kwh-cost/src/main.c

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

#include "main.h"

int main(int argc, char **argv) {
    arguments_t * args = parse_arguments(argc, argv);

    printf("%.2Lf\n", (args->price * args->wattage) * args->interval);

    free(args);
    return 0;
}

arguments_t * parse_arguments(int argc, char **argv) {
    if (argc == 1) {
        print_usage();
        exit(0);
    }

    arguments_t *args = (arguments_t *)calloc(1, sizeof(arguments_t));
    int pos_args_pos = 0;

    for (int i = 1; i < argc; ++i) {
        if (argv[i][0] == '-') {
            if (argv[i][1] == 'h' || argv[i][2] == 'h') {
                print_usage();
                exit(0);
            } else if (argv[i][1] == 'v' || argv[i][2] == 'v') {
                print_version();
                exit(0);
            }
        } else if (pos_args_pos == 0) {
            args->price = to_wattpersecond((price_t)atof(argv[i]));
            pos_args_pos++;
        } else if (pos_args_pos == 1) {
            args->wattage = atof(argv[i]);
            pos_args_pos++;
        } else if (pos_args_pos > 1) {
            args->interval += to_seconds(argv[i]);
            pos_args_pos++;
        }
    }

    if (pos_args_pos < 3) {
        print_usage();
        exit(1);
    }

    return args;
}

interval_t to_seconds(char *interval) {
    interval_t intrvl = (interval_t)atol(interval);
    char unit = interval[strlen(interval) - 1];

    if (!(unit >= '0' && unit <= '9'))
        switch (unit) {
            case 'm':
            case 'M':
                return intrvl * 60;
            case 'h':
            case 'H':
                return intrvl * 60 * 60;
            case 'd':
            case 'D':
                return intrvl * 60 * 60 * 24;
        }
    return intrvl;
}

inline price_t to_wattpersecond(price_t price) {
    return price / 1000.f / 3600.f;
}

void print_version() {
    puts("kwh-calc Ver. " VERSION "\n"
           "Copyright (C) 2021 Alexander \"Arav\" Andreev <me@arav.top>. All rights reserved.\n"
           "License for this program is stored in /usr/share/licenses/kwh-calc/LICENSE.");
}

void print_usage() {
    puts("Usage: kwh-calc [options] price wattage interval [interval ...]\n"
           "Options:\n"
           "  --help, -h    Display this usage information.\n"
           "  --version, -v Display program version.\n"
           "Arguments:\n"
           "  price    Price per kWh.\n"
           "  wattage  Specify power usage in Watts.\n"
           "  interval Time interval in seconds total cost to be calculated for.\n"
           "           You may specify other time units such as:\n"
           "           m'imute, h'our, d'ay. Example: 5d 3h.\n"
           "           All given intervals will be summed up.");
}