/* This is basically tzselect converted to a C program. Unfortunately,
 * the busybox ash shell and awk are not powerful enough to run
 * tzselect.
 *
 * Does not support the POSIX time option.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <ctype.h>


#define TZDIR "/persistent/usr/share/zoneinfo"

#define TZ_COUNTRY_TABLE TZDIR"/iso3166.tab"
#define TZ_ZONE_TABLE    TZDIR"/zone.tab"

static char *continent_list[] = {
	NULL,
#ifdef FULL
	"Africa",
	"Americas",
	"Antarctica",
	"Arctic Ocean",
	"Asia",
	"Atlantic Ocean",
	"Australia",
	"Europe",
	"Indian Ocean",
	"Pacific Ocean",
/*	"none - I want to specify the time zone using the Posix TZ format.", */
#else
	"Americas",
	"Europe",
#endif
};
#define N_CONTINENTS (sizeof(continent_list) / sizeof(char*))
static char *continent_real_list[] = {
	NULL,
#ifdef FULL
	"Africa",
	"America",
	"Antarctica",
	"Arctic",
	"Asia",
	"Atlantic",
	"Australia",
	"Europe",
	"Indian",
	"Pacific",
/* 	"none", */
#else
	"America",
	"Europe",
#endif
};
#define N_REAL_CONTINENTS (sizeof(continent_real_list) / sizeof(char*))


struct country_list {
	char *code;
	char *country;
	int id;
	struct country_list *next;
};
static struct country_list *countries;

struct region_list {
	char *region;
	int id;
	struct region_list *next;
};
static struct region_list *regions;



void new_code(char *code)
{
	static struct country_list *tail;
	static int id;
	struct country_list *c;

	for(c = countries; c; c = c->next)
		if (strcmp(c->code, code) == 0)
			return; /* dup */

	if (!(c = calloc(sizeof(struct country_list), 1)) ||
		!(c->code = strdup(code))) {
		fputs("INTERNAL ERROR: out of memory\n", stderr);
		exit(1);
	}

	c->id = ++id;

	if (tail)
		tail->next = c;
	else
		countries = c;
	tail = c;
}


void add_region(char *region)
{
	static struct region_list *tail;
	static int id;
	struct region_list *r;

	if (!(r = calloc(sizeof(struct region_list), 1)) ||
		!(r->region = strdup(region))) {
		fputs("INTERNAL ERROR: out of memory\n", stderr);
		exit(1);
	}

	r->id = ++id;

	if (tail)
		tail->next = r;
	else
		regions = r;
	tail = r;
}


void file_copy(char *from, char *to)
{
	char cmd[1024];
	int rc;

	sprintf(cmd, "cp %s %s", from, to);

	rc = system(cmd);
	if (rc) {
		fprintf(stderr, "Copy from %s to %s failed\n", from, to);
		exit(1);
	}
}


void file_link(char *from, char *to)
{
	char cmd[1024];
	int rc;

	sprintf(cmd, "ln -s %s %s", from, to);

	rc = system(cmd);
	if (rc) {
		fprintf(stderr, "Soft link from %s to %s failed\n", from, to);
		exit(1);
	}
}


int main(int argc, char *argv[])
{
	FILE *ctfp, *ztfp;
	char str[256], *p;
	char *continent;
	char *code, *country, *region;
	int i, n, line;
	struct country_list *c;
	struct region_list *r;

	if (N_CONTINENTS != N_REAL_CONTINENTS) {
		fputs("INTERNAL ARRAY MISMATCH ERROR\n", stderr);
		exit(1);
	}

	if (!(ctfp= fopen(TZ_COUNTRY_TABLE, "r")) ||
		!(ztfp = fopen(TZ_ZONE_TABLE,"r"))) {
		fputs("time zone files are not set up correctly\n", stderr);
		exit(1);
	}

	fputs("Please identify a location so that time zone rules can be set"
		  " correctly.\n", stderr);

	/* Ask the user for continent or ocean. */
	fputs("Please select a continent or ocean.\n", stderr);

	for (i = 1; i < N_CONTINENTS; ++i)
		printf("%2d) %s\n", i, continent_list[i]);

	do {
		fputs("#? ", stdout); fflush(stdout);

		if (!fgets(str, sizeof(str), stdin)) exit(1);

		i = strtol(str, 0, 0);
		if (i < 1 || i >= N_CONTINENTS)
			fputs("Please enter a number in range.\n", stderr);
	} while(i < 1 || i >= N_CONTINENTS);

	continent = continent_real_list[i];

