/**
 * @file dummynet.c
 * @brief Реализация UDP dummynet эмулятора
 */

#include "dummynet.h"
#include "../lib/u_async.h"
#include "../lib/ll_queue.h"
#include "../lib/memory_pool.h"
#include "../lib/socket_compat.h"
#include "../lib/debug_config.h"
#include "../lib/platform_compat.h"
#include "etcp_connections.h"

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include "../lib/mem.h"

/* Timebase: 0.1 мс */
#define TIMEBASE_US 100
#define MS_TO_TB(ms) ((ms) * 10)

/* Burst allowance для shaper (в timebase units) */
#define SHAPER_BURST_TB 10

/* Debug category */
#ifndef DEBUG_CATEGORY_DUMMYNET
#define DEBUG_CATEGORY_DUMMYNET ((debug_category_t)1 << 14)
#endif

/* Forward declarations */
static void dummynet_read_callback(socket_t sock, void* user_arg);
static void dummynet_delay_callback(void* user_arg);
static void dummynet_shaper_callback(void* user_arg);

/**
 * @brief Пакет в обработке (внутренняя структура)
 */
struct dummynet_pkt {
    uint8_t data[DUMMYNET_MAX_PKT_SIZE];
    size_t len;
    struct sockaddr_storage src_addr;
    socklen_t src_len;
    uint64_t recv_time_tb;
    int direction;
};

/**
 * @brief Направление передачи
 */
struct dummynet_dir {
    uint32_t delay_fixed_ms;
    uint32_t delay_random_ms;
    uint32_t bandwidth_kbps;
    uint32_t max_queue_pkts;
    uint32_t loss_permille;
    struct sockaddr_storage dest_addr;
    socklen_t dest_len;
    int configured;

    struct ll_queue* queue;

    void* shaper_timer;
    int shaper_pending;

    /* Отладочные счетчики */
    uint64_t delay_timer_set;    /* Число установок delay таймеров */
    uint64_t delay_timer_fire;   /* Число срабатываний delay таймеров */
    uint64_t shaper_timer_set;   /* Число установок shaper таймеров */
    uint64_t shaper_timer_fire;  /* Число срабатываний shaper таймеров */

    struct dummynet_stats stats;
};

/**
 * @brief Контекст dummynet
 */
struct dummynet {
    struct UASYNC* ua;
    socket_t sock;
    struct sockaddr_storage bind_addr;
    socklen_t bind_len;
    uint16_t listen_port;

    struct dummynet_dir dirs[DUMMYNET_DIR_COUNT];
    struct memory_pool* pkt_pool;
};

/**
 * @brief Аргумент для delay callback
 */
struct delay_cb_arg {
    struct dummynet* dn;
    struct ll_entry* entry;
};

/**
 * @brief Аргумент для shaper callback
 */
struct shaper_cb_arg {
    struct dummynet* dn;
    int dir_idx;
};

/* Генерация случайного числа 0..max */
static inline uint32_t random_range(uint32_t max) {
    if (max == 0) return 0;
    return (uint32_t)rand() % (max + 1);
}

/* Определяет направление по порту источника */
static int dummynet_get_direction(struct dummynet* dn, uint16_t src_port) {
    if (src_port == dn->listen_port - 1) {
        return DUMMYNET_FORWARD;
    } else if (src_port == dn->listen_port + 1) {
        return DUMMYNET_BACKWARD;
    }
    return -1;
}

/* Отправляет пакет и планирует следующую отправку */
static void dummynet_process_queue(struct dummynet* dn, int dir_idx) {
    struct dummynet_dir* dir = &dn->dirs[dir_idx];

    struct ll_entry* entry = queue_data_get(dir->queue);
    if (!entry) {
        dir->shaper_pending = 0;
        return;
    }

    struct dummynet_pkt* pkt = (struct dummynet_pkt*)entry->data;
    ssize_t n = socket_sendto(dn->sock, pkt->data, pkt->len,
                              (struct sockaddr*)&dir->dest_addr, dir->dest_len);
    if (n < 0) {
        DEBUG_ERROR(DEBUG_CATEGORY_DUMMYNET, "sendto failed: %s", socket_strerror(socket_get_error()));
    } else {
        dir->stats.sent++;
        DEBUG_DEBUG(DEBUG_CATEGORY_DUMMYNET, "Dir %d: sent packet (%zd bytes)", dir_idx, n);
    }

    size_t bytes_sent = (n > 0) ? (size_t)n : 0;
    dir->stats.queue_size = queue_entry_count(dir->queue);
    queue_entry_free(entry);

