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

#include <string.h>
#include <stdlib.h>

#include <myke/cpu/timer.h>
#include <myke/drivers/ports.h>
#include <myke/cpu/isr.h>
#include <myke/libk/libk.h>
#include <myke/libk/kprint.h>
#include <myke/tasks/task.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)

uint32_t tick = 0;

static void timer_callback(isr_registers_t *regs) {
    tick++;
    task_switch_next();
}

uint32_t timer_get_tick() {
    return tick;
}

void sleep(uint32_t milliseconds) {
    uint32_t done = tick + milliseconds;
    while (tick != done) {
        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(uint32_t freq) {
    register_interrupt_handler(IRQ0, timer_callback);

    uint32_t divisor = 1193180 / freq;
    uint8_t low = (uint8_t) (divisor & 0xFF);
    uint8_t high = (uint8_t) ((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;
}