#include <event2/bufferevent.h>
#include <event2/buffer.h>
#include <event2/event.h>
#include <event2/listener.h>
#include <event2/util.h>

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "klog.h"
#include "file_conf.h"
#include "compat_socket.h"
#include "proxy_proto_v2.h"
#include "route.h"
#include "tcp_route.h"

struct tcp_route_ctx {
	struct event_base *accept_base;
	struct worker *worker;
	const struct route *route;
	struct evconnlistener *listener;
};

typedef struct conn_s {
	struct worker *owner;
	const struct route *route;

	struct bufferevent *client;
	struct bufferevent *upstream;

	struct sockaddr_storage peer_addr;
	socklen_t peer_addr_len;
} conn_t;

struct accepted_client {
	evutil_socket_t fd;
	struct sockaddr_storage peer_addr;
	socklen_t peer_addr_len;
	const struct route *route;
};

static void free_conn(conn_t *conn) {
	if (conn == NULL) {
		return;
	}

	if (conn->client != NULL) {
		bufferevent_free(conn->client);
	}

	if (conn->upstream != NULL) {
		bufferevent_free(conn->upstream);
	}

	free(conn);
}

static void pipe_read_cb(struct bufferevent *src, void *arg) {
	conn_t *conn = arg;

	struct bufferevent *dst;

	if (src == conn->client) {
		dst = conn->upstream;
	} else if (src == conn->upstream) {
		dst = conn->client;
	} else {
		return;
	}

	struct evbuffer *input = bufferevent_get_input(src);
	struct evbuffer *output = bufferevent_get_output(dst);

	evbuffer_add_buffer(output, input);
}

static void event_cb(struct bufferevent *bev, short events, void *arg) {
	conn_t *conn = arg;

	if (events & BEV_EVENT_CONNECTED) {
		bufferevent_enable(conn->client, EV_READ | EV_WRITE);
		bufferevent_enable(conn->upstream, EV_READ | EV_WRITE);
		return;
	}

	if (events & (BEV_EVENT_EOF | BEV_EVENT_ERROR | BEV_EVENT_TIMEOUT)) {
		if (events & BEV_EVENT_ERROR) {
			int err = EVUTIL_SOCKET_ERROR();
			LOG_ERROR("connection error", "err", _LOGV(evutil_socket_error_to_string(err)));
		}

		free_conn(conn);
	}

	(void)bev;
}

static void worker_adopt_client_fd(struct worker *w, struct accepted_client *ac) {
	conn_t *conn = calloc(1, sizeof(*conn));
	if (conn == NULL) {
		evutil_closesocket(ac->fd);
		return;
	}

	const struct route *r = ac->route;

	conn->owner = w;
	conn->route = r;

	conn->peer_addr = ac->peer_addr;
	conn->peer_addr_len = ac->peer_addr_len;

	conn->client = bufferevent_socket_new(w->base, ac->fd, BEV_OPT_CLOSE_ON_FREE);
	conn->upstream = bufferevent_socket_new(w->base, -1, BEV_OPT_CLOSE_ON_FREE);

	if (conn->client == NULL || conn->upstream == NULL) {
		free_conn(conn);
		return;
	}

	bufferevent_setcb(
		conn->client,
		pipe_read_cb,
		NULL,
		event_cb,
		conn
	);

	bufferevent_setcb(
		conn->upstream,
		pipe_read_cb,
		NULL,
		event_cb,
		conn
	);

	struct sockaddr_in upstream_addr;
	memset(&upstream_addr, 0, sizeof(upstream_addr));
	upstream_addr.sin_family = AF_INET;
	upstream_addr.sin_port = htons(r->upstream_port);

	if (inet_pton(AF_INET, r->upstream_host, &upstream_addr.sin_addr) != 1) {
		LOG_ERROR("invalid upstream address");
		free_conn(conn);
		return;
	}