    /* Планируем следующую отправку */
    if (dir->stats.queue_size > 0) {
        int delay_tb = 0;

        if (dir->bandwidth_kbps > 0) {
            uint64_t delay_calc = (uint64_t)bytes_sent * 80ULL / (uint64_t)dir->bandwidth_kbps;
            delay_tb = (int)delay_calc;
            if (delay_tb == 0) delay_tb = 1;
        }

        struct shaper_cb_arg* sarg = (struct shaper_cb_arg*)u_malloc(sizeof(struct shaper_cb_arg));
        if (sarg) {
            sarg->dn = dn;
            sarg->dir_idx = dir_idx;
            dir->shaper_timer = uasync_set_timeout(dn->ua, delay_tb, sarg, dummynet_shaper_callback, "dummynet_shaper");
            if (dir->shaper_timer) {
                dir->shaper_timer_set++;
            } else {
                u_free(sarg);
                dir->shaper_pending = 0;
            }
        } else {
            dir->shaper_pending = 0;
        }
    } else {
        dir->shaper_pending = 0;
    }
}

/* Callback шейпера */
static void dummynet_shaper_callback(void* user_arg) {
    struct shaper_cb_arg* arg = (struct shaper_cb_arg*)user_arg;
    struct dummynet* dn = arg->dn;
    int dir_idx = arg->dir_idx;
    u_free(arg);

    dn->dirs[dir_idx].shaper_timer_fire++;
    dummynet_process_queue(dn, dir_idx);
}

/* Callback чтения из UDP сокета */
static void dummynet_read_callback(socket_t sock, void* user_arg) {
    struct dummynet* dn = (struct dummynet*)user_arg;
    uint8_t buf[DUMMYNET_MAX_PKT_SIZE];
    struct sockaddr_storage src_addr;
    socklen_t src_len = sizeof(src_addr);

    ssize_t n = socket_recvfrom(sock, buf, sizeof(buf), (struct sockaddr*)&src_addr, &src_len);
    if (n < 0) {
        if (socket_get_error() != ERR_WOULDBLOCK && socket_get_error() != ERR_AGAIN) {
            DEBUG_ERROR(DEBUG_CATEGORY_DUMMYNET, "recvfrom failed: %s", socket_strerror(socket_get_error()));
        }
        return;
    }

    if (n == 0) return;

    uint16_t src_port = 0;
    if (src_addr.ss_family == AF_INET) {
        src_port = ntohs(((struct sockaddr_in*)&src_addr)->sin_port);
    } else if (src_addr.ss_family == AF_INET6) {
        src_port = ntohs(((struct sockaddr_in6*)&src_addr)->sin6_port);
    }

    int dir_idx = dummynet_get_direction(dn, src_port);
    if (dir_idx < 0) {
        DEBUG_WARN(DEBUG_CATEGORY_DUMMYNET, "Packet from unknown port %u, expected %u or %u",
                   src_port, dn->listen_port - 1, dn->listen_port + 1);
        return;
    }

    struct dummynet_dir* dir = &dn->dirs[dir_idx];
    if (!dir->configured) {
        DEBUG_WARN(DEBUG_CATEGORY_DUMMYNET, "Direction %d not configured, dropping packet", dir_idx);
        return;
    }

    dir->stats.recv++;

    /* Random loss check */
    if (dir->loss_permille > 0) {
        uint32_t roll = (uint32_t)rand() % 1000;
        if (roll < dir->loss_permille) {
            dir->stats.lost++;
            DEBUG_INFO(DEBUG_CATEGORY_DUMMYNET, "Packet lost randomly (roll=%u, threshold=%u)",
                       roll, dir->loss_permille);
            return;
        }
    }

