// tcp_io.c — управление TCP-соединением через uasync + ll_queue
#include "tcp_io.h"
#include "debug_config.h"
#include "mem.h"
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#ifndef _WIN32
#include <unistd.h>
#include <sys/socket.h>
#include <fcntl.h>
#endif
#ifndef MSG_NOSIGNAL
#define MSG_NOSIGNAL 0
#endif

static void read_cb(socket_t sock, void* arg);
static void write_cb(socket_t sock, void* arg);
static void error_cb(socket_t sock, void* arg);
static void resume_read_cb(struct ll_queue* q, void* arg);
static void fin_deferred_cb(struct ll_queue* q, void* arg);
static void write_queue_fetch_cb(struct ll_queue* q, void* arg);
static void flush_write_buf(struct tcp_conn* tc);
static const uint8_t tcp_fin_sentinel;

struct tcp_conn* tcp_conn_create(
    struct UASYNC* ua, socket_t sock,
    size_t entry_data_size, size_t write_chunk_size,
    int read_high_water, int read_low_water,
    void (*on_fin)(struct tcp_conn* tc, void* arg),
    void (*on_error)(struct tcp_conn* tc, int err, void* arg),
    void* arg)
{
    if (!ua || sock == SOCKET_INVALID) { DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "tcp_conn_create: invalid args ua=%p", ua); return NULL; }

    struct tcp_conn* tc = u_calloc(1, sizeof(struct tcp_conn));
    if (!tc) { DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "tcp_conn_create: u_calloc failed"); return NULL; }

    tc->ua = ua;
    tc->sock = sock;
    tc->entry_data_size = entry_data_size;
    tc->write_chunk_size = write_chunk_size;
    tc->read_high_water = read_high_water;
    tc->read_low_water = read_low_water;
    tc->on_fin = on_fin;
    tc->on_error = on_error;
    tc->arg = arg;

    tc->entry_pool = memory_pool_init(sizeof(struct ll_entry));
    {
        size_t ds = entry_data_size > write_chunk_size ? entry_data_size : write_chunk_size;
        tc->data_pool = memory_pool_init(ds);
    }
    if (!tc->entry_pool || !tc->data_pool) {
        DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "tcp_conn_create: memory_pool_init failed");
        if (tc->entry_pool) memory_pool_destroy(tc->entry_pool);
        if (tc->data_pool)  memory_pool_destroy(tc->data_pool);
        u_free(tc); return NULL;
    }

    tc->read_queue = queue_new(ua, 0, 0, 0, "tcp_io_rq");
    tc->write_queue = queue_new(ua, 0, 0, 0, "tcp_io_wq");
    if (!tc->read_queue || !tc->write_queue) {
        DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "tcp_conn_create: queue_new failed");
        if (tc->read_queue) queue_free(tc->read_queue);
        if (tc->write_queue) queue_free(tc->write_queue);
        memory_pool_destroy(tc->entry_pool);
        memory_pool_destroy(tc->data_pool);
        u_free(tc); return NULL;
    }
    queue_set_threshold(tc->read_queue, read_low_water, 0);
    queue_set_threshold(tc->write_queue, 32, 0);
    queue_set_callback(tc->write_queue, write_queue_fetch_cb, tc);
    queue_set_waiter_defer(tc->write_queue, 1);

    tc->socket_id = uasync_add_socket_t(ua, sock, read_cb, write_cb, error_cb, tc);
    if (!tc->socket_id) {
        DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "tcp_conn_create: uasync_add_socket_t failed");
        queue_free(tc->read_queue);
        queue_free(tc->write_queue);
        memory_pool_destroy(tc->entry_pool);
        memory_pool_destroy(tc->data_pool);
        u_free(tc); return NULL;
    }
    tc->write_monitor = 1;

    {
        struct sockaddr_storage addr;
        socklen_t alen = sizeof(addr);
        if (getpeername(sock, (struct sockaddr*)&addr, &alen) == 0) tc->connected = 1;
    }

    DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "tcp_conn_create: fd=%d entry=%zu chunk=%zu hw=%d lw=%d connected=%d",
               (int)sock, entry_data_size, write_chunk_size, read_high_water, read_low_water, tc->connected);
    return tc;
}

void tcp_conn_destroy(struct tcp_conn* tc) {
    if (!tc) return;
    DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "tcp_conn_destroy: fd=%d connected=%d error=%d fin_remote=%d fin_local=%d closed=%d",
               (int)tc->sock, tc->connected, tc->error, tc->fin_remote, tc->fin_local, tc->closed);

    if (tc->socket_id) {
        uasync_remove_socket_t(tc->ua, tc->sock);
        tc->socket_id = NULL;
    }
    queue_waiter_cancel(tc->read_queue, &tc->read_waiter);
    queue_set_empty_callback(tc->read_queue, NULL, NULL);
    queue_set_callback(tc->read_queue, NULL, NULL);
    queue_set_callback(tc->write_queue, NULL, NULL);

    struct ll_entry* e;
    while ((e = queue_data_get(tc->read_queue)) != NULL) {
        if (e->dgram) memory_pool_free(tc->data_pool, e->dgram);
        queue_entry_free(e); queue_resume_callback(tc->read_queue);
    }
    while ((e = queue_data_get(tc->write_queue)) != NULL) {
        if (e->dgram && e->dgram != &tcp_fin_sentinel) memory_pool_free(tc->data_pool, e->dgram);
        queue_entry_free(e); queue_resume_callback(tc->write_queue);
    }
    queue_free(tc->read_queue);
    queue_free(tc->write_queue);

    if (tc->write_buf) memory_pool_free(tc->data_pool, tc->write_buf);
    if (tc->sock != SOCKET_INVALID) socket_close_wrapper(tc->sock);
    memory_pool_destroy(tc->entry_pool);
    memory_pool_destroy(tc->data_pool);
    u_free(tc);
}

// ====================================================================
// Чтение из сокета
// ====================================================================

static void read_cb(socket_t sock, void* arg) {
    (void)sock;
    struct tcp_conn* tc = (struct tcp_conn*)arg;
    if (!tc || tc->sock == SOCKET_INVALID) return;

    struct ll_entry* e = queue_entry_new_from_pool(tc->entry_pool);
    uint8_t* buf = memory_pool_alloc(tc->data_pool);
    if (!e || !buf) {
        DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "tcp_io: read_cb alloc failed fd=%d", (int)tc->sock);
        if (e) queue_entry_free(e);
        if (buf) memory_pool_free(tc->data_pool, buf);
        uasync_set_socket_read(tc->ua, tc->socket_id, 0);
        tc->read_paused = 1;
        return;
    }

    ssize_t n = recv(tc->sock, buf, tc->entry_data_size, 0);
    if (n > 0) {
        e->dgram = buf;
        e->len = (uint16_t)n;
        queue_data_put(tc->read_queue, e);
        if (tc->read_queue->count >= tc->read_high_water && !tc->read_paused) {
            uasync_set_socket_read(tc->ua, tc->socket_id, 0);
            tc->read_paused = 1;
            queue_waiter_wait(tc->read_queue, &tc->read_waiter, resume_read_cb, tc);
        }
    } else if (n == 0) {
        memory_pool_free(tc->data_pool, buf);
        queue_entry_free(e);
        tc->fin_remote = 1;
        DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "tcp_io: FIN fd=%d", (int)tc->sock);
        uasync_set_socket_read(tc->ua, tc->socket_id, 0);
        queue_waiter_cancel(tc->read_queue, &tc->read_waiter);
        if (tc->read_queue->count == 0) {
            if (tc->on_fin) tc->on_fin(tc, tc->arg);
        } else {
            queue_set_empty_callback(tc->read_queue, fin_deferred_cb, tc);
        }
    } else {
        memory_pool_free(tc->data_pool, buf);
        queue_entry_free(e);
        if (errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR) return;
        tc->error = 1;
        DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "tcp_io: recv error fd=%d errno=%d", (int)tc->sock, errno);
        if (tc->on_error) tc->on_error(tc, errno, tc->arg);
    }
}

