#include <stddef.h>
#include <stdint.h>

#include "interrupts.h"
#include "io.h"
#include "keyboard.h"

unsigned char us_layout[] = {
    /*    SHIFT CTRL  ALT */
    0x1B, 0x1B, 0x1B, 0x1B, /* esc (0x01) */
    '1', '!', '1', '1',
    '2', '@', '2', '2',
    '3', '#', '3', '3',
    '4', '$', '4', '4',
    '5', '%', '5', '5',
    '6', '^', '6', '6',
    '7', '&', '7', '7',
    '8', '*', '8', '8',
    '9', '(', '9', '9',
    '0', ')', '0', '0',
    '-', '_', '-', '-',
    '=', '+', '=', '=',
    0x08, 0x08, 0x7F, 0x08, /* backspace */
    0x09, 0x09, 0x09, 0x09, /* tab */
    'q', 'Q', 'q', 'q',
    'w', 'W', 'w', 'w',
    'e', 'E', 'e', 'e',
    'r', 'R', 'r', 'r',
    't', 'T', 't', 't',
    'y', 'Y', 'y', 'y',
    'u', 'U', 'u', 'u',
    'i', 'I', 'i', 'i',
    'o', 'O', 'o', 'o',
    'p', 'P', 'p', 'p',
    '[', '{', '[', '[',
    ']', '}', ']', ']',
    0x0A, 0x0A, 0x0A, 0x0A, /* enter */
    0xFF, 0xFF, 0xFF, 0xFF, /* ctrl */
    'a', 'A', 'a', 'a',
    's', 'S', 's', 's',
    'd', 'D', 'd', 'd',
    'f', 'F', 'f', 'f',
    'g', 'G', 'g', 'g',
    'h', 'H', 'h', 'h',
    'j', 'J', 'j', 'j',
    'k', 'K', 'k', 'k',
    'l', 'L', 'l', 'l',
    ';', ':', ';', ';',
    0x27, 0x22, 0x27, 0x27, /* '" */
    '`', '~', '`', '`',     /* `~ */
    0xFF, 0xFF, 0xFF, 0xFF, /* Lshift (0x2a) */
    '\\', '|', '\\', '\\',
    'z', 'Z', 'z', 'z',
    'x', 'X', 'x', 'x',
    'c', 'C', 'c', 'c',
    'v', 'V', 'v', 'v',
    'b', 'B', 'b', 'b',
    'n', 'N', 'n', 'n',
    'm', 'M', 'm', 'm',
    0x2C, 0x3C, 0x2C, 0x2C, /* ,< */
    0x2E, 0x3E, 0x2E, 0x2E, /* .> */
    0x2F, 0x3F, 0x2F, 0x2F, /* /? */
    0xFF, 0xFF, 0xFF, 0xFF, /* Rshift (0x36) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x37) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x38) */
    ' ', ' ', ' ', ' ',     /* space  */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x3a) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x3b) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x3c) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x3d) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x3e) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x3f) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x40) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x41) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x42) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x43) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x44) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x45) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x46) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x47) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x48) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x49) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x4a) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x4b) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x4c) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x4d) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x4e) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x4f) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x50) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x51) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x52) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x53) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x54) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x55) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x56) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x57) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x58) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x59) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x5a) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x5b) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x5c) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x5d) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x5e) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x5f) */
    0xFF, 0xFF, 0xFF, 0xFF, /* (0x60) */
    0xFF, 0xFF, 0xFF, 0xFF  /* (0x61) */
};

volatile unsigned char buffer[KEYBOARD_BUFFER_SIZE];
volatile size_t buffer_index;
volatile size_t read_index;

void keyboard_clear_buffer(void)
{
    buffer_index = 0;
    read_index = 0;
}

int keyboard_getchar(void)
{
    while (read_index == buffer_index)
        ;

    int c = (int)buffer[read_index];
    ++read_index;
    return c;
}

unsigned char keyboard_getscancode(void)
{
    uint8_t scancode;
    uint16_t index;
    static uint8_t offset = 0;

    scancode = inb(KEYBOARD_DATA);
    --scancode;

    if (scancode < 0x80)
    {
        switch (scancode)
        {
        case LSHIFT:
            offset = 1;
            break;
        case RSHIFT:
            offset = 1;
            break;
        case CTRL:
            offset = 2;
            break;
        case ALT:
            offset = 3;
            break;
        /* Character */
        default:
            index = scancode * 4 + offset;
            return us_layout[index];
        }
    }
    else
    {
        scancode -= 0x80;
        switch (scancode)
        {
        case LSHIFT:
            offset = 0;
            break;
        case RSHIFT:
            offset = 0;
            break;
        case CTRL:
            offset = 0;
            break;
        case ALT:
            offset = 0;
            break;
        }
    }

    return 0;
}

void keyboard_handler(Stack *registers)
{
    (void)(registers);

    unsigned char c = keyboard_getscancode();

    if (c)
    {
        buffer[buffer_index] = c;
        ++buffer_index;
        if (buffer_index == KEYBOARD_BUFFER_SIZE)
            keyboard_clear_buffer();
    }
}

void keyboard_install(void)
{
    keyboard_clear_buffer();
    irq_install_handler(1, keyboard_handler);
}