import numpy as np
import sys

# Character Set and coding
ALPHABET = (
    list('abcdefghijklmnopqrstuvwxyz') +
    list('ABCDEFGHIJKLMNOPQRSTUVWXYZ') +
    list('0123456789') +
    [' ', '.']
)

def get_hadamard(n):
    assert (n & (n - 1) == 0), "Hadamard order must be power of 2"
    H = np.array([[1]])
    while H.shape[0] < n:
        H = np.block([
            [ H,  H],
            [ H, -H]
        ])
    return H

def encode_message(msg, alphabet=ALPHABET):
    msg = msg.strip()
    if len(msg) != 40:
        raise Exception("Message must be exactly 40 characters!")
    # Get Hadamard codes
    H = get_hadamard(64)
    code_length = 64
    # Normalize so signal energy stays bounded
    # Each row has norm sqrt(64) = 8, so scale down by 1/8
    scale = 1 / np.sqrt(code_length)
    signals = []
    for c in msg:
        idx = alphabet.index(c)
        signals.append(H[idx] * scale)
    signal = np.concatenate(signals)
    # Energy check (should be << 2000)
    assert signal.shape[0] == 2560
    energy = np.sum(signal ** 2)
    if energy > 2000:
        raise Exception("Signal energy above allowed!")
    return signal

def main():
    import argparse
    parser = argparse.ArgumentParser(description="Message to signal encoder for PDC Project")
    parser.add_argument('--message_file', type=str, required=True, help="Text file with exactly 40 chars.")
    parser.add_argument('--output_file', type=str, required=True, help="Output signal file for client.py.")
    args = parser.parse_args()

    with open(args.message_file, 'r') as f:
        msg = f.read().strip()
    x = encode_message(msg)
    np.savetxt(args.output_file, x)

if __name__ == '__main__':
    main()