// uasync.c

#include "u_async.h"
#include "debug_config.h"
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <limits.h>
#include <fcntl.h>

#ifndef _WIN32
#include <unistd.h>
#include <poll.h>
#endif

// Platform-specific includes
#ifdef __linux__
#include <sys/epoll.h>
#define HAS_EPOLL 1
#else
#define HAS_EPOLL 0
#endif



// Timeout node with safe cancellation
struct timeout_node {
    void* arg;
    timeout_callback_t callback;
    uint64_t expiration_ms; // absolute expiration time in milliseconds
    struct UASYNC* ua;      // Pointer back to uasync instance for counter updates
    int cancelled;          // Cancellation flag
};

// Socket node with array-based storage
struct socket_node {
    int fd;                     // File descriptor (for pipe, file)
    socket_t sock;              // Socket (for cross-platform sockets)
    int type;                   // SOCKET_NODE_TYPE_FD or SOCKET_NODE_TYPE_SOCK
    socket_callback_t read_cbk;       // For FD type
    socket_callback_t write_cbk;      // For FD type
    socket_t_callback_t read_cbk_sock;  // For SOCK type
    socket_t_callback_t write_cbk_sock; // For SOCK type
    socket_callback_t except_cbk;
    void* user_data;
    int active;  // 1 if socket is active, 0 if freed (for reuse)
};

// Array-based socket management for O(1) operations
struct socket_array {
    struct socket_node* sockets;      // Dynamic array of socket nodes
    int* fd_to_index;                // FD to array index mapping
    int* index_to_fd;                // Array index to FD mapping
    int* active_indices;             // Array of indices of active sockets (for O(1) traversal)
    int capacity;                    // Total allocated capacity
    int count;                       // Number of active sockets
    int max_fd;                      // Maximum FD for bounds checking
};

static struct socket_array* socket_array_create(int initial_capacity);
static void socket_array_destroy(struct socket_array* sa);
static int socket_array_add(struct socket_array* sa, int fd, socket_callback_t read_cbk, socket_callback_t write_cbk, socket_callback_t except_cbk, void* user_data);
static int socket_array_remove(struct socket_array* sa, int fd);
static struct socket_node* socket_array_get(struct socket_array* sa, int fd);

// No global instance - each module must use its own struct UASYNC instance

// Array-based socket management implementation
static struct socket_array* socket_array_create(int initial_capacity) {
    if (initial_capacity < 4) initial_capacity = 4;  // Minimum capacity
    
    struct socket_array* sa = malloc(sizeof(struct socket_array));
    if (!sa) return NULL;
    
    sa->sockets = calloc(initial_capacity, sizeof(struct socket_node));
    sa->fd_to_index = calloc(initial_capacity, sizeof(int));
    sa->index_to_fd = calloc(initial_capacity, sizeof(int));
    sa->active_indices = calloc(initial_capacity, sizeof(int));
    
    if (!sa->sockets || !sa->fd_to_index || !sa->index_to_fd || !sa->active_indices) {
        free(sa->sockets);
        free(sa->fd_to_index);
        free(sa->index_to_fd);
        free(sa->active_indices);
        free(sa);
        return NULL;
    }
    
    // Initialize mapping arrays to -1 (invalid)
    for (int i = 0; i < initial_capacity; i++) {
        sa->fd_to_index[i] = -1;
        sa->index_to_fd[i] = -1;
        sa->active_indices[i] = -1;
        sa->sockets[i].fd = -1;
        sa->sockets[i].active = 0;
    }
    
    sa->capacity = initial_capacity;
    sa->count = 0;
    sa->max_fd = -1;
    
    return sa;
}

static void socket_array_destroy(struct socket_array* sa) {
    if (!sa) return;
    
    free(sa->sockets);
    free(sa->fd_to_index);
    free(sa->index_to_fd);
    free(sa->active_indices);
    free(sa);
}

static int socket_array_add_internal(struct socket_array* sa, int fd, socket_t sock, int type,
                                     socket_callback_t read_cbk_fd, socket_callback_t write_cbk_fd,
                                     socket_t_callback_t read_cbk_sock, socket_t_callback_t write_cbk_sock,
                                     socket_callback_t except_cbk, void* user_data) {
    if (!sa || fd < 0 || fd >= FD_SETSIZE) return -1;
    if (fd >= sa->capacity) {
        // Need to resize - double the capacity
        int new_capacity = sa->capacity * 2;
        if (fd >= new_capacity) new_capacity = fd + 16;  // Ensure enough space
        
        struct socket_node* new_sockets = realloc(sa->sockets, new_capacity * sizeof(struct socket_node));
        int* new_fd_to_index = realloc(sa->fd_to_index, new_capacity * sizeof(int));
        int* new_index_to_fd = realloc(sa->index_to_fd, new_capacity * sizeof(int));
        int* new_active_indices = realloc(sa->active_indices, new_capacity * sizeof(int));
        
        if (!new_sockets || !new_fd_to_index || !new_index_to_fd || !new_active_indices) {
            // Allocation failed
            free(new_sockets);
            free(new_fd_to_index);
            free(new_index_to_fd);
            free(new_active_indices);
            return -1;
        }
        
        // Initialize new elements
        for (int i = sa->capacity; i < new_capacity; i++) {
            new_fd_to_index[i] = -1;
            new_index_to_fd[i] = -1;
            new_active_indices[i] = -1;
            new_sockets[i].fd = -1;
            new_sockets[i].active = 0;
        }
        
        sa->sockets = new_sockets;
        sa->fd_to_index = new_fd_to_index;
        sa->index_to_fd = new_index_to_fd;
        sa->active_indices = new_active_indices;
        sa->capacity = new_capacity;
    }
    
