/* ===== INCLUDES ===== */

#include "test_sample_functions.h"

/* ===== CONSTANTS ===== */

const char *ARGUMENT_TIME = "-t";
const char *ARGUMENT_DELTA = "-d";
const char *ARGUMENT_OUTPUT_FILENAME = "-o";

char *DEFAULT_OUTPUT_FILENAME = "sample_test_output";

/* ===== STRUCTURES ===== */

struct timeval startwtime, endwtime;

/* ===== OTHER ===== */

volatile sig_atomic_t sample_flag = false;

/* ===== FUNCTIONS ===== */

/*
 * testSampling implements the sampling experiment. Three different ways of sampling are
 * implemented. On the first one sleep is used. On the second sleep is used and the sleep times are
 * corrected based on the previous error. On the third alarms are used.
*/
void testSampling(double ***samplesMatrix, Parameters parameters) {
	printf(ANSI_COLOR_CYAN "----- RUNNING FIRST EXPERIMENT\n" ANSI_COLOR_RESET);
	for (int i = 0; i < parameters.numberOfSamples; ++i) {
		gettimeofday (&startwtime, NULL);

		usleep(parameters.delta * 1000000);

		gettimeofday (&endwtime, NULL);
		(*samplesMatrix)[i][0] = (double)((endwtime.tv_usec - startwtime.tv_usec)/1.0e6 +
			endwtime.tv_sec - startwtime.tv_sec);
	}

	printf(ANSI_COLOR_CYAN "----- RUNNING SECOND EXPERIMENT\n" ANSI_COLOR_RESET);
	double totalError = 0;
	for (int i = 0; i < parameters.numberOfSamples; ++i) {
		gettimeofday (&startwtime, NULL);

		usleep((parameters.delta - (totalError / (i + 1))) * 1000000);

		gettimeofday (&endwtime, NULL);
		(*samplesMatrix)[i][1] = (double)((endwtime.tv_usec - startwtime.tv_usec)/1.0e6 +
			endwtime.tv_sec - startwtime.tv_sec);

		totalError += (*samplesMatrix)[i][1] - parameters.delta;
	}

	printf(ANSI_COLOR_CYAN "----- RUNNING THIRD EXPERIMENT\n" ANSI_COLOR_RESET);
	signal(SIGALRM, handle_alarm);

	struct itimerval new;

	new.it_interval.tv_usec = (int) ((parameters.delta - ((int) parameters.delta)) * 1000000);
	new.it_interval.tv_sec = ((int) parameters.delta);
	new.it_value.tv_usec = (int) ((parameters.delta - ((int) parameters.delta)) * 1000000);
	new.it_value.tv_sec = ((int) parameters.delta);

	if (setitimer (ITIMER_REAL, &new, NULL) == -1) {
		perror("setitimer");
		exit(EXIT_FAILURE);
	}

	gettimeofday (&startwtime, NULL);

	int i = 0 ;
	while(i < parameters.numberOfSamples) {
		if (sample_flag) {
			sample_flag = false;
			gettimeofday (&endwtime, NULL);
			(*samplesMatrix)[i][2] = (double)((endwtime.tv_usec - startwtime.tv_usec)/1.0e6 +
				endwtime.tv_sec - startwtime.tv_sec);

			++i;
			gettimeofday (&startwtime, NULL);
		}
	}

	alarm(0);
	printf(ANSI_COLOR_CYAN "----- RUNNING FOURTH EXPERIMENT\n" ANSI_COLOR_RESET);
	if (setitimer (ITIMER_REAL, &new, NULL) == -1) {
		perror("setitimer");
		exit(EXIT_FAILURE);
	}

	for (i = 0; i < parameters.numberOfSamples; ++i){
		gettimeofday (&startwtime, NULL);
		// Sleeps until a signal wakes up the process.
		sleep(parameters.time + 420);

		while (!sample_flag) {
			// Does nothing.
			// Makes sure signal was indeed triggered.
		}

