#include <netinet/in.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <assert.h>

#include <event2/event.h>
#include <event2/listener.h>
#include <event2/bufferevent.h>
#include <event2/bufferevent_ssl.h>
#include <event2/buffer.h>
#include <event2/thread.h>
#include <event2/dns.h>

#include <openssl/ssl.h>
#include <openssl/err.h>
#include <openssl/rand.h>
#include <openssl/x509.h>
#include <openssl/x509v3.h>

#include <tfe_stream.h>
#include <tfe_utils.h>
#include <tfe_future.h>
#include <tfe_plugin.h>

#include <platform.h>
#include <ssl_stream.h>
#include <tcp_stream.h>
#include <proxy.h>

#ifndef TFE_CONFIG_OUTPUT_LIMIT_DEFAULT
#define TFE_CONFIG_OUTPUT_LIMIT_DEFAULT                (1024 * 1024)
#endif

/* forward declaration of libevent callbacks */
static void __stream_bev_readcb(struct bufferevent *, void *);
static void __stream_bev_writecb(struct bufferevent *, void *);
static void __stream_bev_eventcb(struct bufferevent *, short, void *);

/* ====================================================================================================================
 * HELPER FUNCTIONS
 * ===================================================================================================================*/

static inline struct tfe_stream_private * to_stream_private(const struct tfe_stream * stream)
{
	return container_of(stream, struct tfe_stream_private, head);
}

static inline struct tfe_conn_private * __this_conn(struct tfe_stream_private * _stream, enum tfe_conn_dir dir)
{
	return ((dir == CONN_DIR_DOWNSTREAM) ? (_stream->conn_downstream) : (_stream->conn_upstream));
}

static inline struct tfe_conn_private * __peer_conn(struct tfe_stream_private * _stream, enum tfe_conn_dir dir)
{
	return ((dir == CONN_DIR_DOWNSTREAM) ? (_stream->conn_upstream) : (_stream->conn_downstream));
}

static inline enum tfe_conn_dir __bev_dir(struct tfe_stream_private * _stream, struct bufferevent * bev)
{
	return ((bev == _stream->conn_downstream->bev) ? CONN_DIR_DOWNSTREAM : CONN_DIR_UPSTREAM);
}

static inline bool __is_ssl(struct tfe_stream_private * _stream)
{
	return (_stream->session_type == STREAM_PROTO_SSL);
}

/* ====================================================================================================================
 * INTERFACE
 * ===================================================================================================================*/

void tfe_stream_detach(const struct tfe_stream * stream)
{
	struct tfe_stream_private * _stream = to_stream_private(stream);
	int plug_id = _stream->calling_idx;
	_stream->plugin_ctxs[plug_id].state = PLUG_STATE_DETACHED;
	return;
}

int tfe_stream_preempt(const struct tfe_stream * stream)
{
	struct tfe_stream_private * _stream = to_stream_private(stream);
	int plug_id = _stream->calling_idx;
	for (unsigned int i = 0; i < _stream->nr_plugin_ctxs; i++)
	{
		if (_stream->plugin_ctxs[i].state == PLUG_STATE_PREEPTION)
		{
			return -1;
		}
	}
	_stream->plugin_ctxs[plug_id].state = PLUG_STATE_PREEPTION;
	return 0;
}

struct tfe_stream_write_ctx * tfe_stream_write_frag_start(const struct tfe_stream * stream, enum tfe_conn_dir dir)
{
	struct tfe_stream_private * _stream = to_stream_private(stream);
	struct tfe_conn_private * this_conn = __this_conn(_stream, dir);
	struct tfe_conn_private * peer_conn = __peer_conn(_stream, dir);

	if (this_conn->on_writing == 1)
	{
		return NULL;
	}
	this_conn->w_ctx.dir = dir;
	this_conn->w_ctx._stream = _stream;
	this_conn->on_writing = 1;
	bufferevent_disable(peer_conn->bev, EV_READ);
	return &(this_conn->w_ctx);
}

