import os
import os.path

def preparePath(template, **kwargs):
    path = template.format(**kwargs)
    os.makedirs(os.path.dirname(path), exist_ok=True)
    return path

class Cache:
    ROOT = "cache"

    def __init__(self, loader, pathPolicy=lambda *args:str(args)
            , serializer=None, unserializer=None):
        self.RAM = {}
        self.loader = loader
        self.pathPolicy = pathPolicy
        self.serializer = serializer
        self.unserializer = unserializer

    def __call__(self, *args):
        symbolicPath = self.pathPolicy(*args)
        self.heat(symbolicPath)
        if symbolicPath not in self.RAM:
            self.RAM[symbolicPath] = self.loader(*args)
            self.save(symbolicPath)
        return self.RAM[symbolicPath]

    def heat(self, symbolicPath):
        if self.unserializer and symbolicPath not in self.RAM:
            path = "{root}/{path}".format(root=Cache.ROOT, path=symbolicPath)
            if os.path.isfile(path):
                with open(path, 'r') as f:
                    self.RAM[symbolicPath] = self.unserializer(f)

    def save(self, symbolicPath):
        if self.serializer and symbolicPath in self.RAM:
            path = preparePath("{root}/{path}", root=Cache.ROOT, path=symbolicPath)
            os.makedirs(os.path.dirname(path), exist_ok=True)
            with open(path, 'w') as f:
                self.serializer(self.RAM[symbolicPath], f)