from time import time
from tilefetcher import TileFetcher

class TileFetcher_Memory(TileFetcher):
    def _init(self, cachesize = 256):
        '''Cachesize is the amount of tiles to keep after an upkeep() call. The count
        of tiles in cache may temporarily be larger.
        '''
        
        self.cachesize = cachesize
        self.tiles = {}
    
    def upkeep(self):
        if len(self.tiles) > self.cachesize:
            accesstimes = [tile[0] for tile in self.tiles.values()]
            accesstimes.sort(reverse = True) # oldest last
            treshold = accesstimes[self.cachesize]
            
            for key, value in self.tiles.items():
                if value[0] < treshold:
                    del self.tiles[key]
    
    def has_tile(self, coords):
        return self.tiles.has_key(coords)
    
    def _get_tile(self, coords, block):
        '''Only called if has_tile is true'''
        accesstime, image = self.tiles[coords]
        # Update accesstime
        self.tiles[coords] = (time(), image)
        return image
    
    def _put_tile(self, coords, image):
        self.tiles[coords] = (time(), image)