//
// Created by rick on 9/22/19.
//

#include "timer.h"

#include <drivers/ports.h>
#include <cpu/isr.h>
#include <libc/libc.h>
#include <libk.h>
#include <kprint.h>

// https://wiki.osdev.org/PIT
#define PIT_MODE_BIN_BCD                            (1 << 0)
#define PIT_MODE_BIN                                (0 << 0)
#define PIT_MODE_BCD                                (1 << 0)
#define PIT_GENERATOR_MODE                          (0b111 << 1)
#define PIT_MODE_INTERRUPT_ON_TERMINAL_COUNT        (0b000 << 1)
#define PIT_MODE_HARDWARE_RETRIGGERABLE_ONE_SHOT    (0b001 << 1)
#define PIT_MODE_HARDWARE_RATE_GENERATOR            (0b010 << 1)
#define PIT_MODE_HARDWARE_SQUARE_WAVE_GENERATOR     (0b011 << 1)
#define PIT_MODE_SOFTWARE_TRIGGERED_STROBE          (0b100 << 1)
#define PIT_MODE_HARDWARE_TRIGGERED_STROBE          (0b101 << 1)
#define PIT_ACCESS_MODE                             (0b11 << 4)
#define PIT_ACCESS_MODE_LATCH_COUNT                 (0b00 << 4)
#define PIT_ACCESS_MODE_L                           (0b01 << 4)
#define PIT_ACCESS_MODE_H                           (0b10 << 4)
#define PIT_ACCESS_MODE_LH                          (0b11 << 4)
#define PIT_CHANNEL                                 (0b11 << 6)
#define PIT_CHANNEL_0                               (0b00 << 6)
#define PIT_CHANNEL_1                               (0b01 << 6)
#define PIT_CHANNEL_2                               (0b10 << 6)
#define PIT_CHANNEL_READ_BACK                       (0b11 << 6)

u32 tick = 0;

static void timer_callback(registers_t regs) {
    tick++;
}

void sleep(u32 milliseconds) {
    u32 done = tick + milliseconds;
    while (done != milliseconds) {
        k_wait_for_interrupt();
    }
}

void print_current_tick() {
    char msg[32];
    memset(msg, 0, 32);
    itoa(tick, msg, 10);
    kprint(msg);
    kprint("\n");
}

int init_timer(u32 freq) {
    register_interrupt_handler(IRQ0, timer_callback);

    u32 divisor = 1193180 / freq;
    u8 low = (u8) (divisor & 0xFF);
    u8 high = (u8) ((divisor >> 8) & 0xFF);
    port_byte_out(PORT_PIT_COMMAND, PIT_MODE_BIN | PIT_MODE_HARDWARE_SQUARE_WAVE_GENERATOR | PIT_ACCESS_MODE_LH | PIT_CHANNEL_0);
    port_byte_out(PORT_PIT_DATA_0, low);
    port_byte_out(PORT_PIT_DATA_0, high);
    return 0;
}