import json
from itertools import chain

from crawler.Task import Task
from crawler.constants import REDIS


class RedisQueue:

    def __init__(self):
        self.redis = REDIS

    def get_len(self, key):
        keys = self.get_keys(key)
        # 每个键的任务数量
        key_len = [(k, self.redis.llen(k)) for k in keys]
        # 所有键的任务数量
        task_len = sum(dict(key_len).values())
        return task_len, key_len

    def get_keys(self, key):
        # Redis的键支持模式匹配
        keys = [key.decode() for key in self.redis.keys(key + '-[0-9]*')]
        # 按优先级将键降序排序
        keys = sorted(keys, key=lambda x: x.split('-')[-1], reverse=True)
        return keys

    def push_task(self, key, tasks, level=1, name=None):
        """
        双端队列，左边推进任务

        :param name: 键名称
        :param key: 新键名称的前缀
        :param tasks: 任务
        :param level: 优先级(int类型)，数值越大优先级越高，默认1
        :return: 任务队列任务数量
        """
        # 重新定义优先队列的key
        if name is None:
            new_key = key + '-' + str(level)
        else:
            new_key = name
        # 序列化任务参数
        tasks = [json.dumps(t, default=lambda obj: obj.__dict__['data']) for t in tasks]
        print('RedisQueue info > the number of push tasks:', len(tasks))

        if not tasks:
            return self.get_len(key)

        self.redis.lpush(new_key, *tasks)
        return self.get_len(key)

    def pop_task(self, keys, priority=False):
        """
        双端队列 右边弹出任务

        :param keys: 键列表，默认为None（将获取所有任务的keys）
        :param priority: 优先级
        :return: 键名称(_task_key)和任务(_task)
        """
        while True:
            results = []
            # 避免在while循环中修改参数，将keys参数赋值到临时变量
            temp_keys = keys
            all_keys = list(chain(*[self.get_keys(k) for k in temp_keys]))

            # 按优先级高到低弹出任务
            if priority:
                all_keys = sorted(all_keys, key=lambda x: x.split('-')[-1], reverse=True)

            if len(all_keys) > 0:
                try:
                    _task_key, _task = self.redis.brpop(all_keys, timeout=1)
                    results.extend([
                        _task_key.decode(),
                        json.loads(_task.decode(), object_hook=lambda d: Task(**d))
                    ])
                except TypeError:
                    pass
            return results


# if __name__ == '__main__':
    # mrq = RedisQueue()

    # 把任务推入redis 队列
    # lst = [Task(name=i, loop_times=i) for i in range(0, 40)]
    # print(mrq.push_task('C', lst, level=3))

    # 从redis queue取出任务
    # while True:
    #     item = mrq.pop_task(keys=['A', 'B', 'C', 'D', 'E'], priority=True)
    #     if len(item) > 0:
    #         redis_key, task = item
    #         print(redis_key, task)

    # 查看任务数量以及优先级情况
    # count, key_len = mrq.get_len('task')
    # print(key_len)