#!/usr/bin/python3

import numpy as np
from operator import itemgetter

def s2p_to_narray(file):
    """ prebere s2p file v narray. STOLPCI --> VRSTICE!!! """
    return np.loadtxt(file, comments=('!','#')).T

def narray_to_s(narray):
    """ prebran s2p narray posortiram po s parametrih.
        pri tem upostevam vrstni red:
        f s11 s21 s12 s22, kjer sta za vsak s parameter
        dve vrstici: realni in imaginarni del """
    keys = ["s{}{}".format(j,i) for i in range(1,3) for j in range(1,3)]
    s = {}
    for i in range(4):
        s[keys[i]] = narray[(2*i+1),:]+1j*narray[(2*i+2),:]
    s['f'] = narray[0,:]
    return s

def s_to_eps(s, L):
    """ izracunam eps in tand iz s parametrov in dolzin """
    s11, s21, s12, s22, f = itemgetter(*s.keys())(s) 

    X = (s11**2 - s21**2 + 1)/2/s11
    G = X + np.sqrt(X**2 - 1)
    if np.abs(G) > 1:
        G = X - np.sqrt(X**2 - 1)
    P = (s11 + s21 - G)/(1-(s11+s21)*G)
    Lambda2 = - (1/2/np.pi/L * np.log(1/P))**2 #izmisli resitev za korene kompleksnega logaritma
    # argument korena mora biti 2*pi*n, kjer je n=L/lambda_g

    return

a=s2p_to_narray('20.s2p')
b = narray_to_s(a)
s_to_eps(b,0,0,0)