    /* Выделяем пакет */
    struct ll_entry* entry = queue_entry_new_from_pool(dn->pkt_pool);
    if (!entry) {
        DEBUG_ERROR(DEBUG_CATEGORY_DUMMYNET, "Failed to allocate packet entry");
        return;
    }

    struct dummynet_pkt* pkt = (struct dummynet_pkt*)entry->data;
    pkt->len = n;
    memcpy(pkt->data, buf, n);
    pkt->src_addr = src_addr;
    pkt->src_len = src_len;
    pkt->recv_time_tb = get_time_tb();
    pkt->direction = dir_idx;

    /* Вычисляем задержку */
    uint32_t delay_ms = dir->delay_fixed_ms + random_range(dir->delay_random_ms);
    if (delay_ms > DUMMYNET_MAX_DELAY_MS) {
        delay_ms = DUMMYNET_MAX_DELAY_MS;
    }
    int delay_tb = MS_TO_TB(delay_ms);

    DEBUG_DEBUG(DEBUG_CATEGORY_DUMMYNET, "Dir %d: packet recv (%zd bytes), delay %u ms",
                dir_idx, n, delay_ms);

    /* Создаём таймер задержки */
    struct delay_cb_arg* targ = (struct delay_cb_arg*)u_malloc(sizeof(struct delay_cb_arg));
    if (!targ) {
        DEBUG_ERROR(DEBUG_CATEGORY_DUMMYNET, "Failed to allocate timer arg");
        dir->stats.dropped++;
        queue_entry_free(entry);
        return;
    }
    targ->dn = dn;
    targ->entry = entry;

    void* timer = uasync_set_timeout(dn->ua, delay_tb, targ, dummynet_delay_callback, "dummynet_delay");
    if (!timer) {
        DEBUG_ERROR(DEBUG_CATEGORY_DUMMYNET, "Failed to set delay timer");
        dir->stats.dropped++;
        u_free(targ);
        queue_entry_free(entry);
        return;
    }
    dir->delay_timer_set++;
}

/* Callback таймера задержки */
static void dummynet_delay_callback(void* user_arg) {
    struct delay_cb_arg* arg = (struct delay_cb_arg*)user_arg;
    struct dummynet* dn = arg->dn;
    struct ll_entry* entry = arg->entry;
    u_free(arg);

    struct dummynet_pkt* pkt = (struct dummynet_pkt*)entry->data;
    int dir_idx = pkt->direction;
    struct dummynet_dir* dir = &dn->dirs[dir_idx];
    dir->delay_timer_fire++;

    /* Проверяем размер очереди */
    int queue_count = queue_entry_count(dir->queue);
    if ((uint32_t)queue_count >= dir->max_queue_pkts) {
        dir->stats.dropped++;
//        DEBUG_WARN(DEBUG_CATEGORY_DUMMYNET, "Dir %d: queue full (%d packets), dropping packet", dir_idx, queue_count);
        queue_entry_free(entry);
        return;
    }

    /* Добавляем в очередь */
    uint32_t id = (uint32_t)(uintptr_t)entry;
    if (queue_data_put(dir->queue, entry) != 0) {
        dir->stats.dropped++;
        DEBUG_WARN(DEBUG_CATEGORY_DUMMYNET, "Dir %d: queue_data_put failed", dir_idx);
        queue_entry_free(entry);
        return;
    }

    dir->stats.queue_size = queue_count + 1;
    if ((uint32_t)(queue_count + 1) > dir->stats.queue_max) {
        dir->stats.queue_max = queue_count + 1;
    }

    DEBUG_DEBUG(DEBUG_CATEGORY_DUMMYNET, "Dir %d: packet added to queue (size=%d)",
                dir_idx, queue_count + 1);

    /* Запускаем шейпер если не активен */
    if (!dir->shaper_pending) {
        dir->shaper_pending = 1;
        struct shaper_cb_arg* sarg = (struct shaper_cb_arg*)u_malloc(sizeof(struct shaper_cb_arg));
        if (sarg) {
            sarg->dn = dn;
            sarg->dir_idx = dir_idx;
            int shaper_delay_tb = 0;
            if (dir->bandwidth_kbps > 0) {
                uint64_t delay_calc = (uint64_t)pkt->len * 80ULL / (uint64_t)dir->bandwidth_kbps;
                shaper_delay_tb = (int)delay_calc;
                if (shaper_delay_tb == 0) shaper_delay_tb = 1;
            }
            dir->shaper_timer = uasync_set_timeout(dn->ua, shaper_delay_tb, sarg, dummynet_shaper_callback, "dummynet_shaper0");
            if (dir->shaper_timer) dir->shaper_timer_set++;
            else { u_free(sarg); dir->shaper_pending = 0; }
        } else {
            dir->shaper_pending = 0;
        }
    }
}