    // Check if FD already exists
    if (sa->fd_to_index[fd] != -1) return -1;  // FD already exists
    
    // Find first free slot
    int index = -1;
    for (int i = 0; i < sa->capacity; i++) {
        if (!sa->sockets[i].active) {
            index = i;
            break;
        }
    }
    
    if (index == -1) return -1;  // No free slots (shouldn't happen)
    
    // Add the socket
    sa->sockets[index].fd = fd;
    sa->sockets[index].sock = sock;
    sa->sockets[index].type = type;
    sa->sockets[index].read_cbk = read_cbk_fd;
    sa->sockets[index].write_cbk = write_cbk_fd;
    sa->sockets[index].read_cbk_sock = read_cbk_sock;
    sa->sockets[index].write_cbk_sock = write_cbk_sock;
    sa->sockets[index].except_cbk = except_cbk;
    sa->sockets[index].user_data = user_data;
    sa->sockets[index].active = 1;
    
    sa->fd_to_index[fd] = index;
    sa->index_to_fd[index] = fd;
    sa->active_indices[sa->count] = index;  // Add to active list
    sa->count++;
    
    if (fd > sa->max_fd) sa->max_fd = fd;
    
    return index;
}

// Wrapper for adding regular file descriptors (pipe, file)
static int socket_array_add(struct socket_array* sa, int fd, socket_callback_t read_cbk, 
                            socket_callback_t write_cbk, socket_callback_t except_cbk, void* user_data) {
    return socket_array_add_internal(sa, fd, SOCKET_INVALID, SOCKET_NODE_TYPE_FD,
                                     read_cbk, write_cbk, NULL, NULL, except_cbk, user_data);
}

// Wrapper for adding socket_t (cross-platform sockets)
static int socket_array_add_socket_t(struct socket_array* sa, socket_t sock, socket_t_callback_t read_cbk,
                                     socket_t_callback_t write_cbk, socket_callback_t except_cbk, void* user_data) {
    // On Windows, SOCKET is UINT_PTR, so we need to handle indexing differently
#ifdef _WIN32
    int fd = (int)(intptr_t)sock;  // Use socket value as index on Windows (simplified)
#else
    int fd = sock;  // On POSIX, socket_t is int
#endif
    if (fd < 0 || fd >= FD_SETSIZE) return -1;
    return socket_array_add_internal(sa, fd, sock, SOCKET_NODE_TYPE_SOCK,
                                     NULL, NULL, read_cbk, write_cbk, except_cbk, user_data);
}

static int socket_array_remove(struct socket_array* sa, int fd) {
    if (!sa || fd < 0 || fd >= sa->capacity) return -1;
    
    int index = sa->fd_to_index[fd];
    if (index == -1 || !sa->sockets[index].active) return -1;  // FD not found
    
    // Mark as inactive
    sa->sockets[index].active = 0;
    sa->sockets[index].fd = -1;
    sa->sockets[index].sock = SOCKET_INVALID;
    sa->sockets[index].type = SOCKET_NODE_TYPE_FD;
    sa->fd_to_index[fd] = -1;
    sa->index_to_fd[index] = -1;
    
    // Remove from active_indices by swapping with last element
    // Find position in active_indices
    for (int i = 0; i < sa->count; i++) {
        if (sa->active_indices[i] == index) {
            // Swap with last element
            sa->active_indices[i] = sa->active_indices[sa->count - 1];
            sa->active_indices[sa->count - 1] = -1;
            break;
        }
    }
    sa->count--;
    
    return 0;
}

static struct socket_node* socket_array_get(struct socket_array* sa, int fd) {
    if (!sa || fd < 0 || fd >= sa->capacity) return NULL;
    
    int index = sa->fd_to_index[fd];
    if (index == -1 || !sa->sockets[index].active) return NULL;
    
    return &sa->sockets[index];
}

// Get socket_node by socket_t
static struct socket_node* socket_array_get_by_sock(struct socket_array* sa, socket_t sock) {
    if (!sa) return NULL;
#ifdef _WIN32
    int fd = (int)(intptr_t)sock;
#else
    int fd = sock;
#endif
    if (fd < 0 || fd >= sa->capacity) return NULL;
    
    int index = sa->fd_to_index[fd];
    if (index == -1 || !sa->sockets[index].active) return NULL;
    if (sa->sockets[index].type != SOCKET_NODE_TYPE_SOCK) return NULL;
    
    return &sa->sockets[index];
}

// Callback to free timeout node and update counters
static void timeout_node_free_callback(void* user_data, void* data) {
    struct UASYNC* ua = (struct UASYNC*)user_data;
    struct timeout_node* node = (struct timeout_node*)data;
    (void)node; // Not used directly, but keep for consistency
    ua->timer_free_count++;
    free(data);
}

// Helper to get current time
static void get_current_time(struct timeval* tv) {
    gettimeofday(tv, NULL);
}



// Drain wakeup pipe - read all available bytes
static void drain_wakeup_pipe(struct UASYNC* ua) {
    if (!ua || !ua->wakeup_initialized) return;
    
    char buf[64];
    while (1) {
        ssize_t n = read(ua->wakeup_pipe[0], buf, sizeof(buf));
        if (n <= 0) break;
    }
}

