/*File contents: Travel planning using a structure
Authors: Daniel Dedoukh, Mohamed Moustafa, Momme König*/

#define _CRT_SECURE_NO_DEPRECATE
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define PI 3.14159265

double distanceKm(const double *longitude, const double *attitude, double *totalDistance, int numWayPoints);

int main(void)
{
	//This structure will store longitude and latitude
	struct coordinate {
		double *latitude;
		double *longitude;
	} coordinate;

	int numWayPoints;
	double totalDistance = 0.0;

	printf("Enter number of waypoints: ");

	// To avoid user input mistakes.
	while ((!scanf("%d", &numWayPoints)) || (numWayPoints < 0))
	{
			char invalid;

			printf("\nInvalid input: ");
			while ((invalid = getchar()) != '\n')
				putchar(invalid);
			printf("\nTry again: \n");

	}

	//Using memory allocation to specify the number of points with respect to user input
	coordinate.latitude = (double *)calloc(numWayPoints, sizeof(double));
	coordinate.longitude = (double *)calloc(numWayPoints, sizeof(double));

	printf("\nEnter waypoints as \"<latitude> <longitude>\" separated by space");

	// ask the user
	for (int i = 0, count = 1; i < numWayPoints, count <= numWayPoints; i++, count++)
	{
		printf("\nWaypoint %d:", count);

		while (scanf("%lf %lf", &coordinate.latitude[i], &coordinate.longitude[i]) != 2)
		{
			char invalid;

			printf("\nInvalid input: ");
			while ((invalid = getchar()) != '\n')
				putchar(invalid);
			printf("\nTry again: \n");
		}
		getchar();
	}

	printf("By taking this route you will travel: %.1f km", distanceKm(coordinate.latitude, coordinate.longitude, &totalDistance, numWayPoints));

	free(coordinate.latitude);
	free(coordinate.longitude);

	getchar();
	return;
}

double distanceKm(const double *latitude, const double *longitude, double *totalDistance, int numWayPoints)
{

	for (int i = 0; i < numWayPoints - 1; i++)
	{
		*totalDistance += 6378.388 * acos(sin((PI / 180) *latitude[i]) * sin((PI / 180) *latitude[i + 1]) + cos((PI / 180) *latitude[i]) * cos((PI / 180) *latitude[i + 1]) * cos((PI / 180) *(longitude[i] - longitude[i + 1])));
	}

	return *totalDistance;
}