#include <errno.h>
#include <stdio.h>
#include <assert.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <limits.h>
#include <pthread.h>
#include <sys/prctl.h>

#include "utils.h"
#include "snowflake.h"
#include "packet_io.h"
#include "log_private.h"
#include "stellar_stat.h"
#include "stellar_core.h"
#include "stellar_config.h"
#include "packet_private.h"
#include "plugin_manager.h"
#include "session_private.h"
#include "session_manager.h"

#define CORE_LOG_FATAL(format, ...) STELLAR_LOG_FATAL(__thread_local_logger, "core", format, ##__VA_ARGS__)
#define CORE_LOG_ERROR(format, ...) STELLAR_LOG_ERROR(__thread_local_logger, "core", format, ##__VA_ARGS__)
#define CORE_LOG_DEBUG(format, ...) STELLAR_LOG_DEBUG(__thread_local_logger, "core", format, ##__VA_ARGS__)

#ifdef STELLAR_GIT_VERSION
static __attribute__((__used__)) const char *version = STELLAR_GIT_VERSION;
#else
static __attribute__((__used__)) const char *version = "Unknown";
#endif

static const char logo_str[] =
    "        _            _   _\n"
    "  ___  | |_    ___  | | | |   __ _   _ __\n"
    " / __| | __|  / _ \\ | | | |  / _` | | '__|\n"
    " \\__ \\ | |_  |  __/ | | | | | (_| | | |\n"
    " |___/  \\__|  \\___| |_| |_|  \\__,_| |_|\n";

struct stellar_thread
{
    pthread_t tid;
    uint16_t idx;
    uint64_t is_runing;
    uint64_t last_free_expired_session_timestamp;
    uint64_t last_free_expired_ip_frag_timestamp;
    uint64_t last_merge_thread_stat_timestamp;
    struct snowflake *snowflake;
    struct ip_reassembly *ip_mgr;
    struct session_manager *sess_mgr;
    struct stellar *st;
};

struct stellar_runtime
{
    uint64_t need_exit;
    uint64_t stat_last_output_ts;
    struct logger *logger;
    struct stellar_stat *stat;
    struct packet_io *packet_io;
    struct plugin_manager_schema *plug_mgr;
    struct stellar_thread threads[MAX_THREAD_NUM];
};

struct stellar
{
    char stellar_cfg_file[PATH_MAX];
    char plugin_cfg_file[PATH_MAX];
    char log_cfg_file[PATH_MAX];

    struct stellar_runtime runtime;
    struct stellar_config config;
};

static thread_local uint16_t __current_thread_idx = UINT16_MAX;
static thread_local struct snowflake *__current_thread_snowflake = NULL;

uint64_t stellar_generate_session_id(uint64_t now_sec);

/******************************************************************************
 * Stellar Thread Main Loop
 ******************************************************************************/

static void update_session_stat(struct session *sess, struct packet *pkt)
{
    if (sess)
    {
        enum flow_direction dir = session_get_current_flow_direction(sess);
        assert(dir != FLOW_DIRECTION_NONE);
        int is_ctrl = packet_is_ctrl(pkt);
        uint16_t len = packet_get_raw_len(pkt);
        switch (packet_get_action(pkt))
        {
        case PACKET_ACTION_DROP:
            session_inc_stat(sess, dir, (is_ctrl ? STAT_CONTROL_PACKETS_DROPPED : STAT_RAW_PACKETS_DROPPED), 1);
            session_inc_stat(sess, dir, (is_ctrl ? STAT_CONTROL_BYTES_DROPPED : STAT_RAW_BYTES_DROPPED), len);
            break;
        case PACKET_ACTION_FORWARD:
            session_inc_stat(sess, dir, (is_ctrl ? STAT_CONTROL_PACKETS_TRANSMITTED : STAT_RAW_PACKETS_TRANSMITTED), 1);
            session_inc_stat(sess, dir, (is_ctrl ? STAT_CONTROL_BYTES_TRANSMITTED : STAT_RAW_BYTES_TRANSMITTED), len);
            break;
        default:
            assert(0);
            break;
        }

