#!/usr/bin/env python

from gnuradio import gr

from gnuradio import audio

from gnuradio import trellis

from gnuradio import eng_notation

import math

import sys

import random

import fsm_utils

def run_test (f,Kb,bitspersymbol,K,channel,modulation,dimensionality,tot_constellation,N0,seed):

    fg = gr.flow_graph ()

    L = len(channel)

    # TX

    # this for loop is TOO slow in python!!!

    packet = [0]*(K+2*L)

    random.seed(seed)

    for i in range(len(packet)):

        packet[i] = random.randint(0, 2**bitspersymbol - 1) # random symbols

    for i in range(L): # first/last L symbols set to 0

        packet[i] = 0

        packet[len(packet)-i-1] = 0

    src = gr.vector_source_s(packet,False)

    mod = gr.chunks_to_symbols_sf(modulation[1],modulation[0])

    # CHANNEL

    isi = gr.fir_filter_fff(1,channel)

    add = gr.add_ff()

    noise = gr.noise_source_f(gr.GR_GAUSSIAN,math.sqrt(N0/2),seed)

    # RX

    skip = gr.skiphead(gr.sizeof_float, L) # skip the first L samples since you know they are coming from the L zero symbols

    #metrics = trellis.metrics_f(f.O(),dimensionality,tot_constellation,trellis.TRELLIS_EUCLIDEAN) # data preprocessing to generate metrics for Viterbi

    #va = trellis.viterbi_s(f,K+L,-1,0) # Put -1 if the Initial/Final states are not set.

    va = trellis.viterbi_combined_s(f,K+L,0,0,dimensionality,tot_constellation,trellis.TRELLIS_EUCLIDEAN) # using viterbi_combined_s instead of metrics_f/viterbi_s allows larger packet lengths because metrics_f is complaining for not being able to allocate large buffers. This is due to the large f.O() in this application...

    dst = gr.vector_sink_s()

    fg.connect (src,mod)

    fg.connect (mod,isi,(add,0))

    fg.connect (noise,(add,1))

    #fg.connect (add,metrics)

    #fg.connect (metrics,va,dst)

    fg.connect (add,skip,va,dst)

    fg.run()

    data = dst.data() 

    ntotal = len(data) - L

    nright=0

    for i in range(ntotal):

        if packet[i+L]==data[i]:

            nright=nright+1

        #else:

            #print "Error in ", i

    return (ntotal,ntotal-nright)

def main(args):

    nargs = len (args)

    if nargs == 2:

        esn0_db=float(args[0])

        rep=int(args[1])

    else:

        sys.stderr.write ('usage: test_viterbi_equalization1.py Es/No_db  repetitions\n')

        sys.exit (1)

    # system parameters

    Kb=128*16  # packet size in bits (multiple of 16)

    modulation = fsm_utils.pam4 # see fsm_utlis.py for available predefined modulations

    channel = fsm_utils.c_channel # see fsm_utlis.py for available predefined test channels

    f=trellis.fsm(len(modulation[1]),len(channel)) # generate the FSM automatically

    bitspersymbol = int(round(math.log(f.I())/math.log(2))) # bits per FSM input symbol

    K=Kb/bitspersymbol # packet size in trellis steps

    tot_channel = fsm_utils.make_isi_lookup(modulation,channel,True) # generate the lookup table (normalize energy to 1)

    dimensionality = tot_channel[0]

    tot_constellation = tot_channel[1]

    N0=pow(10.0,-esn0_db/10.0); # noise variance

    if len(tot_constellation)/dimensionality != f.O():

        sys.stderr.write ('Incompatible FSM output cardinality and lookup table size.\n')

        sys.exit (1)

    tot_s=0 # total number of transmitted shorts

    terr_s=0 # total number of shorts in error

    terr_p=0 # total number of packets in error

    for i in range(rep):

        (s,e)=run_test(f,Kb,bitspersymbol,K,channel,modulation,dimensionality,tot_constellation,N0,-long(666+i)) # run experiment with different seed to get different noise realizations

        tot_s=tot_s+s

        terr_s=terr_s+e

        terr_p=terr_p+(terr_s!=0)

        if ((i+1)%100==0) : # display progress

            print i+1,terr_p, '%.2e' % ((1.0*terr_p)/(i+1)),tot_s,terr_s, '%.2e' % ((1.0*terr_s)/tot_s)

    # estimate of the (short or symbol) error rate

    print rep,terr_p, '%.2e' % ((1.0*terr_p)/(i+1)),tot_s,terr_s, '%.2e' % ((1.0*terr_s)/tot_s)

if __name__ == '__main__':

    main (sys.argv[1:])