import random

def generate_pressure_reading():
    return random.randint(0,1023)

def generate_euler_angles():
    return [random.uniform(-360,360) for i in range(3)]

def generate_1_sensor_set():
    '''randomly generates 27x1 array of sensor data in a fixed sensor order.'''
    data = [[generate_pressure_reading()] +     # left toe pressure pad
            [generate_pressure_reading()] +     # left arch pressure pad
            [generate_pressure_reading()] +     # left heel pressure pad
            [generate_pressure_reading()] +     # right toe pressure pad
            [generate_pressure_reading()] +     # right arch pressure pad
            [generate_pressure_reading()] +     # right heel pressure pad
            generate_euler_angles() +           # left shoe euler angles
            generate_euler_angles() +           # right shoe euler angles
            generate_euler_angles() +           # left calf euler angles
            generate_euler_angles() +           # right calf euler angles
            generate_euler_angles() +           # right thigh euler angles
            generate_euler_angles() +           # left thigh euler angles
            generate_euler_angles()]            # small of back euler angles

    return data[0]  # I used a 1-long list of data so I could comment each line


def zero_pad(reading, des_len):
    '''takes in a reading and 0-pads it to desired length'''
    reading = str(reading)
    while len(reading) < des_len:       # keep adding '0' until it's long enough
        reading = '0' + reading

    return reading


def pack_pressure_reading(reading):
    '''convert pressure sensor to binary string'''
    if reading > 1000:  # cap to 999
        reading = 999
    bin_str = "{0:b}".format(reading)
    reading = zero_pad(bin_str, 10)

    return reading


def pack_euler_reading(reading):
    '''convert euler sensor to binary string'''
    reading = int(reading*100)
    neg_parity = str(int(reading < 0))
    reading = abs(reading)

    reading = "{0:b}".format(reading)
    reading = zero_pad(reading, 16)
    reading = neg_parity + reading

    return reading


def encode(data):
    '''convert 27x1 list of sensor readings to binary string'''
    encoded = ''
    for i in range(6):
        encoded += pack_pressure_reading(data[i])

    for i in range(6,27):
        encoded += pack_euler_reading(data[i])

    return encoded

def unpack_pressure_binary(bin_reading):
    '''convert binary string to pressure reading'''
    unpacked = int(bin_reading,2)
    return unpacked

def unpack_euler_binary(bin_reading):
    '''convert binary string to euler reading'''
    sign = 1
    if (bin_reading[0] == '1'):
        bin_reading = bin_reading[1:]
        sign = -1

    return sign * int(bin_reading,2)/100.


def decode(bin_msg):
    '''convert binary string to 27x1 list of sensor readings'''
    decoded = []

    idx = 0
    for i in range(6):
        bin_reading = bin_msg[idx:(idx+10)]
        reading = unpack_pressure_binary(bin_reading)
        decoded.append(reading)

        idx += 10

    for i in range(6,27):
        bin_reading = bin_msg[idx:(idx+17)]
        reading = unpack_euler_binary(bin_reading)
        decoded.append(reading)

        idx += 17

    return decoded


# Code demonstration
raw_data = generate_1_sensor_set()
bin_msg = encode(raw_data)
decoded = decode(bin_msg)

# error checking
for i in range(27):
    print raw_data[i] - decoded[i]