/*
	All of the below was authored by me.
	By using any part of this source code, you agree to waive all liabilities from the author.
	Furthermore, you agree that you will not use this source code for personal (or corporate) gain.
	Finally, should you change any part of this source code, you agree to give credit to the author where such credit is due.
*/

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define pi atan2(0.,-1.)
#define n 5120
void deblank (char *s);				// "  ABCD EF   " --> "ABCD EF"
void endnull (char *s);				// Ensures strings end with nulls

int main () {

char outfile[n];
int h,k,l,count,exit;
double theta,bragg, dhkl, wavelength, a, b, c, max_brag, min_brag;
FILE *out;

for(exit=1;exit;) {
	/* Get Lattice Parameters, and Wavelength of Monochromatic X-ray */
	do{ printf("Enter Lattice Parameter 'a' (nm):   "); scanf("%lf",&a); } while(a<0);
	do{ printf("Enter Lattice Parameter 'b' (nm):   "); scanf("%lf",&b); } while(b<0);
	do{ printf("Enter Lattice Parameter 'c' (nm):   "); scanf("%lf",&c);} while(c<0);
	do{ printf("Enter Wavelength 'lamda' (nm):      "); scanf("%lf",&wavelength);	} while (wavelength<0.);
	do{ printf("Min Desired Bragg Angle (degrees):  "); scanf("%lf",&min_brag);
	} while (min_brag<0.  && min_brag<=180.);	
	do{ printf("Max Desired Bragg Angle (degrees):  "); scanf("%lf",&max_brag);
	} while (max_brag<min_brag && max_brag<=180.);
	fflush(stdin);

	/* Get Output File Name */
	do {
		printf("Output path:                   ");
		gets(outfile); endnull(outfile); deblank(outfile);
		out=fopen (outfile, "w");
		if (out==NULL) 	printf ("\nUh oh!\n\n%s cannot be opened.\nMake sure %s exists.\n\n",outfile,outfile);
	} while (out==NULL);
	fflush(stdin);
	fprintf(out,"This file is tab-delimited for your convenience.\n\na: %lf;\tb: %lf;\tc: %lf;\twavelength: %lf;\nPlane\tdhkl\tBragg (Degrees)\n",a,b,c,wavelength);

	/* Find Bragg Angles */
	for(count=l=0;l<10;l++) {
		for(k=0;k<10;k++) {
			for(h=0;h<10;h++) {
				if(h==0 && k==0 && l==0) continue;
				dhkl = sqrt (1/(h*h*(1/a)*(1/a) + k*k*(1/b)*(1/b) + l*l*(1/c)*(1/c)));
				if( (wavelength/(2*dhkl)) <= 1.) {
					theta = asin(wavelength/(2*dhkl));
					theta *= (180 / pi);	// Radian --> Degrees
					bragg = 2*theta;
					if(bragg >= min_brag && bragg <= max_brag) {
						fprintf(out,"(%d%d%d)\t%lf\t%lf\n",h,k,l,dhkl,bragg);
						count++;
					}
				}
			}
		}
	}
	fprintf(out,"\n\n%d Planes diffract within desired range\nDesired Bragg Angle Range (Degrees):%lf - %lf",count,min_brag,max_brag);
	printf("Enter 0 to exit:              "); scanf("%d",&exit);
	}
return 0;
}

void deblank (char *s) {
	char *t=s;
	for(;*s!='\0';s++)	;
	s--;
	for (;*s==' ';s--)	*s='\0';
	for (s=t;*s==' ';s++)	;
	for (;*s!='\0';t++,s++)	*t=*s;
	*t='\0';
	return;
}

void endnull (char *s) {
	int i;
	for(i=0;i<n || *(s+i)=='\0';i++) {
		if(i==n-1)	*(s+i)='\0';
	}
	return;
}