/*
Copyright (C) 2017 Paweł Redman

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 3
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA
*/

#include "shared.h"
#include <netdb.h> // reverse DNS

static job_t *job_queue;
static pthread_cond_t job_queue_cond = PTHREAD_COND_INITIALIZER;
static pthread_mutex_t job_queue_mutex = PTHREAD_MUTEX_INITIALIZER;
static int job_quit_flag = 0;

job_t *job_create(job_type_t type, db_entry *entry)
{
	job_t *job;

	job = calloc(1, sizeof(job_t));
	if (!job) {
		fprintf(stderr, "job_create: calloc failed\n");
		abort();
	}

	job->type = type;
	job->entry = entry;

	return job;
}

void job_destroy(job_t *job)
{
	free(job);
}

void job_enqueue(job_t *job)
{
	pthread_mutex_lock(&job_queue_mutex);
	eli_append(&job_queue, job, queue_list);
	pthread_mutex_unlock(&job_queue_mutex);
	pthread_cond_signal(&job_queue_cond);
}

// FIXME: bad name
void job_quit(void)
{
	pthread_mutex_lock(&job_queue_mutex);
	job_quit_flag = 1;
	pthread_mutex_unlock(&job_queue_mutex);
	pthread_cond_broadcast(&job_queue_cond);
}

// FIXME: refactor with vstrs
static int read_everything(FILE *fp, char **buffer)
{
	size_t read = 0, alloc = 128, partial;

	alloc = 128;
	*buffer = malloc(alloc);
	if (!*buffer)
		goto oom;

	while (1) {
		size_t left = alloc - read;

		if (left == 0) {
			alloc *= 2;
			*buffer = realloc(*buffer, alloc);
			if (!buffer)
				goto oom;

			continue;
		}

		partial = fread((*buffer) + read, 1, left, fp);
		if (partial == 0) {
			if (ferror(fp))
				return 1;

			break;
		}

		read += partial;
	}


	*buffer = realloc(*buffer, read + 1);
	(*buffer)[read] = '\0';
	return 0;

oom:
	fprintf(stderr, "read_everything: out of memory\n");
	abort();
}

// Check if the database entry is complete (all fields are DB_VALID).
// If it is then enqueue all of its waiting jobs.
static void check_waiting_jobs(db_entry *entry)
{
	job_t *job;

	if (entry->revdns.state != DB_VALID
	    || entry->whois.state != DB_VALID)
		return;

	eli_for(job, entry->waiting_jobs, waiting_list)
		job_enqueue(job);

	entry->waiting_jobs = NULL;
}

// Update an entry's field and call check_waiting_jobs.
static void update_entry(db_entry *entry, db_entry_field *field, char *data)
{
	pthread_mutex_lock(&entry->mutex);

	field->state = DB_VALID;
	free(field->data);
	field->data = data;
	field->exp_time = get_time() + 24 * TIME_HOUR;

	// invalidate the result cache
	entry->cached_result_valid = false;

	check_waiting_jobs(entry);

	pthread_mutex_unlock(&entry->mutex);
}

// This job is queued when both WHOIS and revDNS data is available.
// It calls lists_test and sends back the result. 
static void worker_job_reply(job_t *job)
{
	int result;
	char reply[1000];

	pthread_mutex_lock(&job->entry->mutex);

	if (!job->entry->cached_result_valid) {
		DEBUG("result cache miss for %08X\n", job->ipv4);
		result = lists_test(job->entry->revdns.data,
		                    job->entry->whois.data);

		job->entry->cached_result_valid = true;
		job->entry->cached_result = result;
	} else
		result = job->entry->cached_result;

	pthread_mutex_unlock(&job->entry->mutex);

	snprintf(reply, sizeof(reply), "%s%hhu.%hhu.%hhu.%hhu %i\n",
	         RESPONSE_HEADER,
	         (job->ipv4 >> 24) & 0xFF, (job->ipv4 >> 16) & 0xFF,
	         (job->ipv4 >> 8) & 0xFF, job->ipv4 & 0xFF, result);
	// FIXME: handle sendto errors
	sendto(server_sockfd, reply, strlen(reply), 0, (void*)&job->ret_addr,
	       sizeof(job->ret_addr));

	DEBUG("reply %08X %i\n", job->ipv4, result);
}

// This job makes a revDNS query and stores it in the database.
static void worker_job_revdns(job_t *job)
{
	struct sockaddr_in addr;
	char buffer[NI_MAXHOST], *revdns;
	int rv;

	DEBUG("getnameinfo(%08X, ...)\n", job->ipv4);

	addr.sin_family = AF_INET;
	addr.sin_addr.s_addr = htonl(job->ipv4);
	addr.sin_port = 0;

	rv = getnameinfo((void*)&addr, sizeof(addr), buffer, sizeof(buffer),
	                 NULL, 0, NI_NAMEREQD);
	switch (rv) {
	case 0:
		revdns = strdup(buffer);
		break;

	case EAI_NONAME:
		// FIXME: handle errors and missing revDNS entries better
		revdns = strdup("<none>");
		break;

	case EAI_SYSTEM:
		revdns = strdup("<error>");
		perror("getnameinfo");
		break;

	default:
		revdns = strdup("<error>");
		fprintf(stderr, "getnameinfo: %s\n", gai_strerror(rv));
		break;
	}

	update_entry(job->entry, &job->entry->revdns, revdns);
}

// This job makes a WHOIS query and stores it in the database.
static void worker_job_whois(job_t *job)
{
	char command[80];
	FILE *fp;
	char *out;

	snprintf(command, sizeof(command), "whois \"%hhu.%hhu.%hhu.%hhu\"",
	         (job->ipv4 >> 24) & 0xFF, (job->ipv4 >> 16) & 0xFF,
	         (job->ipv4 >> 8) & 0xFF, job->ipv4 & 0xFF);
	DEBUG("%s\n", command);

	fp = popen(command, "r");
	read_everything(fp, &out); // FIXME: handle errors
	fclose(fp);

	update_entry(job->entry, &job->entry->whois, out);
}

void *worker_main(void *unused)
{
	for (;;) {
		job_t *job;

		pthread_mutex_lock(&job_queue_mutex);
		while (!job_queue && !job_quit_flag)
			pthread_cond_wait(&job_queue_cond, &job_queue_mutex);

		if (job_quit_flag) {
			pthread_mutex_unlock(&job_queue_mutex);
			DEBUG("quitting\n");
			return NULL;
		}

		job = job_queue;
		eli_unlink(&job_queue, job, queue_list);
		pthread_mutex_unlock(&job_queue_mutex);

		switch (job->type) {
		case JOB_REPLY:
			worker_job_reply(job);
			break;

		case JOB_REVDNS:
			worker_job_revdns(job);
			break;

		case JOB_WHOIS:
			worker_job_whois(job);
			break;
		}

		job_destroy(job);
	}
}