// hal_keyboard.c - PS/2 keyboard, interrupt-driven, 256-entry ring buffer
#include "hal_api.h"
#include "hal_apic.h"
#include "hal_debug.h"
#include <stdint.h>
#include <stdbool.h>
#include <intrin.h>

#define PS2_DATA  0x60
#define PS2_STAT  0x64
#define PS2_CMD   0x64

#define KBD_BUF_SIZE  256

static uint8_t gBuf[KBD_BUF_SIZE];
static volatile int gHead = 0, gTail = 0;
static void (*gCallback)(uint8_t) = (void *)0;

// Minimal Set-2 to ASCII translation (unshifted only).
static const char gScanToAscii[128] = {
    0,0,'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,
    '7','8','9','-','4','5','6','+','1','2','3','0','.',0,0,0,
};

static void KbdIsr(void) {
    uint8_t sc = __inbyte(PS2_DATA);
    if (sc & 0x80) return;   // key-up, ignore
    int next = (gTail + 1) % KBD_BUF_SIZE;
    if (next != gHead) {
        gBuf[gTail] = sc;
        gTail = next;
    }
    if (gCallback) gCallback(sc);
}

static bool KbdPoll(void) {
    return gHead != gTail;
}

static uint8_t KbdReadScancode(void) {
    while (gHead == gTail) { _mm_pause(); }
    uint8_t sc = gBuf[gHead];
    gHead = (gHead + 1) % KBD_BUF_SIZE;
    return sc;
}

static char KbdReadChar(void) {
    uint8_t sc = KbdReadScancode();
    if (sc < 128) return gScanToAscii[sc];
    return 0;
}

static void KbdSetCallback(void (*cb)(uint8_t sc)) {
    gCallback = cb;
}

void HalKeyboardInitialize(HAL_KEYBOARD *out) {
    // Flush PS/2 output buffer
    while (__inbyte(PS2_STAT) & 1) __inbyte(PS2_DATA);

    out->Poll         = KbdPoll;
    out->ReadScancode = KbdReadScancode;
    out->ReadChar     = KbdReadChar;
    out->SetCallback  = KbdSetCallback;
    out->Isr          = KbdIsr;
    out->IrqNumber    = 1;
}