	/*
	 * Do not read from the client yet.
	 *
	 * Otherwise client bytes may be copied into the upstream output buffer
	 * before the PROXY v2 header is queued.
	 */
	bufferevent_disable(conn->client, EV_READ);

	if (bufferevent_socket_connect(
			conn->upstream,
			(struct sockaddr *)&upstream_addr,
			sizeof(upstream_addr)
		) < 0) {
		LOG_ERROR("upstream connect failed");
		free_conn(conn);
		return;
	}

	if (r->send_proxy_v2) {
		struct sockaddr_in local_addr;
		socklen_t local_len = sizeof(local_addr);

		memset(&local_addr, 0, sizeof(local_addr));

		if (getsockname(ac->fd, (struct sockaddr *)&local_addr, &local_len) < 0) {
			perror("getsockname");
			free_conn(conn);
			return;
		}

		if (ac->peer_addr_len <= 0) {
			LOG_ERROR("invalid client address");
			free_conn(conn);
			return;
		}

		if (ac->peer_addr.ss_family != AF_INET ||
			local_addr.sin_family != AF_INET) {
			LOG_ERROR("PROXY v2 currently only supports IPv4 TCP");
			free_conn(conn);
			return;
		}

		int rc = proxy_v2_write_bufferevent(
			conn->upstream,
			(const struct sockaddr *)&ac->peer_addr,
			ac->peer_addr_len,
			(struct sockaddr *)&local_addr,
			local_len,
			SOCK_STREAM
		);

		if (rc < 0) {
			LOG_ERROR("failed to write PROXY v2 header", "err", _LOGV(strerror(-rc)));
			free_conn(conn);
			return;
		}
	}

	bufferevent_enable(conn->client, EV_READ | EV_WRITE);
	bufferevent_enable(conn->upstream, EV_READ | EV_WRITE);
}

static void dispatch_client_fd(struct worker *w, struct accepted_client *ac) {
	worker_adopt_client_fd(w, ac);
}

static void accept_cb(
	struct evconnlistener *listener,
	evutil_socket_t client_fd,
	struct sockaddr *addr,
	int socklen,
	void *arg
) {
	(void)listener;

	struct tcp_route_ctx *ctx = arg;
	struct accepted_client ac = {
		.fd = client_fd,
		.route = ctx->route,
	};

	if (addr != NULL && socklen > 0 && (size_t)socklen <= sizeof(ac.peer_addr)) {
		memcpy(&ac.peer_addr, addr, (size_t)socklen);
		ac.peer_addr_len = (socklen_t)socklen;
	} else {
		LOG_ERROR("invalid accepted client address", "socklen", _LOGV(socklen));
		evutil_closesocket(client_fd);
		return;
	}

	dispatch_client_fd(ctx->worker, &ac);
}

static void accept_error_cb(struct evconnlistener *listener, void *arg) {
	struct event_base *base = arg;
	int err = EVUTIL_SOCKET_ERROR();

	LOG_ERROR("accept error", "err", _LOGV(evutil_socket_error_to_string(err)));

	evconnlistener_free(listener);
	event_base_loopexit(base, NULL);
}

int start_tcp_route(
	struct worker *w,
	const struct route *r,
	struct tcp_route_ctx **out)
{
	struct sockaddr_in listen_addr;
	memset(&listen_addr, 0, sizeof(listen_addr));
	listen_addr.sin_family = AF_INET;
	listen_addr.sin_port = htons(r->listen_port);

	if (inet_pton(AF_INET, r->listen_host, &listen_addr.sin_addr) != 1) {
		LOG_ERROR("invalid listen address", "listen_host", _LOGV(r->listen_host));
		return -EINVAL;
	}

	struct tcp_route_ctx *ctx = calloc(1, sizeof(*ctx));
	if (ctx == NULL) {
		return -ENOMEM;
	}

	ctx->accept_base = w->base;
	ctx->worker = w;
	ctx->route = r;

	ctx->listener = evconnlistener_new_bind(
		ctx->accept_base,
		accept_cb,
		ctx,
		LEV_OPT_CLOSE_ON_FREE | LEV_OPT_REUSEABLE,
		128,
		(struct sockaddr *)&listen_addr,
		sizeof(listen_addr)
	);

	if (ctx->listener == NULL) {
		LOG_ERROR("evconnlistener_new_bind failed");
		free(ctx);
		return -EADDRINUSE;
	}

	evconnlistener_set_error_cb(ctx->listener, accept_error_cb);

	char opts[128];

	route_options_str(r, opts, sizeof(opts));

	LOG_INFO("route started",
		"line", _LOGV(r->line_no),
		"listen_host", _LOGV(r->listen_host),
		"listen_port", _LOGV(r->listen_port),
		"upstream_host", _LOGV(r->upstream_host),
		"upstream_port", _LOGV(r->upstream_port),
		"options", _LOGV(opts[0] ? opts : "")
	);

	*out = ctx;
	return 0;
}

void free_tcp_route(struct tcp_route_ctx *ctx)
{
	if (ctx == NULL) {
		return;
	}

	if (ctx->listener != NULL) {
		evconnlistener_free(ctx->listener);
	}

	free(ctx);
}