# Source code for coinbase.jwt_generator

    import base64
    import binascii
    import secrets
    import time

    import jwt
    from cryptography.hazmat.primitives import serialization
    from cryptography.hazmat.primitives.asymmetric import ec, ed25519

    from coinbase.constants import BASE_URL

    def _load_private_key(secret_var):
        if secret_var.lstrip().startswith("-----BEGIN"):
            return serialization.load_pem_private_key(
                secret_var.encode("utf-8"), password=None
            )

        # join+split strips whitespace so trailing newlines from .env loaders don't break valid keys
        try:
            raw = base64.b64decode("".join(secret_var.split()), validate=True)
        except (binascii.Error, ValueError):
            raise ValueError("private key is neither PEM nor valid base64")
        if len(raw) not in (32, 64):
            raise ValueError(
                f"Ed25519 raw key must decode to 32 or 64 bytes, got {len(raw)}"
            )
        return ed25519.Ed25519PrivateKey.from_private_bytes(raw[:32])

    def _algorithm_for(private_key) -> str:
        if isinstance(private_key, ed25519.Ed25519PrivateKey):
            return "EdDSA"
        if isinstance(private_key, ec.EllipticCurvePrivateKey):
            return "ES256"
        raise ValueError(
            f"Unsupported private key type: {type(private_key).__name__}. "
            "Expected ECDSA (P-256) or Ed25519."
        )

    def build_jwt(key_var, secret_var, uri=None) -> str:
        """
        :meta private:
        """
        try:
            private_key = _load_private_key(secret_var)
        except (ValueError, TypeError) as e:
            raise Exception(
                f"{e}\n"
                "Are you sure you generated your key at https://cloud.coinbase.com/access/api ?"
            )

        jwt_data = {
            "sub": key_var,
            "iss": "cdp",
            "nbf": int(time.time()),
            "exp": int(time.time()) + 120,
        }

        if uri:
            jwt_data["uri"] = uri

        jwt_token = jwt.encode(
            jwt_data,
            private_key,
            algorithm=_algorithm_for(private_key),
            headers={"kid": key_var, "nonce": secrets.token_hex()},
        )

        return jwt_token

    def build_rest_jwt(uri, key_var, secret_var) -> str:
        """
        **Build REST JWT**
        __________

        **Description:**

        Builds and returns a JWT token for connecting to the REST API.

        __________

        Parameters:

        - **uri (str)** - Formatted URI for the endpoint (e.g. "GET api.coinbase.com/api/v3/brokerage/accounts") Can be generated using ``format_jwt_uri``
        - **key_var (str)** - The API key
        - **secret_var (str)** - The API key secret
        """
        return build_jwt(key_var, secret_var, uri=uri)

    def build_ws_jwt(key_var, secret_var) -> str:
        """
        **Build WebSocket JWT**
        __________

        **Description:**

        Builds and returns a JWT token for connecting to the WebSocket API.

        __________

        Parameters:

        - **key_var (str)** - The API key
        - **secret_var (str)** - The API key secret
        """
        return build_jwt(key_var, secret_var)

    def format_jwt_uri(method, path) -> str:
        """
        **Format JWT URI**
        __________

        **Description:**

        Formats method and path into valid URI for JWT generation.

        __________

        Parameters:

        - **method (str)** - The REST request method. E.g. GET, POST, PUT, DELETE
        - **path (str)** - The path of the endpoint. E.g. "/api/v3/brokerage/accounts"

        """
        return f"{method} {BASE_URL}{path}"