// Helper to add timeval: tv += dt (timebase units)
static void timeval_add_tb(struct timeval* tv, int dt) {
    tv->tv_usec += (dt % 10000) * 100;
    tv->tv_sec += dt / 10000 + tv->tv_usec / 1000000;
    tv->tv_usec %= 1000000;
}

// Convert timeval to milliseconds (uint64_t)
static uint64_t timeval_to_ms(const struct timeval* tv) {
    return (uint64_t)tv->tv_sec * 1000ULL + (uint64_t)tv->tv_usec / 1000ULL;
}



// Simplified timeout handling without reference counting

// Process expired timeouts with safe cancellation
static void process_timeouts(struct UASYNC* ua) {
    if (!ua || !ua->timeout_heap) return;
    
    struct timeval now_tv;
    get_current_time(&now_tv);
    uint64_t now_ms = timeval_to_ms(&now_tv);
    
    while (1) {
        TimeoutEntry entry;
        if (timeout_heap_peek(ua->timeout_heap, &entry) != 0) break;
        if (entry.expiration > now_ms) break;
        
        // Pop the expired timeout
        timeout_heap_pop(ua->timeout_heap, &entry);
        struct timeout_node* node = (struct timeout_node*)entry.data;
        
        if (node && node->callback && !node->cancelled) {
            // Execute callback only if not cancelled
            node->callback(node->arg);
        }
        
        // Always free the node after processing
        if (node && node->ua) {
            node->ua->timer_free_count++;
        }
        free(node);
        break;
    }
}

// Compute time to next timeout
static void get_next_timeout(struct UASYNC* ua, struct timeval* tv) {
    if (!ua || !ua->timeout_heap) {
        tv->tv_sec = 0;
        tv->tv_usec = 0;
        return;
    }
    
    TimeoutEntry entry;
    if (timeout_heap_peek(ua->timeout_heap, &entry) != 0) {
        tv->tv_sec = 0;
        tv->tv_usec = 0;
        return;
    }
    
    struct timeval now_tv;
    get_current_time(&now_tv);
    uint64_t now_ms = timeval_to_ms(&now_tv);
    
    if (entry.expiration <= now_ms) {
        tv->tv_sec = 0;
        tv->tv_usec = 0;
        return;
    }
    
    uint64_t delta_ms = entry.expiration - now_ms;
    tv->tv_sec = delta_ms / 1000;
    tv->tv_usec = (delta_ms % 1000) * 1000;
}



// Instance version
void* uasync_set_timeout(struct UASYNC* ua, int timeout_tb, void* arg, timeout_callback_t callback) {
    if (!ua || timeout_tb < 0 || !callback) return NULL;
    if (!ua->timeout_heap) return NULL;
    
//    DEBUG_DEBUG(DEBUG_CATEGORY_TIMERS, "uasync_set_timeout: timeout=%d.%d ms, arg=%p, callback=%p", timeout_tb/10, timeout_tb%10, arg, callback);
    
    struct timeout_node* node = malloc(sizeof(struct timeout_node));
    if (!node) {
        DEBUG_ERROR(DEBUG_CATEGORY_TIMERS, "uasync_set_timeout: failed to allocate node");
        return NULL;
    }
    ua->timer_alloc_count++;
    
    node->arg = arg;
    node->callback = callback;
    node->ua = ua;
    node->cancelled = 0;
    
    // Calculate expiration time in milliseconds
    struct timeval now;
    get_current_time(&now);
    timeval_add_tb(&now, timeout_tb);
    node->expiration_ms = timeval_to_ms(&now);
    
    // Add to heap
    if (timeout_heap_push(ua->timeout_heap, node->expiration_ms, node) != 0) {
        DEBUG_ERROR(DEBUG_CATEGORY_TIMERS, "uasync_set_timeout: failed to push to heap");
        free(node);
        ua->timer_free_count++;  // Balance the alloc counter
        return NULL;
    }
    
    return node;
}



// Instance version
err_t uasync_cancel_timeout(struct UASYNC* ua, void* t_id) {
    if (!ua || !t_id || !ua->timeout_heap) {
        DEBUG_ERROR(DEBUG_CATEGORY_TIMERS, "uasync_cancel_timeout: invalid parameters ua=%p, t_id=%p, heap=%p", 
                    ua, t_id, ua ? ua->timeout_heap : NULL);
        return ERR_FAIL;
    }

    struct timeout_node* node = (struct timeout_node*)t_id;
    
    // Try to cancel from heap first
    if (timeout_heap_cancel(ua->timeout_heap, node->expiration_ms, node) == 0) {
        // Successfully marked as deleted - free will happen lazily in heap
        node->cancelled = 1;
        node->callback = NULL;
//        DEBUG_DEBUG(DEBUG_CATEGORY_TIMERS, "uasync_cancel_timeout: successfully cancelled timer %p from heap", node);
        return ERR_OK;
    }

    DEBUG_DEBUG(DEBUG_CATEGORY_TIMERS, "uasync_cancel_timeout: not found in heap: ua=%p, t_id=%p, node=%p, expires=%llu ms", 
                ua, t_id, node, (unsigned long long)node->expiration_ms);

    // If not found in heap, it may have already expired or been invalid
    return ERR_FAIL;
}