        session_set_current_packet(sess, NULL);
        session_set_current_flow_direction(sess, FLOW_DIRECTION_NONE);
    }
}

static inline void free_evicted_sessions(struct session_manager *sess_mgr, uint64_t max_free)
{
    void *plugin_ctx = NULL;
    struct session *sess = NULL;
    for (uint64_t i = 0; i < max_free; i++)
    {
        sess = session_manager_get_evicted_session(sess_mgr);
        if (sess)
        {
            plugin_ctx = session_get_user_data(sess);
            plugin_manager_on_session_closing(sess);
            plugin_manager_session_runtime_free((struct plugin_manager_runtime *)plugin_ctx);
            session_manager_free_session(sess_mgr, sess);
        }
        else
        {
            break;
        }
    }
}

static inline void free_expired_sessions(struct session_manager *sess_mgr, uint64_t max_free, uint64_t now_ms)
{
    void *plugin_ctx = NULL;
    struct session *sess = NULL;
    for (uint64_t i = 0; i < max_free; i++)
    {
        sess = session_manager_get_expired_session(sess_mgr, now_ms);
        if (sess)
        {
            plugin_ctx = session_get_user_data(sess);
            plugin_manager_on_session_closing(sess);
            plugin_manager_session_runtime_free((struct plugin_manager_runtime *)plugin_ctx);
            session_manager_free_session(sess_mgr, sess);
        }
        else
        {
            break;
        }
    }
}

static inline void merge_thread_stat(struct stellar_thread *thread)
{
    struct stellar *st = thread->st;
    struct stellar_runtime *runtime = &st->runtime;
    struct thread_stat thr_stat = {
        .packet_io = packet_io_stat(runtime->packet_io, thread->idx),
        .ip_reassembly = ip_reassembly_stat(thread->ip_mgr),
        .session_mgr = session_manager_stat(thread->sess_mgr),
    };
    stellar_stat_merge(runtime->stat, &thr_stat, thread->idx);
}

static inline void print_thread_stat(struct stellar_thread *thread)
{
    struct stellar *st = thread->st;
    struct stellar_runtime *runtime = &st->runtime;
    struct thread_stat thr_stat = {
        .packet_io = packet_io_stat(runtime->packet_io, thread->idx),
        .ip_reassembly = ip_reassembly_stat(thread->ip_mgr),
        .session_mgr = session_manager_stat(thread->sess_mgr),
    };
    stellar_stat_print(runtime->stat, &thr_stat, thread->idx);
}

static void *work_thread(void *arg)
{
    int nr_recv;
    uint64_t now_ms = 0;
    char thd_name[16] = {0};
    void *plugin_ctx = NULL;
    struct packet *pkt = NULL;
    struct packet *defraged_pkt = NULL;
    struct packet packets[RX_BURST_MAX];
    struct session *sess = NULL;
    struct stellar_thread *thread = (struct stellar_thread *)arg;
    struct ip_reassembly *ip_reass = thread->ip_mgr;
    struct session_manager *sess_mgr = thread->sess_mgr;
    struct session_manager_stat *sess_stat = session_manager_stat(sess_mgr);
    struct stellar *st = thread->st;
    struct stellar_config *config = &st->config;
    struct stellar_runtime *runtime = &st->runtime;
    struct packet_io *packet_io = runtime->packet_io;
    struct plugin_manager_schema *plug_mgr = runtime->plug_mgr;
    uint64_t free_expired_session_interval = config->sched_opts.free_expired_session_interval;
    uint64_t free_expired_session_batch = config->sched_opts.free_expired_session_batch;
    uint64_t force_session_expire_before_exit = config->sched_opts.force_session_expire_before_exit;
    uint64_t free_expired_ip_frag_interval = config->sched_opts.free_expired_ip_frag_interval;
    uint64_t free_expired_ip_frag_batch = config->sched_opts.free_expired_ip_frag_batch;
    uint64_t merge_stat_interval = config->sched_opts.merge_stat_interval;
    uint64_t packet_io_yield_interval = config->sched_opts.packet_io_yield_interval;
    uint16_t thr_idx = thread->idx;

