#
# Copyright 2015 Gareth Poole, All Rights Reserved

import sys
import math
from array import array

sample_rate = 44100

def floatToInt(n):
    return int(n * 32768)

def byteToBits(byte):
    bits = []
    for i in range(7, -1, -1):
        bits += [(byte >> i) & 1]
    return bits


def genSine(freq, length):
    samples = []
    length_samples = int(length * sample_rate)
    period = (1 / freq) * sample_rate
    for i in range(0, length_samples):
        samples += [floatToInt(math.sin(i * (2 * math.pi) / period))]
    return samples

def sumSamples(sample_list):
    return int(sum(sample_list) / len(sample_list))

def sumSignals(signal_list):
    return map(sumSamples, zip(*signal_list))

def encodeByte(bits, upshift, length):
    sines = []
    length_samples = int(length * sample_rate)
    for i in range(0, 8):
        if bits[i]:
            sines += [genSine((upshift * 800) + 100 * (i + 1), length)]
        else:
            sines += [[0] * length_samples]
    return sumSignals(sines)

def encodeWord(word, length):
    byte_signals = [genSine(50, length)] # pilot tone
    for i in range(16):
        byte_signals += [encodeByte(word[i], i, length)]
    return sumSignals(byte_signals)

def encodeString(string, length):
    words = []
    current_word = []
    word_position = 0
    strlen = len(string)
    samples = []

    for i in range(strlen):
        if word_position < 16:
            current_word += [byteToBits(string[i])]
            word_position += 1
            if i == strlen - 1:
                words += [current_word] # Otherwise the final word would not get saved
        else:
            words += [current_word]
            current_word = []
            word_position = 0

    for word in words:
        lenword = len(word)
        if(lenword < 16):
            word += [[0,0,0,0,0,0,0,0]] * (16 - lenword)
        samples += encodeWord(word, length)

    return samples

infile = open(sys.argv[0], "rb")
outfile = open(sys.argv[1], "wb")
array('h', encodeString(infile.read(), 0.03125)).tofile(outfile)
outfile.close()