#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/un.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/errno.h>
#include <pthread.h>
#include <assert.h>
#include <event2/listener.h>
#include <event2/util.h>
#include <event2/bufferevent.h>

#include <MESA/MESA_prof_load.h>
#include <tfe_stream.h>
#include <kni_acceptor.h>
#include <proxy.h>
#include <platform.h>

#ifndef TFE_CONFIG_KNI_SCM_SOCKET_FILE
#define TFE_CONFIG_KNI_SCM_SOCKET_FILE            "/var/run/.tfe_kmod_scm_socket"
#endif

/* The KNI and TFE communicate with each other by UNIX-based socket,
 * and the protocol between them is based on TLV format(Type-Length-Value).
 * The byte order for each entry in the protocol are Host-Ordered.
 *
 * I. Magic and Total counts of T-L-V tuples, at front of the SOCKET stream.
 * II. After Magic header, the stream consist of several T-L-V tuples.
 *
 * Note. Magic = 0x4d5a
 * Consider of the byte align problem, the minimum length of the value is 4bytes(32-bits).
 *
 *  0               1               2               3
 *  0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |             Magic             |      Total counts of TLV      |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |              Type             |             Length            |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |                             Value                             |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |              Type             |             Length            |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |                             Value                             |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |                            .......                            |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 */

struct kni_acceptor
{
	/* INPUT */
	struct tfe_proxy * proxy;
	const char * profile;
	void * logger;

	/* CONFIG */
	char str_scm_socket_file[TFE_STRING_MAX];

	/* PERSIST RUNTIME RESOURCE */
	int fd_scm_socket;
	struct event_base * ev_base;
    struct event * ev_scm_socket;
	pthread_t thread;
};

void __kni_event_cb(evutil_socket_t fd, short what, void * user)
{
	struct kni_acceptor * __ctx = (struct kni_acceptor *) user;
	struct cmsghdr * __cmsghdr;
	struct tfe_proxy_accept_para __accept_para{};

	int * __fds = NULL;
	assert(__ctx != NULL && __ctx->thread == pthread_self());
	assert(what & EV_READ);

	/* We use IOVEC to recieve the fds make by KNI.
	 * This is a kind of magic skill to share socket fds between two(or more) process.
     * http://man7.org/tlpi/code/online/dist/sockets/scm_rights_send.c.html
     */

	constexpr static int __TRANS_FDS_MAX = 2;
	constexpr static int __CONTROLLEN = CMSG_SPACE(__TRANS_FDS_MAX * sizeof(int));

	char __buffer[4096] = {0};
	struct iovec __iovec[1];
	struct msghdr __msghdr;

	char __cmptr[__CONTROLLEN];

	__iovec[0].iov_base = __buffer;
	__iovec[0].iov_len = sizeof(__buffer);

	__msghdr.msg_iov = __iovec;
	__msghdr.msg_iovlen = 1;
	__msghdr.msg_name = NULL;
	__msghdr.msg_namelen = 0;
	__msghdr.msg_control = (void *) (__cmptr);
	__msghdr.msg_controllen = (size_t) __CONTROLLEN;

	ssize_t rd = recvmsg(fd, &__msghdr, 0);
	if (rd == -1 && (errno == EINTR || errno == EAGAIN))
	{
		return;
	}
	else if (rd <= 0)
	{
		TFE_LOG_ERROR(__ctx->logger, "failed at recvmsg from scm socket: %s. ", strerror(errno));
		goto __die;
	}

	__cmsghdr = CMSG_FIRSTHDR(&__msghdr);
	if (unlikely(__cmsghdr == NULL))
	{
		TFE_LOG_ERROR(__ctx->logger, "failed at fetch CMSG_FIRSTHDR() from incoming fds.");
		goto __die;
	}
	
	__fds = (int *) (CMSG_DATA(__cmsghdr));
	if (unlikely(__fds == NULL))
	{
		TFE_LOG_ERROR(__ctx->logger, "failed at fetch CMSG_DATA() from incoming fds.");
		goto __die;
	}

#if 0
	if (unlikely(__kni_parse_tlv_data(__ctx, &__accept_para, __buffer, (size_t) rd) < 0))
	{
		TFE_LOG_ERROR(__ctx->logger, "Failed at parsing TLV format, close KNI connection.");
		goto __close_kni_connection;
	}
#endif

	__accept_para.downstream_fd = __fds[0];
	__accept_para.upstream_fd = __fds[1];
	__accept_para.session_type = STREAM_PROTO_SSL;

