//----------------------------------------------------------------------------//
//                                OS on Kaleid                                //
//                                                                            //
//  Desc:  RTC Time  related functions                                        //
//                                                                            //
//                                                                            //
//  Copyright © 2018-2021 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>

static ulong Ticks = 0;
static Time_t OriginTime;

// TODO asnprintf()

static uchar RTC_RATE = 0x05; //2048Hz
static char time24or12Mode;

static void GetTimeFromRTC(void)
{
    Time_t lastTime;

    char updateInProgress = 1;

    // Wait while the RTC updates its value
    while (updateInProgress) {
        IoWriteByteOnPort(0x70, 0x0A);
        updateInProgress = (IoReadByteFromPort(0x71) & 0x80);
    }

    IoWriteByteOnPort(0x70, 0x0);
    OriginTime.sec = IoReadByteFromPort(0x71);

    IoWriteByteOnPort(0x70, 0x02);
    OriginTime.min = IoReadByteFromPort(0x71);

    IoWriteByteOnPort(0x70, 0x04);
    OriginTime.hour = IoReadByteFromPort(0x71);

    IoWriteByteOnPort(0x70, 0x06);
    OriginTime.weekday = IoReadByteFromPort(0x71);

    IoWriteByteOnPort(0x70, 0x07);
    OriginTime.day = IoReadByteFromPort(0x71);

    IoWriteByteOnPort(0x70, 0x08);
    OriginTime.month = IoReadByteFromPort(0x71);

    IoWriteByteOnPort(0x70, 0x09);
    OriginTime.year = IoReadByteFromPort(0x71);

    IoWriteByteOnPort(0x70, 0x32);
    OriginTime.century = IoReadByteFromPort(0x71);

    // Now while we don't get the same value,
    // read the registers (ensure data are valid)
    do {
        lastTime.sec = OriginTime.sec;
        lastTime.min = OriginTime.min;
        lastTime.hour = OriginTime.hour;
        lastTime.weekday = OriginTime.weekday;
        lastTime.day = OriginTime.day;
        lastTime.month = OriginTime.month;
        lastTime.year = OriginTime.year;
        lastTime.century = OriginTime.century;

        while (updateInProgress) {
            IoWriteByteOnPort(0x70, 0x0A);
            updateInProgress = (IoReadByteFromPort(0x71) & 0x80);
        }

        IoWriteByteOnPort(0x70, 0x0);
        OriginTime.sec = IoReadByteFromPort(0x71);

        IoWriteByteOnPort(0x70, 0x02);
        OriginTime.min = IoReadByteFromPort(0x71);

        IoWriteByteOnPort(0x70, 0x04);
        OriginTime.hour = IoReadByteFromPort(0x71);

        IoWriteByteOnPort(0x70, 0x06);
        OriginTime.weekday = IoReadByteFromPort(0x71);

        IoWriteByteOnPort(0x70, 0x07);
        OriginTime.day = IoReadByteFromPort(0x71);

        IoWriteByteOnPort(0x70, 0x08);
        OriginTime.month = IoReadByteFromPort(0x71);

        IoWriteByteOnPort(0x70, 0x09);
        OriginTime.year = IoReadByteFromPort(0x71);

        IoWriteByteOnPort(0x70, 0x32);
        OriginTime.century = IoReadByteFromPort(0x71);

    } while ((lastTime.sec != OriginTime.sec)
              || (lastTime.min != OriginTime.min)
              || (lastTime.hour != OriginTime.hour)
              || (lastTime.weekday != OriginTime.weekday)
              || (lastTime.day != OriginTime.day)
              || (lastTime.month != OriginTime.month)
              || (lastTime.year != OriginTime.year)
              || (lastTime.century != OriginTime.century)
          );

    IoWriteByteOnPort(0x70, 0x0B);
    time24or12Mode = IoReadByteFromPort(0x71);

    // Convert to binary if it is necessary
    if (!(time24or12Mode & 0x04)) {
        OriginTime.sec = (OriginTime.sec & 0x0F)
                        + ((OriginTime.sec / 16) * 10);

        OriginTime.min = (OriginTime.min & 0x0F)
                        + ((OriginTime.min / 16) * 10);

        OriginTime.hour = ( (OriginTime.hour & 0x0F)
                        + (((OriginTime.hour & 0x70) / 16) * 10) )
                        | (OriginTime.hour & 0x80);

        OriginTime.day = (OriginTime.day & 0x0F)
                        + ((OriginTime.day / 16) * 10);

        OriginTime.month = (OriginTime.month & 0x0F)
                        + ((OriginTime.month / 16) * 10);

        OriginTime.year = (OriginTime.year & 0x0F)
                        + ((OriginTime.year / 16) * 10);

        OriginTime.century = (OriginTime.century & 0x0F)
                        + ((OriginTime.century / 16) * 10);

        OriginTime.weekday = (OriginTime.weekday & 0x0F)
                        + ((OriginTime.weekday / 16) * 10);
    }

    // Convert 12 to 24 hour if necessary
    if (!(time24or12Mode & 0x02) && (OriginTime.hour & 0x80)) {
        OriginTime.hour = ((OriginTime.hour & 0x7)+ 10) % 24;
    }

    KeSetCurTime(OriginTime);
}

//
// ISR handler for the real time clock
//
static void HandleRTC(ISRFrame_t *regs)
{
    IoWriteByteOnPort(0x70, 0x0C);  // Selects status reg C
    IoReadByteFromPort(0x71);       // Flush
    Ticks++;
    KeSendEOItoPIC(0x28);
}

ulong KeGetClockTicks(void)
{
    return Ticks;
}

Time_t* KeGetOriginTime(void)
{
    return &OriginTime;
}

void KeEnableRTC(void)
{
    ulong flags = KePauseIRQs();
    char readInterruptConfig;
    char readRegister;

    KeRegisterISR(HandleRTC, 0x28);

    // Setting up the register control and interrupt rates
    IoWriteByteOnPort(0x70, 0x8B);
    readRegister = IoReadByteFromPort(0x71);
    IoWriteByteOnPort(0x70, 0x8B);                  // Because reading flushes
    IoWriteByteOnPort(0x71, readRegister | 0x40);

    IoWriteByteOnPort(0x70, 0x8A);
    readInterruptConfig = IoReadByteFromPort(0x71);
    IoWriteByteOnPort(0x70, 0x8A);                  // Because reading flushes
    IoWriteByteOnPort(0x71, (readInterruptConfig & 0xF0) | RTC_RATE);
    IoWriteByteOnPort(0x70, 0x0C);
    IoReadByteFromPort(0x71);                       // Flush

    // Setting up the IRQ line
    KeUnmaskIRQ(8);

    // Clean-up
    IoWriteByteOnPort(0x70, 0x0C);                  // Select status reg C
    IoReadByteFromPort(0x71);                       // Flush

    GetTimeFromRTC();
    KeRestoreIRQs(flags);
    KeEnableNMI();

    srand(KeGetTimeStamp());                        // init number generator
    DebugLog("RTC interrupt frequency set to %d Hz\n",
              32768 >> (RTC_RATE - 1));
}

void KeDelayExecution(uint time)
{
    ulong frequency = 32768 >> (RTC_RATE - 1);
    ulong beginTick = KeGetClockTicks();

    while (KeGetClockTicks() < beginTick + (frequency/1000) * time) {
        KeRelaxCPU();
    }
}