#include <AP_HAL/AP_HAL.h>

#if CONFIG_HAL_BOARD == HAL_BOARD_LINUX

#include "Scheduler.h"
#include "Storage.h"
#include "RCInput.h"
#include "UARTDriver.h"
#include "Util.h"
#include "SPIUARTDriver.h"
#include "RPIOUARTDriver.h"
#include <algorithm>
#include <poll.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <sys/mman.h>

#if CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_QFLIGHT
#include <rpcmem.h>
#include <AP_HAL_Linux/qflight/qflight_util.h>
#include <AP_HAL_Linux/qflight/qflight_dsp.h>
#include <AP_HAL_Linux/qflight/qflight_buffer.h>
#endif


using namespace Linux;

extern const AP_HAL::HAL& hal;

#define APM_LINUX_TIMER_PRIORITY        15
#define APM_LINUX_UART_PRIORITY         14
#define APM_LINUX_RCIN_PRIORITY         13
#define APM_LINUX_MAIN_PRIORITY         12
#define APM_LINUX_TONEALARM_PRIORITY    11
#define APM_LINUX_IO_PRIORITY           10

#if CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_NAVIO ||    \
    CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_ERLEBRAIN2 || \
    CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_BH || \
    CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_PXFMINI
#define APM_LINUX_UART_PERIOD           10000
#define APM_LINUX_RCIN_PERIOD           500
#define APM_LINUX_TONEALARM_PERIOD      10000
#define APM_LINUX_IO_PERIOD             20000
#else
#define APM_LINUX_UART_PERIOD           10000
#define APM_LINUX_RCIN_PERIOD           10000
#define APM_LINUX_TONEALARM_PERIOD      10000
#define APM_LINUX_IO_PERIOD             20000
#endif // CONFIG_HAL_BOARD_SUBTYPE




Scheduler::Scheduler()
{}

void Scheduler::_create_realtime_thread(pthread_t *ctx, int rtprio,
                                             const char *name,
                                             pthread_startroutine_t start_routine)
{
    struct sched_param param = { .sched_priority = rtprio };
    pthread_attr_t attr;
    int r;

    pthread_attr_init(&attr);
    /*
      we need to run as root to get realtime scheduling. Allow it to
      run as non-root for debugging purposes, plus to allow the Replay
      tool to run
     */
    if (geteuid() == 0) {
        pthread_attr_setinheritsched(&attr, PTHREAD_EXPLICIT_SCHED);
        pthread_attr_setschedpolicy(&attr, SCHED_FIFO);
        pthread_attr_setschedparam(&attr, &param);
    }
    r = pthread_create(ctx, &attr, start_routine, this);
    if (r != 0) {
        hal.console->printf("Error creating thread '%s': %s\n",
                            name, strerror(r));
        AP_HAL::panic("Failed to create thread");
    }
    pthread_attr_destroy(&attr);

    if (name) {
        pthread_setname_np(*ctx, name);
    }
}

void Scheduler::init()
{
    mlockall(MCL_CURRENT|MCL_FUTURE);

    struct sched_param param = { .sched_priority = APM_LINUX_MAIN_PRIORITY };
    sched_setscheduler(0, SCHED_FIFO, &param);

    struct {
        pthread_t *ctx;
        int rtprio;
        const char *name;
        pthread_startroutine_t start_routine;
    } *iter, table[] = {
        { .ctx = &_timer_thread_ctx,
          .rtprio = APM_LINUX_TIMER_PRIORITY,
          .name = "sched-timer",
          .start_routine = &Linux::Scheduler::_timer_thread,
        },
        { .ctx = &_uart_thread_ctx,
          .rtprio = APM_LINUX_UART_PRIORITY,
          .name = "sched-uart",
          .start_routine = &Linux::Scheduler::_uart_thread,
        },
        { .ctx = &_rcin_thread_ctx,
          .rtprio = APM_LINUX_RCIN_PRIORITY,
          .name = "sched-rcin",
          .start_routine = &Linux::Scheduler::_rcin_thread,
        },
        { .ctx = &_tonealarm_thread_ctx,
          .rtprio = APM_LINUX_TONEALARM_PRIORITY,
          .name = "sched-tonealarm",
          .start_routine = &Linux::Scheduler::_tonealarm_thread,
        },
        { .ctx = &_io_thread_ctx,
          .rtprio = APM_LINUX_IO_PRIORITY,
          .name = "sched-io",
          .start_routine = &Linux::Scheduler::_io_thread,
        },
        { }
    };

    if (geteuid() != 0) {
        printf("WARNING: running as non-root. Will not use realtime scheduling\n");
    }

    for (iter = table; iter->ctx; iter++)
        _create_realtime_thread(iter->ctx, iter->rtprio, iter->name,
                                iter->start_routine);
}

void Scheduler::_microsleep(uint32_t usec)
{
    struct timespec ts;
    ts.tv_sec = 0;
    ts.tv_nsec = usec*1000UL;
    while (nanosleep(&ts, &ts) == -1 && errno == EINTR) ;
}