/* Создаёт dummynet контекст */
struct dummynet* dummynet_create(struct UASYNC* ua, const char* bind_ip, uint16_t listen_port) {
    if (!ua || listen_port == 0 || listen_port < 2 || listen_port > 65533) {
        DEBUG_ERROR(DEBUG_CATEGORY_DUMMYNET, "Invalid parameters");
        return NULL;
    }

    struct dummynet* dn = (struct dummynet*)u_calloc(1, sizeof(struct dummynet));
    if (!dn) {
        DEBUG_ERROR(DEBUG_CATEGORY_DUMMYNET, "Failed to allocate dummynet context");
        return NULL;
    }

    dn->ua = ua;
    dn->listen_port = listen_port;

    /* Создаём пул для пакетов */
    dn->pkt_pool = memory_pool_init(sizeof(struct ll_entry) + sizeof(struct dummynet_pkt));
    if (!dn->pkt_pool) {
        DEBUG_ERROR(DEBUG_CATEGORY_DUMMYNET, "Failed to create packet pool");
        u_free(dn);
        return NULL;
    }

    /* Создаём очереди для направлений */
    for (int i = 0; i < DUMMYNET_DIR_COUNT; i++) {
        dn->dirs[i].queue = queue_new(ua, 0, 0, 0, "dummynet1");
        if (!dn->dirs[i].queue) {
            DEBUG_ERROR(DEBUG_CATEGORY_DUMMYNET, "Failed to create queue for direction %d", i);
            dummynet_destroy(dn);
            return NULL;
        }
    }

    /* Создаём UDP сокет */
    dn->sock = socket_create_udp(AF_INET);
    if (dn->sock == SOCKET_INVALID) {
        DEBUG_ERROR(DEBUG_CATEGORY_DUMMYNET, "Failed to create UDP socket");
        dummynet_destroy(dn);
        return NULL;
    }

    if (socket_set_nonblocking(dn->sock) != 0) {
        DEBUG_ERROR(DEBUG_CATEGORY_DUMMYNET, "Failed to set nonblocking");
        dummynet_destroy(dn);
        return NULL;
    }

    /* Привязываем сокет */
    struct sockaddr_in bind_addr;
    memset(&bind_addr, 0, sizeof(bind_addr));
    bind_addr.sin_family = AF_INET;
    bind_addr.sin_port = htons(listen_port);

    if (bind_ip && strcmp(bind_ip, "0.0.0.0") != 0) {
        if (inet_pton(AF_INET, bind_ip, &bind_addr.sin_addr) != 1) {
            DEBUG_ERROR(DEBUG_CATEGORY_DUMMYNET, "Invalid bind IP: %s", bind_ip);
            dummynet_destroy(dn);
            return NULL;
        }
    } else {
        bind_addr.sin_addr.s_addr = INADDR_ANY;
    }

    if (bind(dn->sock, (struct sockaddr*)&bind_addr, sizeof(bind_addr)) != 0) {
        DEBUG_ERROR(DEBUG_CATEGORY_DUMMYNET, "Failed to bind to %s:%u: %s",
                   bind_ip ? bind_ip : "0.0.0.0", listen_port, socket_strerror(socket_get_error()));
        dummynet_destroy(dn);
        return NULL;
    }

    /* Добавляем сокет в uasync */
    void* sock_id = uasync_add_socket_t(ua, dn->sock, dummynet_read_callback, NULL, NULL, dn);
    if (!sock_id) {
        DEBUG_ERROR(DEBUG_CATEGORY_DUMMYNET, "Failed to add socket to uasync");
        dummynet_destroy(dn);
        return NULL;
    }

    DEBUG_INFO(DEBUG_CATEGORY_DUMMYNET, "Dummynet created on %s:%u (forward: %u->%u, backward: %u->%u)",
               bind_ip ? bind_ip : "0.0.0.0", listen_port,
               listen_port - 1, listen_port + 1,
               listen_port + 1, listen_port - 1);

    return dn;
}

/* Уничтожает dummynet контекст */
void dummynet_destroy(struct dummynet* dn) {
    if (!dn) return;