// Instance version
void* uasync_add_socket(struct UASYNC* ua, int fd, socket_callback_t read_cbk, socket_callback_t write_cbk, socket_callback_t except_cbk, void* user_data) {
    if (!ua || fd < 0 || fd >= FD_SETSIZE) return NULL;  // Bounds check

    int index = socket_array_add(ua->sockets, fd, read_cbk, write_cbk, except_cbk, user_data);
    if (index < 0) return NULL;
    
    ua->socket_alloc_count++;
    ua->poll_fds_dirty = 1;  // Mark poll_fds as needing rebuild
    
#if HAS_EPOLL
    // Add to epoll if using epoll
    if (ua->use_epoll && ua->epoll_fd >= 0) {
        struct epoll_event ev;
        ev.events = 0;
        if (read_cbk) ev.events |= EPOLLIN;
        if (write_cbk) ev.events |= EPOLLOUT;
        // Use level-triggered mode (default) for compatibility with UDP sockets
        ev.data.ptr = &ua->sockets->sockets[index];
        
        if (epoll_ctl(ua->epoll_fd, EPOLL_CTL_ADD, fd, &ev) < 0) {
            // Failed to add to epoll - remove from socket array and return error
            socket_array_remove(ua->sockets, fd);
            ua->socket_alloc_count--;
            return NULL;
        }
    }
#endif
    
    // Return pointer to the socket node as ID
    return &ua->sockets->sockets[index];
}

err_t uasync_remove_socket(struct UASYNC* ua, void* s_id) {
    if (!ua || !s_id) return ERR_FAIL;
    
    struct socket_node* node = (struct socket_node*)s_id;
    if (!node->active || node->fd < 0) return ERR_FAIL;
    
    int fd = node->fd;
    
#if HAS_EPOLL
    // Remove from epoll if using epoll
    if (ua->use_epoll && ua->epoll_fd >= 0) {
        epoll_ctl(ua->epoll_fd, EPOLL_CTL_DEL, fd, NULL);
    }
#endif
    
    int ret = socket_array_remove(ua->sockets, fd);
    if (ret == 0) {
        ua->socket_free_count++;
        ua->poll_fds_dirty = 1;  // Mark poll_fds as needing rebuild
        return ERR_OK;
    }
    return ERR_FAIL;
}

// Add socket_t (cross-platform socket)
void* uasync_add_socket_t(struct UASYNC* ua, socket_t sock, socket_t_callback_t read_cbk, 
                          socket_t_callback_t write_cbk, socket_t_callback_t except_cbk, void* user_data) {
    if (!ua || sock == SOCKET_INVALID) return NULL;
    
    int index = socket_array_add_socket_t(ua->sockets, sock, read_cbk, write_cbk, 
                                          (socket_callback_t)except_cbk, user_data);
    if (index < 0) return NULL;
    
    ua->socket_alloc_count++;
    ua->poll_fds_dirty = 1;
    
#if HAS_EPOLL
    if (ua->use_epoll && ua->epoll_fd >= 0) {
        struct epoll_event ev;
        ev.events = 0;
        if (read_cbk) ev.events |= EPOLLIN;
        if (write_cbk) ev.events |= EPOLLOUT;
        ev.data.ptr = &ua->sockets->sockets[index];
        
        // On Windows, need to cast socket_t to int for epoll_ctl
#ifdef _WIN32
        int fd = (int)(intptr_t)sock;
#else
        int fd = sock;
#endif
        if (epoll_ctl(ua->epoll_fd, EPOLL_CTL_ADD, fd, &ev) < 0) {
            socket_array_remove(ua->sockets, fd);
            ua->socket_alloc_count--;
            return NULL;
        }
    }
#endif
    
    return &ua->sockets->sockets[index];
}

// Remove socket by socket_t
err_t uasync_remove_socket_t(struct UASYNC* ua, socket_t sock) {
    if (!ua || sock == SOCKET_INVALID) return ERR_FAIL;
    
    struct socket_node* node = socket_array_get_by_sock(ua->sockets, sock);
    if (!node || !node->active) return ERR_FAIL;
    
#if HAS_EPOLL
    if (ua->use_epoll && ua->epoll_fd >= 0) {
#ifdef _WIN32
        int fd = (int)(intptr_t)sock;
#else
        int fd = sock;
#endif
        epoll_ctl(ua->epoll_fd, EPOLL_CTL_DEL, fd, NULL);
    }
#endif
    
#ifdef _WIN32
    int fd = (int)(intptr_t)sock;
#else
    int fd = sock;
#endif
    int ret = socket_array_remove(ua->sockets, fd);
    if (ret == 0) {
        ua->socket_free_count++;
        ua->poll_fds_dirty = 1;
        return ERR_OK;
    }
    return ERR_FAIL;
}

// Helper function to rebuild cached pollfd array
static void rebuild_poll_fds(struct UASYNC* ua) {
    if (!ua || !ua->sockets) return;
    
    int socket_count = ua->sockets->count;
    int wakeup_fd_present = ua->wakeup_initialized && ua->wakeup_pipe[0] >= 0;
    int total_fds = socket_count + wakeup_fd_present;
    
    // Ensure poll_fds capacity is sufficient
    if (total_fds > ua->poll_fds_capacity) {
        int new_capacity = total_fds * 2;
        if (new_capacity < 16) new_capacity = 16;
        
        struct pollfd* new_poll_fds = realloc(ua->poll_fds, sizeof(struct pollfd) * new_capacity);
        if (!new_poll_fds) return;  // Keep old allocation on failure
        
        ua->poll_fds = new_poll_fds;
        ua->poll_fds_capacity = new_capacity;
    }
    
    int idx = 0;
    
