import base64
import hmac
import json
import random
from urllib.parse import urlencode, urljoin


class MagentaRequest:
    def __init__(self, client_id, client_secret, nonce, scopes, callback_url):
        self.client_id = client_id

        self.client_secret = client_secret
        if not isinstance(client_secret, bytes):
            self.client_secret = base64.b32decode(client_secret.upper())

        self.nonce = nonce
        if nonce is None:
            self.nonce = random.randint(10000000, 99999999)

        self.scopes = scopes
        if not isinstance(scopes, list):
            self.scopes = [
                scopes,
            ]

        self.callback_url = callback_url

    def sign(self):
        data = {
            "client_id": self.client_id,
            "nonce": self.nonce,
            "scopes": self.scopes,
            "callback_url": self.callback_url,
        }

        payload = json.dumps(data).encode("utf-8")
        payload = base64.urlsafe_b64encode(payload)
        signature = hmac.digest(self.client_secret, payload, "sha256")
        signature = base64.urlsafe_b64encode(signature)

        return (payload, signature)

    def begin_url(self, magenta_base):
        payload, signature = self.sign()
        params = {
            "client": self.client_id,
            "payload": payload,
            "signature": signature,
        }

        params = urlencode(params)

        url = urljoin(magenta_base, f"/sso/begin?{params}")
        return url

    @classmethod
    def verify(cls, payload, signature, client_secret):
        if not isinstance(client_secret, bytes):
            client_secret = base64.b32decode(client_secret.upper())

        if not isinstance(signature, bytes):
            signature = signature.encode("utf-8")

        if not isinstance(payload, bytes):
            payload = payload.encode("utf-8")

        signature_check = hmac.digest(client_secret, payload, "sha256")
        signature = base64.urlsafe_b64decode(signature)

        if signature != signature_check:
            raise ValueError("mismatching signatures")

        payload = base64.urlsafe_b64decode(payload)
        payload = json.loads(payload.decode("utf-8"))

        scopes = payload["scopes"]
        if not isinstance(scopes, list):
            scopes = [
                scopes,
            ]

        output = cls(
            payload["client_id"],
            client_secret,
            payload["nonce"],
            scopes,
            payload["callback_url"],
        )

        return output

    def __repr__(self):
        return "MagentaRequest(client_id=%r nonce=%r scopes=%r callback_url=%r)" % (
            self.client_id,
            self.nonce,
            self.scopes,
            self.callback_url,
        )