use std::time::Duration;

use smithay::desktop::Window;
use smithay::input::touch::{
    DownEvent, GrabStartData as TouchGrabStartData, MotionEvent, OrientationEvent, ShapeEvent,
    TouchGrab, TouchInnerHandle, UpEvent,
};
use smithay::input::SeatHandler;
use smithay::output::Output;
use smithay::utils::{IsAlive, Logical, Point, Serial};

use crate::layout::workspace::{Workspace, WorkspaceId};
use crate::niri::State;
use crate::window::Mapped;

// When the touch is stationary for this much time, it becomes an interactive move.
const INTERACTIVE_MOVE_THRESHOLD: Duration = Duration::from_millis(500);

pub struct TouchOverviewGrab {
    start_data: TouchGrabStartData<State>,
    start_timestamp: Duration,
    last_location: Point<f64, Logical>,
    output: Output,
    start_pos_within_output: Point<f64, Logical>,
    workspace_id: Option<WorkspaceId>,
    workspace_matched_narrow: bool,
    window: Option<Window>,
    gesture: GestureState,
}

#[derive(Debug, Clone, Copy)]
enum GestureState {
    Recognizing,
    ViewOffset,
    WorkspaceSwitch,
    InteractiveMove,
}

impl TouchOverviewGrab {
    pub fn new(
        start_data: TouchGrabStartData<State>,
        start_timestamp: Duration,
        output: Output,
        start_pos_within_output: Point<f64, Logical>,
        workspace_id: Option<WorkspaceId>,
        workspace_matched_narrow: bool,
        window: Option<Window>,
    ) -> Self {
        Self {
            last_location: start_data.location,
            start_timestamp,
            start_data,
            output,
            start_pos_within_output,
            workspace_id,
            workspace_matched_narrow,
            window,
            gesture: GestureState::Recognizing,
        }
    }

    fn on_ungrab(&mut self, state: &mut State) {
        let layout = &mut state.niri.layout;
        match self.gesture {
            GestureState::Recognizing => {
                // Tap to activate.
                layout.focus_output(&self.output);

                // Activate the workspace if necessary.
                if self.window.is_some() || self.workspace_matched_narrow {
                    // When activating a window, we want to activate the window's current
                    // workspace. Otherwise, find the workspace that we tapped on.
                    let ws_matches = |ws: &Workspace<Mapped>| {
                        if let Some(window) = &self.window {
                            ws.has_window(window)
                        } else if let Some(ws_id) = self.workspace_id {
                            ws.id() == ws_id
                        } else {
                            false
                        }
                    };

                    let ws_idx = if let Some((Some(mon), ws_idx, _)) =
                        layout.workspaces().find(|(_, _, ws)| ws_matches(ws))
                    {
                        // The workspace could've moved to a different output in the meantime.
                        (*mon.output() == self.output).then_some(ws_idx)
                    } else {
                        None
                    };

                    if let Some(ws_idx) = ws_idx {
                        layout.toggle_overview_to_workspace(ws_idx);
                    }
                }

                if let Some(window) = self.window.as_ref() {
                    layout.activate_window(window);
                }
            }
            GestureState::ViewOffset => {
                layout.view_offset_gesture_end(Some(false));
            }
            GestureState::WorkspaceSwitch => {
                layout.workspace_switch_gesture_end(Some(false));
            }
            GestureState::InteractiveMove => {
                layout.interactive_move_end(self.window.as_ref().unwrap());
            }
        };

        state.niri.queue_redraw_all();
    }
}

impl TouchGrab<State> for TouchOverviewGrab {
    fn down(
        &mut self,
        data: &mut State,
        handle: &mut TouchInnerHandle<'_, State>,
        _focus: Option<(<State as SeatHandler>::TouchFocus, Point<f64, Logical>)>,
        event: &DownEvent,
        seq: Serial,
    ) {
        handle.down(data, None, event, seq);

        if event.slot == self.start_data.slot {
            return;
        }

        if matches!(self.gesture, GestureState::InteractiveMove) {
            if let Some(window) = &self.window.as_ref() {
                data.niri.layout.toggle_window_floating(Some(window));
                data.niri.queue_redraw_all();
            }
        }
    }