int tfe_stream_write_frag(struct tfe_stream_write_ctx * w_ctx, const unsigned char * data, size_t size)
{
	struct tfe_conn_private * this_conn = __this_conn(w_ctx->_stream, w_ctx->dir);;
	int ret = bufferevent_write(this_conn->bev, data, size);
	return ret;
}
void tfe_stream_write_frag_end(struct tfe_stream_write_ctx * w_ctx)
{
	struct tfe_conn_private * this_conn = __this_conn(w_ctx->_stream, w_ctx->dir);
	struct tfe_conn_private * peer_conn = __peer_conn(w_ctx->_stream, w_ctx->dir);
	this_conn->on_writing = 0;
	bufferevent_enable(peer_conn->bev, EV_READ);
	return;
}

int tfe_stream_write(const struct tfe_stream * stream, enum tfe_conn_dir dir, const unsigned char * data, size_t size)
{
	int ret = 0;
	struct tfe_stream_write_ctx * wctx = tfe_stream_write_frag_start(stream, dir);
	ret = tfe_stream_write_frag(wctx, data, size);
	tfe_stream_write_frag_end(wctx);
	return ret;
}

static tfe_conn_private * __conn_private_create_by_bev(struct tfe_stream_private * stream, struct bufferevent * bev)
{
	struct tfe_conn_private * __conn_private = ALLOC(struct tfe_conn_private, 1);
	__conn_private->bev = bev;
	__conn_private->fd = bufferevent_getfd(bev);

	bufferevent_setcb(__conn_private->bev, __stream_bev_readcb, __stream_bev_writecb, __stream_bev_eventcb, stream);
	bufferevent_enable(__conn_private->bev, EV_READ | EV_WRITE);

	return __conn_private;
}

int tfe_stream_action_set_opt(const struct tfe_stream * stream, enum tfe_stream_action_opt type,
	void * value, size_t size)
{
	struct tfe_stream_private * _stream = to_stream_private(stream);

#define __SAVE_PARAM(what) do {                                        \
    if(size != sizeof(__typeof__(what))) { return -EINVAL; }        \
    else { what = *(__typeof(what) *)value;    } } while(0)            \

	switch (type)
	{
		case ACTION_OPT_FOWARD_BYTES: __SAVE_PARAM(_stream->forward_bytes);
			break;
		case ACTION_OPT_DEFER_BYTES: __SAVE_PARAM(_stream->defer_bytes);
			break;
		case ACTION_OPT_DEFER_TIME_TV: __SAVE_PARAM(_stream->defer_timeval);
			break;
		case ACTION_OPT_DROP_BYTES: __SAVE_PARAM(_stream->drop_bytes);
			break;
	}

#undef __SAVE_PARAM
	return 0;
}

/* ====================================================================================================================
 * CONNECTION STRUCTURE AND OPERATION FUCTIONS
 * ===================================================================================================================*/

evutil_socket_t __conn_private_release_fd(struct tfe_conn_private * conn)
{
	evutil_socket_t __to_release_fd = conn->fd;
	conn->fd = 0;
	return __to_release_fd;
}

static void __conn_private_destory(struct tfe_conn_private * conn)
{
	bufferevent_disable(conn->bev, EV_READ | EV_WRITE);
	bufferevent_free(conn->bev);

	if (conn->fd > 0) evutil_closesocket(conn->fd);
	free(conn);
}

static void __stream_bev_passthrough_readcb(struct bufferevent * bev, void * arg)
{
	struct tfe_stream_private * _stream = (struct tfe_stream_private *) arg;
	struct tfe_conn_private * peer_conn = __peer_conn(_stream, __bev_dir(_stream, bev));

	struct evbuffer * __input_buffer = bufferevent_get_input(bev);
	if (peer_conn == NULL)
	{
		evbuffer_drain(__input_buffer, evbuffer_get_length(__input_buffer));
		return;
	}

	struct evbuffer * __output_buffer = bufferevent_get_output(peer_conn->bev);
	evbuffer_add_buffer(__output_buffer, __input_buffer);
}

static void __stream_bev_passthrough_writecb(struct bufferevent * bev, void * arg)
{
	struct tfe_stream_private * _stream = (struct tfe_stream_private *) arg;
	struct tfe_conn_private ** ref_this_conn{};
	struct tfe_conn_private ** ref_peer_conn{};

	if (__bev_dir(_stream, bev) == CONN_DIR_UPSTREAM)
	{
		ref_this_conn = &_stream->conn_upstream;
		ref_peer_conn = &_stream->conn_downstream;
	}