    DEBUG_INFO(DEBUG_CATEGORY_DUMMYNET, "Destroying dummynet");

    if (dn->sock != SOCKET_INVALID) {
        uasync_remove_socket_t(dn->ua, dn->sock);
        socket_close_wrapper(dn->sock);
    }

    for (int i = 0; i < DUMMYNET_DIR_COUNT; i++) {
        if (dn->dirs[i].shaper_timer) {
            uasync_cancel_timeout(dn->ua, dn->dirs[i].shaper_timer);
        }
        if (dn->dirs[i].queue) {
            struct ll_entry* entry;
            while ((entry = queue_data_get(dn->dirs[i].queue)) != NULL) {
                queue_entry_free(entry);
            }
            queue_free(dn->dirs[i].queue);
        }
    }

    if (dn->pkt_pool) {
        memory_pool_destroy(dn->pkt_pool);
    }

    u_free(dn);
}

/* Настраивает параметры направления */
int dummynet_set_direction(struct dummynet* dn, int direction,
                           uint32_t delay_fixed_ms, uint32_t delay_random_ms,
                           uint32_t bandwidth_kbps, uint32_t max_queue_pkts,
                           uint32_t loss_permille,
                           const char* dest_ip, uint16_t dest_port) {
    if (!dn || direction < 0 || direction >= DUMMYNET_DIR_COUNT) {
        return -1;
    }

    if (!dest_ip || dest_port == 0) {
        DEBUG_ERROR(DEBUG_CATEGORY_DUMMYNET, "Invalid destination");
        return -1;
    }

    if (loss_permille > DUMMYNET_MAX_LOSS_PERMILLE) {
        DEBUG_WARN(DEBUG_CATEGORY_DUMMYNET, "Loss permille %u clamped to %d",
                   loss_permille, DUMMYNET_MAX_LOSS_PERMILLE);
        loss_permille = DUMMYNET_MAX_LOSS_PERMILLE;
    }

    struct dummynet_dir* dir = &dn->dirs[direction];

    dir->delay_fixed_ms = delay_fixed_ms;
    dir->delay_random_ms = delay_random_ms;
    dir->bandwidth_kbps = bandwidth_kbps;
    dir->max_queue_pkts = max_queue_pkts;
    dir->loss_permille = loss_permille;

    memset(&dir->dest_addr, 0, sizeof(dir->dest_addr));
    struct sockaddr_in* dest_sin = (struct sockaddr_in*)&dir->dest_addr;
    dest_sin->sin_family = AF_INET;
    dest_sin->sin_port = htons(dest_port);

    if (inet_pton(AF_INET, dest_ip, &dest_sin->sin_addr) != 1) {
        DEBUG_ERROR(DEBUG_CATEGORY_DUMMYNET, "Invalid destination IP: %s", dest_ip);
        return -1;
    }
    dir->dest_len = sizeof(struct sockaddr_in);
    dir->configured = 1;

    DEBUG_INFO(DEBUG_CATEGORY_DUMMYNET, "Direction %d configured: delay=%u+%u ms, bw=%u kbps, "
               "queue=%u pkts, loss=%u.%u%%, dest=%s:%u",
               direction, delay_fixed_ms, delay_random_ms, bandwidth_kbps,
               max_queue_pkts, loss_permille / 10, loss_permille % 10,
               dest_ip, dest_port);

    return 0;
}

/* Получает статистику направления */
const struct dummynet_stats* dummynet_get_stats(struct dummynet* dn, int direction) {
    if (!dn || direction < 0 || direction >= DUMMYNET_DIR_COUNT) {
        return NULL;
    }
    return &dn->dirs[direction].stats;
}

/* Сбрасывает статистику */
void dummynet_reset_stats(struct dummynet* dn, int direction) {
    if (!dn) return;

    if (direction < 0) {
        for (int i = 0; i < DUMMYNET_DIR_COUNT; i++) {
            memset(&dn->dirs[i].stats, 0, sizeof(struct dummynet_stats));
        }
    } else if (direction >= 0 && direction < DUMMYNET_DIR_COUNT) {
        memset(&dn->dirs[direction].stats, 0, sizeof(struct dummynet_stats));
    }
}

