/*********************************************************
  
           xlinear, the X11 linear equation solver

                  Brett van de Sande
		  bvds@geneva.edu

  This is my first attempt at an X-windows application.  
  I learned how to do this by looking at:

    http://www.kerguelen.org/x/index.html
    http://www.cs.uregina.ca/~cdshaw/X11/x11notes.html

  compiling command:
  
    gcc -o xlinear xlinear.c -lXaw3d -L/usr/X11R6/lib\  
      -llapack -lblas -lg2c

  This uses the Athena widget set for the interface and 
  LAPACK and BLAS to solve the system of linear equations.
  I compiled it on LINUX using the standard GNU Fortran
  to C interface <g2c.h>

  This program is free for non-commercial use.
  Please send me any corrections/improvements!

**********************************************************/

#include <stdlib.h>
#include <stdio.h>
#include <X11/StringDefs.h>
#include <X11/Intrinsic.h> 
#include <X11/Shell.h>
#include <X11/Xaw3d/Form.h>
#include <X11/Xaw3d/Command.h> 
#include <X11/Xaw3d/AsciiText.h>
#include <X11/Xaw3d/Box.h>
#include <X11/Xaw3d/Dialog.h>

#define DEBUG 0  /*  debug print messages */
#define FLOAT_DIGITS "%g" /* print format for numbers */
XtAppContext app_context;

void quit_app(Widget,XtPointer,XtPointer);
void solve(Widget w, XtPointer client, XtPointer call);
Widget *a_input,*b_input,*x_output,message;
long int n;

/**********************************************************/
/*
           The following is taken from xfig source file
	   e_edit.c, see /usr/src/redhat/SOURCES/xfig.3.2.3d
*/

/* don't do anything when return is hit */

static String edit_text_translations ="<Key>Return: no-op()\n";

void text_transl(Widget w){
  /* modify default text parsing rules for a given widget */
  XtOverrideTranslations(w,
			 XtParseTranslationTable(edit_text_translations));
}

/**********************************************************/


int main(int argc, char **argv){
  Widget temp;
  Widget toplevel;
  Widget quit, math,form,equation,a_matrix,x_vector,b_vector;
  int i,j,width=90;
  char xin[20];
  char intromessage[]="Input matrix A and vector b\n"
    "choose \"Find solution\"";
  XFontStruct *font;
  int textheight;
#if 0  /* attempt to draw brackets */
  Widget line;
  Display *display;
  Window window;
  Pixmap p;
  GC gc;
#endif
  
  /*
    Initialize Widgets and parse input parameters.
  */

  toplevel = XtOpenApplication(&app_context, "linear", NULL, 0, &argc,argv, NULL, 
			       applicationShellWidgetClass, NULL,0);
  if(argc!=2||sscanf(argv[--argc],"%li",&n)!=1||n<1){
    fprintf(stderr,"\nUsage:  xlinear [X options] n\n");
    fprintf(stderr,"  The positive integer n is the number of equations be solved.\n");
    fprintf(stderr,"  See \"man X\" for a list of possible X options.\n");
    exit(1);
  }

  a_input=malloc(n*n*sizeof(Widget));
  b_input=malloc(n*sizeof(Widget));
  x_output=malloc(n*sizeof(Widget));

  
  form = XtVaCreateManagedWidget("form", boxWidgetClass, toplevel,
				       XtNorientation,XtorientVertical,
				 NULL);
  
  XtVaCreateManagedWidget("Solve a sytem of liner equations A x = b", 
			  labelWidgetClass,form, 
			  XtNborderWidth,0,
			  NULL);
  equation = XtVaCreateManagedWidget("equation", boxWidgetClass, form,
				     XtNorientation,XtorientHorizontal,
				     XtNborderWidth,0,
				     NULL);
  message=XtVaCreateManagedWidget("message",asciiTextWidgetClass,form,
				  XtNeditType,XawtextRead,
				  XtNstring,intromessage,
				  XtNborderWidth,3,
				  XtNdisplayCaret,False,
				  NULL);
/*
  Find appropriate window sizes based on
  the font size of the message window.
*/  
  
  XtVaGetValues(message,XtNfont,&font,NULL);
  textheight=font->ascent+font->descent;
  sprintf(xin,FLOAT_DIGITS,-8.0e-11/9.0);
  width=XTextWidth(font,xin,strlen(xin))+
    XTextWidth(font,"8",1);        /* extra padding */
  
#if DEBUG
  printf("Font sizes ht=%i hw=%i width=%i\n",ht,hw,width);
#endif
  
  /* Use the part of intromessage to estimate width
     XTextWidth does not handle \n well. */
  XtVaSetValues(message,XtNheight,2*textheight+6,
		XtNwidth,XTextWidth(font,intromessage,30),
		NULL);
  
