//----------------------------------------------------------------------------//
//                           GNU GPL OS/K                                     //
//                                                                            //
//  Desc:  PIT Time  related functions                                        //
//                                                                            //
//                                                                            //
//  Copyright © 2018-2020 The OS/K Team                                       //
//                                                                            //
//  This file is part of OS/K.                                                //
//                                                                            //
//  OS/K is free software: you can redistribute it and/or modify              //
//  it under the terms of the GNU General Public License as published by      //
//  the Free Software Foundation, either version 3 of the License, or         //
//  any later version.                                                        //
//                                                                            //
//  OS/K is distributed in the hope that it will be useful,                   //
//  but WITHOUT ANY WARRANTY//without even the implied warranty of            //
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the             //
//  GNU General Public License for more details.                              //
//                                                                            //
//  You should have received a copy of the GNU General Public License         //
//  along with OS/K.  If not, see <https://www.gnu.org/licenses/>.            //
//----------------------------------------------------------------------------//

#include <libbuf.h>
#include <ke/time.h>
#include <ke/idt.h>
#include <ke/sched.h>

#define COUNTDONE 1
#define PIT_FREQUENCY 1000 // Hz = 1ms

static Timer_t Timer[20]; //20 concurrent sleep max
static ulong Ticks = 0;
static Time_t CurTime;
static char TimeFmtBuf[22] = { 0 };

extern bool PsInitialized;

//
// ISR handler for the Programmable Interval Timer
//

#pragma GCC push_options
#pragma GCC optimize ("O0")
static void HandlePIT(ISRFrame_t *regs)
{
    Ticks++;
    for (uchar i = 0; i < 20; i++) {

        if (Timer[i].countDown > 0) {
            Timer[i].countDown--;

            if (Timer[i].countDown == 0)
                Timer[i].sema = 1;
        }

        KeSendEOItoPIC(0x28);

        if (PsInitialized && !(Ticks % 100)) {
            PsSchedOnTick();
        }
    }
}
#pragma GCC pop_options

static Timer_t* KeFindTimerBlock(void)
{
    for(uchar i = 0; i < 20; i++) {
        if (Timer[i].countDown == 0)
            return &Timer[i];
    }

    return NULL;
}

#pragma GCC push_options
#pragma GCC optimize ("O0")
void KeSleep(uint delay)
{
    Timer_t *timerBlock;

    if ((timerBlock = (Timer_t*)KeFindTimerBlock()) == NULL)
        return;

    timerBlock->countDown = delay * PIT_FREQUENCY / 1000;

    while (!timerBlock->sema) {
        KeRelaxCPU();
    }
    timerBlock->sema = 0;
}
#pragma GCC pop_options

#pragma GCC push_options
#pragma GCC optimize ("O0")
Timer_t *KeSetTimer(uint delay)
{
    Timer_t *timerBlock;

    if ((timerBlock = (Timer_t*)KeFindTimerBlock()) == NULL)
        return NULL;

    timerBlock->countDown = delay * PIT_FREQUENCY / 1000;

    return timerBlock;
}
#pragma GCC pop_options

int KeGetTimer(Timer_t *timerBlock)
{
    if (!(timerBlock->sema)) {
        return 0;
    } else {
        timerBlock->sema = 0;
        return 1;
    }
}

void KeEnablePIT(void)
{
    ulong flags = KePauseIRQs();
    uint divisor = 1193180 / PIT_FREQUENCY; // PIT base frequency / Needed frequency

    KeRegisterISR(HandlePIT, 0x20);

    IoWriteByteOnPort(0x43, 0x36);          // 0x36 for rate gen

    IoWriteByteOnPort(0x40, (char)(divisor & 0xFF ));      // low byte of freq
    IoWriteByteOnPort(0x40, (char)((divisor >> 8)& 0xFF)); // high byte of freq

    // Setting up the IRQ line
    KeUnmaskIRQ(0);

    DebugLog("PIT activated with period %d ms\n", 1000/PIT_FREQUENCY);

    KeRestoreIRQs(flags);
    KeEnableNMI();
}

char *KeFormatCurTime(void)
{
    Time_t *RtcTime = KeGetCurTime();
    snprintf(TimeFmtBuf, sizeof(TimeFmtBuf),
            "%02d/%02d/%04d - %02d:%02d:%02d",
            RtcTime->day,
            RtcTime->month,
            RtcTime->year + RtcTime->century*100,
            RtcTime->hour,
            RtcTime->min,
            RtcTime->sec
            );
    return TimeFmtBuf;
}


static void UpdateCurTime(void)
{
    ulong frequency = PIT_FREQUENCY;
    uchar minRemain, hourRemain, dayRemain;

    CurTime.sec =
            (uchar)(((ulong)KeGetOriginTime()->sec * frequency + Ticks) / frequency % 60);

    minRemain =
            (uchar)(((ulong)KeGetOriginTime()->sec * frequency + Ticks) / (60 * frequency));

    CurTime.min =
            (uchar)(((ulong)KeGetOriginTime()->min +  minRemain) % 60);

    hourRemain =
            (uchar)(((ulong)KeGetOriginTime()->min +  minRemain) / 60);

    CurTime.hour =
            (uchar)(((ulong)KeGetOriginTime()->hour +  hourRemain) % 24);

    dayRemain =
            (uchar)(((ulong)KeGetOriginTime()->hour +  hourRemain) / 24);

    CurTime.day =
            (uchar)(((ulong)KeGetOriginTime()->day +  dayRemain) % 30);

}

Time_t* KeGetCurTime(void)
{
    UpdateCurTime();
    return &CurTime;
}

void KeSetCurTime(Time_t time)
{
    CurTime = time;
}

static uint IsLeapYear(uint year)
{
    if (!(year % 4)) {
        return 0;
    }

    return year % 100 == 0
            ? (year % 400 == 0)
            : 1;
}

static uint DaysInMonth(uint month, uint year)
{
    return (month == 2)
            ? (28 + IsLeapYear(year))
            : 31 - (month - 1) % 7 % 2;
}

ulong KeGetTimeStamp(void)
{
    Time_t *time = KeGetCurTime();

    uint dpy = 365 + IsLeapYear(time->year);
    uint dim = DaysInMonth(time->month, time->year + time->century * 100);

    return time->sec
         + time->min  * 60
         + time->hour * 60 * 60
         + time->day  * 24 * 60 * 60
         + time->month * dim * 24 * 60 * 60
         + (time->year + time->century * 100)
             * dpy * 24 * 60 * 60;
}

ulong KeGetTicks(void)
{
    return Ticks;
}