/* --------------------------------------------------------------------- 
**  Figure 17.13:  2D point transformation - main program.
**  Figure 17.14:  Reading and displaying the data.
**  Figure 17.15:  The transformation.
** --------------------------------------------------------------------- 
*/
#include "tools.h"

#define MAXPOINTS 10                  /* maximum number of points */
#define DIM 2                         /* points are 2D */

typedef double point [DIM];           /* type point is 2D array */
typedef point object [MAXPOINTS];     /* an object is many points */

typedef double vector [DIM];          /* vector is for translation */
typedef double matrix [DIM][DIM];     /* matrix is for rotation */

int read_points( object obj );
void display_points( object obj1, object obj2, int numpts );
void get_transform( matrix R, vector t );
void transform_point( point p, matrix R, vector t, point newp );

void main( void )
{
  object old_obj, new_obj;            /* points sets before and after */
  vector translation;                 /* transformation movement */
  matrix rotation;                    /* transformation rotation matrix */
  int num_points;                     /* actual number of points */
  int k;                              /* loop counter */

  banner();
  puts( "Welcome to the 2D point transformation program" );

  num_points = read_points( old_obj );    /* input points and transform */
  get_transform( rotation, translation );
                                          /* rotate and translate pts */
  for (k = 0; k < num_points; k++)
    transform_point( old_obj[k], rotation, translation, new_obj[k] );

  display_points( old_obj, new_obj, num_points ); /* print result table */
  bye();
}

/* ---------------------------------------------------------------------  
** Read (x,y) coordinates of point set from indicated data file. Read as  
** many points as are in file or until data array is full.                
*/
int 
read_points ( object obj )
{
    char filename[80];                /* name of data file */
    stream f_in;                      /* input stream to read data */
    int count;                        /* number of data values read */
    int k;                            /* loop counter */

    printf( "\nPlease enter name of file containing object points: " );
    scanf( "%79s", filename);
    f_in = fopen( filename, "r" );    /* open file in read mode */

    if (f_in == NULL) 
       fatal( "Cannot open file %s for input.", filename );

    /* read data points until array is full, end of file or error occurs */
    for ( k = 0; k < MAXPOINTS; k++ ) {
        count = fscanf( f_in, "%lg %lg", &obj[k][0], &obj[k][1] );

        if (count != 2)                    /* if bad read */
            if (feof( f_in )) break;       /* End of file -- leave loop. */
            else fatal( "Error reading file %s", filename );
    }

    fclose(f_in);
    return k;
}

/* ---------------------------------------------------------------------  
**  Print out old point and new point coordinates in a table.             
*/
void 
display_points ( object obj1, object obj2, int numpts )
{
  int k;                          /* loop counter */

  puts ( "\n\t Transformation of coordinates \n");  
  puts ( "Pt\t  Old X\t  Old Y\t\t  New X\t  New Y" );

  for ( k = 0; k < numpts; k++ )          /* put both points on one line */
      printf( "%2i \t%7.2f %7.2f \t%7.2f %7.2f\n", 
              k+1, obj1[k][0], obj1[k][1], obj2[k][0], obj2[k][1] );
}

/* ---------------------------------------------------------------------  
**  Input rotation angle and translation vector for transform from user.   
**  Compute components of rotation matrix assuming ccw rotation angle.    
*/
void 
get_transform ( matrix R, vector t )
{
  double theta;                        /* rotation angle */

  for (;;) {                           /* read rotation angle */
     printf( "Please enter number of degrees to rotate object counterclockwise: " );
     scanf( "%lg", &theta );

     if (theta >= 0 && theta <= 360) break;

     puts( "Error: Angle must be in the range 0 - 360 degrees" );
  }

  theta = PI * theta / 180.0;     /* convert angle to radians for math */

  R[0][0] = cos( theta );         /* compute rotation matrix elements */
  R[0][1] = -sin( theta );
  R[1][0] = sin( theta );
  R[1][1] = cos( theta );

  printf ( "Please enter the translation amount ( X, Y ): " );
  scanf( "%lg %lg", &t[0], &t[1] );
}

/* ---------------------------------------------------------------------  
** Apply rotation and translation transforms to p and return new point.    
*/
void 
transform_point ( point p, matrix R, vector t, point newp )
{
  int r, c;                         /* loop counters */

  for (r = 0; r < DIM; ++r) {       /* multiply each row by point for new */
    for (newp[r] = 0, c = 0; c < DIM; ++c)              /* do dot product */
      newp[r] += R[r][c] * p[c];
  }

  for (r = 0; r < DIM; ++r)         /* add translation vector to point    */
    newp[r] += t[r];
}