#ifndef INCLUDED_C_BUDDYALLOCATOR_H
#define INCLUDED_C_BUDDYALLOCATOR_H

#ifndef INCLUDED_C_BUDDY_H
#include <c_Buddy.h>
#endif /*INCLUDED_C_BUDDY_H*/


#ifndef INCLUDED_C_ALLOCATOR_H
#include <c_Allocator.h>
#endif /*INCLUDED_C_ALLOCATOR_H*/


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

typedef struct {
    c_Buddy_t* buddy;
}c_BuddyAllocator_t;

C_STATIC_FORCE_INLINE
void c_BuddyAllocator_Init(c_BuddyAllocator_t* allocator, c_Buddy_t* buddy) {
    allocator->buddy = buddy;
}

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

C_STATIC_FORCE_INLINE
C_ALLOCATOR_ALLOC_FN(c_BuddyAllocator_Alloc) {
    c_BuddyAllocator_t* self = (c_BuddyAllocator_t*)ud;
    if (!self || !self->buddy) return NULL;
    return c_Buddy_Alloc(self->buddy, (int)nBytes);
}

C_STATIC_FORCE_INLINE
C_ALLOCATOR_FREE_FN(c_BuddyAllocator_Free) {
    c_BuddyAllocator_t* self = (c_BuddyAllocator_t*)ud;
    if (!self || !self->buddy) return;
    c_Buddy_Free(self->buddy, ptr);
}

C_STATIC_FORCE_INLINE
C_ALLOCATOR_REALLOC_FN(c_BuddyAllocator_Realloc) {
    c_BuddyAllocator_t* self = (c_BuddyAllocator_t*)ud;
    if (!self || !self->buddy) return NULL;
    // 情况 1: 指针为空，直接分配新内存
    if (!ptr) {
        return c_Buddy_Alloc(self->buddy, (int)nNewSize);
    }
    // 情况 2: 新大小为 0，直接释放内存
    if (nNewSize==0) {
        c_Buddy_Free(self->buddy, ptr);
        return NULL;
    }
    // 核心优化：利用 Header 逆向获取该块在底层伙伴系统中的真实物理大小
    const c_BuddyBlock_t *block = (c_BuddyBlock_t *) ((uint8_t *) ptr - self->buddy->alignment);
    const int actual_block_size = block->size;

    // 【就地复用判定】：如果新申请的大小没有超过当前伙伴块的物理承载上限，并且新大小不至于小到需要缩容割裂
    // 直接返回原指针，零拷贝，零内存搬迁！
    if ((int)nNewSize <= actual_block_size && (int)nNewSize > (actual_block_size / 2)) {
        return ptr;
    }

    // 情况 3: 伙伴块大小不匹配（需要升级或降级阶数），申请新块
    void* new_ptr = c_Buddy_Alloc(self->buddy, (int)nNewSize);
    if (!new_ptr) return NULL;

    // 计算安全的拷贝长度
    const c_size_t copy_size = ((c_size_t)actual_block_size < nNewSize) ? (c_size_t)actual_block_size : nNewSize;

    // 数据迁移
    memcpy(new_ptr, ptr, copy_size);

    // 释放旧伙伴块
    c_Buddy_Free(self->buddy, ptr);

    return new_ptr;
}

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

C_STATIC_FORCE_INLINE
c_Allocator_t c_BuddyAllocator_Build(c_BuddyAllocator_t* self, c_Buddy_t* buddy) {
    c_BuddyAllocator_Init(self, buddy);
    c_Allocator_t allocator={0};
    allocator.ud = self;
    allocator.alloc = c_BuddyAllocator_Alloc;
    allocator.free = c_BuddyAllocator_Free;
    allocator.realloc = c_BuddyAllocator_Realloc;
    return allocator;
}

#endif /*INCLUDED_C_BUDDYALLOCATOR_H*/