	if (__bev_dir(_stream, bev) == CONN_DIR_DOWNSTREAM)
	{
		ref_this_conn = &_stream->conn_downstream;
		ref_peer_conn = &_stream->conn_upstream;
	}

	struct evbuffer * __output_buffer = bufferevent_get_output(bev);
	assert(__output_buffer != NULL);

	if (*ref_peer_conn == NULL && evbuffer_get_length(__output_buffer) == 0)
	{
		__conn_private_destory(*ref_this_conn);
		*ref_this_conn = NULL;
	}

	if (*ref_peer_conn == NULL && *ref_this_conn == NULL)
	{
		tfe_stream_destory(_stream);
	}

	return;
}

static void __stream_bev_passthrough_eventcb(struct bufferevent * bev, short events, void * arg)
{
	struct tfe_stream_private * _stream = (struct tfe_stream_private *) arg;
	struct tfe_conn_private ** ref_this_conn{};
	struct tfe_conn_private ** ref_peer_conn{};

	if (__bev_dir(_stream, bev) == CONN_DIR_UPSTREAM)
	{
		ref_this_conn = &_stream->conn_upstream;
		ref_peer_conn = &_stream->conn_downstream;
	}

	if (__bev_dir(_stream, bev) == CONN_DIR_DOWNSTREAM)
	{
		ref_this_conn = &_stream->conn_downstream;
		ref_peer_conn = &_stream->conn_upstream;
	}

	if (events & BEV_EVENT_ERROR || events & BEV_EVENT_EOF)
	{
		if (evbuffer_get_length(bufferevent_get_input(bev)))
		{
			__stream_bev_passthrough_readcb(bev, arg);
		}

		goto __close_connection;
	}

	return;

__close_connection:
	if (*ref_peer_conn != NULL)
	{
		struct bufferevent * __peer_bev = (*ref_peer_conn)->bev;
		struct evbuffer * __peer_output_buffer = bufferevent_get_output(__peer_bev);

		if (evbuffer_get_length(__peer_output_buffer) == 0)
		{
			__conn_private_destory(*ref_peer_conn);
			*ref_peer_conn = NULL;
		}
	}

	if (*ref_this_conn != NULL)
	{
		__conn_private_destory(*ref_this_conn);
		*ref_this_conn = NULL;
	}

	if (*ref_this_conn == NULL && *ref_peer_conn == NULL)
	{
		tfe_stream_destory(_stream);
	}

	return;
}

/*
 * Callback for read events on the up- and downstream connection bufferevents.
 * Called when there is data ready in the input evbuffer.
 */

static void __stream_bev_readcb(struct bufferevent * bev, void * arg)
{
	struct tfe_stream_private * _stream = (struct tfe_stream_private *) arg;
	enum tfe_conn_dir dir = __bev_dir(_stream, bev);
	struct tfe_conn_private * peer_conn = __peer_conn(_stream, dir);

	enum tfe_stream_action action_tmp = ACTION_FORWARD_DATA;
	enum tfe_stream_action action_final = ACTION_FORWARD_DATA;

	struct evbuffer * inbuf = bufferevent_get_input(bev);
	struct evbuffer * outbuf = bufferevent_get_output(peer_conn->bev);

	size_t drain_size = 0;
	size_t contigous_len = evbuffer_get_length(inbuf);
	const unsigned char * contiguous_data = (const unsigned char *) evbuffer_pullup(inbuf, contigous_len);

	_stream->defer_bytes = 0;
	_stream->drop_bytes = 0;
	_stream->forward_bytes = 0;

	unsigned int plugin_id_iter = 0;
	unsigned int plugin_id = 0;

	for (const struct tfe_plugin * p_info_iter = tfe_plugin_iterate(&plugin_id_iter);
		 p_info_iter != NULL; p_info_iter = tfe_plugin_iterate(&plugin_id_iter))
	{
		_stream->calling_idx = plugin_id;
		struct plugin_ctx * plug_ctx = &_stream->plugin_ctxs[plugin_id];