static void resume_read_cb(struct ll_queue* q, void* arg) {
    (void)q;
    struct tcp_conn* tc = (struct tcp_conn*)arg;
    if (!tc || tc->sock == SOCKET_INVALID) return;
    uasync_set_socket_read(tc->ua, tc->socket_id, 1);
    tc->read_paused = 0;
}

static void fin_deferred_cb(struct ll_queue* q, void* arg) {
    (void)q;
    struct tcp_conn* tc = (struct tcp_conn*)arg;
    if (tc->on_fin) tc->on_fin(tc, tc->arg);
}

// ====================================================================
// Запись в сокет
// ====================================================================

static void flush_write_buf(struct tcp_conn* tc) {
    while (tc->write_buf && tc->write_offset < tc->write_len) {
        ssize_t n = send(tc->sock, tc->write_buf + tc->write_offset, tc->write_len - tc->write_offset, MSG_NOSIGNAL);
        if (n > 0) {
            tc->write_offset += (size_t)n;
            if (tc->write_offset >= tc->write_len) {
                memory_pool_free(tc->data_pool, tc->write_buf);
                tc->write_buf = NULL;
                tc->write_len = 0;
                tc->write_offset = 0;
                DEBUG_TRACE(DEBUG_CATEGORY_SOCKET, "tcp_io: flush_wbuf done fd=%d", (int)tc->sock);
                return;
            }
            continue;
        }
        if (n < 0 && (errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR)) return;
        tc->error = 1;
        DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "tcp_io: send error fd=%d errno=%d", (int)tc->sock, errno);
        if (tc->on_error) tc->on_error(tc, errno, tc->arg);
        return;
    }
}

static void write_queue_fetch_cb(struct ll_queue* q, void* arg) {
    struct tcp_conn* tc = (struct tcp_conn*)arg;

    if (tc->error || tc->closed) { DEBUG_TRACE(DEBUG_CATEGORY_SOCKET, "tcp_io: wq_fetch skip fd=%d error=%d closed=%d", (int)tc->sock, tc->error, tc->closed); return; }

    if (tc->write_buf) {
        flush_write_buf(tc);
        if (tc->write_buf) return;         // остался остаток, ждём write_cb
    }

    if (!tc->connected) { DEBUG_TRACE(DEBUG_CATEGORY_SOCKET, "tcp_io: wq_fetch skip fd=%d not connected", (int)tc->sock); return; }

    struct ll_entry* e = queue_data_get(q);
    if (!e) {
        uasync_set_socket_write(tc->ua, tc->socket_id, 0);
        tc->write_monitor = 0;
        DEBUG_TRACE(DEBUG_CATEGORY_SOCKET, "tcp_io: wq_fetch POLLOUT OFF fd=%d (queue empty)", (int)tc->sock);
        queue_resume_callback(q);
        if (tc->on_flushed) {
            void (*cb)(struct tcp_conn*, void*) = tc->on_flushed;
            tc->on_flushed = NULL;
            cb(tc, tc->arg);
        }
        return;
    }

    if (e->len == 0) {
        if (!e->dgram) {
            DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "tcp_io: CLOSE fd=%d", (int)tc->sock);
            queue_entry_free(e); queue_resume_callback(q);
            uasync_remove_socket_t(tc->ua, tc->sock);
            socket_close_wrapper(tc->sock);
            tc->socket_id = NULL; tc->sock = SOCKET_INVALID; tc->closed = 1;
            if (tc->on_closed) tc->on_closed(tc, tc->arg);
        } else if (e->dgram == &tcp_fin_sentinel) {
            DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "tcp_io: FIN fd=%d", (int)tc->sock);
            queue_entry_free(e); queue_resume_callback(q);
            shutdown(tc->sock, SHUT_WR);
            tc->fin_local = 1;
            if (tc->on_fin_sent) tc->on_fin_sent(tc, tc->arg);
        } else {
            DEBUG_WARN(DEBUG_CATEGORY_SOCKET, "tcp_io: wq_fetch zero-len entry with unknown dgram=%p fd=%d", (void*)e->dgram, (int)tc->sock);
            queue_entry_free(e); queue_resume_callback(q);
        }
        return;
    }