    // Add wakeup fd first if present
    if (wakeup_fd_present) {
        ua->poll_fds[idx].fd = ua->wakeup_pipe[0];
        ua->poll_fds[idx].events = POLLIN;
        ua->poll_fds[idx].revents = 0;
        idx++;
    }
    
    // Add socket fds using active_indices for O(1) traversal
    for (int i = 0; i < socket_count; i++) {
        int socket_array_idx = ua->sockets->active_indices[i];
        struct socket_node* cur = &ua->sockets->sockets[socket_array_idx];
        
        // Handle socket_t vs int fd
        if (cur->type == SOCKET_NODE_TYPE_SOCK) {
            // socket_t - cast to int for pollfd
#ifdef _WIN32
            ua->poll_fds[idx].fd = (int)(intptr_t)cur->sock;
#else
            ua->poll_fds[idx].fd = cur->sock;
#endif
        } else {
            // Regular fd
            ua->poll_fds[idx].fd = cur->fd;
        }
        ua->poll_fds[idx].events = 0;
        ua->poll_fds[idx].revents = 0;
        
        if (cur->type == SOCKET_NODE_TYPE_SOCK) {
            if (cur->read_cbk_sock) ua->poll_fds[idx].events |= POLLIN;
            if (cur->write_cbk_sock) ua->poll_fds[idx].events |= POLLOUT;
        } else {
            if (cur->read_cbk) ua->poll_fds[idx].events |= POLLIN;
            if (cur->write_cbk) ua->poll_fds[idx].events |= POLLOUT;
        }
        if (cur->write_cbk) ua->poll_fds[idx].events |= POLLOUT;
        if (cur->except_cbk) ua->poll_fds[idx].events |= POLLPRI;
        
        idx++;
    }
    
    ua->poll_fds_count = total_fds;
    ua->poll_fds_dirty = 0;
}

// Process events from epoll (Linux only)
#if HAS_EPOLL
static void process_epoll_events(struct UASYNC* ua, struct epoll_event* events, int n_events) {
    for (int i = 0; i < n_events; i++) {
        // Check if this is the wakeup fd (data.ptr is NULL)
        if (events[i].data.ptr == NULL) {
            if (events[i].events & EPOLLIN) {
                drain_wakeup_pipe(ua);
            }
            continue;
        }
        
        // Socket event
        struct socket_node* node = (struct socket_node*)events[i].data.ptr;
        if (!node || !node->active) continue;
        
        /* Check for error conditions first */
        if (events[i].events & (EPOLLERR | EPOLLHUP)) {
            if (node->except_cbk) {
                node->except_cbk(node->fd, node->user_data);
            }
        }
        
        /* Read readiness - use appropriate callback based on socket type */
        if (events[i].events & EPOLLIN) {
            if (node->type == SOCKET_NODE_TYPE_SOCK) {
                if (node->read_cbk_sock) {
                    node->read_cbk_sock(node->sock, node->user_data);
                }
            } else {
                if (node->read_cbk) {
                    node->read_cbk(node->fd, node->user_data);
                }
            }
        }
        
        /* Write readiness - use appropriate callback based on socket type */
        if (events[i].events & EPOLLOUT) {
            if (node->type == SOCKET_NODE_TYPE_SOCK) {
                if (node->write_cbk_sock) {
                    node->write_cbk_sock(node->sock, node->user_data);
                }
            } else {
                if (node->write_cbk) {
                    node->write_cbk(node->fd, node->user_data);
                }
            }
        }
    }
}
#endif

// Instance version
void uasync_poll(struct UASYNC* ua, int timeout_tb) {
    if (!ua) return;
    if (!ua->sockets || !ua->timeout_heap) return;

    DEBUG_DEBUG(DEBUG_CATEGORY_TIMERS, "poll");
    
    // Handle negative or zero timeout
    if (timeout_tb < 0) timeout_tb = -1;  // Infinite wait
    else if (timeout_tb == 0) timeout_tb = 0;  // No wait
    
    // Get next timeout
    struct timeval next_timeout;
    get_next_timeout(ua, &next_timeout);
    
    // Convert requested timeout to timeval
    struct timeval req_timeout = {0};
    if (timeout_tb >= 0) {
        req_timeout.tv_sec = timeout_tb / 10000;
        req_timeout.tv_usec = (timeout_tb % 10000) * 100;
    }
    
    // Use minimum of requested and next timer if both finite
    struct timeval poll_timeout;
    if (timeout_tb < 0) {
        // Infinite requested - use next timer if any
        poll_timeout = next_timeout;
    } else {
        // Finite requested - min of requested and next
        if (next_timeout.tv_sec < req_timeout.tv_sec ||
            (next_timeout.tv_sec == req_timeout.tv_sec && next_timeout.tv_usec < req_timeout.tv_usec)) {
            poll_timeout = next_timeout;
        } else {
            poll_timeout = req_timeout;
        }
    }
    
    int timeout_ms;
    if (timeout_tb < 0 && (next_timeout.tv_sec > 0 || next_timeout.tv_usec > 0)) {
        timeout_ms = (poll_timeout.tv_sec * 1000) + (poll_timeout.tv_usec / 1000);
    } else if (timeout_tb < 0) {
        timeout_ms = -1;  // Infinite
    } else {
        timeout_ms = (poll_timeout.tv_sec * 1000) + (poll_timeout.tv_usec / 1000);
    }
    