		if (_stream->is_plugin_opened == 0)
		{
			p_info_iter->on_open(&_stream->head, _stream->thread_ref->thread_id, dir, &(plug_ctx->pme));
			_stream->is_plugin_opened = 1;
		}
		else
		{
			action_tmp = p_info_iter->on_data(&_stream->head, _stream->thread_ref->thread_id,
				dir, contiguous_data, contigous_len, &(plug_ctx->pme));
		}

		if (plug_ctx->state == PLUG_STATE_PREEPTION)
		{
			action_final = action_tmp;
		}

		plugin_id++;
	}

	switch (action_final)
	{
		case ACTION_FORWARD_DATA:
			if (_stream->forward_bytes > 0)
			{
				evbuffer_remove_buffer(inbuf, outbuf, _stream->forward_bytes);
			}
			else
			{
				evbuffer_add_buffer(outbuf, inbuf);
			}
			break;

		case ACTION_DROP_DATA:
			if (_stream->drop_bytes > 0)
			{
				drain_size = _stream->drop_bytes;
			}
			else
			{
				drain_size = evbuffer_get_length(inbuf);
			}
			evbuffer_drain(inbuf, drain_size);
			break;

		case ACTION_DEFER_DATA:
			if (_stream->defer_bytes > 0)
			{
				bufferevent_setwatermark(bev, EV_WRITE, _stream->defer_bytes, 0);
			}
			break;
		default: assert(0);
			break;
	}

	if (evbuffer_get_length(inbuf) != 0)
	{
		bufferevent_trigger(bev, EV_READ, BEV_OPT_DEFER_CALLBACKS);
	}

	if (evbuffer_get_length(outbuf) >= TFE_CONFIG_OUTPUT_LIMIT_DEFAULT)
	{
		bufferevent_setwatermark(peer_conn->bev, EV_WRITE,
			TFE_CONFIG_OUTPUT_LIMIT_DEFAULT / 2, TFE_CONFIG_OUTPUT_LIMIT_DEFAULT);
		bufferevent_disable(bev, EV_READ);
	}

	return;
}

/*
 * Callback for write events on the up- and downstream connection bufferevents.
 * Called when either all data from the output evbuffer has been written,
 * or if the outbuf is only half full again after having been full.
 */
static void __stream_bev_writecb(struct bufferevent * bev, void * arg)
{
	struct tfe_stream_private * _stream = (struct tfe_stream_private *) arg;
	enum tfe_conn_dir dir = __bev_dir(_stream, bev);
	struct tfe_conn_private * peer_conn = __peer_conn(_stream, dir);

//	struct evbuffer * outbuf = bufferevent_get_output(bev);

	if (peer_conn->bev && !(bufferevent_get_enabled(peer_conn->bev) & EV_READ))
	{
		/* data source temporarily disabled;
		 * re-enable and reset watermark to 0. */
		bufferevent_setwatermark(bev, EV_WRITE, 0, 0);
		bufferevent_enable(peer_conn->bev, EV_READ);
	}
}

/*
 * Callback for meta events on the up- and downstream connection bufferevents.
 * Called when EOF has been reached, a connection has been made, and on errors.
 */
static void __stream_bev_eventcb(struct bufferevent * bev, short events, void * arg)
{
	struct tfe_stream_private * _stream = (struct tfe_stream_private *) arg;
	enum tfe_conn_dir dir = __bev_dir(_stream, bev);
	struct tfe_conn_private * this_conn = __this_conn(_stream, dir);
	struct tfe_conn_private * peer_conn = __peer_conn(_stream, dir);

	const struct tfe_plugin * plugins = _stream->thread_ref->modules;
	struct plugin_ctx * plug_ctx = NULL;
	int plug_num = _stream->thread_ref->nr_modules, i = 0;
	enum tfe_stream_close_reason reason = REASON_PASSIVE_CLOSED;

	if (events & BEV_EVENT_ERROR)
	{
		this_conn->closed = 1;
		reason = REASON_ERROR;
		if (__is_ssl(_stream))
		{
			ssl_stream_log_error(bev, dir, __STREAM_LOGGER(_stream));
		}
		goto call_plugin_close;
	}

	if (events & BEV_EVENT_EOF)
	{
		//generate a 0 size read callback to notify plugins.
		__stream_bev_readcb(bev, arg);
		this_conn->closed = 1;
	}