void Scheduler::delay(uint16_t ms)
{
    if (_stopped_clock_usec) {
        return;
    }
    uint64_t start = AP_HAL::millis64();

    while ((AP_HAL::millis64() - start) < ms) {
        // this yields the CPU to other apps
        _microsleep(1000);
        if (_min_delay_cb_ms <= ms) {
            if (_delay_cb) {
                _delay_cb();
            }
        }
    }
}

void Scheduler::delay_microseconds(uint16_t us)
{
    if (_stopped_clock_usec) {
        return;
    }
    _microsleep(us);
}

void Scheduler::register_delay_callback(AP_HAL::Proc proc,
                                             uint16_t min_time_ms)
{
    _delay_cb = proc;
    _min_delay_cb_ms = min_time_ms;
}

void Scheduler::register_timer_process(AP_HAL::MemberProc proc)
{
    for (uint8_t i = 0; i < _num_timer_procs; i++) {
        if (_timer_proc[i] == proc) {
            return;
        }
    }

    if (_num_timer_procs < LINUX_SCHEDULER_MAX_TIMER_PROCS) {
        _timer_proc[_num_timer_procs] = proc;
        _num_timer_procs++;
    } else {
        hal.console->printf("Out of timer processes\n");
    }
}

bool Scheduler::register_timer_process(AP_HAL::MemberProc proc,
                                       uint8_t freq_div)
{
#if CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_BEBOP
    if (freq_div > 1) {
        return _register_timesliced_proc(proc, freq_div);
    }
    /* fallback to normal timer process */
#endif
    register_timer_process(proc);
    return false;
}

bool Scheduler::_register_timesliced_proc(AP_HAL::MemberProc proc,
                                          uint8_t freq_div)
{
    unsigned int i, j;
    uint8_t distance, min_distance, best_distance;
    uint8_t best_timeslot;

    if (_num_timesliced_procs > LINUX_SCHEDULER_MAX_TIMESLICED_PROCS) {
        hal.console->printf("Out of timesliced processes\n");
        return false;
    }

    /* if max_freq_div increases, update the timeslots accordingly */
    if (freq_div > _max_freq_div) {
        for (i = 0; i < _num_timesliced_procs; i++) {
            _timesliced_proc[i].timeslot =  _timesliced_proc[i].timeslot
                                            / _max_freq_div * freq_div;
        }
        _max_freq_div = freq_div;
    }

    best_distance = 0;
    best_timeslot = 0;

    /* Look for the timeslot that maximizes the min distance with other timeslots */
    for (i = 0; i < _max_freq_div; i++) {
        min_distance = _max_freq_div;
        for (j = 0; j < _num_timesliced_procs; j++) {
            distance = std::min(i - _timesliced_proc[j].timeslot,
                            _max_freq_div + _timesliced_proc[j].timeslot - i);
            if (distance < min_distance) {
                min_distance = distance;
                if (min_distance == 0) {
                    break;
                }
            }
        }
        if (min_distance > best_distance) {
            best_distance = min_distance;
            best_timeslot = i;
        }
    }

    _timesliced_proc[_num_timesliced_procs].proc = proc;
    _timesliced_proc[_num_timesliced_procs].timeslot = best_timeslot;
    _timesliced_proc[_num_timesliced_procs].freq_div = freq_div;
    _num_timesliced_procs++;
    return true;
}

void Scheduler::register_io_process(AP_HAL::MemberProc proc)
{
    for (uint8_t i = 0; i < _num_io_procs; i++) {
        if (_io_proc[i] == proc) {
            return;
        }
    }

    if (_num_io_procs < LINUX_SCHEDULER_MAX_IO_PROCS) {
        _io_proc[_num_io_procs] = proc;
        _num_io_procs++;
    } else {
        hal.console->printf("Out of IO processes\n");
    }
}

void Scheduler::register_timer_failsafe(AP_HAL::Proc failsafe, uint32_t period_us)
{
    _failsafe = failsafe;
}

void Scheduler::suspend_timer_procs()
{
    if (!_timer_semaphore.take(0)) {
        printf("Failed to take timer semaphore\n");
    }
}

void Scheduler::resume_timer_procs()
{
    _timer_semaphore.give();
}

void Scheduler::_run_timers(bool called_from_timer_thread)
{
    int i;

    if (_in_timer_proc) {
        return;
    }
    _in_timer_proc = true;

    if (!_timer_semaphore.take(0)) {
        printf("Failed to take timer semaphore in _run_timers\n");
    }
    // now call the timer based drivers
    for (i = 0; i < _num_timer_procs; i++) {
        if (_timer_proc[i]) {
            _timer_proc[i]();
        }
    }

#if CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_RASPILOT
    //SPI UART use SPI
    if (!((RPIOUARTDriver *)hal.uartC)->isExternal() )
    {
        ((RPIOUARTDriver *)hal.uartC)->_timer_tick();
    }
#endif

    for (i = 0; i < _num_timesliced_procs; i++) {
        if ((_timeslices_count + _timesliced_proc[i].timeslot)
            % _timesliced_proc[i].freq_div == 0) {
            _timesliced_proc[i].proc();
        }
    }

    if (_max_freq_div != 0) {
        _timeslices_count++;
        if (_timeslices_count == _max_freq_div) {
            _timeslices_count = 0;
        }
    }

