/* ============================================================================
 * Pactor64 — PS/2 Keyboard Driver (x86-64)
 * IRQ1 (INT 0x21), scancode set 1, circular buffer
 * ============================================================================ */
#include "../include/pactor64.h"

/* === Scancode → ASCII lookup (scancode set 1) === */
static const char sc1_to_ascii[128] = {
    0,   0,  '1', '2', '3', '4', '5', '6',   /* 0x00-0x07 */
   '7', '8', '9', '0', '-', '=', '\b', '\t',  /* 0x08-0x0F */
   'q', 'w', 'e', 'r', 't', 'y', 'u', 'i',   /* 0x10-0x17 */
   'o', 'p', '[', ']', '\n',  0,  'a', 's',   /* 0x18-0x1F */
   'd', 'f', 'g', 'h', 'j', 'k', 'l', ';',   /* 0x20-0x27 */
   '\'', '`',  0, '\\', 'z', 'x', 'c', 'v',  /* 0x28-0x2F */
   'b', 'n', 'm', ',', '.', '/',  0,  '*',    /* 0x30-0x37 */
    0,  ' ',  0,   0,   0,   0,   0,   0,     /* 0x38-0x3F */
    0,   0,   0,   0,   0,   0,   0,   0,     /* 0x40-0x47 */
    0,   0,  '-',  0,   0,   0,  '+',  0,     /* 0x48-0x4F */
    0,   0,   0,   0,   0,   0,   0,   0,     /* 0x50-0x57 */
    0,   0,   0,   0,   0,   0,   0,   0,     /* 0x58-0x5F */
    0,   0,   0,   0,   0,   0,   0,   0,     /* 0x60-0x67 */
    0,   0,   0,   0,   0,   0,   0,   0,     /* 0x68-0x6F */
    0,   0,   0,   0,   0,   0,   0,   0,     /* 0x70-0x77 */
    0,   0,   0,   0,   0,   0,   0,   0      /* 0x78-0x7F */
};

/* === Circular scancode buffer === */
#define KBD_BUF_SIZE 256
static volatile char    kbd_buf[KBD_BUF_SIZE];
static volatile int     kbd_buf_head = 0;
static volatile int     kbd_buf_tail = 0;

/* Forward declaration */
extern void irq_install(int irq, void (*handler)(registers_t *regs));

/* === Keyboard ISR (IRQ1) === */
static void keyboard_isr(registers_t *regs) {
    (void)regs;
    uint8_t scancode = inb(KBD_DATA_PORT);

    /* Ignore key releases (bit 7 set) */
    if (scancode & 0x80) return;

    char c = sc1_to_ascii[scancode];
    if (c == 0) return;

    /* Insert into circular buffer */
    int next = (kbd_buf_head + 1) % KBD_BUF_SIZE;
    if (next != kbd_buf_tail) {
        kbd_buf[kbd_buf_head] = c;
        kbd_buf_head = next;
    }
}

/* === Initialize keyboard === */
void keyboard_init(void) {
    kbd_buf_head = 0;
    kbd_buf_tail = 0;

    /* Drain any pending data */
    while (inb(KBD_STATUS_PORT) & 0x01) {
        inb(KBD_DATA_PORT);
    }

    irq_install(0x21, keyboard_isr);
    pic_unmask_irq(1);
}

/* === Read a character from keyboard buffer (non-blocking, returns -1 if empty) === */
int keyboard_getchar(void) {
    if (kbd_buf_head == kbd_buf_tail) return -1;
    char c = kbd_buf[kbd_buf_tail];
    kbd_buf_tail = (kbd_buf_tail + 1) % KBD_BUF_SIZE;
    return c;
}