use crossterm_winapi::{ControlKeyState, EventFlags, KeyEventRecord, MouseEvent, ScreenBuffer};
use winapi::um::{
    wincon::{
        LEFT_ALT_PRESSED, LEFT_CTRL_PRESSED, RIGHT_ALT_PRESSED, RIGHT_CTRL_PRESSED, SHIFT_PRESSED,
    },
    winuser::{
        VK_BACK, VK_CONTROL, VK_DELETE, VK_DOWN, VK_END, VK_ESCAPE, VK_F1, VK_F24, VK_HOME,
        VK_INSERT, VK_LEFT, VK_MENU, VK_NEXT, VK_PRIOR, VK_RETURN, VK_RIGHT, VK_SHIFT, VK_UP,
    },
};

use crate::{
    event::{Event, KeyCode, KeyEvent, KeyModifiers, MouseButton, MouseEventKind},
    Result,
};

pub(crate) fn handle_mouse_event(mouse_event: MouseEvent) -> Result<Option<Event>> {
    if let Ok(Some(event)) = parse_mouse_event_record(&mouse_event) {
        return Ok(Some(Event::Mouse(event)));
    }
    Ok(None)
}

pub(crate) fn handle_key_event(key_event: KeyEventRecord) -> Result<Option<Event>> {
    if key_event.key_down {
        if let Some(event) = parse_key_event_record(&key_event) {
            return Ok(Some(Event::Key(event)));
        }
    }

    Ok(None)
}

impl From<ControlKeyState> for KeyModifiers {
    fn from(state: ControlKeyState) -> Self {
        let shift = state.has_state(SHIFT_PRESSED);
        let alt = state.has_state(LEFT_ALT_PRESSED | RIGHT_ALT_PRESSED);
        let control = state.has_state(LEFT_CTRL_PRESSED | RIGHT_CTRL_PRESSED);

        let mut modifier = KeyModifiers::empty();

        if shift {
            modifier |= KeyModifiers::SHIFT;
        }
        if control {
            modifier |= KeyModifiers::CONTROL;
        }
        if alt {
            modifier |= KeyModifiers::ALT;
        }

        modifier
    }
}

fn parse_key_event_record(key_event: &KeyEventRecord) -> Option<KeyEvent> {
    let modifiers = KeyModifiers::from(key_event.control_key_state);

    let key_code = key_event.virtual_key_code as i32;

    let parse_result = match key_code {
        VK_SHIFT | VK_CONTROL | VK_MENU => None,
        VK_BACK => Some(KeyCode::Backspace),
        VK_ESCAPE => Some(KeyCode::Esc),
        VK_RETURN => Some(KeyCode::Enter),
        VK_F1..=VK_F24 => Some(KeyCode::F((key_event.virtual_key_code - 111) as u8)),
        VK_LEFT => Some(KeyCode::Left),
        VK_UP => Some(KeyCode::Up),
        VK_RIGHT => Some(KeyCode::Right),
        VK_DOWN => Some(KeyCode::Down),
        VK_PRIOR => Some(KeyCode::PageUp),
        VK_NEXT => Some(KeyCode::PageDown),
        VK_HOME => Some(KeyCode::Home),
        VK_END => Some(KeyCode::End),
        VK_DELETE => Some(KeyCode::Delete),
        VK_INSERT => Some(KeyCode::Insert),
        _ => {
            // Modifier Keys (Ctrl, Alt, Shift) Support
            let character_raw = key_event.u_char;

            if character_raw < 255 {
                // Invalid character
                if character_raw == 0 {
                    return None;
                }

                let mut character = character_raw as u8 as char;

                if modifiers.contains(KeyModifiers::CONTROL)
                    && !modifiers.contains(KeyModifiers::ALT)
                {
                    // we need to do some parsing
                    character = match character_raw as u8 {
                        c @ b'\x01'..=b'\x1A' => (c as u8 - 0x1 + b'a') as char,
                        c @ b'\x1C'..=b'\x1F' => (c as u8 - 0x1C + b'4') as char,
                        _ => return None,
                    }
                }

                if modifiers.contains(KeyModifiers::SHIFT) && character == '\t' {
                    Some(KeyCode::BackTab)
                } else if character == '\t' {
                    Some(KeyCode::Tab)
                } else {
                    Some(KeyCode::Char(character))
                }
            } else {
                match std::char::from_u32(character_raw as u32) {
                    Some(ch) => Some(KeyCode::Char(ch)),
                    None => None,
                }
            }
        }
    };

    if let Some(key_code) = parse_result {
        return Some(KeyEvent::new(key_code, modifiers));
    }

    None
}

// The 'y' position of a mouse event or resize event is not relative to the window but absolute to screen buffer.
// This means that when the mouse cursor is at the top left it will be x: 0, y: 2295 (e.g. y = number of cells conting from the absolute buffer height) instead of relative x: 0, y: 0 to the window.
pub fn parse_relative_y(y: i16) -> Result<i16> {
    let window_size = ScreenBuffer::current()?.info()?.terminal_window();
    Ok(y - window_size.top)
}

fn parse_mouse_event_record(event: &MouseEvent) -> Result<Option<crate::event::MouseEvent>> {
    let modifiers = KeyModifiers::from(event.control_key_state);

    let xpos = event.mouse_position.x as u16;
    let ypos = parse_relative_y(event.mouse_position.y)? as u16;

    let button_state = event.button_state;
    let button = if button_state.right_button() {
        MouseButton::Right
    } else if button_state.middle_button() {
        MouseButton::Middle
    } else {
        MouseButton::Left
    };

    let kind = match event.event_flags {
        EventFlags::PressOrRelease => {
            if button_state.release_button() {
                // in order to read the up button type, we have to check the last down input record.
                Some(MouseEventKind::Up(MouseButton::Left))
            } else {
                Some(MouseEventKind::Down(button))
            }
        }
        EventFlags::MouseMoved => {
            if button_state.release_button() {
                Some(MouseEventKind::Moved)
            } else {
                Some(MouseEventKind::Drag(button))
            }
        }
        EventFlags::MouseWheeled => {
            // Vertical scroll
            // from https://docs.microsoft.com/en-us/windows/console/mouse-event-record-str
            // if `button_state` is negative then the wheel was rotated backward, toward the user.
            if button_state.scroll_down() {
                Some(MouseEventKind::ScrollDown)
            } else if button_state.scroll_up() {
                Some(MouseEventKind::ScrollUp)
            } else {
                None
            }
        }
        EventFlags::DoubleClick => None, // double click not supported by unix terminals
        EventFlags::MouseHwheeled => None, // horizontal scroll not supported by unix terminals
    };

    Ok(kind.map(|kind| crate::event::MouseEvent {
        kind,
        column: xpos,
        row: ypos,
        modifiers,
    }))
}
