/*
 * FreeRTOS Kernel V10.4.1
 * Copyright (C) 2020 Cambridge Consultants Ltd.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * https://www.FreeRTOS.org
 * https://github.com/FreeRTOS
 *
 * 1 tab == 4 spaces!
 */

/*-----------------------------------------------------------
 * Implementation of functions defined in portable.h for the Posix port.
 *
 * Each task has a pthread which eases use of standard debuggers
 * (allowing backtraces of tasks etc). Threads for tasks that are not
 * running are blocked in sigwait().
 *
 * Task switch is done by resuming the thread for the next task by
 * signaling the condition variable and then waiting on a condition variable
 * with the current thread.
 *
 * The timer interrupt uses SIGALRM and care is taken to ensure that
 * the signal handler runs only on the thread for the current task.
 *
 * Use of part of the standard C library requires care as some
 * functions can take pthread mutexes internally which can result in
 * deadlocks as the FreeRTOS kernel can switch tasks while they're
 * holding a pthread mutex.
 *
 * stdio (printf() and friends) should be called from a single task
 * only or serialized with a FreeRTOS primitive such as a binary
 * semaphore or mutex.
 *----------------------------------------------------------*/

#include <errno.h>
#include <pthread.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#include <sys/times.h>
#include <time.h>

/* Scheduler includes. */
#include "FreeRTOS.h"
#include "task.h"
#include "timers.h"
#include "utils/wait_for_event.h"
/*-----------------------------------------------------------*/

#define SIG_RESUME SIGUSR1

typedef struct THREAD
{
	pthread_t pthread;
	pdTASK_CODE pxCode;
	void *pvParams;
	BaseType_t xDying;
	struct event *ev;
} Thread_t;

/*
 * The additional per-thread data is stored at the beginning of the
 * task's stack.
 */
static inline Thread_t *prvGetThreadFromTask(TaskHandle_t xTask)
{
StackType_t *pxTopOfStack = *(StackType_t **)xTask;

	return (Thread_t *)(pxTopOfStack + 1);
}

/*-----------------------------------------------------------*/

static pthread_once_t hSigSetupThread = PTHREAD_ONCE_INIT;
static sigset_t xResumeSignals;
static sigset_t xAllSignals;
static sigset_t xSchedulerOriginalSignalMask;
static pthread_t hMainThread = ( pthread_t )NULL;
static volatile portBASE_TYPE uxCriticalNesting;
/*-----------------------------------------------------------*/

static portBASE_TYPE xSchedulerEnd = pdFALSE;
/*-----------------------------------------------------------*/

static void prvSetupSignalsAndSchedulerPolicy( void );
static void prvSetupTimerInterrupt( void );
static void *prvWaitForStart( void * pvParams );
static void prvSwitchThread( Thread_t * xThreadToResume,
                             Thread_t *xThreadToSuspend );
static void prvSuspendSelf( Thread_t * thread);
static void prvResumeThread( Thread_t * xThreadId );
static void vPortSystemTickHandler( int sig );
static void vPortStartFirstTask( void );
/*-----------------------------------------------------------*/

static void prvFatalError( const char *pcCall, int iErrno )
{
	fprintf( stderr, "%s: %s\n", pcCall, strerror( iErrno ) );
	abort();
}

/*
 * See header file for description.
 */
portSTACK_TYPE *pxPortInitialiseStack( portSTACK_TYPE *pxTopOfStack,
                                       portSTACK_TYPE *pxEndOfStack,
                                       pdTASK_CODE pxCode, void *pvParameters )
{
Thread_t *thread;
pthread_attr_t xThreadAttributes;
size_t ulStackSize;
int iRet;

	(void)pthread_once( &hSigSetupThread, prvSetupSignalsAndSchedulerPolicy );