#if 0    /* attempt to draw brackets */     
  line =  XtVaCreateManagedWidget("line",coreWidgetClass,equation,
				  XtNwidth,20+100, 
				  XtNheight,n*24+100,
				  NULL);
#endif
  a_matrix= XtVaCreateManagedWidget("a", formWidgetClass, equation,
				    XtNborderWidth,0,
				    NULL);
  x_vector = XtVaCreateManagedWidget("x", boxWidgetClass, equation, 
				     XtNborderWidth,0,
				     NULL);
  XtVaCreateManagedWidget("=",labelWidgetClass,equation, 
			  XtNborderWidth,0,
			  XtNinternalHeight,(n*(textheight+10)-14)/2,
			  NULL);
  b_vector = XtVaCreateManagedWidget ("b", boxWidgetClass, equation, 
				      XtNborderWidth,0,
				      NULL);
  
  math = XtVaCreateManagedWidget("Find solution",
				 commandWidgetClass, form, NULL, 0);

  quit = XtVaCreateManagedWidget("Quit",
				      commandWidgetClass, form, NULL, 0);
  
  for(i=0; i<n; i++){
    for(j=0; j<n; j++){
      temp=XtVaCreateManagedWidget(
				   "a",asciiTextWidgetClass,a_matrix,
				   XtNeditType,XawtextEdit,
				   XtNfromHoriz,
				   (i==0)?NULL:a_input[(i-1)*n+j],
				   XtNfromVert,
				   (j==0)?NULL:a_input[i*n+j-1],
				   XtNwidth,width,
				   NULL);
      text_transl(temp);
      a_input[i*n+j]=temp;
    }
    sprintf(xin,"x%i",i+1);
    x_output[i]=XtVaCreateManagedWidget("x",asciiTextWidgetClass,x_vector,
					XtNeditType,XawtextRead,
					XtNstring,xin,
					XtNdisplayCaret,False,
					XtNwidth,width,
					NULL);
    temp=XtVaCreateManagedWidget("b",asciiTextWidgetClass,b_vector,
				       XtNeditType,XawtextEdit,
				       XtNwidth,width,
				       NULL);
    text_transl(temp);
    b_input[i]=temp;
  }
  

  XtAddCallback(quit,XtNcallback,quit_app, NULL);
  XtAddCallback(math,XtNcallback,solve, NULL);
  
  XtRealizeWidget(toplevel);
  
  /* I give up, the drawing commands must be
     executed in the main event loop.
     One must have an XtAddCallback in the case
     of an "exposure"
  */
#if 0  /* attempt to draw brackets */
  display=XtDisplay(line);
  window=XtWindow(line);
  /*   window=RootWindowOfScreen(XtScreen(line));*/
  gc = XtGetGC(line,0,NULL);
  /*       p = XCreatePixmap(display, window ,100, 100,
	   DefaultDepthOfScreen(XtScreen(line)));*/
  XSetForeground(display, gc,1);
  XSetBackground(display, gc,0);
  XDrawLine(display, window, gc, 5, 10, 3, 4);
  XDrawRectangle(display, window, gc, 75, 110, 150, 100);
  XDrawArc(display, window, gc, 75, 110, 150, 100, 45*64, 120*64);
  /*       XFreePixmap(display,p);*/
  XFreeGC(display,gc);
  
#endif
  
  
  XtAppMainLoop(app_context); 
  return 0;
}


void quit_app(Widget w, XtPointer client, XtPointer call){
  XtDestroyApplicationContext(app_context);
  free(a_input);
  free(b_input);
  exit(0);
}

/*
  The following routine actually solves the system of
  linear equations using LAPACK routine SGESV.
  Everything is done in single precision (Else, why would you
  be inputting the matrix by hand?).
*/

#include <g2c.h>  /* This is for interfacing with LAPACK routine */

/* Subroutine */ int sgesv_(integer *n, integer *nrhs, real *a, integer *lda, 
			    integer *ipiv, real *b, integer *ldb, integer *info);

void solve(Widget w, XtPointer client, XtPointer call){
  integer nrhs=1,*ipiv,info;
  int i,j;
  float *a,*b;
  String aa;
  char bb[128];
  a=malloc(n*n*sizeof(float));
  b=malloc(n*sizeof(float));
  ipiv=malloc(n*sizeof(integer));
  
  for(i=0; i<n; i++)
    for(j=0; j<n; j++){
      XtVaGetValues(a_input[i*n+j],XtNstring,&aa,NULL);
      if(sscanf(aa,"%f",a+i*n+j)!=1){
	sprintf(bb,"No number entered for a(%i,%i)",j+1,i+1);
	XtVaSetValues(message,XtNstring,bb,NULL);
	goto end;
      }
#if DEBUG
      printf(" i=%i j=%i a_val=%s %g\n",i,j,aa,a[i*n+j]);
#endif
    }
  for(i=0; i<n; i++){
    XtVaGetValues(b_input[i],XtNstring,&aa,NULL);
    if(sscanf(aa,"%f",b+i)!=1){
      sprintf(bb,"No number entered for b(%i)",i+1);
      XtVaSetValues(message,XtNstring,bb,NULL);
      goto end;
    }
#if DEBUG
      printf(" i=%i b_val=%s %g\n",i,aa,b[i]);
#endif
  }
  
  
  sgesv_(&n,&nrhs,a,&n,ipiv,b,&n,&info);
  
  if(info!=0){
    sprintf(bb,"No solution, info=%li\nModify A and b and try again",info);
    XtVaSetValues(message,XtNstring,bb,NULL);
    goto end;
  }
  
  sprintf(bb,"Solution found\nModify A and b and try again");
  XtVaSetValues(message,XtNstring,bb,NULL);
  
#if DEBUG
  printf("info=%li\n",info);
#endif
  for(i=0; i<n; i++){
#if DEBUG
    printf(" %g",b[i]);
#endif
    sprintf(bb,FLOAT_DIGITS,b[i]);
    XtVaSetValues(x_output[i],XtNstring,bb,NULL);
  }
#if DEBUG
  printf("\n");
#endif

 end:
  free(a);
  free(b);
  return;
}