use crate::drivers::platform::pic;
use crate::io::{disable_interrupts, enable_interrupts, inb};

const DATA_PORT: u16 = 0x60;
const STATUS_PORT: u16 = 0x64;
const OUTPUT_FULL: u8 = 1 << 0;
const BUFFER_SIZE: usize = 256;

static mut KEYBOARD: Ps2Keyboard = Ps2Keyboard::new();

pub struct Ps2Keyboard {
    buffer: [u8; BUFFER_SIZE],
    read_index: usize,
    write_index: usize,
    shift: bool,
    extended: bool,
}

impl Ps2Keyboard {
    const fn new() -> Self {
        Self {
            buffer: [0; BUFFER_SIZE],
            read_index: 0,
            write_index: 0,
            shift: false,
            extended: false,
        }
    }

    fn push(&mut self, byte: u8) {
        let next = (self.write_index + 1) % BUFFER_SIZE;
        if next != self.read_index {
            self.buffer[self.write_index] = byte;
            self.write_index = next;
        }
    }

    fn pop(&mut self) -> Option<u8> {
        if self.read_index == self.write_index {
            return None;
        }

        let byte = self.buffer[self.read_index];
        self.read_index = (self.read_index + 1) % BUFFER_SIZE;
        Some(byte)
    }

    fn handle_scancode(&mut self, scancode: u8) {
        if scancode == 0xe0 {
            self.extended = true;
            return;
        }

        if self.extended {
            self.extended = false;
            if scancode & 0x80 != 0 {
                return;
            }
            match scancode {
                0x48 => self.push_escape_sequence(b"\x1b[A"),
                0x50 => self.push_escape_sequence(b"\x1b[B"),
                0x4b => self.push_escape_sequence(b"\x1b[D"),
                0x4d => self.push_escape_sequence(b"\x1b[C"),
                0x47 => self.push_escape_sequence(b"\x1b[H"),
                0x4f => self.push_escape_sequence(b"\x1b[F"),
                0x53 => self.push_escape_sequence(b"\x1b[3~"),
                _ => {}
            }
            return;
        }

        let released = scancode & 0x80 != 0;
        let code = scancode & 0x7f;

        match code {
            0x2a | 0x36 => {
                self.shift = !released;
                return;
            }
            _ if released => return,
            _ => {}
        }

        if let Some(ascii) = scancode_set1_to_ascii(code, self.shift) {
            self.push(ascii);
        }
    }

    fn push_escape_sequence(&mut self, bytes: &[u8]) {
        for byte in bytes {
            self.push(*byte);
        }
    }
}

pub unsafe fn init() {
    unsafe {
        drain_output_buffer();
        pic::unmask_irq(pic::KEYBOARD_IRQ);
    }
}

#[unsafe(no_mangle)]
pub extern "C" fn zeroos_ps2_keyboard_interrupt() {
    unsafe {
        if inb(STATUS_PORT) & OUTPUT_FULL != 0 {
            let scancode = inb(DATA_PORT);
            (*(&raw mut KEYBOARD)).handle_scancode(scancode);
        }

        pic::end_of_interrupt(pic::KEYBOARD_IRQ);
    }
}

pub fn read_char() -> Option<u8> {
    disable_interrupts();
    let ch = unsafe { (*(&raw mut KEYBOARD)).pop() };
    enable_interrupts();
    ch
}

pub fn has_char() -> bool {
    disable_interrupts();
    let ready = unsafe {
        let keyboard = &*(&raw const KEYBOARD);
        keyboard.read_index != keyboard.write_index
    };
    enable_interrupts();
    ready
}

unsafe fn drain_output_buffer() {
    unsafe {
        while inb(STATUS_PORT) & OUTPUT_FULL != 0 {
            let _ = inb(DATA_PORT);
        }
    }
}

fn scancode_set1_to_ascii(code: u8, shift: bool) -> Option<u8> {
    let byte = match code {
        0x01 => 0x1b,
        0x02 => {
            if shift {
                b'!'
            } else {
                b'1'
            }
        }
        0x03 => {
            if shift {
                b'@'
            } else {
                b'2'
            }
        }
        0x04 => {
            if shift {
                b'#'
            } else {
                b'3'
            }
        }
        0x05 => {
            if shift {
                b'$'
            } else {
                b'4'
            }
        }
        0x06 => {
            if shift {
                b'%'
            } else {
                b'5'
            }
        }
        0x07 => {
            if shift {
                b'^'
            } else {
                b'6'
            }
        }
        0x08 => {
            if shift {
                b'&'
            } else {
                b'7'
            }
        }
        0x09 => {
            if shift {
                b'*'
            } else {
                b'8'
            }
        }
        0x0a => {
            if shift {
                b'('
            } else {
                b'9'
            }
        }
        0x0b => {
            if shift {
                b')'
            } else {
                b'0'
            }
        }
        0x0c => {
            if shift {
                b'_'
            } else {
                b'-'
            }
        }
        0x0d => {
            if shift {
                b'+'
            } else {
                b'='
            }
        }
        0x0e => 0x08,
        0x0f => b'\t',
        0x10 => letter(b'q', shift),
        0x11 => letter(b'w', shift),
        0x12 => letter(b'e', shift),
        0x13 => letter(b'r', shift),
        0x14 => letter(b't', shift),
        0x15 => letter(b'y', shift),
        0x16 => letter(b'u', shift),
        0x17 => letter(b'i', shift),
        0x18 => letter(b'o', shift),
        0x19 => letter(b'p', shift),
        0x1a => {
            if shift {
                b'{'
            } else {
                b'['
            }
        }
        0x1b => {
            if shift {
                b'}'
            } else {
                b']'
            }
        }
        0x1c => b'\r',
        0x1e => letter(b'a', shift),
        0x1f => letter(b's', shift),
        0x20 => letter(b'd', shift),
        0x21 => letter(b'f', shift),
        0x22 => letter(b'g', shift),
        0x23 => letter(b'h', shift),
        0x24 => letter(b'j', shift),
        0x25 => letter(b'k', shift),
        0x26 => letter(b'l', shift),
        0x27 => {
            if shift {
                b':'
            } else {
                b';'
            }
        }
        0x28 => {
            if shift {
                b'"'
            } else {
                b'\''
            }
        }
        0x29 => {
            if shift {
                b'~'
            } else {
                b'`'
            }
        }
        0x2b => {
            if shift {
                b'|'
            } else {
                b'\\'
            }
        }
        0x2c => letter(b'z', shift),
        0x2d => letter(b'x', shift),
        0x2e => letter(b'c', shift),
        0x2f => letter(b'v', shift),
        0x30 => letter(b'b', shift),
        0x31 => letter(b'n', shift),
        0x32 => letter(b'm', shift),
        0x33 => {
            if shift {
                b'<'
            } else {
                b','
            }
        }
        0x34 => {
            if shift {
                b'>'
            } else {
                b'.'
            }
        }
        0x35 => {
            if shift {
                b'?'
            } else {
                b'/'
            }
        }
        0x39 => b' ',
        _ => return None,
    };

    Some(byte)
}

const fn letter(lower: u8, shift: bool) -> u8 {
    if shift { lower - 32 } else { lower }
}