/* See LICENSE file for copyright and license details. */

#include <errno.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#include "config.h"
#include "date.h"
#include "strlcpy.h"

#define BUF_MAX_SIZE 64
#define DATE_SIZE 11 /* 'YYYY-MM-DD\0' */

/* Execution modes */
enum {
	DEF_MODE,
	CHECKIN_MODE,
	CREATE_MODE
};

/* Output formats */
enum {
	LONG_OUT,
	SHORT_OUT
};

/* Auxiliary procedures */
static void die(const char *fmt, ...);
static void usage(void);
static void read_file(char *date, int *num, const char *path);
static void write_file(const char *path, const char *date, int num);

static void
die(const char *fmt, ...)
{
	va_list ap;

	va_start(ap, fmt);

	vfprintf(stderr, fmt, ap);
	fputc('\n', stderr);

	va_end(ap);

	exit(1);
}

static void
usage(void)
{
	die("usage: schain [-krsv] [-cK num] [-w date] [file]");
}

static void
read_file(char *date, int *num, const char *path)
{
	FILE *fp;
	char *ptr;
	char buf[BUF_MAX_SIZE];

	if ((fp = fopen(path, "r")) == NULL)
		die("%s: %s.", path, strerror(errno));
	fgets(buf, BUF_MAX_SIZE, fp);
	fclose(fp);

	ptr = strtok(buf, "\t");
	if (ptr == NULL)
		goto parsedie;

	if (date != NULL)
		strlcpy(date, ptr, DATE_SIZE);

	ptr = strtok(NULL, "\n");
	if (ptr == NULL)
		goto parsedie;

	if (sscanf(ptr, "%d", num) == 0 || *num < 0)
		goto parsedie;

	return;

parsedie:
	die("%s: Not an schain file.", path);
}

static void
write_file(const char *path, const char *date, int num)
{
	FILE *fp;

	if ((fp = fopen(path, "w")) == NULL)
		die("%s: %s.", path, strerror(errno));

	fprintf(fp, "%s\t%d\n", date, num);

	fclose(fp);
}

int
main(int argc, char *argv[])
{
	int opt, mode, out_fmt, num, check_diff;
	const char *filepath;
	char *datearg;
	char date[DATE_SIZE];

	num = 0;
	datearg = NULL;
	check_diff = 1;
	mode = DEF_MODE;
	out_fmt = LONG_OUT;

	while ((opt = getopt(argc, argv, ":krsvc:K:w:")) != -1) {
		switch (opt) {
		case 'k':
			mode = CHECKIN_MODE;
			break;
		case 'r':
			mode = CREATE_MODE;
			num = 0;
			break;
		case 's':
			out_fmt = SHORT_OUT;
			break;
		case 'v':
			die("schain %s", VERSION);
			break; /* UNREACHABLE */
		case 'c':
			mode = CREATE_MODE;
			sscanf(optarg, "%d", &num);
			break;
		case 'K':
			mode = CHECKIN_MODE;
			sscanf(optarg, "%d", &check_diff);
			break;
		case 'w':
			datearg = optarg;
			break;
		default:
			usage();
			break; /* UNREACHABLE */
		}
	}

	if (optind < argc) {
		filepath = argv[optind];
	} else {
		if ((filepath = getenv("SCHAIN_DEF_FILE")) == NULL)
			die("SCHAIN_DEF_FILE environment variable not set.");
	}

	if (num < 0 || check_diff < 0)
		die("Error: not a positive number.");

	if (datearg != NULL) {
		if (strncmp(datearg, "y", DATE_SIZE) == 0)
			strlcpy(date, date_str(time(NULL) - 86400), DATE_SIZE);
		else
			strlcpy(date, datearg, DATE_SIZE);
	} else {
		strlcpy(date, date_str(time(NULL)), DATE_SIZE);
	}

	if (is_date(date) < 0)
		die("Error: not a valid YYYY-MM-DD date.");

	switch (mode) {
	case CREATE_MODE:
		write_file(filepath, date, num);
		break;
	case CHECKIN_MODE:
		read_file(NULL, &num, filepath);
		if (num + check_diff < 0)
			die("Check-in error: count in file too big. Abort.");

		num += check_diff;

		write_file(filepath, date, num);
		break;
	default:
		read_file(date, &num, filepath);
		break;
	}

	if (out_fmt == SHORT_OUT)
		printf("%d\n", num);
	else
		printf("%s: %d %s.\n", date, num, unit);

	return 0;
}