'''
Record the spikes at a synapse with Brian 2. Note that you cannot use
SpikeMonitor for this task, as it is only meant to record from a NeuronGroup
(or another SpikeSource such as PoissonGroup).
'''
from brian2 import *
# The record_spikes function only works with the numpy target
prefs.codegen.target = 'numpy'

synapse_spikes = []
@check_units(i=1, j=1, k=1, t=second, result=1)
def record_spikes(i, j, k, t):
    for i, j, k in zip(i, j, k):
        synapse_spikes.append((i, j, k, t/second))
    return 0.0  # dummy result

G = NeuronGroup(2, 'dv/dt = 100*Hz : 1', threshold='v>1', reset='v=0')
G.v = [0, 0.5]
G2 = NeuronGroup(2, 'v:1')
S = Synapses(G, G2, pre='dummy=record_spikes(i, j, k, t)',
             multisynaptic_index='k')
S.connect('i==j', n=5)
S.delay = 'k*1*ms'
run(20*ms)
# Transform to a 2D array (one row per spike)
synapse_spikes = np.array(synapse_spikes)
print(synapse_spikes)