#include <c_ArrayQueue.h>
#include <c_Memory.h>

#define DEFAULT_INITIAL_CAPACITY    4
#define MIN_SHRINK_CAPACITY         4

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

c_err_t c_ArrayQueue_Init(c_ArrayQueue_t* self, int obj_size, c_size_t capacity) {
    if (!self || obj_size == 0) return C_ERR_PARAM;

    self->obj_size = obj_size;
    self->capacity = (capacity > 0) ? capacity : DEFAULT_INITIAL_CAPACITY;
    self->size = 0;

    self->array = C_ALLOC(self->capacity * self->obj_size);
    if (!self->array) {
        self->capacity = 0;
        return C_ERR_NOMEM;
    }

    return C_ERR_OK;
}

void c_ArrayQueue_Destroy(c_ArrayQueue_t* self) {
    if (!self) return;

    C_FREE(self->array);

    self->capacity = 0;
    self->size = 0;
    self->obj_size = 0;
}

c_err_t c_ArrayQueue_Push(c_ArrayQueue_t* self, void* obj) {
    if (!self || !self->array || !obj) return C_ERR_PARAM;

    if (self->size >= self->capacity) {
        const c_size_t new_capacity = self->capacity << 1;
        void* new_array = C_REALLOC(self->array, new_capacity * self->obj_size);
        if (!new_array) {
            return C_ERR_NOMEM;
        }
        self->array = new_array;
        self->capacity = new_capacity;
    }

    char* target = (char*)self->array + (self->size * self->obj_size);
    memcpy(target, obj, self->obj_size);
    self->size++;

    return C_ERR_OK;
}

c_err_t c_ArrayQueue_Pop(c_ArrayQueue_t* self, void* obj) {
    if (!self || !self->array ) return C_ERR_PARAM;
    if (self->size == 0) return C_ERR_EMPTY; // 佇列已空

    char* pop_src = (char*)self->array; // 最前端索引 0 的地址

    // 1. 直接值複製到呼叫端提供的記憶體中
    if (obj) {
        memcpy(obj, pop_src, self->obj_size);
    }

    // 2. 如果佇列內還有其他元素，將它們向前平移一個單位
    if (self->size > 1) {
        char* dest = pop_src;
        const char* src = pop_src + self->obj_size;
        const c_size_t num_elements_to_move = self->size - 1;
        memmove(dest, src, num_elements_to_move * self->obj_size);
    }

    self->size--;

    if (self->size > 0 && self->size <= (self->capacity >> 2)) {
        c_size_t new_capacity = self->capacity >> 1; // 容量减半

        void* new_array = C_REALLOC(self->array, new_capacity * self->obj_size);
        if (new_array) { // 如果 realloc 失败不影响原有数据安全，这里采用安全赋值
            self->array = new_array;
            self->capacity = new_capacity;
        }
    }


    return C_ERR_OK;
}

c_err_t c_ArrayQueue_Remove(c_ArrayQueue_t* self, c_size_t index) {
    if (!self || !self->array) return C_ERR_PARAM;
    if (index >= self->size) return C_ERR_OUTOFBOUND;

    if (index < self->size - 1) {
        char* dest = (char*)self->array + (index * self->obj_size);
        const char* src = dest + self->obj_size;
        const c_size_t num_elements_to_move = self->size - index - 1;
        memmove(dest, src, num_elements_to_move * self->obj_size);
    }

    self->size--;
    return C_ERR_OK;
}

void* c_ArrayQueue_Peek(c_ArrayQueue_t* self) {
    if (!self || !self->array || self->size == 0) return NULL;
    return self->array; // 最前端索引 0 的起始地址即是 array 本身
}