    __current_thread_idx = thr_idx;
    __thread_local_logger = runtime->logger;
    __current_thread_snowflake = thread->snowflake;

    memset(packets, 0, sizeof(packets));

    for (int i = 0; i < RX_BURST_MAX; i++)
    {
        packet_set_user_data(&packets[i], (void *)plug_mgr);
    }

    snprintf(thd_name, sizeof(thd_name), "stellar:%d", thr_idx);
    prctl(PR_SET_NAME, (unsigned long long)thd_name, NULL, NULL, NULL);

    if (packet_io_init(packet_io, thr_idx) != 0)
    {
        CORE_LOG_ERROR("unable to init packet io");
        return NULL;
    }

    ATOMIC_SET(&thread->is_runing, 1);
    CORE_LOG_FATAL("worker thread %d runing", thr_idx);

    while (ATOMIC_READ(&runtime->need_exit) == 0)
    {
        /*
         * We use the system's real time instead of monotonic time for the following reasons:
         *     -> Session creation/closure times require real time (e.g., for logging session activities).
         *     -> Session ID generation relies on real time        (e.g., for reverse calculating session creation time from the session ID).
         *
         * Note: Modifying the system time will affect the timing wheel, impacting session expiration, IP reassembly expiration, and TCP reassembly expiration.
         * Suggestion: After modifying the system time, restart the service to ensure consistent timing.
         */
        now_ms = clock_get_real_time_ms();
        nr_recv = packet_io_input(packet_io, thr_idx, packets, RX_BURST_MAX);
        if (nr_recv == 0)
        {
            goto idle_tasks;
        }

        for (int i = 0; i < nr_recv; i++)
        {
            sess = NULL;
            defraged_pkt = NULL;
            pkt = &packets[i];

            plugin_manager_on_packet_ingress(plug_mgr, pkt);
            if (packet_is_fragment(pkt))
            {
                defraged_pkt = ip_reassembly_packet(ip_reass, pkt, now_ms);
                if (defraged_pkt == NULL)
                {
                    goto fast_path;
                }
                else
                {
                    pkt = defraged_pkt;
                    plugin_manager_on_packet_ingress(plug_mgr, defraged_pkt);
                }
            }

            sess = session_manager_lookup_session_by_packet(sess_mgr, pkt);
            if (sess == NULL)
            {
                sess = session_manager_new_session(sess_mgr, pkt, now_ms);
                if (sess == NULL)
                {
                    goto fast_path;
                }
                plugin_ctx = plugin_manager_session_runtime_new(plug_mgr, sess);
                session_set_user_data(sess, plugin_ctx);
            }
            else
            {
                if (session_manager_update_session(sess_mgr, sess, pkt, now_ms) == -1)
                {
                    goto fast_path;
                }
            }
            if (packet_get_session_id(pkt) == 0)
            {
                packet_set_session_id(pkt, session_get_id(sess));
            }
            plugin_manager_on_session_ingress(sess, pkt);

        fast_path:
            plugin_manager_on_session_egress(sess, pkt);
            if (pkt == defraged_pkt)
            {
                plugin_manager_on_packet_egress(plug_mgr, defraged_pkt);
                plugin_manager_on_packet_egress(plug_mgr, &packets[i]);
            }
            else
            {
                plugin_manager_on_packet_egress(plug_mgr, pkt);
            }

            if (sess && session_get_current_state(sess) == SESSION_STATE_DISCARD)
            {
                packet_set_action(pkt, PACKET_ACTION_DROP);
            }
            update_session_stat(sess, pkt);
            if (packet_get_action(pkt) == PACKET_ACTION_DROP)
            {
                if (pkt == defraged_pkt)
                {
                    packet_io_drop(packet_io, thr_idx, &packets[i], 1);
                    packet_free(defraged_pkt);
                }
                else
                {
                    packet_io_drop(packet_io, thr_idx, pkt, 1);
                }
            }
            else // PACKET_ACTION_FORWARD
            {
                if (pkt == defraged_pkt)
                {
                    // TODO
                    // copy meta from defraged_pkt to packets[i]
                    packet_io_output(packet_io, thr_idx, &packets[i], 1);
                    packet_free(defraged_pkt);
                }
                else
                {
                    packet_io_output(packet_io, thr_idx, pkt, 1);
                }
            }
        }

    idle_tasks:
        // nr_recv packet atmost trigger nr_recv session evicted
        free_evicted_sessions(sess_mgr, nr_recv);
        plugin_manager_on_polling(plug_mgr);

