect();
                    if targets.is_empty() {
                        return None;
                    }
                    let current = self
                        .guest_focus
                        .as_ref()
                        .and_then(|focus| targets.iter().position(|mount| mount.id == focus.mount));
                    let index = if self.modifiers.shift_key() {
                        current
                            .map(|i| (i + targets.len() - 1) % targets.len())
                            .unwrap_or(targets.len() - 1)
                    } else {
                        current.map(|i| (i + 1) % targets.len()).unwrap_or(0)
                    };
                    Some(crate::events::Input {
                        session: frame.session,
                        layout_version: frame.layout_version,
                        mount: targets[index].id,
                        kind: "focus".into(),
                        point: None,
                        press_point: None,
                    })
                });
                if let Some(next) = next {
                    self.guest_key = None;
                    self.guest_focus = Some(next.clone());
                    self.send_guest(next);
                    return true;
                }
                return false;
            }
            return self.guest_focus.is_some();
        }
        if matches!(key, NamedKey::Enter | NamedKey::Space) && self.guest_focus.is_some() {
            if event.state == ElementState::Pressed {
                if !event.repeat {
                    self.guest_key = self.guest_focus.clone().map(|focus| (*key, focus));
                }
            } else if let Some((pressed, mut input)) = self.guest_key.take()
                && pressed == *key
            {
                input.kind = "click".into();
                self.send_guest(input);
            }
            return true;
        }
        false
    }

    fn redraw(&mut self) {
        let guest_cursor = self.guest_hit().is_some();
        let (Some(window), Some(surface)) = (self.window.as_ref(), self.surface.as_mut()) else {
            return;
        };
        let size = window.inner_size();
        let (Some(width), Some(height)) =
            (NonZeroU32::new(size.width), NonZeroU32::new(size.height))
        else {
            return;
        };

        let Ok(namespace) = self.namespace.read() else {
            return;
        };
        let scene = scene::build_scene(
            size.width,
            size.height,
            window.scale_factor() as f32,
            &namespace.document,
            &mut self.developer_tools,
            &self.activity,
        );
        drop(namespace);
        self.layout = scene.layout;
        window.set_cursor(if guest_cursor {
            winit::window::CursorIcon::Pointer
        } else {
            self.developer_tools
                .cursor_kind(&self.layout.developer_tools)
        });
        if self.developer_tools.repaint {
            self.developer_tools.repaint = false;
            window.request_redraw();
        }
        let ime = self
            .developer_tools
            .ime_position(&self.layout.developer_tools);
        window.set_ime_cursor_area(
            LogicalPosition::new(ime.x as f64, ime.y as f64),
            LogicalSize::new(1.0, 19.0),
        );

        surface
            .resize(width, height)
            .expect("resize software surface");
        let mut buffer = surface.buffer_mut().expect("acquire software buffer");
        SoftwareRenderer::render(&scene.display_list, &mut buffer, size.width, size.height);
        buffer.present().expect("present software-rendered frame");
    }
}

impl ApplicationHandler<AppEvent> for TesseraApp {
    fn resumed(&mut self, event_loop: &ActiveEventLoop) {
        if self.window.is_some() {
            return;
        }

        let attributes = WindowAttributes::default()
            .with_title("Tessera")
            .with_inner_size(LogicalSize::new(1_280.0, 800.0))
            .with_min_inner_size(LogicalSize::new(720.0, 480.0))
            .with_max_inner_size(LogicalSize::new(
                crate::window::MAX_WINDOW_DIMENSION,
                crate::window::MAX_WINDOW_DIMENSION,
            ));
        let window = Arc::new(
            event_loop
                .create_window(attributes)
                .expect("create Tessera window"),
        );
        let context = Context::new(window.clone()).expect("create software-rendering context");
        let surface =
            Surface::new(&context, window.clone()).expect("create software-rendering surface");

        window.set_ime_allowed(true);
        self.window = Some(window.clone());
        self.context = Some(context);
        self.surface = Some(surface);
        self.apply_window_commands();
        self.publish_viewport();
        window.request_redraw();
    }

