/* $Id$ */

#include <arpa/inet.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <assert.h>
#include <event.h>
#include "list.h"
#include "parser.h"
#include "log.h"
#include "main.h"
#include "base.h"
#include "redsocks.h"


#define THE_ANSWER_TO_THE_ULTIMATE_QUESTION_OF_LIFE_THE_UNIVERSE_AND_EVERYTHING 42

#define REDSOCKS_RELAY_HALFBUFF  4096


/** simple fcntl(2) wrapper, provides errno and all logging to caller
 * I have to use it in event-driven code because of accept(2) (see NOTES)
 * and connect(2) (see ERRORS about EINPROGRESS)
 */
static int fcntl_nonblock(int fd)
{
	int error;
	int flags;
   
	flags = fcntl(fd, F_GETFL);
	if (flags == -1)
		return -1;

	error = fcntl(fd, F_SETFL, flags | O_NONBLOCK);
	if (error)
		return -1;

	return 0;
}

extern relay_subsys http_connect_subsys;
extern relay_subsys socks4_subsys;
extern relay_subsys socks5_subsys;
static relay_subsys *relay_subsystems[] = 
{
	&http_connect_subsys,
	&socks4_subsys,
	&socks5_subsys,
};

static redsocks_instance instance = 
{ // almost NULL-initializer
	.clients = LIST_HEAD_INIT(instance.clients)
};

static parser_entry redsocks_entries[] = 
{
	{ .key = "local_ip",   .type = pt_uint16,  .addr = &instance.config.bindaddr.sin_addr },
	{ .key = "local_port", .type = pt_uint16,  .addr = &instance.config.bindaddr.sin_port },
	{ .key = "ip",         .type = pt_in_addr, .addr = &instance.config.relayaddr.sin_addr },
	{ .key = "port",       .type = pt_uint16,  .addr = &instance.config.relayaddr.sin_port },
	{ .key = "type",       .type = pt_pchar,   .addr = &instance.config.type },
	{ .key = "login",      .type = pt_pchar,   .addr = &instance.config.login },
	{ .key = "password",   .type = pt_pchar,   .addr = &instance.config.password },
	{ }
};

static int redsocks_onenter(parser_section *section)
{
	if (instance.config.type) {
		parser_error(section->context, "only one instance of redsocks is valid");
		return -1;
	}
	instance.config.bindaddr.sin_family = AF_INET;
	instance.config.bindaddr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
	instance.config.relayaddr.sin_family = AF_INET;
	instance.config.relayaddr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
	return 0;
}

static int redsocks_onexit(parser_section *section)
{
	const char *err = NULL;
	instance.config.bindaddr.sin_port = htons(instance.config.bindaddr.sin_port);
	instance.config.relayaddr.sin_port = htons(instance.config.relayaddr.sin_port);
	
	if (instance.config.type) {
		relay_subsys **ss;
		FOREACH(ss, relay_subsystems) {
			if (!strcmp((*ss)->name, instance.config.type)) {
				instance.relay_ss = *ss;
				break;
			}
		}
		if (!instance.relay_ss)
			err = "invalid `type` for redsocks";
	}
	else {
		err = "no `type` for redsocks";
	}
	
	if (err)
		parser_error(section->context, err);

	return err ? -1 : 0;
}

static parser_section redsocks_conf_section = 
{ 
	.name    = "redsocks", 
	.entries = redsocks_entries, 
	.onenter = redsocks_onenter, 
	.onexit  = redsocks_onexit
};

static void redsocks_relay_readcb(struct bufferevent *from, struct bufferevent *to)
{
	// debug: log_error("to->output->off: %i, from->input->off: %i", to->output->off, from->input->off);
	if (EVBUFFER_LENGTH(to->output) < to->wm_write.high) {
		// debug: log_error("\"%.20s\"...", from->input->buffer);
		bufferevent_write_buffer(to, from->input);
	}
	else {
		bufferevent_disable(from, EV_READ);
		// debug: log_error("source reading disable");
	}
}

static void redsocks_relay_writecb(struct bufferevent *from, struct bufferevent *to)
{
	// debug: log_error("to->output->off: %i, from->input->off: %i", to->output->off, from->input->off);
	if (EVBUFFER_LENGTH(to->output) < to->wm_write.high) {
		// debug: log_error("\"%.20s\"...", from->input->buffer);
		bufferevent_write_buffer(to, from->input);
		bufferevent_enable(from, EV_READ);
	}
}


static void redsocks_relay_relayreadcb(struct bufferevent *from, void *_client)
{
	redsocks_client *client = _client;
	// debug: log_error("");
	redsocks_relay_readcb(client->relay, client->client);
}

static void redsocks_relay_relaywritecb(struct bufferevent *to, void *_client)
{
	redsocks_client *client = _client;
	// debug: log_error("");
	redsocks_relay_writecb(client->client, client->relay);
}

static void redsocks_relay_clientreadcb(struct bufferevent *from, void *_client)
{
	redsocks_client *client = _client;
	// debug: log_error("");
	redsocks_relay_readcb(client->client, client->relay);
}