	/*
	 * Store the additional thread data at the start of the stack.
	 */
	thread = (Thread_t *)(pxTopOfStack + 1) - 1;
	pxTopOfStack = (portSTACK_TYPE *)thread - 1;
	ulStackSize = (pxTopOfStack + 1 - pxEndOfStack) * sizeof(*pxTopOfStack);

	thread->pxCode = pxCode;
	thread->pvParams = pvParameters;
	thread->xDying = pdFALSE;

	pthread_attr_init( &xThreadAttributes );
	pthread_attr_setstack( &xThreadAttributes, pxEndOfStack, ulStackSize );

	thread->ev = event_create();

	vPortEnterCritical();

	iRet = pthread_create( &thread->pthread, &xThreadAttributes,
						   prvWaitForStart, thread );
	if ( iRet )
	{
		prvFatalError( "pthread_create", iRet );
	}

	vPortExitCritical();

	return pxTopOfStack;
}
/*-----------------------------------------------------------*/

void vPortStartFirstTask( void )
{
Thread_t *pxFirstThread = prvGetThreadFromTask( xTaskGetCurrentTaskHandle() );

	/* Start the first task. */
	prvResumeThread( pxFirstThread );
}
/*-----------------------------------------------------------*/

/*
 * See header file for description.
 */
portBASE_TYPE xPortStartScheduler( void )
{
int iSignal;
sigset_t xSignals;

	hMainThread = pthread_self();

	/* Start the timer that generates the tick ISR(SIGALRM).
	   Interrupts are disabled here already. */
	prvSetupTimerInterrupt();

	/* Start the first task. */
	vPortStartFirstTask();

	/* Wait until signaled by vPortEndScheduler(). */
	sigemptyset( &xSignals );
	sigaddset( &xSignals, SIG_RESUME );

	while ( !xSchedulerEnd )
	{
		sigwait( &xSignals, &iSignal );
	}

	/* Cancel the Idle task and free its resources */
	vPortCancelThread( xTaskGetIdleTaskHandle() );
#if ( configUSE_TIMERS == 1 )
	/* Cancel the Timer task and free its resources */
	vPortCancelThread( xTimerGetTimerDaemonTaskHandle() );
#endif /* configUSE_TIMERS */

	/* Restore original signal mask. */
	(void)pthread_sigmask( SIG_SETMASK, &xSchedulerOriginalSignalMask,  NULL );

	return 0;
}
/*-----------------------------------------------------------*/

void vPortEndScheduler( void )
{
struct itimerval itimer;
struct sigaction sigtick;
Thread_t *xCurrentThread;

	/* Stop the timer and ignore any pending SIGALRMs that would end
	 * up running on the main thread when it is resumed. */
	itimer.it_value.tv_sec = 0;
	itimer.it_value.tv_usec = 0;

	itimer.it_interval.tv_sec = 0;
	itimer.it_interval.tv_usec = 0;
	(void)setitimer( ITIMER_REAL, &itimer, NULL );

	sigtick.sa_flags = 0;
	sigtick.sa_handler = SIG_IGN;
	sigemptyset( &sigtick.sa_mask );
	sigaction( SIGALRM, &sigtick, NULL );

	/* Signal the scheduler to exit its loop. */
	xSchedulerEnd = pdTRUE;
	(void)pthread_kill( hMainThread, SIG_RESUME );

	xCurrentThread = prvGetThreadFromTask( xTaskGetCurrentTaskHandle() );
	prvSuspendSelf(xCurrentThread);
}
/*-----------------------------------------------------------*/

void vPortEnterCritical( void )
{
	if ( uxCriticalNesting == 0 )
	{
		vPortDisableInterrupts();
	}
	uxCriticalNesting++;
}
/*-----------------------------------------------------------*/

void vPortExitCritical( void )
{
	uxCriticalNesting--;

	/* If we have reached 0 then re-enable the interrupts. */
	if( uxCriticalNesting == 0 )
	{
		vPortEnableInterrupts();
	}
}
/*-----------------------------------------------------------*/

void vPortYieldFromISR( void )
{
Thread_t *xThreadToSuspend;
Thread_t *xThreadToResume;

	xThreadToSuspend = prvGetThreadFromTask( xTaskGetCurrentTaskHandle() );

	vTaskSwitchContext();

	xThreadToResume = prvGetThreadFromTask( xTaskGetCurrentTaskHandle() );

	prvSwitchThread( xThreadToResume, xThreadToSuspend );
}
/*-----------------------------------------------------------*/

