/* snapshot.c: Functions for taking snapshots of a 1D grid. */

#include "fdtd3.h"

static int temporalStride = 0, spatialStride, startTime,
  startNode, endNode, frame = 0;
static char basename[80];

void snapshotInit(Grid *g) { 
  
  printf("For the snapshots:\n");
  printf("  Duration of simulation is %d steps.\n", MaxTime);
  printf("  Enter start time and temporal stride: ");
  scanf(" %d %d", &startTime, &temporalStride);
  printf("  Grid has %d total nodes (ranging from 0 to %d).\n",
	 SizeX, SizeX-1);
  printf("  Enter first node, last node, and spatial stride: ");
  scanf(" %d %d %d", &startNode, &endNode, &spatialStride);
  printf("  Enter the base name: ");
  scanf(" %s", basename);

  return;
}

void snapshot(Grid *g) { 
  int mm;
  char filename[100];
  FILE *snapshot;

  /* ensure temporal stride set to a reasonable value */
  if (temporalStride <= 0) {
    fprintf(stderr,
      "snapshot: snapshotInit must be called before snapshot.\n"
      "          Temporal stride must be set to positive value.\n");
    exit(-1);
  }

  /* get snapshot if temporal conditions met */
  if (Time >= startTime && 
      (Time - startTime) % temporalStride == 0) {
    sprintf(filename, "%s.%d", basename, frame++);
    snapshot = fopen(filename, "w");
    for (mm = startNode; mm <= endNode; mm += spatialStride)
      fprintf(snapshot, "%g\n", Ez(mm));
    fclose(snapshot);
  }

  return;
}