#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <time.h>
#include <sys/stat.h>
#include <string.h>
#include <pthread.h>
#include "fscomch.h"

cancelToken_t init_cancel_token_timeout(int seconds) {
	cancelToken_t token;
	token.timeout = seconds;
	token.value = calloc(1, sizeof(char));
	pthread_t cancelTimer;
	cancelToken_t* memToken = malloc(sizeof(cancelToken_t));
	*memToken = token;
	pthread_create(&cancelTimer, NULL, cancel_in_secs, (void*)memToken);
	return token;
}
cancelToken_t init_cancel_token_never() {
	cancelToken_t token;
	token.timeout = -1;
	token.value = NULL;
	return token;
}
match_t init_match(char* uuid, FILE* streamIn, FILE* streamOut) {
	match_t match;
	match.uuid = uuid;
	match.streamIn = streamIn;
	match.streamOut = streamOut;
	return match;
}
void destroy_match(match_t match) {
	free(match.uuid);
	fclose(match.streamIn);
	fclose(match.streamOut);
}
FILE* try_lock_match() {
	mkdir("/tmp/chess/", 0777);
	mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
	int fd = open("/tmp/chess/match", O_RDONLY | O_CREAT | O_EXCL, mode);
	if (fd == -1) {
		return NULL;
	}
	return fdopen(fd, "r");
}
match_t await_match(FILE* matchFile, cancelToken_t cancelToken) {
	/* await match UUID */
	char* uuid = calloc(37, sizeof(char));
	while (cancelToken.value == NULL || !*cancelToken.value) {
		if (fgets(uuid, 37, matchFile) != NULL) {
			break;
		}
		fseek(matchFile, 0, SEEK_SET);
		struct timespec req;
		req.tv_sec = 0;
		req.tv_nsec = awaitMatchNs;
		nanosleep(&req, NULL);
	}
	/* connect to streams */
	char aName[256];
	char bName[256];
	snprintf(aName, 256, "/tmp/chess/%s.a", uuid);
	snprintf(bName, 256, "/tmp/chess/%s.b", uuid);
	FILE* streamIn = fopen(aName, "r");
	FILE* streamOut = fopen(bName, "a");
	/* connection complete, delete the match file and the join lock */
	remove("/tmp/chess/match");
	remove("/tmp/chess/matchjoin");
	match_t match = init_match(uuid, streamIn, streamOut);
	send_message("ping", match);
	return match;
}
match_t join_match() {
	/* create a join lock so that no one else can join this match */
	mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
	int fd = open("/tmp/chess/matchjoin", O_WRONLY | O_CREAT | O_EXCL, mode);
	if (fd == -1) {
		/* another process is in the process of joining this game */
		match_t match;
		return match;
	}
	close(fd);
	/* this is definitely the only process joining the game
	proceed to generate a uuid */
	char* uuid = make_uuid();
	/* create and connect to streams */
	char aName[256];
	char bName[256];
	snprintf(aName, 256, "/tmp/chess/%s.a", uuid);
	snprintf(bName, 256, "/tmp/chess/%s.b", uuid);
	FILE* streamIn = fopen(bName, "w+");
	FILE* streamOut = fopen(aName, "a");
	match_t match = init_match(uuid, streamIn, streamOut);
	/* send uuid to the host */
	FILE* matchFile = fopen("/tmp/chess/match", "a");
	fputs(uuid, matchFile);
	fclose(matchFile);
	/* handshake */
	cancelToken_t token = init_cancel_token_timeout(2);
	char* message = read_message(match, token);
	if (message != NULL) {
		if (strcmp(message, "ping") == 0) {
			return match;
		}
		else {
			printf("Extreme de-sync. Aborting\n");
			exit(1);
		}
	}
	printf("Host is dead. Cleaning up\n");
	fclose(streamIn);
	fclose(streamOut);
	remove("/tmp/chess/match");
	remove("/tmp/chess/matchjoin");
	remove(aName);
	remove(bName);
	exit(1);
}
void send_message(char* content, match_t match) {
	fprintf(match.streamOut, "%s\n", content);
	fflush(match.streamOut);
}
char* read_message(match_t match, cancelToken_t cancelToken) {
	char* buffer = calloc(256, sizeof(char));
	while (cancelToken.value == NULL || !*cancelToken.value) {
		if (fgets(buffer, 256, match.streamIn) != NULL) {
			break;
		}
		/* wtf? */
		fseek(match.streamIn, ftell(match.streamIn), SEEK_SET);
		struct timespec req;
		req.tv_sec = 0;
		req.tv_nsec = awaitMoveNs;
		nanosleep(&req, NULL);
	}
	/* if we cancelled via token, return NULL */
	if (cancelToken.value != NULL && *cancelToken.value == 1) {
		free(buffer);
		return NULL;
	}
	/* overwrite potential newline */
	buffer[strlen(buffer) - 1] = '\0';
	return buffer;
}
char* make_uuid() {
	char sym[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', 'a', 'b', 'c', 'd', 'e', 'f'};
	char* out = calloc(37, sizeof(char));
	srand(time(NULL));
	for (int i = 0; i < 36; i++) {
		if (i == 8 || i == 13 || i == 18 || i == 23) {
			out[i] = '-';
		}
		else {
			out[i] = sym[rand() % 16];
		}
	}
	out[37] = '\0';
	return out;
}
void* cancel_in_secs(void* token) {
	sleep(((cancelToken_t*)token)->timeout);
	*(((cancelToken_t*)token)->value) = 1;
	free(token);
}