void vPortYield( void )
{
	vPortEnterCritical();

	vPortYieldFromISR();

	vPortExitCritical();
}
/*-----------------------------------------------------------*/

void vPortDisableInterrupts( void )
{
	pthread_sigmask( SIG_BLOCK, &xAllSignals, NULL );
}
/*-----------------------------------------------------------*/

void vPortEnableInterrupts( void )
{
	pthread_sigmask( SIG_UNBLOCK, &xAllSignals, NULL );
}
/*-----------------------------------------------------------*/

portBASE_TYPE xPortSetInterruptMask( void )
{
	/* Interrupts are always disabled inside ISRs (signals
	   handlers). */
	return pdTRUE;
}
/*-----------------------------------------------------------*/

void vPortClearInterruptMask( portBASE_TYPE xMask )
{
}
/*-----------------------------------------------------------*/

static uint64_t prvGetTimeNs(void)
{
struct timespec t;

	clock_gettime(CLOCK_MONOTONIC, &t);

	return t.tv_sec * 1000000000ull + t.tv_nsec;
}

static uint64_t prvStartTimeNs;
static uint64_t prvTickCount;

/*
 * Setup the systick timer to generate the tick interrupts at the required
 * frequency.
 */
void prvSetupTimerInterrupt( void )
{
struct itimerval itimer;
int iRet;

	/* Initialise the structure with the current timer information. */
	iRet = getitimer( ITIMER_REAL, &itimer );
	if ( iRet )
	{
		prvFatalError( "getitimer", errno );
	}

	/* Set the interval between timer events. */
	itimer.it_interval.tv_sec = 0;
	itimer.it_interval.tv_usec = portTICK_RATE_MICROSECONDS;

	/* Set the current count-down. */
	itimer.it_value.tv_sec = 0;
	itimer.it_value.tv_usec = portTICK_RATE_MICROSECONDS;

	/* Set-up the timer interrupt. */
	iRet = setitimer( ITIMER_REAL, &itimer, NULL );
	if ( iRet )
	{
		prvFatalError( "setitimer", errno );
	}

	prvStartTimeNs = prvGetTimeNs();
}
/*-----------------------------------------------------------*/

static void vPortSystemTickHandler( int sig )
{
Thread_t *pxThreadToSuspend;
Thread_t *pxThreadToResume;
uint64_t xExpectedTicks;

	uxCriticalNesting++; /* Signals are blocked in this signal handler. */

#if ( configUSE_PREEMPTION == 1 )
	pxThreadToSuspend = prvGetThreadFromTask( xTaskGetCurrentTaskHandle() );
#endif

	/* Tick Increment, accounting for any lost signals or drift in
	 * the timer. */
/*
 *      Comment code to adjust timing according to full demo requirements
 *      xExpectedTicks = (prvGetTimeNs() - prvStartTimeNs)
 *		/ (portTICK_RATE_MICROSECONDS * 1000);
 * do { */
		xTaskIncrementTick();
/*		prvTickCount++;
 *	} while (prvTickCount < xExpectedTicks);
*/

#if ( configUSE_PREEMPTION == 1 )
	/* Select Next Task. */
	vTaskSwitchContext();

	pxThreadToResume = prvGetThreadFromTask( xTaskGetCurrentTaskHandle() );

	prvSwitchThread(pxThreadToResume, pxThreadToSuspend);
#endif

	uxCriticalNesting--;
}
/*-----------------------------------------------------------*/

void vPortThreadDying( void *pxTaskToDelete, volatile BaseType_t *pxPendYield )
{
Thread_t *pxThread = prvGetThreadFromTask( pxTaskToDelete );

	pxThread->xDying = pdTRUE;
}

void vPortCancelThread( void *pxTaskToDelete )
{
Thread_t *pxThreadToCancel = prvGetThreadFromTask( pxTaskToDelete );

	/*
	 * The thread has already been suspended so it can be safely cancelled.
	 */
	pthread_cancel( pxThreadToCancel->pthread );
	pthread_join( pxThreadToCancel->pthread, NULL );
	event_delete( pxThreadToCancel->ev );
}
/*-----------------------------------------------------------*/

static void *prvWaitForStart( void * pvParams )
{
Thread_t *pxThread = pvParams;

	prvSuspendSelf(pxThread);

