// timeout_heap.h

#ifndef TIMEOUT_HEAP_H
#define TIMEOUT_HEAP_H

#include <stdint.h>  // For uint64_t
#include <stddef.h>  // For size_t

typedef uint64_t TimeoutTime;  // e.g., milliseconds since epoch or from now

typedef struct {
    TimeoutTime expiration;  // Sort key (smaller = earlier)
    void *data;              // User data (e.g., callback or ID)
    int deleted;             // 0 = active, 1 = deleted
} TimeoutEntry;

typedef struct TimeoutHeap TimeoutHeap;

struct TimeoutHeap {
    TimeoutEntry *heap;      // Dynamic array
    size_t size;             // Current number of elements
    size_t capacity;         // Allocated size
    size_t freed_count;      // Number of freed timer nodes
    void* user_data;         // User data for free callback
    void (*free_callback)(void* user_data, void* data); // Callback to free data
};

/**
 * Create a new timeout heap with initial capacity.
 * @param initial_capacity Starting capacity (will grow as needed).
 * @return Pointer to the heap, or NULL on failure.
 */
TimeoutHeap *timeout_heap_create(size_t initial_capacity);

/**
 * Destroy the timeout heap and free resources.
 * @param h The heap to destroy.
 */
void timeout_heap_destroy(TimeoutHeap *h);

/**
 * Set a callback function to free data when deleted nodes are removed.
 * @param h The heap.
 * @param user_data User data passed to callback.
 * @param callback Callback function (if NULL, data is freed with free()).
 */
void timeout_heap_set_free_callback(TimeoutHeap *h, void* user_data, void (*callback)(void* user_data, void* data));

/**
 * Insert a new timeout into the heap.
 * @param h The heap.
 * @param expiration The expiration time.
 * @param data User data associated with the timeout.
 * @return 0 on success, -1 on allocation failure.
 */
int timeout_heap_push(TimeoutHeap *h, TimeoutTime expiration, void *data);

/**
 * Peek at the earliest non-deleted timeout without removing it.
 * @param h The heap.
 * @param out Where to store the entry.
 * @return 0 on success, -1 if empty.
 */
int timeout_heap_peek(TimeoutHeap *h, TimeoutEntry *out);

/**
 * Pop the earliest non-deleted timeout from the heap.
 * @param h The heap.
 * @param out Where to store the entry.
 * @return 0 on success, -1 if empty.
 */
int timeout_heap_pop(TimeoutHeap *h, TimeoutEntry *out);

/**
 * Cancel a timeout by matching expiration and data.
 * Scans the heap linearly, so O(n) time.
 * Assumes combinations are unique; cancels the first match.
 * @param h The heap.
 * @param expiration The expiration time to match.
 * @param data The data to match.
 * @return 0 if found and canceled, -1 if not found.
 */
int timeout_heap_cancel(TimeoutHeap *h, TimeoutTime expiration, void *data);

/**
 * Get the number of freed timer nodes.
 * @param h The heap.
 * @return Count of freed timer nodes.
 */
size_t timeout_heap_get_freed_count(TimeoutHeap *h);

#endif // TIMEOUT_HEAP_H