        // per free_expired_session_interval MAX free_expired_session_batch sessions are released
        if (now_ms - thread->last_free_expired_session_timestamp >= free_expired_session_interval)
        {
            free_expired_sessions(sess_mgr, free_expired_session_batch, now_ms);
            thread->last_free_expired_session_timestamp = now_ms;
        }

        // per merge_stat_interval merge thread stat
        if (now_ms - thread->last_merge_thread_stat_timestamp >= merge_stat_interval)
        {
            merge_thread_stat(thread);
            thread->last_merge_thread_stat_timestamp = now_ms;
        }

        // per free_expired_ip_frag_interval MAX free_expired_ip_frag_batch ip fragments are released
        if (now_ms - thread->last_free_expired_ip_frag_timestamp >= free_expired_ip_frag_interval)
        {
            ip_reassembly_expire(ip_reass, free_expired_ip_frag_batch, now_ms);
            thread->last_free_expired_ip_frag_timestamp = now_ms;
        }

        if (nr_recv == 0)
        {
            packet_io_yield(packet_io, thr_idx, packet_io_yield_interval);
        }
    }

    while (sess_stat->tcp_sess_used > 0 || sess_stat->udp_sess_used > 0)
    {
        // force session expire
        if (force_session_expire_before_exit)
        {
            free_expired_sessions(sess_mgr, free_expired_session_batch, UINT64_MAX);
        }
        // wait session expire
        else
        {
            now_ms = clock_get_real_time_ms();
            free_expired_sessions(sess_mgr, free_expired_session_batch, now_ms);
            usleep(1000); // 1ms
        }
    }

    merge_thread_stat(thread);
    print_thread_stat(thread);

    ATOMIC_SET(&thread->is_runing, 0);
    CORE_LOG_FATAL("worker thread %d exit", thr_idx);

    return NULL;
}

/******************************************************************************
 * Stellar Main Function
 ******************************************************************************/

static int stellar_thread_init(struct stellar *st)
{
    struct stellar_runtime *runtime = &st->runtime;
    struct stellar_config *config = &st->config;

    uint64_t now_ms = clock_get_real_time_ms();
    for (uint16_t i = 0; i < config->pkt_io_opts.nr_threads; i++)
    {
        struct stellar_thread *thread = &runtime->threads[i];
        thread->idx = i;
        thread->is_runing = 0;

        thread->last_free_expired_session_timestamp = now_ms;
        thread->last_free_expired_ip_frag_timestamp = now_ms;
        thread->last_merge_thread_stat_timestamp = now_ms;

        thread->snowflake = snowflake_new(i, config->snowflake_opts.snowflake_base, config->snowflake_opts.snowflake_offset);
        if (thread->snowflake == NULL)
        {
            CORE_LOG_ERROR("unable to create snowflake id generator");
            return -1;
        }
        thread->sess_mgr = session_manager_new(&config->sess_mgr_opts, now_ms);
        if (thread->sess_mgr == NULL)
        {
            CORE_LOG_ERROR("unable to create session manager");
            return -1;
        }
        session_manager_set_session_id_generator(thread->sess_mgr, stellar_generate_session_id);
        thread->ip_mgr = ip_reassembly_new(&config->ip_reass_opts);
        if (thread->ip_mgr == NULL)
        {
            CORE_LOG_ERROR("unable to create ip reassemble manager");
            return -1;
        }
        thread->st = st;
    }

    return 0;
}

static void stellar_thread_clean(struct stellar *st)
{
    struct stellar_runtime *runtime = &st->runtime;
    struct stellar_config *config = &st->config;

