import pickle
import time
import threading

def deferFunc(func):
    def wrapper(*args):
        self = args[0]
        self.lock.acquire()
        try:
            result = func(*args)
            self.cacheKeysNum = self.cacheKeysNum + 1
            self.writeToDisk()
            return result
        finally:
            self.lock.release()
    return wrapper

class dbCache():
    def __init__(self,loadFiles):
        self.cacheFile = loadFiles
        self.lastTimes = time.time()
        self.cacheKeysNum = 0
        self.lock = threading.Lock()
        self.cacheSetting()

        try:
            with open("db.cache","rb") as f:
                self.caches = pickle.load(f)
        except Exception as e:
            print("open file errors" , e)
            self.caches = {}

    def cacheSetting(self,queueMaxKeys = 3,ageSec = 10):
        self.queueMaxKeys = queueMaxKeys
        self.ageSec = ageSec

    def writeToDisk(self):
        if self.cacheKeysNum >= self.queueMaxKeys or (time.time() - self.lastTimes) >= self.ageSec:
            with open(self.cacheFile, "wb") as f:
                pickle.dump(self.caches, f)

            self.lastTimes = time.time()
            self.cacheKeysNum = 0

    @deferFunc
    def get(self,key):
        if key in self.caches:
            return self.caches[key]
        else:
            return None

    @deferFunc
    def set(self,key,value):
        if key != "":
            self.caches[key] = value
        else:
            raise "key cannot be empty"

    def isExists(self,key):
        if key in self.caches:
            return True
        else:
            return False

    @deferFunc
    def update(self,key,value):
        if self.isExists(key):
            self.caches[key] = value
            return True
        else:
            return False

    @deferFunc
    def delete(self,key):
        if self.isExists(key):
            del self.caches[key]
            return True
        else:
            return False

def main() -> None:
    c = dbCache("db.cache")
    c.cacheSetting(queueMaxKeys=3,ageSec=3)
    c.set("name","pdudo")
    time.sleep(5)
    c.set("site","juejin")
    print(c.get("name"))
    c.delete("name")
    c.update("site","pdudo")


if __name__ == '__main__':
    main()