    _timer_semaphore.give();

    // and the failsafe, if one is setup
    if (_failsafe != NULL) {
        _failsafe();
    }

    _in_timer_proc = false;
}

void *Scheduler::_timer_thread(void* arg)
{
    Scheduler* sched = (Scheduler *)arg;

    while (sched->system_initializing()) {
        poll(NULL, 0, 1);
    }

#if CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_QFLIGHT
    printf("Initialising rpcmem\n");
    rpcmem_init();
#endif
    
/*
      this aims to run at an average of 1kHz, so that it can be used
      to drive 1kHz processes without drift
     */
    uint64_t next_run_usec = AP_HAL::micros64() + 1000;
    while (true) {
        uint64_t dt = next_run_usec - AP_HAL::micros64();
        if (dt > 2000) {
            // we've lost sync - restart
            next_run_usec = AP_HAL::micros64();
        } else {
            sched->_microsleep(dt);
        }
        next_run_usec += 1000;
        // run registered timers
        sched->_run_timers(true);

#if HAL_LINUX_UARTS_ON_TIMER_THREAD
        /*
          some boards require that UART calls happen on the same
          thread as other calls of the same time. This impacts the
          QFLIGHT calls where UART output is an RPC call to the DSPs
         */
        _run_uarts();
        RCInput::from(hal.rcin)->_timer_tick();
#endif
    }
    return NULL;
}

void Scheduler::_run_io(void)
{
    if (!_io_semaphore.take(0)) {
        return;
    }

    // now call the IO based drivers
    for (int i = 0; i < _num_io_procs; i++) {
        if (_io_proc[i]) {
            _io_proc[i]();
        }
    }

    _io_semaphore.give();
}

void *Scheduler::_rcin_thread(void *arg)
{
    Scheduler* sched = (Scheduler *)arg;

    while (sched->system_initializing()) {
        poll(NULL, 0, 1);
    }
    while (true) {
        sched->_microsleep(APM_LINUX_RCIN_PERIOD);
#if !HAL_LINUX_UARTS_ON_TIMER_THREAD
        RCInput::from(hal.rcin)->_timer_tick();
#endif
    }
    return NULL;
}


/*
  run timers for all UARTs
 */
void Scheduler::_run_uarts(void)
{
    // process any pending serial bytes
    UARTDriver::from(hal.uartA)->_timer_tick();
    UARTDriver::from(hal.uartB)->_timer_tick();
#if CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_RASPILOT
    //SPI UART not use SPI
    if (RPIOUARTDriver::from(hal.uartC)->isExternal()) {
        RPIOUARTDriver::from(hal.uartC)->_timer_tick();
    }
#else
    UARTDriver::from(hal.uartC)->_timer_tick();
#endif
    UARTDriver::from(hal.uartE)->_timer_tick();
}

void *Scheduler::_uart_thread(void* arg)
{
    Scheduler* sched = (Scheduler *)arg;

    while (sched->system_initializing()) {
        poll(NULL, 0, 1);
    }
    while (true) {
        sched->_microsleep(APM_LINUX_UART_PERIOD);
#if !HAL_LINUX_UARTS_ON_TIMER_THREAD
        _run_uarts();
#endif
    }
    return NULL;
}

void *Scheduler::_tonealarm_thread(void* arg)
{
    Scheduler* sched = (Scheduler *)arg;

    while (sched->system_initializing()) {
        poll(NULL, 0, 1);
    }
    while (true) {
        sched->_microsleep(APM_LINUX_TONEALARM_PERIOD);

        // process tone command
        Util::from(hal.util)->_toneAlarm_timer_tick();
    }
    return NULL;
}

void *Scheduler::_io_thread(void* arg)
{
    Scheduler* sched = (Scheduler *)arg;

    while (sched->system_initializing()) {
        poll(NULL, 0, 1);
    }
    while (true) {
        sched->_microsleep(APM_LINUX_IO_PERIOD);

        // process any pending storage writes
        Storage::from(hal.storage)->_timer_tick();

        // run registered IO procepsses
        sched->_run_io();
    }
    return NULL;
}

bool Scheduler::in_timerprocess()
{
    return _in_timer_proc;
}

void Scheduler::begin_atomic()
{}

void Scheduler::end_atomic()
{}

bool Scheduler::system_initializing() {
    return !_initialized;
}

void Scheduler::system_initialized()
{
    if (_initialized) {
        AP_HAL::panic("PANIC: scheduler::system_initialized called more than once");
    }
    _initialized = true;
}

void Scheduler::reboot(bool hold_in_bootloader)
{
    exit(1);
}

void Scheduler::stop_clock(uint64_t time_usec)
{
    if (time_usec >= _stopped_clock_usec) {
        _stopped_clock_usec = time_usec;
        _run_io();
    }
}

#endif // CONFIG_HAL_BOARD