    CORE_LOG_FATAL("cleaning worker thread context ...");
    for (uint16_t i = 0; i < config->pkt_io_opts.nr_threads; i++)
    {
        struct stellar_thread *thread = &runtime->threads[i];
        if (ATOMIC_READ(&thread->is_runing) == 0)
        {
            ip_reassembly_free(thread->ip_mgr);
            session_manager_free(thread->sess_mgr);
            snowflake_free(thread->snowflake);
        }
    }
    CORE_LOG_FATAL("worker thread context cleaned");
}

static int stellar_thread_run(struct stellar *st)
{
    struct stellar_runtime *runtime = &st->runtime;
    struct stellar_config *config = &st->config;

    for (uint16_t i = 0; i < config->pkt_io_opts.nr_threads; i++)
    {
        struct stellar_thread *thread = &runtime->threads[i];
        if (pthread_create(&thread->tid, NULL, work_thread, (void *)thread) < 0)
        {
            CORE_LOG_ERROR("unable to create worker thread, error %d: %s", errno, strerror(errno));
            return -1;
        }
    }

    return 0;
}

static void stellar_thread_join(struct stellar *st)
{
    struct stellar_runtime *runtime = &st->runtime;
    struct stellar_config *config = &st->config;

    CORE_LOG_FATAL("waiting worker thread stop ...");
    for (uint16_t i = 0; i < config->pkt_io_opts.nr_threads; i++)
    {
        struct stellar_thread *thread = &runtime->threads[i];
        while (ATOMIC_READ(&thread->is_runing) == 1)
        {
            usleep(1000); // 1ms
        }
    }
    CORE_LOG_FATAL("all worker thread stoped");
}

struct stellar *stellar_new(const char *stellar_cfg_file, const char *plugin_cfg_file, const char *log_cfg_file)
{
    if (stellar_cfg_file == NULL)
    {
        printf("stellar config file is null\n");
        return NULL;
    }
    if (plugin_cfg_file == NULL)
    {
        printf("plugin config file is null\n");
        return NULL;
    }
    if (log_cfg_file == NULL)
    {
        printf("log config file is null\n");
        return NULL;
    }

    struct stellar *st = (struct stellar *)calloc(1, sizeof(struct stellar));
    if (st == NULL)
    {
        return NULL;
    }

    memcpy(st->stellar_cfg_file, stellar_cfg_file, strlen(stellar_cfg_file));
    memcpy(st->plugin_cfg_file, plugin_cfg_file, strlen(plugin_cfg_file));
    memcpy(st->log_cfg_file, log_cfg_file, strlen(log_cfg_file));

    struct stellar_runtime *runtime = &st->runtime;
    struct stellar_config *config = &st->config;

    runtime->logger = log_new(st->log_cfg_file);
    if (runtime->logger == NULL)
    {
        printf("unable to create logger");
        goto error_out;
    }
    __thread_local_logger = runtime->logger;
    CORE_LOG_FATAL("stellar start (version: %s)\n %s", version, logo_str);
    CORE_LOG_FATAL("stellar config file : %s", st->stellar_cfg_file);
    CORE_LOG_FATAL("plugin  config file : %s", st->plugin_cfg_file);
    CORE_LOG_FATAL("log     config file : %s", st->log_cfg_file);

    if (stellar_config_load(config, st->stellar_cfg_file) != 0)
    {
        CORE_LOG_ERROR("unable to load config file");
        goto error_out;
    }
    stellar_config_print(config);

    runtime->stat = stellar_stat_new(config->pkt_io_opts.nr_threads);
    if (runtime->stat == NULL)
    {
        CORE_LOG_ERROR("unable to create stellar stat");
        goto error_out;
    }
    runtime->plug_mgr = plugin_manager_init(st, st->plugin_cfg_file);
    if (runtime->plug_mgr == NULL)
    {
        CORE_LOG_ERROR("unable to create plugin manager");
        goto error_out;
    }

    runtime->packet_io = packet_io_new(&config->pkt_io_opts);
    if (runtime->packet_io == NULL)
    {
        CORE_LOG_ERROR("unable to create packet io");
        goto error_out;
    }

    if (stellar_thread_init(st) != 0)
    {
        CORE_LOG_ERROR("unable to init thread context");
        goto error_out;
    }

    return st;

error_out:
    if (st == NULL)
    {
        stellar_free(st);
        st = NULL;
    }

