#include <pit.h>
#include <common.h>
#include <string_utils.h>
#include <pic.h>
#include <serial.h>

static inline void outb(UINT16 port, UINT8 val) {
    ASM("outb %0, %1" : : "a"(val), "Nd"(port));
}

static volatile UINT64 g_ticks = 0;
static timer_callback_t g_tick_handler = NULL;

extern "C" void pit_irq_handler(void) {
    g_ticks++;
    if (g_tick_handler) {
        g_tick_handler();
    }
}

void pit_init(void) {
    serial_write("PIT: initializing channel 0 at ");
    serial_write_hex(PIT_TICK_HZ);
    serial_write(" Hz\n");

    UINT32 divisor = PIT_BASE_FREQ / PIT_TICK_HZ;

    // Command byte: channel 0, lobyte/hibyte, rate generator, binary
    outb(PIT_COMMAND_PORT, 0x36);

    // Send divisor (low byte first, then high byte)
    outb(PIT_CHANNEL0_DATA, (UINT8)(divisor & 0xFF));
    outb(PIT_CHANNEL0_DATA, (UINT8)((divisor >> 8) & 0xFF));

    // Unmask IRQ 0 (timer)
    pic_unmask_irq(0);

    serial_write("PIT: divisor = ");
    serial_write_hex(divisor);
    serial_write("\n");
}

void pit_set_tick_handler(timer_callback_t handler) {
    g_tick_handler = handler;
}

UINT64 pit_get_ticks(void) {
    return g_ticks;
}