		sample_flag = false;
		gettimeofday (&endwtime, NULL);
		(*samplesMatrix)[i][3] = (double)((endwtime.tv_usec - startwtime.tv_usec)/1.0e6 +
			endwtime.tv_sec - startwtime.tv_sec);
	}
}

void handle_alarm(int sig) {
	sample_flag = true;
}


// ==================== PROGRAM INPUT AND OUTPUT UTILS ====================

/*
 * parseArguments parses the command line arguments given by the user.
*/
void parseArguments(int argumentCount, char **argumentVector, Parameters *parameters) {
	if (argumentCount > 7) {
		validUsage(argumentVector[0]);
	}

	(*parameters).time = 7200;
	(*parameters).delta = 0.1;
	(*parameters).outputFilename = DEFAULT_OUTPUT_FILENAME;

	char *endPointer;
	int argumentIndex = 1;

	while (argumentIndex < argumentCount) {
		if (!strcmp(argumentVector[argumentIndex], ARGUMENT_TIME)) {
			argumentIndex = checkIncrement(argumentIndex, argumentCount, argumentVector[0]);

			double timeInput = strtod(argumentVector[argumentIndex], &endPointer);
			if ((timeInput <= 0) && endPointer) {
				printf("Invalid time argument\n");
				exit(EXIT_FAILURE);
			}
			(*parameters).time = timeInput;
		} else if (!strcmp(argumentVector[argumentIndex], ARGUMENT_DELTA)) {
			argumentIndex = checkIncrement(argumentIndex, argumentCount, argumentVector[0]);

			double deltaInput = strtod(argumentVector[argumentIndex], &endPointer);
			if ((deltaInput <= 0) && endPointer) {
				printf("Invalid time argument\n");
				exit(EXIT_FAILURE);
			}
			(*parameters).delta = deltaInput;
		} else if (!strcmp(argumentVector[argumentIndex], ARGUMENT_OUTPUT_FILENAME)) {
			argumentIndex = checkIncrement(argumentIndex, argumentCount, argumentVector[0]);

			if (fopen(argumentVector[argumentIndex], "w") == NULL) {
				printf("Invalid output filename. Reverting to default.\n");
				continue;
			}
			(*parameters).outputFilename = argumentVector[argumentIndex];
		} else {
			validUsage(argumentVector[0]);
			exit(EXIT_FAILURE);
		}
		++argumentIndex;
	}
}

/*
 * validUsage outputs a message to the console that informs the user of the
 * correct (valid) way to use the program.
*/
void validUsage(char *programName) {
	printf("Usage:\t%s [-t time] [-d delta] [-o output]" \
		"\n-t time" \
		"\n\ttotal duration of the sampling in seconds, default value is 7200" \
		"\n-d delta" \
		"\n\tsampling period in seconds, default value is 0.1" \
		"\n-o output" \
		"\n\tfilename and path for the output, default filename is 'sample_test_output'" \
		"\n", programName);
	exit(EXIT_FAILURE);
}

/*
 * checkIncrement is a helper function for parseArguments function.
*/
int checkIncrement(int previousIndex, int maxIndex, char *programName) {
	if (previousIndex == maxIndex) {
		validUsage(programName);
		exit(EXIT_FAILURE);
	}
	return ++previousIndex;
}

void saveSamplesToFile(char *filename, double **samplesMatrix, int matrixRows) {
	FILE *outputFile;

	outputFile = fopen(filename, "a");

	if (outputFile == NULL) {
		printf("Error while opening the output file.\n");
		return;
	}

	// Saves the samples matrix
	for (int i=0; i<matrixRows; ++i) {
		fprintf(outputFile, "%.10g\t%.10g\t%.10g\t%.10g\n",
			samplesMatrix[i][0], samplesMatrix[i][1], samplesMatrix[i][2], samplesMatrix[i][3]);
	}

	fclose(outputFile);
}