#include <c_LinkQueue.h>
#include <c_Memory.h>
#include "c_Alignment.h"
#include "c_Macros.h"

c_err_t c_LinkQueue_Init(c_LinkQueue_t* self, int obj_size) {
    if (!self || obj_size == 0) return C_ERR_PARAM;
    self->head = NULL;
    self->tail = NULL;
    self->obj_size = (int)obj_size;
    self->size = 0;
    return C_ERR_OK;
}

void c_LinkQueue_Destroy(c_LinkQueue_t* self) {
    if (!self) return;

    c_LinkQueueNode_t* current = self->head;
    while (current != NULL) {
        c_LinkQueueNode_t* next = current->next;
        C_FREE(current);
        current = next;
    }
    self->head = NULL;
    self->tail = NULL;
    self->size = 0;
}

c_err_t c_LinkQueue_Push(c_LinkQueue_t* self, void* obj) {
    if (!self || !obj) return C_ERR_PARAM;

    // 1. 配置新節點與資料空間
    int size = (int)sizeof(c_LinkQueueNode_t) + self->obj_size;
    size = C_ALIGN_UPB(size, C_ALIGN_SIZE);
    c_LinkQueueNode_t* new_node = (c_LinkQueueNode_t*)C_ALLOC(size);
    if (!new_node) return C_ERR_NOMEM;
    new_node->data = new_node+1;

    // 深複製資料內容
    memcpy(new_node->data, obj, self->obj_size);
    new_node->next = NULL;

    // 2. 將新節點追加到串列尾端
    if (self->tail == NULL) {
        // 佇列原本為空
        self->head = new_node;
        self->tail = new_node;
    } else {
        // 佇列不為空，讓原本尾端的 next 指向新節點，並更新 tail
        self->tail->next = new_node;
        self->tail = new_node;
    }

    self->size++;
    return C_ERR_OK;
}

c_err_t c_LinkQueue_Pop(c_LinkQueue_t* self, void* obj) {
    if (!self ) return C_ERR_PARAM;
    if (self->size == 0 || !self->head) return C_ERR_EMPTY;

    c_LinkQueueNode_t* to_delete = self->head;

    // 1. 複製資料到使用者緩衝區
    if (obj) {
        memcpy(obj, to_delete->data, self->obj_size);
    }

    // 2. 將 head 移至下一個節點
    self->head = to_delete->next;

    if (self->head == NULL) {
        self->tail = NULL;
    }

    // 3. 釋放斷開的節點資源
    C_FREE(to_delete);

    self->size--;
    return C_ERR_OK;
}

c_err_t c_LinkQueue_Peek(c_LinkQueue_t* self, void* obj) {
    if (!self ) return C_ERR_PARAM;
    if (self->size == 0 || !self->head) return C_ERR_EMPTY;

    // 複製最前端的資料內容
    if (obj) {
        memcpy(obj, self->head->data, self->obj_size);
    }
    return C_ERR_OK;
}

void c_LinkQueueIter_Remove(c_LinkQueueIter_t* self) {
    if (!self || !self->queue || !self->node || !*(self->node)) return;

    c_LinkQueueNode_t* to_delete = *(self->node);
    c_LinkQueue_t* q = self->queue;

    // 檢查目前要刪除的是否為尾端節點
    const c_bool_t is_tail = (to_delete == q->tail);

    // 讓上一個節點的 next（或 head）直接指向下一個節點，將 to_delete 從串列中斷開
    *(self->node) = to_delete->next;

    // 如果刪除的是尾端節點，必須更新 tail 指標
    if (is_tail) {
        if (q->head == NULL) {
            // 情況 A：刪除後佇列完全空了
            q->tail = NULL;
        } else {
            // 情況 B：刪除的是尾巴，但前方還有元素。
            // 沿著 head 重新走訪一遍，找出現在最尾端的節點（即 next 為 NULL 的節點）
            c_LinkQueueNode_t* curr = q->head;
            while (curr->next != NULL) {
                curr = curr->next;
            }
            q->tail = curr; // 更新新的尾端
        }
    }

    // 釋放記憶體資源
    C_FREE(to_delete);

    // 同步遞減佇列大小
    q->size--;

    // 此時 self->node 已自動留在原本的下一個節點上，呼叫端可直接繼續 Get() 或 Next()
}