    // Count active sockets
    int socket_count = ua->sockets->count;
    if (socket_count == 0 && timeout_ms == -1) {
        // No sockets and infinite wait - but we have timers? Wait for timer
        if (ua->timeout_heap->size > 0) {
            timeout_ms = (poll_timeout.tv_sec * 1000) + (poll_timeout.tv_usec / 1000);
        } else {
            // Nothing to do - return immediately
            return;
        }
    }
    
#if HAS_EPOLL
    // Use epoll on Linux if available
    if (ua->use_epoll && ua->epoll_fd >= 0) {
        struct epoll_event events[64];  // Stack-allocated array for events
        int max_events = 64;
        
        int ret = epoll_wait(ua->epoll_fd, events, max_events, timeout_ms);
        if (ret < 0) {
            if (errno == EINTR) {
                return;
            }
            perror("epoll_wait");
            return;
        }
        
        /* Process socket events */
        if (ret > 0) {
            process_epoll_events(ua, events, ret);
        }
        
        /* Process timeouts that may have expired during poll or socket processing */
        process_timeouts(ua);
        return;
    }
#endif
    
    // Fallback to poll() for non-Linux or if epoll failed
    
    // Include wakeup pipe if initialized
    int wakeup_fd_present = ua->wakeup_initialized && ua->wakeup_pipe[0] >= 0;
    int total_fds = socket_count + wakeup_fd_present;
    
    // Rebuild poll_fds if dirty or not allocated
    if (ua->poll_fds_dirty || !ua->poll_fds) {
        rebuild_poll_fds(ua);
    }
    
    // Ensure poll_fds_count matches current state (in case sockets changed without dirty flag)
    if (ua->poll_fds_count != total_fds) {
        rebuild_poll_fds(ua);
    }
    
    /* Call poll with cached fds */
    int ret = poll(ua->poll_fds, ua->poll_fds_count, timeout_ms);
    if (ret < 0) {
        if (errno == EINTR) {
            return;
        }
        perror("poll");
        return;
    }
    
    /* Process socket events first to give sockets higher priority */
    if (ret > 0) {
        for (int i = 0; i < ua->poll_fds_count; i++) {
            if (ua->poll_fds[i].revents == 0) continue;
            
            /* Handle wakeup fd separately */
            if (wakeup_fd_present && i == 0) {
                if (ua->poll_fds[i].revents & POLLIN) {
                    drain_wakeup_pipe(ua);
                }
                continue;
            }
            
            /* Socket event - lookup by fd */
            struct socket_node* node = socket_array_get(ua->sockets, ua->poll_fds[i].fd);
            if (!node) {  // Try by socket_t (in case this is a socket)
                socket_t lookup_sock;
#ifdef _WIN32
                lookup_sock = (socket_t)(intptr_t)ua->poll_fds[i].fd;
#else
                lookup_sock = ua->poll_fds[i].fd;
#endif
                node = socket_array_get_by_sock(ua->sockets, lookup_sock);
            }
            if (!node) continue;  // Socket may have been removed
            
            /* Check for error conditions first */
            if (ua->poll_fds[i].revents & (POLLERR | POLLHUP | POLLNVAL)) {
                /* Treat as exceptional condition */
                if (node->except_cbk) {
                    node->except_cbk(node->fd, node->user_data);
                }
            }
            
            /* Exceptional data (out-of-band) */
            if (ua->poll_fds[i].revents & POLLPRI) {
                if (node->except_cbk) {
                    node->except_cbk(node->fd, node->user_data);
                }
            }
            
            /* Read readiness - use appropriate callback based on socket type */
            if (ua->poll_fds[i].revents & POLLIN) {
                if (node->type == SOCKET_NODE_TYPE_SOCK) {
                    if (node->read_cbk_sock) {
                        node->read_cbk_sock(node->sock, node->user_data);
                    }
                } else {
                    if (node->read_cbk) {
                        node->read_cbk(node->fd, node->user_data);
                    }
                }
            }
            
            /* Write readiness - use appropriate callback based on socket type */
            if (ua->poll_fds[i].revents & POLLOUT) {
                if (node->type == SOCKET_NODE_TYPE_SOCK) {
                    if (node->write_cbk_sock) {
                        node->write_cbk_sock(node->sock, node->user_data);
                    }
                } else {
                    if (node->write_cbk) {
                        node->write_cbk(node->fd, node->user_data);
                    }
                }
            }
        }
    }
    
    /* Process timeouts that may have expired during poll or socket processing */
    process_timeouts(ua);
}



// ========== Instance management functions ==========

struct UASYNC* uasync_create(void) {
    // Initialize socket platform first (WSAStartup on Windows)
    if (socket_platform_init() != 0) {
        DEBUG_ERROR(DEBUG_CATEGORY_SOCKET, "Failed to initialize socket platform");
        return NULL;
    }

    struct UASYNC* ua = malloc(sizeof(struct UASYNC));
    if (!ua) {
        socket_platform_cleanup();
        return NULL;
    }
    
    memset(ua, 0, sizeof(struct UASYNC));
    ua->wakeup_pipe[0] = -1;
    ua->wakeup_pipe[1] = -1;
    ua->wakeup_initialized = 0;
    
