#ifndef INCLUDED_C_INDEXPQ_H
#define INCLUDED_C_INDEXPQ_H

#ifndef INCLUDED_C_BASE_H
#include <c_Base.h>
#endif /*INCLUDED_C_BASE_H*/


/* ------------------------------------------------------------------------------------------------------------------ */
/*  */

// User priority comparison callback: returns <0 if a < b, 0 if a == b, >0 if a > b
typedef int (*c_IndexPQ_Compare_f)(const void* a, const void* b);

typedef struct {
    void* keys_data;             // Array storing user element data values indexed by ID
    c_size_t* heap;              // Binary heap array containing element IDs
    c_size_t* inverse_heap;      // Maps element ID -> its current position index within the heap array
    int obj_size;                // Memory size of each user element structure
    c_size_t max_size;           // Maximum number of items the Indexed PQ can handle
    c_size_t size;               // Current number of active elements inside the queue
    c_IndexPQ_Compare_f compare; // User-defined priority comparison callback
} c_IndexPQ_t;

c_err_t c_IndexPQ_Init(c_IndexPQ_t* self, int obj_size, c_size_t max_size, c_IndexPQ_Compare_f compare);
void c_IndexPQ_Destroy(c_IndexPQ_t* self);

c_err_t c_IndexPQ_Push(c_IndexPQ_t* self, c_size_t id, const void* obj);
c_err_t c_IndexPQ_Pop(c_IndexPQ_t* self, c_size_t* out_id, void* out_obj);
c_err_t c_IndexPQ_Change(c_IndexPQ_t* self, c_size_t id, const void* new_obj);
c_bool_t c_IndexPQ_Contains(const c_IndexPQ_t* self, c_size_t id);

void* c_IndexPQ_PeekValue(c_IndexPQ_t* self);
long long c_IndexPQ_PeekID(c_IndexPQ_t* self);
c_size_t c_IndexPQ_GetSize(const c_IndexPQ_t* self);
c_bool_t c_IndexPQ_IsEmpty(const c_IndexPQ_t* self);

#endif /*INCLUDED_C_INDEXPQ_H*/