static void redsocks_relay_clientwritecb(struct bufferevent *to, void *_client)
{
	redsocks_client *client = _client;
	// debug: log_error("");
	redsocks_relay_writecb(client->relay, client->client);
}

void redsocks_start_relay(redsocks_client *client)
{
	int error;
	
	client->relay->wm_read.low = 0;
	client->relay->wm_write.low = 0;
	client->client->wm_read.low = 0;
	client->client->wm_write.low = 0;
	client->relay->wm_read.high = REDSOCKS_RELAY_HALFBUFF;
	client->relay->wm_write.high = REDSOCKS_RELAY_HALFBUFF;
	client->client->wm_read.high = REDSOCKS_RELAY_HALFBUFF;
	client->client->wm_write.high = REDSOCKS_RELAY_HALFBUFF;
	
	client->client->readcb = redsocks_relay_clientreadcb;
	client->client->writecb = redsocks_relay_clientwritecb;
	client->relay->readcb = redsocks_relay_relayreadcb;
	client->relay->writecb = redsocks_relay_relaywritecb;
	
	error = bufferevent_enable(client->client, EV_READ | EV_WRITE);
	if (!error)
		error = bufferevent_enable(client->relay, EV_READ | EV_WRITE);
	if (error) {
		log_errno("bufferevent_enable");
		redsocks_drop_client(client);
	}
}

void redsocks_drop_client(redsocks_client *client)
{
	close(EVENT_FD(&client->client->ev_write));
	close(EVENT_FD(&client->relay->ev_write));
	bufferevent_free(client->client);
	bufferevent_free(client->relay);
	list_del(&client->list);
	free(client);
}

static void redsocks_client_error(struct bufferevent *bufev, short what, void *_arg)
{
	redsocks_client *client = _arg;
	// TODO: EVBUFFER_READ, EVBUFFER_WRITE, EVBUFFER_EOF, EVBUFFER_ERROR, EVBUFFER_TIMEOUT
	if ( (what & EVBUFFER_EOF) == 0 )
		log_error("some error");
	redsocks_drop_client(client);
}

static void redsocks_relay_error(struct bufferevent *bufev, short what, void *_arg)
{
	redsocks_client *client = _arg;
	// TODO: EVBUFFER_READ, EVBUFFER_WRITE, EVBUFFER_EOF, EVBUFFER_ERROR, EVBUFFER_TIMEOUT
	if ( (what & EVBUFFER_EOF) == 0 )
		log_error("some error");
	redsocks_drop_client(client);
}

int sizes_equal(size_t a, size_t b) 
{
	return a == b;
}

int sizes_greater_equal(size_t a, size_t b) 
{
	return a >= b;
}

int redsocks_read_expected(redsocks_client *client, struct evbuffer *input, void *data, size_comparator comparator, size_t expected)
{
	size_t len = EVBUFFER_LENGTH(input);
	if (comparator(len, expected)) {
		int read = evbuffer_remove(input, data, expected);
		assert(read == expected);
		return 0;
	}
	else {
		log_error("Socks server has gone away...");
		redsocks_drop_client(client);
		return -1;
	}
}

struct evbuffer *mkevbuffer(void *data, size_t len)
{
	struct evbuffer *buff = NULL, *retval = NULL;

	buff = evbuffer_new();
	if (!buff) {
		log_errno("evbuffer_new");
		goto fail;
	}

	if (evbuffer_add(buff, data, len) < 0) {
		log_errno("evbuffer_add");
		goto fail;
	}

	retval = buff;
	buff = NULL;

fail:
	if (buff)
		evbuffer_free(buff);
	return retval;
}

void redsocks_write_helper_ex(
	struct bufferevent *buffev, redsocks_client *client,
	redsocks_message_maker mkmessage, int state, size_t wm_low, size_t wm_high)
{
	int len;
	struct evbuffer *buff = NULL;
	int drop = 1;
	
	if (mkmessage) {
		buff = mkmessage(client);
		if (!buff)
			goto fail;
		
		len = bufferevent_write_buffer(client->relay, buff);
		if (len < 0) {
			log_errno("bufferevent_write_buffer");
			goto fail;
		}
	}

	client->state = state;
	buffev->wm_read.low = wm_low;
	buffev->wm_read.high = wm_high;
	bufferevent_enable(buffev, EV_READ);
	drop = 0;
	
fail:
	if (buff)
		evbuffer_free(buff);
	if (drop)
		redsocks_drop_client(client);
}

void redsocks_write_helper(
	struct bufferevent *buffev, redsocks_client *client,
	redsocks_message_maker mkmessage, int state, size_t wm_only)
{
	redsocks_write_helper_ex(buffev, client, mkmessage, state, wm_only, wm_only);
}

static void redsocks_relay_connected(struct bufferevent *buffev, void *_arg)
{
	redsocks_client *client = _arg;
	int error;
	int pseudo_errno;
	socklen_t optlen = sizeof(pseudo_errno);

	error = getsockopt(EVENT_FD(&buffev->ev_write), SOL_SOCKET, SO_ERROR, &pseudo_errno, &optlen);
	if (error) {
		log_errno("getsockopt");
		goto fail;
	}

