<?php

declare(strict_types=1);

namespace authkit2\Oidc;

use Firebase\JWT\JWT;
use Firebase\JWT\JWK;

/**
 * A OpenId Connect token, optionally with a refresh token.
 */
class Token
{
	/**
	 * OIDC client.
	 * @var Client
	 */
	protected $client = null;

	/**
	 * OIDC JWT access token.
	 * @var string
	 */
	protected $access_token;

	/**
	 * OIDC JWT refresh token.
	 * @var ?string
	 */
	protected $refresh_token;

	/**
	 * Cache of userinfo endpoint response.
	 * @var array<string,scalar>
	 */
	protected $user_info = null;

	/**
	 * Decoded access token JWT data.
	 * @var array<string,mixed>
	 */
	protected $access_token_data = null;

	/**
	 * Decoded refresh token JWT data.
	 * @var array<string,mixed>
	 */
	protected $refresh_token_data = null;

	/**
	 * Callback to be notified when this token is refreshed.
	 * @var callable
	 */
	protected $refresh_callback;

	/**
	 * Initialize token with the from*() static methods.
	 */
	protected function __construct()
	{
	}

	/**
	 * Create a token given a access_token and optionally refresh_token, passed
	 * as a string.
	 *
	 * @param  Client  $client
	 * @param  string  $access_token
	 * @param  ?string $refresh_token
	 * @return Token
	 */
	public static function fromString(Client $client, string $access_token, ?string $refresh_token = null): Token
	{
		$token = new Token();
		$token->client = $client;
		$token->access_token = $access_token;
		$token->refresh_token = $refresh_token;
		return $token;
	}

	/**
	 * Get a HTTP client that's authenticated with this token's credentials.
	 *
	 * @param  array<string,mixed> $options
	 * @return \GuzzleHttp\Client
	 */
	public function getClient(array $options = []): \GuzzleHttp\Client
	{
		// Create the token auth implementation; this holds a callback to the token
		// to ask it to refresh itself
		$state = new \stdClass();

		$state->refresher =
			function(Token $token) use ($state): Token {
				$client = $this->client;
				$refresh_callback = $this->refresh_callback;

				// Refresh the token
				if (!isset($this->refresh_token))
				{
					throw new \Exception('Token expired');
				}
				$new_token = $client->createTokenFromRefreshToken($this->refresh_token);

				// Rebind this callback to the new token
				$state->refresher->bindTo($new_token);

				// Call the refresh callback
				if (isset($refresh_callback))
				{
					// Copy over the token-level refresh callback
					$new_token->setRefreshCallback($refresh_callback);
					$refresh_callback($new_token);
				}

				return $new_token;
			};

		$auth = new Authentication\TokenAuthentication($this, $state->refresher);
		return $auth->getClient($options);
	}

	/**
	 * Callback to notify when this token is refreshed.
	 *
	 * @param  callable $callback
	 * @return void
	 */
	public function setRefreshCallback(callable $callback): void
	{
		$this->refresh_callback = $callback;
	}

	/**
	 * Create a token from a OIDC response from the token endpoint.
	 *
	 * @param  Client $client
	 * @param  object $response
	 * @return Token
	 */
	public static function fromResponse(Client $client, object $response): Token
	{
		$token = new Token();
		$token->client = $client;
		$token->access_token = $response->access_token ?? null;
		$token->refresh_token = $response->refresh_token ?? null;
		return $token;
	}

	/**
	 * Fetch the raw decoded data out of our JWT access token.
	 *
	 * @return array<string,mixed>
	 */
	public function getAccessTokenData(): array
	{
		if (!isset($this->access_token_data))
		{
			$this->access_token_data = json_decode(json_encode($this->decode($this->access_token)), true);
		}
		return $this->access_token_data;
	}

	/**
	 * Fetch the raw decoded data out of our JWT refresh token.
	 *
	 * @return array<string,mixed>
	 */
	public function getRefreshTokenData(): array
	{
		if (!isset($this->refresh_token_data))
		{
			if (!isset($this->refresh_token))
			{
				throw new \UnexpectedValueException('Refresh token not set!');
			}
			$this->refresh_token_data = json_decode(json_encode($this->decode($this->refresh_token)), true);
		}
		return $this->refresh_token_data;
	}

	/**
	 * Decode a token as a JWT token.
	 *
	 * @param  string $token
	 * @return object
	 */
	protected function decode(string $token): object
	{
		return JWT::decode($token, JWK::parseKeySet($this->client->getJsonWebKeySet()), $this->client->getTokenSigningAlgorithms());
	}

	/**
	 * Check whether the token is valid -- that is, whether you could actually
	 * use it for things.
	 *
	 * To be considered valid, the access token must be parseable and signed by
	 * the correct keys but _may_ be expired. The refresh token must be parseable,
	 * signed by the correct key, and may not be expired.
	 *
	 * @return bool
	 */
	public function isValid(): bool
	{
		try
		{
			$this->getAccessTokenData();
			return true;
		}
		catch (\UnexpectedValueException $ex)
		{
			if ($ex instanceof \Firebase\JWT\ExpiredException)
			{
				try
				{
					$this->getRefreshTokenData();
					return true;
				}
				catch (\UnexpectedValueException $ex)
				{
					return false;
				}
			}
			return false;
		}
	}

	/**
	 * Check whether the access token is expired.
	 *
	 * As long as the refresh token is valid, this is recoverly by calling
	 * passing this token to refresh on the client.
	 *
	 * @return bool
	 */
	public function isExpired(): bool
	{
		try
		{
			$token_data = $this->getAccessTokenData();
			if ($token_data['exp'] <= time())
			{
				return true;
			}
			return false;
		}
		catch (\Firebase\JWT\ExpiredException $ex)
		{
			return true;
		}
	}

	/**
	 * Check whether this token needs a refresh to be used.
	 *
	 * @return bool
	 */
	public function needsRefresh(): bool
	{
		return $this->isValid() && $this->isExpired() && isset($this->refresh_token);
	}

	/**
	 * Fetch the underlying access token this token represents.
	 *
	 * @return string
	 */
	public function getAccessToken(): string
	{
		return $this->access_token;
	}

	/**
	 * Fetch the user's refresh token.
	 *
	 * @return ?string
	 */
	public function getRefreshToken(): ?string
	{
		return $this->refresh_token;
	}

	/**
	 * Fetch the user info associated with this token from the OIDC
	 * provider.
	 *
	 * @return array<string,scalar>
	 */
	public function getUserInfo(): array
	{
		return $this->client->getTokenUserInfo($this);
	}

	/**
	 * Fetch the roles encoded in this token.
	 *
	 * @return string[]
	 */
	public function getRoles(): array
	{
		return $this->getAccessTokenData()['realm_access']['roles'];
	}

	/**
	 * Fetch the uuid encoded in this token.
	 *
	 * @return string
	 */
	public function getUserId(): string
	{
		return 'crn:user:'.$this->getAccessTokenData()['sub'];
	}
}