    fn user_event(&mut self, _event_loop: &ActiveEventLoop, event: AppEvent) {
        match event {
            AppEvent::RuntimeFailed { message } => {
                self.developer_tools.input_error = message;
                self.developer_tools.open = true;
                self.guest_pressed = None;
                self.guest_key = None;
                self.request_redraw();
            }
            AppEvent::DocumentUpdated => self.document_updated(),
            AppEvent::ConsoleFailed { message, source } => {
                self.developer_tools.input_error = format!("Request failed: {message}");
                if self.developer_tools.input.is_empty() {
                    self.developer_tools.input = source;
                    self.developer_tools.cursor = self.developer_tools.input.len();
                    self.developer_tools.reveal_cursor();
                }
                self.request_redraw();
            }
        }
    }

    fn window_event(
        &mut self,
        event_loop: &ActiveEventLoop,
        window_id: WindowId,
        event: WindowEvent,
    ) {
        let Some(window) = self.window.as_ref().cloned() else {
            return;
        };
        if window.id() != window_id {
            return;
        }

        match event {
            WindowEvent::CloseRequested => event_loop.exit(),
            WindowEvent::Resized(_) | WindowEvent::ScaleFactorChanged { .. } => {
                self.publish_viewport();
                window.request_redraw();
            }
            WindowEvent::CursorMoved {
                position: PhysicalPosition { x, y },
                ..
            } => {
                let scale = window.scale_factor() as f32;
                let next = Point::new(x as f32 / scale, y as f32 / scale);
                let delta = Point::new(next.x - self.pointer.x, next.y - self.pointer.y);
                self.pointer = next;
                self.developer_tools.move_pointer(
                    next,
                    delta,
                    &self.layout.developer_tools,
                    window.inner_size().width as f32 / scale,
                );
                window.set_cursor(if self.guest_hit().is_some() {
                    winit::window::CursorIcon::Pointer
                } else {
                    self.developer_tools
                        .cursor_kind(&self.layout.developer_tools)
                });
                window.request_redraw();
            }
            WindowEvent::CursorLeft { .. } => {
                self.guest_pressed = None;
                self.developer_tools.pointer_left();
                window.set_cursor(winit::window::CursorIcon::Default);
                window.request_redraw();
            }
            WindowEvent::MouseInput {
                state,
                button: MouseButton::Left,
                ..
            } => {
                if state == ElementState::Pressed {
                    self.guest_keyboard = !self.guest_covered(self.pointer);
                    self.guest_pressed = self.guest_hit();
                    if self.guest_keyboard {
                        self.developer_tools.blur();
                    }
                    self.developer_tools.press(
                        &self.layout.developer_tools,
                        self.pointer,
                        &self.activity,
                    );
                } else {
                    if let Some(pressed) = self.guest_pressed.take()
                        && let Some(mut released) = self.guest_hit()
                        && released.session == pressed.session
                        && released.layout_version == pressed.layout_version
                    {
                        released.press_point = pressed.point;
                        self.send_guest(released);
                    }
                    self.developer_tools.release(
                        &self.layout.developer_tools,
                        self.pointer,
                        &self.activity,
                    );
                }
                window.request_redraw();
            }
            WindowEvent::MouseWheel { delta, .. } => {
                let (mut dx, mut dy) = match delta {
                    MouseScrollDelta::LineDelta(x, y) => (x * 38.0, y * 38.0),
                    MouseScrollDelta::PixelDelta(p) => (
                        p.x as f32 / window.scale_factor() as f32,
                        p.y as f32 / window.scale_factor() as f32,
                    ),
                };
                if self.modifiers.shift_key() && dx.abs() < 0.1 {
                    dx = dy;
                    dy = 0.0;
                }
                self.developer_tools
                    .wheel(&self.layout.developer_tools, self.pointer, dx, dy);
                window.request_redraw();
            }
            WindowEvent::Ime(Ime::Preedit(value, _)) => {
                self.developer_tools.preedit = value;
                window.request_redraw();
            }
            WindowEvent::Ime(Ime::Commit(value)) => {
                self.developer_tools.preedit.clear();
                if self.developer_tools.open {
                    self.developer_tools.insert(&value);
                }
                window.request_redraw();
            }
            WindowEvent::Focused(false) => {
                self.guest_pressed = None;
                self.guest_key = None;
                self.developer_tools.blur();
                self.modifiers = ModifiersState::default();
                window.request_redraw();
            }
            WindowEvent::ModifiersChanged(modifiers) => self.modifiers = modifiers.state(),
            WindowEvent::KeyboardInput { event, .. } => self.handle_keyboard(&event),
            WindowEvent::RedrawRequested => self.redraw(),
            _ => {}
        }
    }
}