	TFE_PROXY_STAT_INCREASE(STAT_FD_OPEN_BY_KNI_ACCEPT, 2);
	if (tfe_proxy_fds_accept(__ctx->proxy, &__accept_para) < 0)
	{
		goto __drop_recieved_fds;
	}

	return;

__die:
    DIE("Broken kni scm socket connection, abort.");
    return;

__drop_recieved_fds:
	TFE_PROXY_STAT_INCREASE(STAT_FD_CLOSE_BY_KNI_ACCEPT_FAIL, 2);
	if (__fds != NULL) evutil_closesocket(__fds[0]);
	if (__fds != NULL) evutil_closesocket(__fds[1]);
}

void * kni_acceptor_event_thread_entry(void * args)
{
	struct kni_acceptor * __ctx = (struct kni_acceptor *) args;
	assert(__ctx != NULL && __ctx->thread == pthread_self());

	TFE_LOG_INFO(__ctx->logger, "kni acceptor thread is running.");
	event_base_dispatch(__ctx->ev_base);
	DIE("kni acceptor thread is exited, abort.");
}

void kni_acceptor_deinit(struct kni_acceptor * ctx)
{
	if (ctx != NULL && ctx->ev_base != NULL)
	{
		event_base_free(ctx->ev_base);
	}

	if (ctx != NULL && ctx->fd_scm_socket != 0)
	{
		close(ctx->fd_scm_socket);
	}

	if (ctx != NULL)
	{
		free(ctx);
	}

	return;
}

struct kni_acceptor * kni_acceptor_init(struct tfe_proxy * proxy, const char * profile, void * logger)
{
	struct kni_acceptor * __ctx = ALLOC(struct kni_acceptor, 1);
	struct sockaddr_un __sockaddr_un{};
	int ret = 0;

	__ctx->proxy = proxy;
	__ctx->profile = profile;
	__ctx->logger = logger;

	/* Read the unix domain socket file, this file is used to recieve fds from KNI */
	MESA_load_profile_string_def(profile, "kni", "scm_socket_file", __ctx->str_scm_socket_file,
		sizeof(__ctx->str_scm_socket_file), TFE_CONFIG_KNI_SCM_SOCKET_FILE);

	__sockaddr_un.sun_family = AF_UNIX;
	strncpy(__sockaddr_un.sun_path, __ctx->str_scm_socket_file, sizeof(__sockaddr_un.sun_path));

	/* Create new event base, this event base will be dispatched at separated thread */
	__ctx->ev_base = event_base_new();
	if (unlikely(__ctx->ev_base == NULL))
	{
		TFE_LOG_ERROR(__ctx->logger, "Failed at creating event_base. ");
		goto __errout;
	}

	__ctx->fd_scm_socket = socket(AF_UNIX, SOCK_DGRAM, 0);
	if (unlikely(__ctx->fd_scm_socket < 0))
    {
        TFE_LOG_ERROR(__ctx->logger, "Failed at create scm socket fd: %s", strerror(errno));
        goto __errout;
    }

    ret = connect(__ctx->fd_scm_socket, (struct sockaddr *)&__sockaddr_un, sizeof(__sockaddr_un));
	if (unlikely(ret < 0))
    {
	    TFE_LOG_ERROR(__ctx->logger, "Failed at connecting to %s: %s", __sockaddr_un.sun_path, strerror(errno));
	    goto __errout;
    }

    __ctx->ev_scm_socket = event_new(__ctx->ev_base, __ctx->fd_scm_socket, EV_READ | EV_PERSIST, __kni_event_cb, __ctx);
    if (unlikely(__ctx->ev_scm_socket == NULL))
    {
        TFE_LOG_ERROR(__ctx->logger, "Failed at setup READ event for scm socket fd %d.", __ctx->fd_scm_socket);
        goto __errout;
    }

    ret = event_add(__ctx->ev_scm_socket, NULL);
    if (unlikely(ret < 0))
    {
        TFE_LOG_ERROR(__ctx->logger, "Failed at adding scm socket event to evbase. ");
        goto __errout;
    }

    /* Create a thread to dispatch ctx->evbase */
	ret = pthread_create(&__ctx->thread, NULL, kni_acceptor_event_thread_entry, (void *) __ctx);
	if (unlikely(ret < 0))
	{
		TFE_LOG_ERROR(__ctx->logger, "Failed at creating event thread: %s", strerror(errno));
		goto __errout;
	}

	TFE_LOG_INFO(__ctx->logger, "KNI scm socket file: %s", __ctx->str_scm_socket_file);
	return __ctx;

__errout:
	kni_acceptor_deinit(__ctx);
	return NULL;
}