/* Возвращает файловый дескриптор сокета */
int dummynet_get_socket(struct dummynet* dn) {
    if (!dn) return SOCKET_INVALID;
    return dn->sock;
}

/* Возвращает listen_port */
uint16_t dummynet_get_listen_port(struct dummynet *dn) {
    if (!dn) return 0;
    return dn->listen_port;
}

/* Возвращает указатель на UASYNC */
struct UASYNC *dummynet_get_uasync(struct dummynet *dn) {
    if (!dn) return NULL;
    return dn->ua;
}

/* Возвращает размер очереди направления */
int dummynet_get_queue_size(struct dummynet *dn, int direction) {
    if (!dn || direction < 0 || direction >= DUMMYNET_DIR_COUNT) {
        return -1;
    }
    return queue_entry_count(dn->dirs[direction].queue);
}

/* Получает отладочные счетчики направления */
void dummynet_get_debug_counters(struct dummynet *dn, int direction,
                                  uint64_t *delay_set, uint64_t *delay_fire,
                                  uint64_t *shaper_set, uint64_t *shaper_fire) {
    if (!dn || direction < 0 || direction >= DUMMYNET_DIR_COUNT) {
        *delay_set = *delay_fire = *shaper_set = *shaper_fire = 0;
        return;
    }
    struct dummynet_dir *dir = &dn->dirs[direction];
    *delay_set = dir->delay_timer_set;
    *delay_fire = dir->delay_timer_fire;
    *shaper_set = dir->shaper_timer_set;
    *shaper_fire = dir->shaper_timer_fire;
}

// === Inline filter: send_hook для etcp_udp_send ===

struct dummynet_filter {
    struct UASYNC* ua;
    uint32_t loss_permille;
    uint32_t delay_ms;
    uint32_t jitter_ms;
    struct ETCP_LINK* link;
    struct dummynet_stats stats;
};

static ssize_t dummynet_filter_send_hook(socket_t fd, const void* buf, size_t len,
                                          const struct sockaddr* addr, socklen_t addr_len,
                                          struct ETCP_LINK* link, void* ctx) {
    struct dummynet_filter* df = (struct dummynet_filter*)ctx;
    (void)link;
    df->stats.recv++;
    if (df->loss_permille > 0) {
        uint32_t roll = (uint32_t)rand() % 1000;
        if (roll < df->loss_permille) {
            df->stats.lost++;
            return (ssize_t)len;
        }
    }
    ssize_t sent = socket_sendto(fd, buf, len, addr, addr_len);
    if (sent > 0) df->stats.sent++;
    return sent;
}

struct dummynet_filter* dummynet_filter_create(struct UASYNC* ua) {
    struct dummynet_filter* df = u_calloc(1, sizeof(*df));
    if (!df) return NULL;
    df->ua = ua;
    return df;
}

void dummynet_filter_set_loss(struct dummynet_filter* df, uint32_t loss_permille) {
    if (!df) return;
    if (loss_permille > 1000) loss_permille = 1000;
    df->loss_permille = loss_permille;
}

void dummynet_filter_set_delay(struct dummynet_filter* df, uint32_t delay_ms, uint32_t jitter_ms) {
    if (!df) return;
    df->delay_ms = delay_ms;
    df->jitter_ms = jitter_ms;
}

void dummynet_filter_attach(struct dummynet_filter* df, struct ETCP_LINK* link) {
    if (!df || !link) return;
    dummynet_filter_detach(df);
    df->link = link;
    link->send_hook = dummynet_filter_send_hook;
    link->send_hook_ctx = df;
}

void dummynet_filter_detach(struct dummynet_filter* df) {
    if (!df || !df->link) return;
    df->link->send_hook = NULL;
    df->link->send_hook_ctx = NULL;
    df->link = NULL;
}

void dummynet_filter_destroy(struct dummynet_filter* df) {
    if (!df) return;
    dummynet_filter_detach(df);
    u_free(df);
}

const struct dummynet_stats* dummynet_filter_get_stats(struct dummynet_filter* df) {
    return df ? &df->stats : NULL;
}