    // Create wakeup pipe
    if (pipe(ua->wakeup_pipe) < 0) {
        DEBUG_WARN(DEBUG_CATEGORY_UASYNC, "Failed to create wakeup pipe: %s", strerror(errno));
        // Continue without wakeup mechanism
        ua->wakeup_pipe[0] = -1;
        ua->wakeup_pipe[1] = -1;
    } else {
        ua->wakeup_initialized = 1;
        // Set non-blocking on read end to avoid blocking if pipe is full
        int flags = fcntl(ua->wakeup_pipe[0], F_GETFL, 0);
        if (flags >= 0) {
            fcntl(ua->wakeup_pipe[0], F_SETFL, flags | O_NONBLOCK);
        }
    }
    
    ua->sockets = socket_array_create(16);
    if (!ua->sockets) {
        if (ua->wakeup_initialized) {
            close(ua->wakeup_pipe[0]);
            close(ua->wakeup_pipe[1]);
        }
        free(ua);
        return NULL;
    }
    
    ua->timeout_heap = timeout_heap_create(16);
    if (!ua->timeout_heap) {
        socket_array_destroy(ua->sockets);
        if (ua->wakeup_initialized) {
            close(ua->wakeup_pipe[0]);
            close(ua->wakeup_pipe[1]);
        }
        free(ua);
        return NULL;
    }
    
    // Set callback to free timeout nodes and update counters
    timeout_heap_set_free_callback(ua->timeout_heap, ua, timeout_node_free_callback);
    
    // Initialize epoll on Linux
    ua->epoll_fd = -1;
    ua->use_epoll = 0;
#if HAS_EPOLL
    ua->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
    if (ua->epoll_fd >= 0) {
        ua->use_epoll = 1;
        DEBUG_INFO(DEBUG_CATEGORY_UASYNC, "Using epoll for socket monitoring");
        // Add wakeup pipe to epoll
        if (ua->wakeup_initialized) {
            struct epoll_event ev;
            ev.events = EPOLLIN;
            ev.data.ptr = NULL;  // NULL ptr indicates wakeup fd
            if (epoll_ctl(ua->epoll_fd, EPOLL_CTL_ADD, ua->wakeup_pipe[0], &ev) < 0) {
                DEBUG_WARN(DEBUG_CATEGORY_UASYNC, "Failed to add wakeup pipe to epoll: %s", strerror(errno));
            }
        }
    } else {
        DEBUG_WARN(DEBUG_CATEGORY_UASYNC, "Failed to create epoll fd, falling back to poll: %s", strerror(errno));
    }
#endif
    
    return ua;
}

// Print all resources for debugging
void uasync_print_resources(struct UASYNC* ua, const char* prefix) {
    if (!ua) {
        printf("%s: NULL uasync instance\n", prefix);
        return;
    }
    
    printf("\n🔍 %s: UASYNC Resource Report for %p\n", prefix, ua);
    printf("   Timer Statistics: allocated=%zu, freed=%zu, active=%zd\n",
           ua->timer_alloc_count, ua->timer_free_count,
           (ssize_t)(ua->timer_alloc_count - ua->timer_free_count));
    printf("   Socket Statistics: allocated=%zu, freed=%zu, active=%zd\n",
           ua->socket_alloc_count, ua->socket_free_count,
           (ssize_t)(ua->socket_alloc_count - ua->socket_free_count));
    
    // Показать активные таймеры
    if (ua->timeout_heap) {
        size_t active_timers = 0;
        // Безопасное чтение без извлечения - просто итерируем по массиву
        for (size_t i = 0; i < ua->timeout_heap->size; i++) {
            if (!ua->timeout_heap->heap[i].deleted) {
                active_timers++;
                struct timeout_node* node = (struct timeout_node*)ua->timeout_heap->heap[i].data;
                printf("   Timer: node=%p, expires=%llu ms, cancelled=%d\n",
                       node, (unsigned long long)ua->timeout_heap->heap[i].expiration, node->cancelled);
            }
        }
        printf("   Active timers in heap: %zu\n", active_timers);
    }
    
    // Показать активные сокеты
    if (ua->sockets) {
        int active_sockets = 0;
        printf("   Socket array capacity: %d, active: %d\n",
               ua->sockets->capacity, ua->sockets->count);
        for (int i = 0; i < ua->sockets->capacity; i++) {
            if (ua->sockets->sockets[i].active) {
                active_sockets++;
                printf("   Socket: fd=%d, active=%d\n",
                       ua->sockets->sockets[i].fd,
                       ua->sockets->sockets[i].active);
            }
        }
        printf("   Total active sockets: %d\n", active_sockets);
    }
    
    printf("🔚 %s: End of resource report\n\n", prefix);
}

void uasync_destroy(struct UASYNC* ua, int close_fds) {
    if (!ua) return;
    
    DEBUG_DEBUG(DEBUG_CATEGORY_TIMERS, "uasync_destroy: starting cleanup for ua=%p", ua);
    
    // Диагностика ресурсов перед очисткой
    uasync_print_resources(ua, "BEFORE_DESTROY");
    
    // Check for potential memory leaks
    if (ua->timer_alloc_count != ua->timer_free_count || ua->socket_alloc_count != ua->socket_free_count) {
        DEBUG_ERROR(DEBUG_CATEGORY_MEMORY, "Memory leaks detected before cleanup: timers %zu/%zu, sockets %zu/%zu",
                   ua->timer_alloc_count, ua->timer_free_count, ua->socket_alloc_count, ua->socket_free_count);
        DEBUG_ERROR(DEBUG_CATEGORY_TIMERS, "Timer leak: allocated=%zu, freed=%zu, diff=%zd",
                   ua->timer_alloc_count, ua->timer_free_count, 
                   (ssize_t)(ua->timer_alloc_count - ua->timer_free_count));
        DEBUG_ERROR(DEBUG_CATEGORY_TIMERS, "Socket leak: allocated=%zu, freed=%zu, diff=%zd", 
                   ua->socket_alloc_count, ua->socket_free_count,
                   (ssize_t)(ua->socket_alloc_count - ua->socket_free_count));
        // Continue cleanup, will abort after if leaks remain
    }
    
