#![no_std]

use port_input_device::{InputDevice, InputEvent, Key};

const UART_VA: usize = 0x20000;
const UART_LSR_OFFSET: usize = 5;

pub struct UartInputDevice;

impl UartInputDevice {
    pub fn new() -> Self {
        Self
    }

    fn read_byte(&self) -> Option<u8> {
        let lsr = unsafe { core::ptr::read_volatile((UART_VA + UART_LSR_OFFSET) as *const u8) };
        if lsr & 1 != 0 {
            Some(unsafe { core::ptr::read_volatile(UART_VA as *const u8) })
        } else {
            None
        }
    }

    fn byte_to_key(byte: u8) -> Key {
        match byte {
            b'w' | b'W' => Key::Up,
            b's' | b'S' => Key::Down,
            b'a' | b'A' => Key::Left,
            b'd' | b'D' => Key::Right,
            b'\r' | b'\n' => Key::Enter,
            0x1B => Key::Escape,
            c => Key::Char(c),
        }
    }
}

impl InputDevice for UartInputDevice {
    fn poll(&mut self) -> Option<InputEvent> {
        let byte = self.read_byte()?;
        Some(InputEvent::KeyDown(Self::byte_to_key(byte)))
    }

    fn has_event(&self) -> bool {
        let lsr = unsafe { core::ptr::read_volatile((UART_VA + UART_LSR_OFFSET) as *const u8) };
        lsr & 1 != 0
    }
}