#include "keyboard.h"
#include "idt.h"
#include "kernel.h"
#include "vga.h"

#define SCANCODE_LEFT_SHIFT 42
#define SCANCODE_RIGHT_SHIFT 54
#define SCANCODE_CAPS_LOCK 58

#define KEYBOARD_HANDLERS_LENGTH 32

unsigned const char us_keymap[128] = {
    0,   27,  '1', '2', '3',  '4', '5', '6',  '7', '8', '9',  '0', '-', '=', '\b', '\t', 'q', 'w',
    'e', 'r', 't', 'y', 'u',  'i', 'o', 'p',  '[', ']', '\n', 0,   'a', 's', 'd',  'f',  'g', 'h',
    'j', 'k', 'l', ';', '\'', '`', 0,   '\\', 'z', 'x', 'c',  'v', 'b', 'n', 'm',  ',',  '.', '/',
    0,   '*', 0,   ' ', 0,    0,   0,   0,    0,   0,   0,    0,   0,   0,   0,    0,    0,   0,
    0,   0,   '-', 0,   0,    0,   '+', 0,    0,   0,   0,    0,   0,   0,   0,    0,    0,   0,
};

unsigned const char us_keymap_shift[128] = {
    0,   27,  '!', '@', '#', '$', '%', '^', '&', '*', '(',  ')', '_', '+', '\b', '\t', 'Q', 'W',
    'E', 'R', 'T', 'Y', 'U', 'I', 'O', 'P', '{', '}', '\n', 0,   'A', 'S', 'D',  'F',  'G', 'H',
    'J', 'K', 'L', ':', '"', '~', 0,   '|', 'Z', 'X', 'C',  'V', 'B', 'N', 'M',  '<',  '>', '?',
    0,   '*', 0,   ' ', 0,   0,   0,   0,   0,   0,   0,    0,   0,   0,   0,    0,    0,   0,
    0,   0,   '-', 0,   0,   0,   '+', 0,   0,   0,   0,    0,   0,   0,   0,    0,    0,   0,
};

bool shift = false;
bool caps_lock = false;

// todo(nub): make dynamic when a memory allocator is implemented
static keyboard_handler_t keyboard_handlers[KEYBOARD_HANDLERS_LENGTH];
static int handler_index = 0;

char scan_code_to_ascii(u8 scan_code)
{
    if (scan_code >= 128)
    {
        return 0;
    }

    if ((!caps_lock && shift) || (caps_lock && !shift))
    {
        return us_keymap_shift[scan_code];
    }
    else
    {
        return us_keymap[scan_code];
    }
}

void handle_keyboard(const isr_frame_t* frame)
{
    u8 code = inb(0x60);
    u8 scan_code = code & 0x7F;
    bool pressed = (code & 0x80) == 0;

    switch (scan_code)
    {
    case SCANCODE_LEFT_SHIFT:
    case SCANCODE_RIGHT_SHIFT:
    {
        shift = pressed;
        break;
    }
    case SCANCODE_CAPS_LOCK:
    {
        if (pressed)
        {
            caps_lock = !caps_lock;
        }
        break;
    }
    default:
    {
        keyboard_event_t event = {
            .scan_code = scan_code,
            .pressed = pressed,
            .caps_lock = caps_lock,
            .shift = shift,
            .ascii = scan_code_to_ascii(scan_code),
        };

        for (int i = 0; i < handler_index; i++)
        {
            keyboard_handlers[i](&event);
        }
    }
    }
}

void register_keypress_handler(const keyboard_handler_t handler)
{
    // todo(nub31): remove when a memory allocator is implemented and
    // keyboard_handlers is a dynamic list
    if (handler_index >= KEYBOARD_HANDLERS_LENGTH)
    {
        vga_print_error();
        vga_print(" Maximum keyboard handlers reached\n");
        kernel_panic();
    }

    keyboard_handlers[handler_index] = handler;
    handler_index += 1;
}

void init_keyboard()
{
    register_irq_handler(1, handle_keyboard);
}