	/* Get list of names of countries in the continent or ocean. */
	line = 0;
	while(fgets(str, sizeof(str), ztfp)) {
		if ((p = strrchr(str, '\n')) == NULL) {
			fputs("INTERNAL ERROR: String too short!!!\n", stderr);
			exit(1);
		}
		*p = '\0';
		++line;

		if (*str == '#') continue; /* comment */

		code = strtok(str, "\t");
		p = strtok(NULL, "\t");
		country = strtok(NULL, "/");
		region = strtok(NULL, "\t");
		if (!code || !p || !country || !region) {
			fprintf(stderr, "INTERNAL ERROR: bad line %d in zone file\n", line);
			exit(1);
		}

		/* Add the code to the list */
		if (strcmp(country, continent) == 0)
			new_code(code);
	}

	/* Lookup the country codes */
	line = 0;
	while (fgets(str, sizeof(str), ctfp)) {

		if ((p = strrchr(str, '\n')) == NULL) {
			fputs("INTERNAL ERROR: String 2 too short!!!\n", stderr);
			exit(1);
		}
		*p = '\0';
		++line;

		if (*str == '#') continue; /* comment */

		code = strtok(str, "\t");
		country = strtok(NULL, "\t");
		if (!code || !country) {
			fprintf(stderr, "INTERNAL ERROR: bad line %d in country file\n", line);
			exit(1);
		}

		for (c = countries; c; c = c->next)
			if (strcmp(code, c->code) == 0) {
				if (!(c->country = strdup(country))) {
					fputs("INTERNAL ERROR: out of memory\n", stderr);
					exit(1);
				}
				break;
			}
	}

	/* did we get all of them? */
	for (c = countries; c; c = c->next)
		if (c->country == NULL) {
			fprintf(stderr, "Did not match code %s\n", c->code);
			exit(1);
		}

	/* Pick the country */
	fputs("Please select a country.\n", stderr);
	for (i = 0, c = countries; c; c = c->next, ++i) {
		printf("%2d) %-22s", c->id, c->country);
		if ((i % 3) == 2) putchar('\n');
	}
	n = i;
	if ((i % 3)) putchar('\n');

	do {
		fputs("#? ", stdout); fflush(stdout);

		if (!fgets(str, sizeof(str), stdin)) exit(1);

		i = strtol(str, 0, 0);
		if (i < 1 || i > n)
			fputs("Please enter a number in range.\n", stderr);
	} while(i < 1 || i > n);

	for(n = 1, c = countries; n < i; ++n, c = c->next) ;

	/* Now get the regions */
	rewind(ztfp);
	while(fgets(str, sizeof(str), ztfp)) {
		p = strrchr(str, '\n');
		*p = '\0';

		if (*str == '#') continue; /* comment */

		code = strtok(str, "\t");
		p = strtok(NULL, "\t");
		country = strtok(NULL, "/");
		region = strtok(NULL, "\t");

		if (strcmp(code, c->code) == 0)
			add_region(region);
	}

	if (regions->next) {
		/* Pick a region */
		fputs("Please select one of the following"
			  " time zone regions\n", stderr);

		for (i = 0, r = regions; r; r = r->next, ++i) {
			printf("%2d) %-22s", r->id, r->region);
			if ((i % 3) == 2) putchar('\n');
		}
		n = i;
		if ((i % 3)) putchar('\n');

		do {
			fputs("#? ", stdout); fflush(stdout);

			if (!fgets(str, sizeof(str), stdin)) exit(1);

			i = strtol(str, 0, 0);
			if (i < 1 || i > n)
				fputs("Please enter a number in range.\n", stderr);
		} while(i < 1 || i > n);

		for(n = 1, r = regions; n < i; ++n, r = r->next) ;
	} else
		r = regions;

	fclose(ctfp);
	fclose(ztfp);

	/* See if the file exists */
	sprintf(str, TZDIR "/%s/%s", continent, r->region);
	if (access(str, R_OK)) {
		fputs("time zone files are not set up correctly\n", stderr);
		exit(1);
	}

	/* Copy - this allows them to remove the /usr/share/zoneinfo directory. */
	file_copy(str, "/persistent/etc/localtime");
	/* It's ok if this fails. */
	file_link("/persistent/etc/localtime", "/etc/localtime");

	return 0;
}
/*
 * Local Variables:
 * compile-command: "${CROSS_COMPILE}gcc -O3 -Wall timezone.c -o timezone"
 * End:
 */