    ssize_t n = send(tc->sock, e->dgram, e->len, MSG_NOSIGNAL);
    if (n == (ssize_t)e->len) {
        memory_pool_free(tc->data_pool, e->dgram);
        queue_entry_free(e);
        queue_resume_callback(q);
    } else if (n > 0) {
        size_t rem = e->len - (size_t)n;
        tc->write_buf = memory_pool_alloc(tc->data_pool);
        if (!tc->write_buf) {
            DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "tcp_io: write_buf alloc failed fd=%d", (int)tc->sock);
            tc->error = 1;
            memory_pool_free(tc->data_pool, e->dgram);
            queue_entry_free(e);
            return;
        }
        memcpy(tc->write_buf, e->dgram + n, rem);
        tc->write_len = rem;
        tc->write_offset = 0;
        memory_pool_free(tc->data_pool, e->dgram);
        queue_entry_free(e);
        uasync_set_socket_write(tc->ua, tc->socket_id, 1);
        tc->write_monitor = 1;
        DEBUG_TRACE(DEBUG_CATEGORY_SOCKET, "tcp_io: wq_fetch POLLOUT ON fd=%d (partial send, wbuf=%zu bytes)", (int)tc->sock, tc->write_len);
    } else if (n < 0 && (errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR)) {
        tc->write_buf = memory_pool_alloc(tc->data_pool);
        if (!tc->write_buf) {
            DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "tcp_io: write_buf alloc failed fd=%d", (int)tc->sock);
            tc->error = 1;
            memory_pool_free(tc->data_pool, e->dgram);
            queue_entry_free(e);
            return;
        }
        memcpy(tc->write_buf, e->dgram, e->len);
        tc->write_len = e->len;
        tc->write_offset = 0;
        memory_pool_free(tc->data_pool, e->dgram);
        queue_entry_free(e);
        uasync_set_socket_write(tc->ua, tc->socket_id, 1);
        tc->write_monitor = 1;
        DEBUG_TRACE(DEBUG_CATEGORY_SOCKET, "tcp_io: wq_fetch POLLOUT ON fd=%d (EAGAIN, wbuf=%zu bytes)", (int)tc->sock, tc->write_len);
    } else {
        tc->error = 1;
        DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "tcp_io: send error fd=%d errno=%d", (int)tc->sock, errno);
        if (tc->on_error) tc->on_error(tc, errno, tc->arg);
        memory_pool_free(tc->data_pool, e->dgram);
        queue_entry_free(e);
    }
}

static void write_cb(socket_t sock, void* arg) {
    (void)sock;
    struct tcp_conn* tc = (struct tcp_conn*)arg;
    if (!tc || tc->sock == SOCKET_INVALID) return;

    if (!tc->connected) {
        int err = 0;
        socklen_t len = sizeof(err);
        if (getsockopt(tc->sock, SOL_SOCKET, SO_ERROR, &err, &len) == 0 && err == 0) {
            tc->connected = 1;
            DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "tcp_io: connect ok fd=%d", (int)tc->sock);
        } else {
            tc->error = 1;
            DEBUG_TRACE(DEBUG_CATEGORY_SOCKET, "tcp_io: write_cb connect fail fd=%d err=%d wmon=%d (POLLOUT still active)", (int)tc->sock, err, tc->write_monitor);
            DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "tcp_io: connect fail fd=%d err=%d", (int)tc->sock, err);
            if (tc->on_error) tc->on_error(tc, err ? err : -1, tc->arg);
            return;
        }
    }

    flush_write_buf(tc);
    if (!tc->write_buf) {
        DEBUG_TRACE(DEBUG_CATEGORY_SOCKET, "tcp_io: write_cb flushed fd=%d wmon=%d (resume WQ cb)", (int)tc->sock, tc->write_monitor);
        queue_resume_callback(tc->write_queue);
    }
}

