# Copyright (c) 2005, the Lawrence Journal-World
# Copyright (c) 2006 L. C. Rees
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'''File-based cache

shove's psuedo-URL for file caches follows the form:

file://<path>

Where the path is a URL path to a directory on a local filesystem.
Alternatively, a native pathname to the directory can be passed as the 'engine'
argument.
'''

import time

from shove import FileBase
from shove.cache.simple import SimpleCache

__all__ = ['FileCache']


class FileCache(FileBase, SimpleCache):

    '''File-based cache backend'''    
    
    def __init__(self, engine, **kw):
        super(FileCache, self).__init__(engine, **kw)

    def __getitem__(self, key):
        try:
            exp, value = super(FileCache, self).__getitem__(key)
            # Remove item if time has expired.
            if exp < time.time():
                del self[key]
                raise KeyError('%s' % key)  
            return value
        except:
            raise KeyError('%s' % key)                

    def __setitem__(self, key, value):
        if len(self) >= self._max_entries: self._cull()
        super(FileCache, self).__setitem__(
            key, 
            (time.time() + self.timeout, value)
        )