#include "ioqueue.h"
#include "../kernel/debug.h"
#include "../kernel/interrupt.h"

/// @brief 返回 pos 在缓冲区的下一个位置
static int32_t next_pos(int32_t pos);
/// @brief 使生产者或消费者在此缓冲区上等待
/// @param waiter
static void ioq_wait(struct task_struct **waiter);
/// @brief 唤醒 waiter
static void wakeup(struct task_struct **waiter);

/// @brief 初始化 ioqueue 队列
void ioqueue_init(struct ioqueue *ioq)
{
    lock_init(&ioq->lock);
    ioq->producer = NULL;
    ioq->consumer = NULL;
    ioq->head = 0;
    ioq->tail = 0;
}
/// @brief 返回 pos 在缓冲区的下一个位置
static int32_t next_pos(int32_t pos)
{
    return (pos + 1) % BUF_SIZE;
}

/// @brief 判断队列是否已满
/// @param ioq
/// @return TRUE OR FALSE
bool ioq_full(struct ioqueue *ioq)
{
    ASSERT(intr_get_status() == INTR_OFF);
    return next_pos(ioq->head) == ioq->tail;
}
/// @brief 判断队列是否为空
/// @param ioq
/// @return TRUE OR FALSE
bool ioq_empty(struct ioqueue *ioq)
{
    ASSERT(intr_get_status() == INTR_OFF);
    return ioq->head == ioq->tail;
}
/// @brief 使生产者或消费者在此缓冲区上等待
/// @param waiter
static void ioq_wait(struct task_struct **waiter)
{
    ASSERT(*waiter == NULL && waiter != NULL);
    *waiter = running_thread();
    thread_block(TASK_BLOCKED); // 阻塞自己
}
/// @brief 唤醒 waiter
static void wakeup(struct task_struct **waiter)
{
    ASSERT(waiter != NULL);
    thread_unblock(*waiter);
    *waiter = NULL;
}
/// @brief 消费者从 ioq 队列中获取一个字符
char ioq_getchar(struct ioqueue *ioq)
{
    ASSERT(intr_get_status() == INTR_OFF);
    // 如果 ioq 为空, 使消费者在此缓冲区上等待
    // 把 ioq->consumer 记为当前线程自己，
    // 目的是让生产者生产后唤醒
    while (ioq_empty(ioq))
    {
        lock_acquire(&ioq->lock);
        ioq_wait(&ioq->consumer);
        lock_release(&ioq->lock);
    }

    // 获取字符并从 ioq 队列中删除
    char ret = ioq->buf[ioq->tail];
    ioq->tail = next_pos(ioq->tail);

    // 唤醒生产者
    if (ioq->producer != NULL)
    {
        wakeup(&ioq->producer);
    }

    return ret;
}
/// @brief 生产者往 ioq 队列中添加一个字符
void ioq_putchar(struct ioqueue *ioq, char byte)
{
    ASSERT(intr_get_status() == INTR_OFF);
    // 如果 ioq 已满, 使生产者在此缓冲区上等待
    // 把 ioq->producer 记为当前线程自己，
    // 目的是让消费者消费后唤醒
    while (ioq_full(ioq))
    {
        lock_acquire(&ioq->lock);
        ioq_wait(&ioq->producer);
        lock_release(&ioq->lock);
    }

    // 往 ioq 队列中添加字符并使消费者在此缓冲区上等待
    ioq->buf[ioq->head] = byte;
    ioq->head = next_pos(ioq->head);

    // 唤醒消费者
    if (ioq->consumer != NULL)
    {
        wakeup(&ioq->consumer);
    }
}