//
// Simple filter to average every N input lines.
//
//  - Assumes one data point per line.
//  - Displays output with same precision as input.
//

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

long SkipCount = 0;
long Window = 1;

void main (int argc, char *argv[])
{
    long In, Out, Index;
    char Line[1000];
    int Dp = 0;
    void MaxDp (char *p, int *dp);
    double Sum, Value;

    if (argc > 1 && strcmp(argv[1], "/?") == 0) {
        fprintf(stderr, "%s [Window] [skip]\n", argv[0]);
        exit(0);
    }

    if (argc > 1) {
        sscanf(argv[1], "%ld", &Window);
        if (Window < 1) {
            Window = 1;
        }
    }

    if (argc > 2) {
        sscanf(argv[2], "%ld", &SkipCount);
        if (SkipCount < 0) {
            SkipCount = 0;
        }
    }

    In = Out = Index = 0;
    Sum = 0.0;

    while (1) {
        if (fgets(Line, sizeof(Line), stdin) == NULL) {
            break;
        }
        In += 1;

        if (In > SkipCount) {
            MaxDp(Line, &Dp);
            sscanf(Line, "%lf", &Value);
            Sum += Value;
            Index += 1;
            if (Index == Window) {
                printf("%.*lf\n", Dp, Sum / (double)Window);
                Out += 1;
                Index = 0;
                Sum = 0.0;
            }
        }
    }

    fprintf(stderr, "%ld lines in, %ld lines skipped, %ld lines out, %ld lines left\n",
            In, SkipCount, Out, Index);

    return;
}

//
// Recalculate maximum number of decimal places.
//

void MaxDp (char *p, int *dp)
{
    int n = 0;

    p = strchr(p, '.');
    if (p) {
        for (p++; *p != '\0'; p++, n++) {
            if (*p < '0' || *p > '9') {
                break;
            }
        }
    }
    if (n > *dp) {
        *dp = n;
    }

    return;
}