    return NULL;
}

void stellar_run(struct stellar *st)
{
    if (st == NULL)
    {
        return;
    }

    struct stellar_runtime *runtime = &st->runtime;
    struct stellar_config *config = &st->config;

    if (stellar_thread_run(st) != 0)
    {
        CORE_LOG_ERROR("unable to create worker thread");
        return;
    }

    runtime->stat_last_output_ts = clock_get_real_time_ms();
    while (!ATOMIC_READ(&runtime->need_exit))
    {
        if (clock_get_real_time_ms() - runtime->stat_last_output_ts >= config->sched_opts.output_stat_interval)
        {
            runtime->stat_last_output_ts = clock_get_real_time_ms();
            stellar_stat_output(runtime->stat);
        }
        usleep(1000); // 1ms

        // only available in dumpfile mode
        if (packet_io_isbreak(runtime->packet_io))
        {
            ATOMIC_SET(&runtime->need_exit, 1);
            CORE_LOG_FATAL("notify worker thread to exit");
            stellar_stat_output(runtime->stat); // flush stat
            break;
        }
    }

    stellar_thread_join(st);
    stellar_stat_output(runtime->stat);
}

void stellar_free(struct stellar *st)
{
    if (st)
    {
        struct stellar_runtime *runtime = &st->runtime;

        stellar_thread_clean(st);
        packet_io_free(runtime->packet_io);
        plugin_manager_exit(runtime->plug_mgr);
        stellar_stat_free(runtime->stat);
        CORE_LOG_FATAL("stellar exit\n");
        log_free(runtime->logger);

        free(st);
        st = NULL;
    }
}

void stellar_loopbreak(struct stellar *st)
{
    if (st)
    {
        struct stellar_runtime *runtime = &st->runtime;
        ATOMIC_SET(&runtime->need_exit, 1);
    }
}

void stellar_reload_log_level(struct stellar *st)
{
    if (st)
    {
        log_reload_level(st->runtime.logger);
    }
}

/******************************************************************************
 * Stellar Utility Function
 ******************************************************************************/

struct packet_io *stellar_get_packet_io(const struct stellar *st)
{
    return st->runtime.packet_io;
}

struct plugin_manager_schema *stellar_get_plugin_manager(const struct stellar *st)
{
    return st->runtime.plug_mgr;
}

void stellar_set_plugin_manger(struct stellar *st, struct plugin_manager_schema *plug_mgr)
{
    st->runtime.plug_mgr = plug_mgr;
}

struct session_manager *stellar_get_session_manager(const struct stellar *st)
{
    uint16_t idx = stellar_get_current_thread_index();
    return st->runtime.threads[idx].sess_mgr;
}

uint16_t stellar_get_current_thread_index()
{
    if (__current_thread_idx == UINT16_MAX)
    {
        printf("get current thread index before set\n");
        abort();
        return UINT16_MAX;
    }
    else
    {
        return __current_thread_idx;
    }
}

uint64_t stellar_generate_session_id(uint64_t now_sec)
{
    if (__current_thread_snowflake == NULL)
    {
        printf("get current thread snowflake before set\n");
        abort();
        return 0;
    }
    else
    {
        return snowflake_generate(__current_thread_snowflake, now_sec);
    }
}

// only send user crafted packet, can't send packet which come from network
void stellar_send_build_packet(struct stellar *st, struct packet *pkt)
{
    uint16_t thr_idx = stellar_get_current_thread_index();
    struct packet_io *packet_io = stellar_get_packet_io(st);
    struct session_manager *sess_mgr = stellar_get_session_manager(st);
    session_manager_record_duplicated_packet(sess_mgr, pkt);

    if (packet_get_origin_ctx(pkt))
    {
        // TODO
        abort();
        packet_io_output(packet_io, thr_idx, pkt, 1);
    }
    else
    {
        packet_io_inject(packet_io, thr_idx, pkt, 1);
    }
}

int stellar_get_worker_thread_num(struct stellar *st)
{
    return st->config.pkt_io_opts.nr_threads;
}

struct logger *stellar_get_logger(struct stellar *st)
{
    if (st)
    {
        return st->runtime.logger;
    }
    else
    {
        return NULL;
    }
}