    // Free all remaining timeouts
    if (ua->timeout_heap) {
        size_t freed_count = 0;
        while (1) {
            TimeoutEntry entry;
            if (timeout_heap_pop(ua->timeout_heap, &entry) != 0) break;
            struct timeout_node* node = (struct timeout_node*)entry.data;
            
            // Free all timer nodes (avoid double-free bug)
            if (node) {
                ua->timer_free_count++;
                free(node);
            }
        }
        timeout_heap_destroy(ua->timeout_heap);
    }
    
    // Free all socket nodes using array approach
    if (ua->sockets) {
        // Count and free all active sockets
        int freed_count = 0;
        for (int i = 0; i < ua->sockets->capacity; i++) {
            if (ua->sockets->sockets[i].active) {
                if (close_fds && ua->sockets->sockets[i].fd >= 0) {
                    close(ua->sockets->sockets[i].fd);
                }
                ua->socket_free_count++;
                freed_count++;
            }
        }
        DEBUG_DEBUG(DEBUG_CATEGORY_MEMORY, "Freed %d socket nodes in destroy", freed_count);
        socket_array_destroy(ua->sockets);
    }
    
    // Close wakeup pipe
    if (ua->wakeup_initialized) {
        close(ua->wakeup_pipe[0]);
        close(ua->wakeup_pipe[1]);
    }
    
    // Free cached poll_fds
    free(ua->poll_fds);
    
    // Close epoll fd on Linux
#if HAS_EPOLL
    if (ua->epoll_fd >= 0) {
        close(ua->epoll_fd);
    }
#endif
    
    // Final leak check
    if (ua->timer_alloc_count != ua->timer_free_count || ua->socket_alloc_count != ua->socket_free_count) {
        DEBUG_ERROR(DEBUG_CATEGORY_MEMORY, "Memory leaks detected after cleanup: timers %zu/%zu, sockets %zu/%zu",
                   ua->timer_alloc_count, ua->timer_free_count, ua->socket_alloc_count, ua->socket_free_count);
        DEBUG_ERROR(DEBUG_CATEGORY_TIMERS, "FINAL Timer leak: allocated=%zu, freed=%zu, diff=%zd",
                   ua->timer_alloc_count, ua->timer_free_count,
                   (ssize_t)(ua->timer_alloc_count - ua->timer_free_count));
        DEBUG_ERROR(DEBUG_CATEGORY_TIMERS, "FINAL Socket leak: allocated=%zu, freed=%zu, diff=%zd",
                   ua->socket_alloc_count, ua->socket_free_count,
                   (ssize_t)(ua->socket_alloc_count - ua->socket_free_count));
        abort();
    }
    
    DEBUG_DEBUG(DEBUG_CATEGORY_TIMERS, "uasync_destroy: completed successfully for ua=%p", ua);
    free(ua);
    
    // Cleanup socket platform (WSACleanup on Windows)
    socket_platform_cleanup();
}

void uasync_init_instance(struct UASYNC* ua) {
    if (!ua) return;
    
    // Initialize socket array if not present
    if (!ua->sockets) {
        ua->sockets = socket_array_create(16);
    }
    
    if (!ua->timeout_heap) {
        ua->timeout_heap = timeout_heap_create(16);
        if (ua->timeout_heap) {
            timeout_heap_set_free_callback(ua->timeout_heap, ua, timeout_node_free_callback);
        }
    }
}

// Debug statistics
void uasync_get_stats(struct UASYNC* ua, size_t* timer_alloc, size_t* timer_free, size_t* socket_alloc, size_t* socket_free) {
    if (!ua) return;
    if (timer_alloc) *timer_alloc = ua->timer_alloc_count;
    if (timer_free) *timer_free = ua->timer_free_count;
    if (socket_alloc) *socket_alloc = ua->socket_alloc_count;
    if (socket_free) *socket_free = ua->socket_free_count;
}

// Get global instance for backward compatibility

// Wakeup mechanism
int uasync_wakeup(struct UASYNC* ua) {
    if (!ua || !ua->wakeup_initialized) return -1;
    
    char byte = 0;
    ssize_t ret = write(ua->wakeup_pipe[1], &byte, 1);
    if (ret != 1) {
        // Don't print error from signal handler
        return -1;
    }
    return 0;
}

int uasync_get_wakeup_fd(struct UASYNC* ua) {
    if (!ua || !ua->wakeup_initialized) return -1;
    return ua->wakeup_pipe[1];
}

/* Lookup socket by file descriptor - returns current pointer even after realloc */
int uasync_lookup_socket(struct UASYNC* ua, int fd, void** socket_id) {
    if (!ua || !ua->sockets || !socket_id || fd < 0 || fd >= FD_SETSIZE) {
        return -1;
    }
    
    *socket_id = socket_array_get(ua->sockets, fd);
    return (*socket_id != NULL) ? 0 : -1;
}

void uasync_mainloop(struct UASYNC* ua) {
    while (1) {
        uasync_poll(ua, -1);  // Infinite wait
    }
}