	/* Resumed for the first time, unblocks all signals. */
	uxCriticalNesting = 0;
	vPortEnableInterrupts();

	/* Call the task's entry point. */
	pxThread->pxCode( pxThread->pvParams );

	/* A function that implements a task must not exit or attempt to return to
	* its caller as there is nothing to return to. If a task wants to exit it
	* should instead call vTaskDelete( NULL ). Artificially force an assert()
	* to be triggered if configASSERT() is defined, so application writers can
        * catch the error. */
	configASSERT( pdFALSE );

	return NULL;
}
/*-----------------------------------------------------------*/

static void prvSwitchThread( Thread_t *pxThreadToResume,
							 Thread_t *pxThreadToSuspend )
{
BaseType_t uxSavedCriticalNesting;

	if ( pxThreadToSuspend != pxThreadToResume )
	{
		/*
		 * Switch tasks.
		 *
		 * The critical section nesting is per-task, so save it on the
		 * stack of the current (suspending thread), restoring it when
		 * we switch back to this task.
		 */
		uxSavedCriticalNesting = uxCriticalNesting;

		prvResumeThread( pxThreadToResume );
		if ( pxThreadToSuspend->xDying )
		{
			pthread_exit( NULL );
		}
		prvSuspendSelf( pxThreadToSuspend );

		uxCriticalNesting = uxSavedCriticalNesting;
	}
}
/*-----------------------------------------------------------*/

static void prvSuspendSelf( Thread_t *thread )
{
int iSig;

	/*
	 * Suspend this thread by waiting for a pthread_cond_signal event.
	 *
	 * A suspended thread must not handle signals (interrupts) so
	 * all signals must be blocked by calling this from:
	 *
	 * - Inside a critical section (vPortEnterCritical() /
	 *   vPortExitCritical()).
	 *
	 * - From a signal handler that has all signals masked.
	 *
	 * - A thread with all signals blocked with pthread_sigmask().
        */
    event_wait(thread->ev);
}

/*-----------------------------------------------------------*/

static void prvResumeThread( Thread_t *xThreadId )
{
	if ( pthread_self() != xThreadId->pthread )
	{
		event_signal(xThreadId->ev);
	}
}
/*-----------------------------------------------------------*/

static void prvSetupSignalsAndSchedulerPolicy( void )
{
struct sigaction sigresume, sigtick;
int iRet;

	hMainThread = pthread_self();

	/* Initialise common signal masks. */
	sigemptyset( &xResumeSignals );
	sigaddset( &xResumeSignals, SIG_RESUME );
	sigfillset( &xAllSignals );
	/* Don't block SIGINT so this can be used to break into GDB while
	 * in a critical section. */
	sigdelset( &xAllSignals, SIGINT );

	/*
	 * Block all signals in this thread so all new threads
	 * inherits this mask.
	 *
	 * When a thread is resumed for the first time, all signals
	 * will be unblocked.
	 */
	(void)pthread_sigmask( SIG_SETMASK, &xAllSignals,
						   &xSchedulerOriginalSignalMask );

	/* SIG_RESUME is only used with sigwait() so doesn't need a
	   handler. */
	sigresume.sa_flags = 0;
	sigresume.sa_handler = SIG_IGN;
	sigfillset( &sigresume.sa_mask );

	sigtick.sa_flags = 0;
	sigtick.sa_handler = vPortSystemTickHandler;
	sigfillset( &sigtick.sa_mask );

	iRet = sigaction( SIG_RESUME, &sigresume, NULL );
	if ( iRet )
	{
		prvFatalError( "sigaction", errno );
	}

	iRet = sigaction( SIGALRM, &sigtick, NULL );
	if ( iRet )
	{
		prvFatalError( "sigaction", errno );
	}
}
/*-----------------------------------------------------------*/

unsigned long ulPortGetRunTime( void )
{
struct tms xTimes;

	times( &xTimes );

	return ( unsigned long ) xTimes.tms_utime;
}
/*-----------------------------------------------------------*/