from ca.nengo.util import MU

import random
def destroy_connections(w,proportion):
    if proportion>1: proportion=1
    total=len(w)*len(w)
    
    pool=list(xrange(total))
    for i in xrange(int(proportion*total)):
        x=random.randrange(total-i)        
        w[x/len(w)][x%len(w)]=0
        pool[x]=pool[total-i-1]        
        
    return w
    
    
def make_weights(network,source,origin,target,termination,pstc,transform=None,destroy=0): 
    source=network.getNode(source)
    target=network.getNode(target)   
    
    decoder=source.getOrigin(origin).decoders    
    
    if transform is not None:
        decoder=MU.prod(decoder,transform)
    
    w=MU.prod(target.encoders,MU.transpose(decoder))
    
    if destroy>0:
        destroy_connections(w,destroy)
    
    t=target.addTermination(termination,w,pstc,False)
    network.addProjection(source.getOrigin('AXON'),t)