    fn up(
        &mut self,
        data: &mut State,
        handle: &mut TouchInnerHandle<'_, State>,
        event: &UpEvent,
        seq: Serial,
    ) {
        handle.up(data, event, seq);

        if event.slot != self.start_data.slot {
            return;
        }

        handle.unset_grab(self, data);
    }

    fn motion(
        &mut self,
        data: &mut State,
        handle: &mut TouchInnerHandle<'_, State>,
        _focus: Option<(<State as SeatHandler>::TouchFocus, Point<f64, Logical>)>,
        event: &MotionEvent,
        seq: Serial,
    ) {
        handle.motion(data, None, event, seq);

        if event.slot != self.start_data.slot {
            return;
        }

        let timestamp = Duration::from_millis(u64::from(event.time));
        let layout = &mut data.niri.layout;

        // Check if we should become interactive move.
        if matches!(self.gesture, GestureState::Recognizing) {
            if let Some(window) = self.window.as_ref().filter(|win| win.alive()) {
                let passed = timestamp.saturating_sub(self.start_timestamp);
                if INTERACTIVE_MOVE_THRESHOLD <= passed
                    && layout.interactive_move_begin(
                        window.clone(),
                        &self.output,
                        self.start_pos_within_output,
                    )
                {
                    self.gesture = GestureState::InteractiveMove;
                }
            }
        }

        // Check if we should become a spatial scroll.
        if matches!(self.gesture, GestureState::Recognizing) {
            let c = event.location - self.start_data.location;

            // Check if the gesture moved far enough to decide. Threshold copied from libadwaita.
            if c.x * c.x + c.y * c.y >= 16. * 16. {
                if let Some(ws_id) = self.workspace_id.filter(|_| c.x.abs() > c.y.abs()) {
                    if let Some((ws_idx, ws)) = layout.find_workspace_by_id(ws_id) {
                        if ws.current_output() == Some(&self.output) {
                            layout.view_offset_gesture_begin(&self.output, Some(ws_idx), false);
                            self.gesture = GestureState::ViewOffset;
                        }
                    }
                }

                if matches!(self.gesture, GestureState::Recognizing) {
                    layout.workspace_switch_gesture_begin(&self.output, false);
                    self.gesture = GestureState::WorkspaceSwitch;
                }
            }
        }

        // Do nothing if still recognizing.
        if matches!(self.gesture, GestureState::Recognizing) {
            return;
        }

        let delta = event.location - self.last_location;
        self.last_location = event.location;

        let ongoing = match self.gesture {
            GestureState::Recognizing => unreachable!(),
            GestureState::ViewOffset => layout
                .view_offset_gesture_update(-delta.x, timestamp, false)
                .is_some(),
            GestureState::WorkspaceSwitch => layout
                .workspace_switch_gesture_update(-delta.y, timestamp, false)
                .is_some(),
            GestureState::InteractiveMove => {
                let window = self.window.as_ref().unwrap();
                if let Some((output, pos_within_output)) = data.niri.output_under(event.location) {
                    let output = output.clone();
                    data.niri.layout.interactive_move_update(
                        window,
                        delta,
                        output,
                        pos_within_output,
                    )
                } else {
                    false
                }
            }
        };

        if ongoing {
            data.niri.queue_redraw_all();
        } else {
            handle.unset_grab(self, data);
        }
    }

    fn frame(&mut self, data: &mut State, handle: &mut TouchInnerHandle<'_, State>, seq: Serial) {
        handle.frame(data, seq);
    }

    fn cancel(&mut self, data: &mut State, handle: &mut TouchInnerHandle<'_, State>, seq: Serial) {
        handle.cancel(data, seq);
        handle.unset_grab(self, data);
    }

    fn shape(
        &mut self,
        data: &mut State,
        handle: &mut TouchInnerHandle<'_, State>,
        event: &ShapeEvent,
        seq: Serial,
    ) {
        handle.shape(data, event, seq);
    }

    fn orientation(
        &mut self,
        data: &mut State,
        handle: &mut TouchInnerHandle<'_, State>,
        event: &OrientationEvent,
        seq: Serial,
    ) {
        handle.orientation(data, event, seq);
    }

    fn start_data(&self) -> &TouchGrabStartData<State> {
        &self.start_data
    }

    fn unset(&mut self, data: &mut State) {
        self.on_ungrab(data);
    }
}