import json
from itertools import chain

from common.execptions import TaskError
from common.log import logger
from crawler.Task import Task
from settings 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):
        """
        双端队列，左边推进任务

        :param key: 键名称
        :param tasks: 任务列表
        :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
        new_key = key + '-' + str(level)

        # 序列化任务参数
        tasks = [json.dumps(t, default=lambda obj: obj.__dict__['data']) for t in tasks]
        logger.info(f'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: list, priority=False):
        """
        双端队列 右边弹出任务

        :param keys: 键列表
        :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
            if not isinstance(keys, list):
                raise TaskError(f'keys类型:list,当前类型:{type(keys).__name__}')
            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