/*
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 * 
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following disclaimer
 *   in the documentation and/or other materials provided with the
 *   distribution.
 * * Neither the name of the  nor the names of its
 *   contributors may be used to endorse or promote products derived from
 *   this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * 
 */

/*
 * parametry
 * -v delsi vypis
 * -s simple - usporny vypis
 * -l[label] vlastni nadpis
 * -p vypis v procentech
 */

#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <getopt.h>
#include <string.h>
#include <strings.h>

#define MAX_LABEL_LENGTH 32
#define MEMORY_INFO_PERCENT 1
#define MEMORY_INFO_VERBOSE 2

static void show_help(void)
{
	puts("parametry:");
	puts("  -p  zobrazi hodnoty v procentech");
	puts("  -v  podrobnejsi vypis");
	puts("  -s  kratky vypis");
	puts("  -l <nadpis>");
}

static int print_output(const char *szlabel, uint_fast32_t params)
{
	FILE *pfile = fopen("/proc/meminfo", "r");
	if (NULL == pfile) {
		printf("ERROR");
		return EXIT_FAILURE;
	}
	char line[256];
	unsigned int mem_total = 0;
	unsigned int mem_avail = 0;
	unsigned int swap_total = 0;
	unsigned int swap_free = 0;
	unsigned int end = 0;
	while (fgets(line, sizeof(line), pfile)) {
		if (sscanf(line, "MemTotal: %u kB", &mem_total) == 1) {
			end |= 1;
			continue;
		}
		if (sscanf(line, "MemAvailable: %u kB", &mem_avail) == 1) {
			end |= 2;
			continue;
		}
		if (sscanf(line, "SwapTotal: %u kB", &swap_total) == 1) {
			end |= 4;
			continue;
		}
		if (sscanf(line, "SwapFree: %u kB", &swap_free) == 1) {
			end |= 8;
			continue;
		}
		if (0xF == end)
			break;
	}
	fclose(pfile);
	if (0 == mem_total)
		return EXIT_FAILURE;
	char sztext[32];
	char outbuff[64 + MAX_LABEL_LENGTH];
	*sztext = 0;
	*outbuff = 0;
	if ((NULL != szlabel) && (*szlabel != 0)) {
		strncat(outbuff, szlabel,
			sizeof(outbuff) - strlen(outbuff) - 1);
		strncat(outbuff, " ", sizeof(outbuff) - strlen(outbuff) - 1);
	}
	if (MEMORY_INFO_PERCENT & params) {
		sprintf(sztext, "%u", 100*(mem_total - mem_avail) / mem_total);
		strncat(sztext, "%", sizeof(outbuff) - strlen(outbuff) - 1);
	} 
	else {
		sprintf(sztext, (MEMORY_INFO_VERBOSE & params) ? "%.2f GiB" :  "%.2f",
			(double)(mem_total - mem_avail) / (1024 * 1024));
	}
	strncat(outbuff, sztext, sizeof(outbuff) - strlen(outbuff) - 1);
	if (0 == swap_total)
		return EXIT_SUCCESS;
	if (MEMORY_INFO_PERCENT & params) {
		sprintf(sztext, " %u", 100*(swap_total - swap_free) / swap_total);
		strncat(sztext, "%", sizeof(outbuff) - strlen(outbuff) - 1);
	}
	else
		sprintf(sztext, (MEMORY_INFO_VERBOSE & params) ? " - %.2f GiB" : " %.2f G",
			(double)(swap_total - swap_free) / (1024 * 1024));
	strncat(outbuff, sztext, sizeof(outbuff) - strlen(outbuff) - 1);
	puts(outbuff);
	return EXIT_SUCCESS;
}

int main(int argc, char **argv)
{
	int opt;
	uint_fast32_t params = 0;
	char szlabel[MAX_LABEL_LENGTH];
	*szlabel = 0;
	if (argc > 1) {
		while ((opt = getopt(argc, argv, "vsphl:")) != -1) {
			switch (opt) {
			case 'l':
				if (strlen(optarg) <= sizeof(szlabel) - 1)
					strncpy(szlabel, optarg,
						sizeof(szlabel) - strlen(szlabel) - 1);
				break;
			case 'p':
				params |= MEMORY_INFO_PERCENT;
				break;
			case 's':
				params &= ~MEMORY_INFO_VERBOSE;
				break;
			case 'v':
				params |= MEMORY_INFO_VERBOSE;
				break;
			case 'h':
				show_help();
				return EXIT_SUCCESS;
				break;
			}
		}
	}
	return print_output(szlabel, params);
}