	if (peer_conn->closed == 1 && this_conn->closed == 1)
	{
		reason = REASON_PASSIVE_CLOSED;
		goto call_plugin_close;
	}
	return;

call_plugin_close:
	for (i = 0; i < plug_num; i++)
	{
		_stream->calling_idx = i;
		plug_ctx = _stream->plugin_ctxs + i;
		plugins[i].on_close(&(_stream->head), _stream->thread_ref->thread_id, reason, &(plug_ctx->pme));
	}

	tfe_stream_destory(_stream);
	return;
}

static tfe_conn_private * __conn_private_create_by_fd(struct tfe_stream_private * stream, evutil_socket_t fd)
{
	struct tfe_conn_private * __conn_private = ALLOC(struct tfe_conn_private, 1);
	struct event_base * __ev_base = stream->thread_ref->evbase;

	__conn_private->bev = bufferevent_socket_new(__ev_base, fd, BEV_OPT_DEFER_CALLBACKS);
	__conn_private->fd = fd;

	if (!__conn_private->bev)
	{
		TFE_LOG_ERROR(__STREAM_LOGGER(stream), "Failed at creating bufferevent for fd %d", fd);
		goto __errout;
	}

	if (stream->passthough)
	{
		bufferevent_setcb(__conn_private->bev, __stream_bev_passthrough_readcb,
			__stream_bev_passthrough_writecb, __stream_bev_passthrough_eventcb, stream);
	}
	else
	{
		bufferevent_setcb(__conn_private->bev, __stream_bev_readcb,
			__stream_bev_writecb, __stream_bev_eventcb, stream);
	}

	return __conn_private;

__errout:
	if (__conn_private != NULL) free(__conn_private);
	return NULL;
}

void __conn_private_enable(struct tfe_conn_private * conn_private)
{
	assert(conn_private != NULL && conn_private->bev != NULL);
	bufferevent_enable(conn_private->bev, EV_READ | EV_WRITE);
}

void ssl_downstream_create_on_success(future_result_t * result, void * user)
{
	struct tfe_stream_private * _stream = (struct tfe_stream_private *) user;
	struct ssl_stream * downstream = ssl_downstream_create_result_release_stream(result);
	struct bufferevent * bev = ssl_downstream_create_result_release_bev(result);

	_stream->conn_downstream = __conn_private_create_by_bev(_stream, bev);
	_stream->ssl_downstream = downstream;

	future_destroy(_stream->future_downstream_create);
	_stream->future_downstream_create = NULL;
	_stream->defer_fd_downstream = 0;

	assert(_stream->conn_downstream != NULL && _stream->conn_upstream != NULL);
	__conn_private_enable(_stream->conn_downstream);
	__conn_private_enable(_stream->conn_upstream);

	return;
}

void ssl_downstream_create_on_fail(enum e_future_error err, const char * what, void * user)
{
	return;
}

void ssl_upstream_create_on_success(future_result_t * result, void * user)
{
	struct tfe_stream_private * _stream = (struct tfe_stream_private *) user;
	struct event_base * ev_base = _stream->thread_ref->evbase;

	struct ssl_stream * upstream = ssl_upstream_create_result_release_stream(result);
	struct bufferevent * bev = ssl_upstream_create_result_release_bev(result);
	assert(upstream != NULL && bev != NULL);

	/* Create connection ctx by bev */
	_stream->conn_upstream = __conn_private_create_by_bev(_stream, bev);
	_stream->ssl_upstream = upstream;

	future_destroy(_stream->future_upstream_create);
	_stream->future_upstream_create = NULL;
	_stream->defer_fd_upstream = 0;

