controller.py

"""
controller.py

A simple PID controller. Tune the gains below and run this file to save C3PO's life.
The final answer would be the name showing on the correct hyperlink.
"""

import base64
import hashlib
import time

from cryptography.fernet import Fernet, InvalidToken

# ==================== TUNE YOUR CONTROLLER ====================
Kp = 0.0
Ki = 0.0
Kd = 0.0
# ================================================================

# ==================== BUILD-TIME EMBEDDED CONFIG ====================
_SALT_B64 = "eShUEgQx+m80w0XCKTvDZA=="
_TOKEN = "gAAAAABqm2zReLhMDeHo2O1PfZK1I33AXZaTZPqouHtQMOwVkejM7wAYRVcj-Ma5Ie9nmVklqg_63s5ymi0IKfMJFSnU_yni_Kzz-9GmZHpm629UKwD0nKg="
_PRECISION = 4
_SCRYPT_N = 262144
_SCRYPT_R = 8
_SCRYPT_P = 1
_WRONG_KEY_B64 = "DC3SfDrdUmKuRje4-zcNkDYTmFaOfkThpd77vihB63M="
_WRONG_TOKEN = "gAAAAABqm2zQdQ8KTlAXZywW5RVKSilyDBAMurTfEVxmnpMdjoJlsdSjToYmDIan0X6NW8nHsILHifz4qsV1C9Xnao9kw5int_P892Sg1Jpmf_vTeGbWdCw="
# ======================================================================


def _canonical(p: float, i: float, d: float, precision: int) -> str:
    return f"{p:.{precision}f}|{i:.{precision}f}|{d:.{precision}f}"


def _derive_key(secret_str: str, salt: bytes) -> bytes:

    raw = hashlib.scrypt(
        secret_str.encode(),
        salt=salt,
        n=_SCRYPT_N,
        r=_SCRYPT_R,
        p=_SCRYPT_P,
        dklen=32,
        maxmem=_SCRYPT_N * _SCRYPT_R * 256,
    )
    return base64.urlsafe_b64encode(raw)


def _resolve_output(p: float, i: float, d: float):

    salt = base64.b64decode(_SALT_B64)
    secret_str = _canonical(p, i, d, _PRECISION)
    key = _derive_key(secret_str, salt)
    try:
        return Fernet(key).decrypt(_TOKEN.encode()).decode()
    except InvalidToken:
        return None


def _resolve_wrong_link() -> str:
    return Fernet(_WRONG_KEY_B64.encode()).decrypt(_WRONG_TOKEN.encode()).decode()


def simulate_step(error, integral, prev_error, dt=1.0):
    """One PID update step — output, updated integral, and error."""
    integral += error * dt
    derivative = (error - prev_error) / dt
    output = Kp * error + Ki * integral + Kd * derivative
    return output, integral, error


def run_controller():
    error, integral, prev_error = 1.0, 0.0, 0.0
    for _ in range(5):
        output, integral, prev_error = simulate_step(error, integral, prev_error)
        error = max(0.0, error - 0.15)
        time.sleep(0.05)

    result = _resolve_output(Kp, Ki, Kd)
    print("Controller output:")
    print(result if result else _resolve_wrong_link())


if __name__ == "__main__":
    run_controller()