// ====================================================================
// Асинхронная ошибка сокета
// ====================================================================

static void error_cb(socket_t sock, void* arg) {
    (void)sock;
    struct tcp_conn* tc = (struct tcp_conn*)arg;
    if (!tc || tc->sock == SOCKET_INVALID) return;
    tc->error = 1;
    DEBUG_TRACE(DEBUG_CATEGORY_SOCKET, "tcp_io: error_cb fd=%d connected=%d fin_remote=%d wmon=%d", (int)tc->sock, tc->connected, tc->fin_remote, tc->write_monitor);
    DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "tcp_io: async error fd=%d", (int)tc->sock);
    if (tc->on_error) tc->on_error(tc, -1, tc->arg);
}

// ====================================================================
// FIN / Close через очередь отправки
// ====================================================================

int tcp_conn_push_fin(struct tcp_conn* tc) {
    if (!tc || tc->sock == SOCKET_INVALID) { DEBUG_WARN(DEBUG_CATEGORY_SOCKET, "tcp_io: push_fin invalid tc"); return -1; }
    if (tc->fin_local) { DEBUG_WARN(DEBUG_CATEGORY_SOCKET, "tcp_io: push_fin already fin_local fd=%d", (int)tc->sock); return -1; }
    if (tc->closed) { DEBUG_WARN(DEBUG_CATEGORY_SOCKET, "tcp_io: push_fin already closed fd=%d", (int)tc->sock); return -1; }
    struct ll_entry* e = queue_entry_new_from_pool(tc->entry_pool);
    if (!e) { DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "tcp_io: push_fin entry_pool exhausted fd=%d", (int)tc->sock); return -1; }
    e->dgram = (uint8_t*)&tcp_fin_sentinel; e->len = 0;
    DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "tcp_io: push_fin fd=%d wq=%d", (int)tc->sock, tc->write_queue->count + 1);
    queue_data_put(tc->write_queue, e);
    return 0;
}

int tcp_conn_push_close(struct tcp_conn* tc) {
    if (!tc || tc->sock == SOCKET_INVALID) { DEBUG_WARN(DEBUG_CATEGORY_SOCKET, "tcp_io: push_close invalid tc"); return -1; }
    if (tc->closed) { DEBUG_WARN(DEBUG_CATEGORY_SOCKET, "tcp_io: push_close already closed fd=%d", (int)tc->sock); return -1; }
    struct ll_entry* e = queue_entry_new_from_pool(tc->entry_pool);
    if (!e) { DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "tcp_io: push_close entry_pool exhausted fd=%d", (int)tc->sock); return -1; }
    e->dgram = NULL; e->len = 0;
    DEBUG_INFO(DEBUG_CATEGORY_SOCKET, "tcp_io: push_close fd=%d wq=%d", (int)tc->sock, tc->write_queue->count + 1);
    queue_data_put(tc->write_queue, e);
    return 0;
}

void tcp_conn_set_flushed(struct tcp_conn* tc, void (*on_flushed)(struct tcp_conn* tc, void* arg)) {
    if (!tc) return;
    tc->on_flushed = on_flushed;
}

void tcp_conn_pause_read(struct tcp_conn* tc) {
    if (!tc || tc->sock == SOCKET_INVALID) return;
    uasync_set_socket_read(tc->ua, tc->socket_id, 0);
    queue_waiter_cancel(tc->read_queue, &tc->read_waiter);
    tc->read_paused = 1;
}