	if (pseudo_errno) {
		errno = pseudo_errno;
		log_errno("connect");
		goto fail;
	}

	client->relay->readcb = client->instance->relay_ss->readcb;
	client->relay->writecb = client->instance->relay_ss->writecb;
	client->relay->writecb(buffev, _arg);
	return;

fail:
	redsocks_relay_error(buffev, EVBUFFER_WRITE | EVBUFFER_ERROR, _arg);
}

static void redsocks_accept_client(int fd, short what, void *_arg)
{
	redsocks_instance *self = _arg;
	redsocks_client   *client = NULL;
	struct sockaddr_in clientaddr;
	struct sockaddr_in destaddr;
	socklen_t          addrlen = sizeof(clientaddr);
	int client_fd = -1;
	int relay_fd = -1;
	int error;
	
	// working with client_fd
	client_fd = accept(fd, (struct sockaddr*)&clientaddr, &addrlen);
	if (client_fd == -1) {
		log_errno("accept");
		goto fail;
	}

	error = getdestaddr(client_fd, &clientaddr, &self->config.bindaddr, &destaddr);
	if (error) {
		goto fail;
	}

	// working with relay_fd
	relay_fd = socket(AF_INET, SOCK_STREAM, 0);
	if (relay_fd == -1) {
		log_errno("socket");
		goto fail;
	}

	error = fcntl_nonblock(relay_fd);
	if (error) {
		log_errno("fcntl");
		goto fail;
	}

	error = connect(relay_fd, (struct sockaddr*)&self->config.relayaddr, sizeof(self->config.relayaddr));
	if (error && errno != EINPROGRESS) {
		log_errno("connect");
		goto fail;
	}

	// everything seems to be ok, let's allocate some memory
	client = calloc(1, sizeof(redsocks_client) + self->relay_ss->payload_len);
	if (!client) {
		log_errno("calloc");
		goto fail;
	}
	client->instance = self;
	memcpy(&client->clientaddr, &clientaddr, sizeof(clientaddr));
	memcpy(&client->destaddr, &destaddr, sizeof(destaddr));
	INIT_LIST_HEAD(&client->list);
	self->relay_ss->init(client);
	
	client->client = bufferevent_new(client_fd, NULL, NULL, redsocks_client_error, client);
	if (!client->client) {
		log_errno("bufferevent_new");
		goto fail;
	}

	client->relay = bufferevent_new(relay_fd, NULL, redsocks_relay_connected, redsocks_relay_error, client);
	if (!client->client) {
		log_errno("bufferevent_new");
		goto fail;
	}

	error = bufferevent_enable(client->relay, EV_WRITE); // we wait for connection...
	if (error) {
		log_errno("bufferevent_enable");
		goto fail;
	}

	list_add(&client->list, &self->clients);
	return;

fail:
	if (client) {
		if (client->client)
			bufferevent_free(client->client);
		if (client->relay)
			bufferevent_free(client->relay);
		free(client);
	}
	if (relay_fd != -1)
		close(relay_fd);
	if (client_fd != -1)
		close(client_fd);
}

static int redsocks_init()
{
	int error;
	int on = 1;
	int fd = -1;

	fd = socket(AF_INET, SOCK_STREAM, 0);
	if (fd == -1) {
		log_errno("socket");
		return -1;
	}

	error = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
	if (error) {
		log_errno("setsockopt");
		goto fail;
	}

	error = bind(fd, (struct sockaddr*)&instance.config.bindaddr, sizeof(instance.config.bindaddr));
	if (error) {
		log_errno("bind");
		goto fail;
	}

	error = fcntl_nonblock(fd);
	if (error) {
		log_errno("fcntl");
		goto fail;
	}

	error = listen(fd, THE_ANSWER_TO_THE_ULTIMATE_QUESTION_OF_LIFE_THE_UNIVERSE_AND_EVERYTHING); // does anyone know better value?
	if (error) {
		log_errno("listen");
		goto fail;
	}

	event_set(&instance.listener, fd, EV_READ | EV_PERSIST, redsocks_accept_client, &instance);
	error = event_add(&instance.listener, NULL);
	if (error) {
		log_errno("event_add");
		goto fail;
	}
	
	return 0;
fail:
	if (event_initialized(&instance.listener)) {
		event_del(&instance.listener);
		memset(&instance.listener, 0, sizeof(instance.listener));
	}

	if (fd != -1) {
		close(fd);
	}
	return -1;
}

static int redsocks_fini()
{
	if (event_initialized(&instance.listener)) {
		event_del(&instance.listener);
		close(EVENT_FD(&instance.listener));
		memset(&instance.listener, 0, sizeof(instance.listener));
	}
	return 0;
}

app_subsys redsocks_subsys = 
{
	.init = redsocks_init,
	.fini = redsocks_fini,
	.conf_section = &redsocks_conf_section,
};



/* vim:set tabstop=4 softtabstop=4 shiftwidth=4: */
/* vim:set foldmethod=marker foldlevel=32 foldmarker={,}: */