<?php

namespace BookStack\Access\Oidc;

use BookStack\Access\GroupSyncService;
use BookStack\Access\LoginService;
use BookStack\Access\RegistrationService;
use BookStack\Exceptions\JsonDebugException;
use BookStack\Exceptions\StoppedAuthenticationException;
use BookStack\Exceptions\UserRegistrationException;
use BookStack\Facades\Theme;
use BookStack\Http\HttpRequestService;
use BookStack\Theming\ThemeEvents;
use BookStack\Users\Models\User;
use Illuminate\Support\Arr;
use Illuminate\Support\Facades\Cache;
use League\OAuth2\Client\OptionProvider\HttpBasicAuthOptionProvider;
use League\OAuth2\Client\Provider\Exception\IdentityProviderException;

/**
 * Class OpenIdConnectService
 * Handles any app-specific OIDC tasks.
 */
class OidcService
{
    public function __construct(
        protected RegistrationService $registrationService,
        protected LoginService $loginService,
        protected HttpRequestService $http,
        protected GroupSyncService $groupService
    ) {
    }

    /**
     * Initiate an authorization flow.
     * Provides back an authorize redirect URL, in addition to other
     * details which may be required for the auth flow.
     *
     * @throws OidcException
     *
     * @return array{url: string, state: string}
     */
    public function login(): array
    {
        $settings = $this->getProviderSettings();
        $provider = $this->getProvider($settings);

        $url = $provider->getAuthorizationUrl();
        session()->put('oidc_pkce_code', $provider->getPkceCode() ?? '');

        return [
            'url'   => $url,
            'state' => $provider->getState(),
        ];
    }

    /**
     * Process the Authorization response from the authorization server and
     * return the matching, or new if registration active, user matched to the
     * authorization server. Throws if the user cannot be auth if not authenticated.
     *
     * @throws JsonDebugException
     * @throws OidcException
     * @throws StoppedAuthenticationException
     * @throws IdentityProviderException
     */
    public function processAuthorizeResponse(?string $authorizationCode): User
    {
        $settings = $this->getProviderSettings();
        $provider = $this->getProvider($settings);

        // Set PKCE code flashed at login
        $pkceCode = session()->pull('oidc_pkce_code', '');
        $provider->setPkceCode($pkceCode);

        // Try to exchange authorization code for access token
        $accessToken = $provider->getAccessToken('authorization_code', [
            'code' => $authorizationCode,
        ]);

        return $this->processAccessTokenCallback($accessToken, $settings);
    }

    /**
     * @throws OidcException
     */
    protected function getProviderSettings(): OidcProviderSettings
    {
        $config = $this->config();
        $settings = new OidcProviderSettings([
            'issuer'                => $config['issuer'],
            'clientId'              => $config['client_id'],
            'clientSecret'          => $config['client_secret'],
            'authorizationEndpoint' => $config['authorization_endpoint'],
            'tokenEndpoint'         => $config['token_endpoint'],
            'endSessionEndpoint'    => is_string($config['end_session_endpoint']) ? $config['end_session_endpoint'] : null,
            'userinfoEndpoint'      => $config['userinfo_endpoint'],
        ]);

        // Use keys if configured
        if (!empty($config['jwt_public_key'])) {
            $settings->keys = [$config['jwt_public_key']];
        }

        // Run discovery
        if ($config['discover'] ?? false) {
            try {
                $settings->discoverFromIssuer($this->http->buildClient(5), Cache::store(null), 15);
            } catch (OidcIssuerDiscoveryException $exception) {
                throw new OidcException('OIDC Discovery Error: ' . $exception->getMessage());
            }
        }

        // Prevent use of RP-initiated logout if specifically disabled
        // Or force use of a URL if specifically set.
        if ($config['end_session_endpoint'] === false) {
            $settings->endSessionEndpoint = null;
        } else if (is_string($config['end_session_endpoint'])) {
            $settings->endSessionEndpoint = $config['end_session_endpoint'];
        }

        $settings->validate();

        return $settings;
    }

    /**
     * Load the underlying OpenID Connect Provider.
     */
    protected function getProvider(OidcProviderSettings $settings): OidcOAuthProvider
    {
        $provider = new OidcOAuthProvider([
            ...$settings->arrayForOAuthProvider(),
            'redirectUri' => url('/oidc/callback'),
        ], [
            'httpClient'     => $this->http->buildClient(5),
            'optionProvider' => new HttpBasicAuthOptionProvider(),
        ]);

        foreach ($this->getAdditionalScopes() as $scope) {
            $provider->addScope($scope);
        }

        return $provider;
    }

    /**
     * Get any user-defined addition/custom scopes to apply to the authentication request.
     *
     * @return string[]
     */
    protected function getAdditionalScopes(): array
    {
        $scopeConfig = $this->config()['additional_scopes'] ?: '';

