/*
   Name- interpolateProfile.c

   Language- C     Type- MAIN

   Version- 1.0    Date-  2/28/2026   Programmer- Mike Pettey (STC)

   Function- This function interpolates a data value to a given pressure.
*/

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

void interpolateProfile(int num_before_levels, float *before_pressures, float *before_data,
                        int num_after_levels, float *after_pressures, float *after_data)
  {
  int   level, index;
  float data_value, t1, t2, p1, p2;

  // Initialize the output array with missing values

  for (level=0; level<num_after_levels; level++)
    after_data[level] = 32768.0;

  // Loop through the pressures. At each level, look for or interpolate
  // a value from the input data.

  for (level=0; level<num_after_levels; level++)
    {
    data_value = -32768.0;
    index = 0;

    while ((data_value == -32768.0) && (index < num_before_levels))
      {
      if (before_pressures[index] == after_pressures[level])
        {
        data_value = before_data[index];
        index = num_before_levels;
        }
      else if (before_pressures[index] > after_pressures[level])
        {
        if (index != 0)
          {
          t1 = before_data[index-1];
          t2 = before_data[index];
          p1 = before_pressures[index-1];
          p2 = before_pressures[index];

          if ((t1 != -32768.0) && (t2 != -32768.0) && (p1 != -32768.0) && (p2 != -32768.0))
            {
            data_value = (float)(t1 + (t2 - t1) / log(p2/p1) * log(after_pressures[level] / p1));
            }
          }

        index = num_before_levels;;
        }
      else
        {
        index++;
        }
      }

    after_data[level] = data_value;
    }
  }

// end of file