#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>
#include <limits.h>

#define LINE_LEN 1024

typedef struct {
	long a;
	long n;
} sum_t;

typedef struct {
	/* stores all results */
	long * s_result;
	/* stores the sum of all */
	long sum;
} sum_result_t;

int readSumParams(sum_t * sum, char * line);
void __shutdown();

/* store program name */
char * program = NULL;
/* storage for file-handle */
FILE * fh = NULL;

int main (int argc, char * argv[]) {
    int i = 0;
	/* storage for the x's
	 * as count of x's is not yet known
	 * we're going to allocate on demand
	 */
	long * x;
	/* storage for file line */
	char line[LINE_LEN+1];
	/* stores a and n */
	sum_t sum_params;
	/* stores all single results */
	sum_result_t sum_result;
	/* stores time needed for execution */
	clock_t start, stop;
	
	/* storing program name used for error output */
	program = argv[0];
	
	/* checking if required arguments were passed */
	if(argc < 2) {
		fprintf(stderr, "%s: You must pass a file containing, a,n and x's\n", program); 
		__shutdown();
		return EXIT_FAILURE;
	}
	
	/* if file was passed content is opened and read */
	fh = fopen(argv[1], "r");
	if(fh == NULL) {
		fprintf(stderr, "%s: Couldn't open file '%s'", program, argv[1]);
		__shutdown();
		return EXIT_FAILURE;
	}
	if(fgets(line, LINE_LEN, fh) == NULL) {
		fprintf(stderr, "%s: Couldn't read first line!\n", program);
		__shutdown();
		return EXIT_FAILURE;
	}
	
	/* get a and n in a structure */
	if(!readSumParams(& sum_params, line)) {
		__shutdown();
		return EXIT_FAILURE;
	}
	
	x = (long *)calloc(1,sizeof(long));
	if(fgets(line, LINE_LEN, fh) == NULL) {
		fprintf(stderr, "%s: No values given for x. Check syntax please!\n", program);
		__shutdown();
		return EXIT_FAILURE;
	}
	x[i] = strtol(line, NULL, 10);
	
	/* store all x's */
	while(fgets(line, LINE_LEN, fh) != NULL) {
		x = (long *)realloc(x, sizeof(long));
		x[i] = strtol(line, NULL, 10);
		i++;
	}
	
	/* check whether less values are given */
	if((i+1) < sum_params.n) {
		fprintf(stderr, "%s: Not enough values for x are given!. Check n!\n");
		__shutdown();
		return EXIT_FAILURE;
	}
	
	/* check whether more values for x are given than n */
	if((i+1) > sum_params.n) {
		fprintf(stderr, "%s: More values for x than given by n! These are gonna be ignored!\n", program);
	}
	
	start = clock();
	
	i = 0;
	/* doing the calculation for each x */
	sum_result.s_result = (long *)calloc(1, sizeof(long));
	sum_result.sum = 0;
	for(i = 0; i < sum_params.n; i++) {
		sum_result.s_result = (long *)realloc(sum_result.s_result, sizeof(long));
		sum_result.s_result[i] = sum_params.a*x[i];
		if(LONG_MAX - (sum_result.sum + sum_result.s_result[i]) < 0) {
			fprintf(stderr, "%s: Sorry, Sum is already bigger than %ld\n", program, LONG_MAX);
			__shutdown();
			return EXIT_FAILURE;
		}
		/*printf("Sum x%d: %d\n", i,sum_result.s_result[i]); */
		sum_result.sum += sum_result.s_result[i];
	}
	
	stop = clock();
	
	printf("Start: %ld\nStop: %ld: %d\n", start, stop, CLOCKS_PER_SEC);
	
	
	fprintf(stdout, "Result for Calculation: %ld\n", sum_result.sum);
	fprintf(stdout, "Time for Caluclation: %ld\n", (double)((clock() - start)/CLOCKS_PER_SEC));
	__shutdown();
	
    return 0;
}

int readSumParams(sum_t * sum, char * line) {
	/* token for splitting */
	char token[] = " ";
	char * buffer;
	
	buffer = strtok(line, token);
	if(buffer != NULL) {
		sum->a = strtol(buffer, NULL, 10);
	}
	else {
		fprintf(stderr, "%s: Couldn't read value for a. Please check your file syntax!\n", program);
		return 0;
	}
	
	buffer = strtok(NULL, token);
	if(buffer != NULL) {
		sum->n = strtol(buffer, NULL, 10);
	}
	else {
		fprintf(stderr, "%s: Couldn't read value for n. Check file syntax!\n", program);
		return 0;
	}
	
	return 1;
}

void __shutdown() {
	/* close file */
	if(fh != NULL) fclose(fh);
}