#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>

#define DEBUG 1
#define MAX_DATA 12
#define SUBWAYS 4

typedef struct subway{
	double nStartDistance[SUBWAYS];
	double nNowDistance[SUBWAYS];
	double nSpeed[SUBWAYS];
}subway_t;

void ReadLine(int Line);
void StartThread(int Subway);
void *GoSubwayGo(void *index);
void PrintList(int Subway);
void Usage();

FILE *file;

subway_t value;

pthread_t thread1, thread2, thread3, thread4;
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t cond;

char *pProgname;
char *pFilename;
int GlobalSubway;

int main(int argc, char *argv[])
{
	char cBuffer[MAX_DATA];
	int nCount;
	int Subway;
  	
	pProgname = argv[0];
	
	if(argc != 2)
	{
		Usage();
 		return EXIT_FAILURE;
	}

	pFilename = argv[1];

	if((file = fopen(pFilename, "r")) == NULL)
	{
		fprintf(stderr, "%s: Can't open file %s\n", pProgname, pFilename);
		return EXIT_FAILURE;
	}

	for(nCount = 0; nCount < SUBWAYS; nCount++)
	{
		ReadLine(nCount);
	}
	
#if DEBUG
	for(nCount = 0; nCount < SUBWAYS; nCount++) PrintList(nCount);	
#endif
	while((cBuffer[0] = getchar()) != 'S')
	{
		continue;
	}

	Subway = 0;

	if(pthread_create(&thread1, NULL, &GoSubwayGo, &Subway) != 0)
	{
		fprintf(stderr, "%s: Error creating Thread\n", pProgname);
		exit(EXIT_FAILURE);	
	}
	pthread_join(thread1, NULL);

	Subway = 1;

	if(pthread_create(&thread2, NULL, &GoSubwayGo, &Subway) != 0)
	{
		fprintf(stderr, "%s: Error creating Thread\n", pProgname);
		exit(EXIT_FAILURE);	
	}
	pthread_join(thread2, NULL);

	Subway = 2;

	if(pthread_create(&thread3, NULL, &GoSubwayGo, &Subway) != 0)
	{
		fprintf(stderr, "%s: Error creating Thread\n", pProgname);
		exit(EXIT_FAILURE);	
	}
	pthread_join(thread3, NULL);

	Subway = 3;

	if(pthread_create(&thread4, NULL, &GoSubwayGo, &Subway) != 0)
	{
		fprintf(stderr, "%s: Error creating Thread\n", pProgname);
		exit(EXIT_FAILURE);	
	}
	pthread_join(thread4, NULL);	

#if DEBUG
	for(nCount = 0; nCount < SUBWAYS; nCount++) PrintList(nCount);
#endif
	return EXIT_SUCCESS;	
}	

void ReadLine(int Line)
{
	char cBuffer[MAX_DATA];

	if(fgets(cBuffer, MAX_DATA -1, file) == NULL)
	{
		fprintf(stderr, "%s: invalid file layout %s\n", pProgname, pFilename);
		exit(EXIT_FAILURE);
	}
	sscanf(cBuffer,"%lf %lf", &value.nStartDistance[Line], &value.nSpeed[Line]);
	value.nNowDistance[Line] = value.nStartDistance[Line] * 1000;
	value.nSpeed[Line] = value.nSpeed[Line] / 3.6;
}

void *GoSubwayGo(void *index)
{
	int Status;
	int GotWhere = 1;

	printf("Subway %d started\n", *((int *) (index)));
   	while (GotWhere != 0)
   	{
#if DEBUG
		printf("Subway: %d\n", *((int *) (index)));
#endif
		pthread_detach(pthread_self());
	    Status = pthread_mutex_lock(&mutex);

		if(value.nNowDistance[*((int *) (index))] >= value.nSpeed[*((int *) (index))])
		{
			value.nNowDistance[*((int *) (index))] = value.nNowDistance[*((int *) (index))] - value.nSpeed[*((int *) (index))];
		}
        else
        {
        	value.nNowDistance[*((int *) (index))] = 0;	
        	pthread_cond_wait(&cond, &mutex);
		}

		GotWhere = value.nNowDistance[*((int *) (index))];

		Status = pthread_mutex_unlock(&mutex);
		sleep (1);		
	}
	return NULL;
}

void PrintList(int Subway)
{
	printf("%d: StartDistance: %.2lf km, NowDistance: %.2lf m, Speed: %.2lf m/s\n", 
			Subway, value.nStartDistance[Subway], value.nNowDistance[Subway], value.nSpeed[Subway]);
}

void Usage()
{
	printf("Usage %s:\n", pProgname);
	printf("%s filename\n", pProgname);
}