	/* Next, create downstream */
	_stream->future_downstream_create = future_create("ssl_down", ssl_downstream_create_on_success,
		ssl_downstream_create_on_fail, _stream);

	ssl_async_downstream_create(_stream->future_downstream_create, _stream->ssl_mgr,
		_stream->ssl_upstream, _stream->defer_fd_downstream, /* KEYRING ID */ 0, ev_base);
}

void ssl_upstream_create_on_fail(enum e_future_error err, const char * what, void * user)
{
	assert(0);
}

struct tfe_stream * tfe_stream_create(struct tfe_proxy * pxy, struct tfe_thread_ctx * thread_ctx)
{
	struct tfe_stream_private * _stream = ALLOC(struct tfe_stream_private, 1);
	_stream->thread_ref = thread_ctx;
	_stream->proxy_ref = pxy;

	unsigned int total_plugin_count = tfe_plugin_total_counts();
	_stream->plugin_ctxs = ALLOC(struct plugin_ctx, total_plugin_count);
	return (struct tfe_stream *) &_stream->head;
}

void tfe_stream_destory(struct tfe_stream_private * stream)
{
	struct tfe_thread_ctx * thread = stream->thread_ref;
	struct event_base * ev_base = thread->evbase;

	if (__is_ssl(stream) && stream->ssl_upstream)
	{
		evutil_socket_t __to_closed_fd = __conn_private_release_fd(stream->conn_upstream);
		ssl_stream_free_and_close_fd(stream->ssl_upstream, ev_base, __to_closed_fd);
	}

	if (__is_ssl(stream) && stream->ssl_downstream)
	{
		evutil_socket_t __to_closed_fd = __conn_private_release_fd(stream->conn_downstream);
		ssl_stream_free_and_close_fd(stream->ssl_downstream, ev_base, __to_closed_fd);
	}

	if (stream->conn_upstream)
	{
		__conn_private_destory(stream->conn_upstream);
	}

	if (stream->conn_downstream)
	{
		__conn_private_destory(stream->conn_downstream);
	}

	if (stream->defer_fd_downstream)
	{
		evutil_closesocket(stream->defer_fd_downstream);
	}

	if (stream->defer_fd_upstream)
	{
		evutil_closesocket(stream->defer_fd_upstream);
	}

	if (stream->future_downstream_create)
	{
		future_destroy(stream->future_downstream_create);
	}

	if (stream->future_upstream_create)
	{
		future_destroy(stream->future_upstream_create);
	}
	stream->proxy_ref = NULL;
	free(stream);
	thread->load--;
}

void tfe_stream_init_by_fds(struct tfe_stream * stream, evutil_socket_t fd_downstream, evutil_socket_t fd_upstream)
{
	struct tfe_stream_private * _stream = container_of(stream, struct tfe_stream_private, head);
	struct event_base * ev_base = _stream->thread_ref->evbase;

	_stream->defer_fd_downstream = fd_downstream;
	_stream->defer_fd_upstream = fd_upstream;

	evutil_make_socket_nonblocking(fd_downstream);
	evutil_make_socket_nonblocking(fd_upstream);

	if (_stream->session_type == STREAM_PROTO_PLAIN)
	{
		_stream->conn_downstream = __conn_private_create_by_fd(_stream, fd_downstream);
		_stream->conn_upstream = __conn_private_create_by_fd(_stream, fd_upstream);

		assert(_stream->conn_downstream != NULL);
		assert(_stream->conn_upstream != NULL);

		__conn_private_enable(_stream->conn_downstream);
		__conn_private_enable(_stream->conn_upstream);
	}

	if (_stream->session_type == STREAM_PROTO_SSL)
	{
		_stream->ssl_mgr = _stream->proxy_ref->ssl_mgr_handler;

		_stream->future_upstream_create = future_create("ssl_up",
			ssl_upstream_create_on_success, ssl_upstream_create_on_fail, (void *) _stream);

		/* Defer setup conn_downstream & conn_upstream in async callbacks. */
		ssl_async_upstream_create(_stream->future_upstream_create,
			_stream->ssl_mgr, fd_upstream, fd_downstream, ev_base);
	}

	return;
}

int tfe_stream_option_set(struct tfe_stream * stream, enum tfe_stream_option opt, const void * arg, size_t sz_arg)
{
	struct tfe_stream_private * _stream = container_of(stream, struct tfe_stream_private, head);

	if (opt == TFE_STREAM_OPT_SESSION_TYPE)
	{
		assert(sz_arg == sizeof(enum tfe_stream_proto));
		_stream->session_type = *(enum tfe_stream_proto *) arg;
	}
	else if (opt == TFE_STREAM_OPT_PASSTHROUGH)
	{
		assert(sz_arg == sizeof(bool));
		_stream->passthough = *(bool *) arg;
	}

	return 0;
}