        $scopeArr = explode(',', $scopeConfig);
        $scopeArr = array_map(fn (string $scope) => trim($scope), $scopeArr);

        return array_filter($scopeArr);
    }

    /**
     * Calculate the display name.
     */
    protected function getUserDisplayName(OidcIdToken $token, string $defaultValue): string
    {
        $displayNameAttrString = $this->config()['display_name_claims'] ?? '';
        $displayNameAttrs = explode('|', $displayNameAttrString);

        $displayName = [];
        foreach ($displayNameAttrs as $dnAttr) {
            $dnComponent = $token->getClaim($dnAttr) ?? '';
            if ($dnComponent !== '') {
                $displayName[] = $dnComponent;
            }
        }

        if (count($displayName) == 0) {
            $displayName[] = $defaultValue;
        }

        return implode(' ', $displayName);
    }

    /**
     * Extract the assigned groups from the id token.
     *
     * @return string[]
     */
    protected function getUserGroups(OidcIdToken $token): array
    {
        $groupsAttr = $this->config()['groups_claim'];
        if (empty($groupsAttr)) {
            return [];
        }

        $groupsList = Arr::get($token->getAllClaims(), $groupsAttr);
        if (!is_array($groupsList)) {
            return [];
        }

        return array_values(array_filter($groupsList, function ($val) {
            return is_string($val);
        }));
    }

    /**
     * Extract the details of a user from an ID token.
     *
     * @return array{name: string, email: string, external_id: string, groups: string[]}
     */
    protected function getUserDetails(OidcIdToken $token): array
    {
        $idClaim = $this->config()['external_id_claim'];
        $id = $token->getClaim($idClaim);

        return [
            'external_id' => $id,
            'email'       => $token->getClaim('email'),
            'name'        => $this->getUserDisplayName($token, $id),
            'groups'      => $this->getUserGroups($token),
        ];
    }

    /**
     * Processes a received access token for a user. Login the user when
     * they exist, optionally registering them automatically.
     *
     * @throws OidcException
     * @throws JsonDebugException
     * @throws StoppedAuthenticationException
     */
    protected function processAccessTokenCallback(OidcAccessToken $accessToken, OidcProviderSettings $settings): User
    {
        $idTokenText = $accessToken->getIdToken();
        $idToken = new OidcIdToken(
            $idTokenText,
            $settings->issuer,
            $settings->keys,
        );

        session()->put("oidc_id_token", $idTokenText);

        // TODO - This should not affect id token validation
        // TODO - Should only call if we're missing properties
        if (!empty($settings->userinfoEndpoint)) {
            $provider = $this->getProvider($settings);
            $request = $provider->getAuthenticatedRequest('GET', $settings->userinfoEndpoint, $accessToken->getToken());
            $response = $provider->getParsedResponse($request);
            // TODO - Ensure response content-type is "application/json" before using in this way (5.3.2)
            // TODO - The sub Claim in the UserInfo Response MUST be verified to exactly match the sub Claim in the ID Token; if they do not match, the UserInfo Response values MUST NOT be used. (5.3.2)
            // TODO - Response validation (5.3.4)
               // TODO - Verify that the OP that responded was the intended OP through a TLS server certificate check, per RFC 6125 [RFC6125].
               // TODO - If the Client has provided a userinfo_encrypted_response_alg parameter during Registration, decrypt the UserInfo Response using the keys specified during Registration.
               // TODO - If the response was signed, the Client SHOULD validate the signature according to JWS [JWS].
            $claims = $idToken->getAllClaims();
            foreach ($response as $key => $value) {
                $claims[$key] = $value;
            }
            // TODO - Should maybe remain separate from IdToken completely
            $idToken->replaceClaims($claims);
        }

        $returnClaims = Theme::dispatch(ThemeEvents::OIDC_ID_TOKEN_PRE_VALIDATE, $idToken->getAllClaims(), [
            'access_token' => $accessToken->getToken(),
            'expires_in' => $accessToken->getExpires(),
            'refresh_token' => $accessToken->getRefreshToken(),
        ]);

        if (!is_null($returnClaims)) {
            $idToken->replaceClaims($returnClaims);
        }

        if ($this->config()['dump_user_details']) {
            throw new JsonDebugException($idToken->getAllClaims());
        }

        try {
            $idToken->validate($settings->clientId);
        } catch (OidcInvalidTokenException $exception) {
            throw new OidcException("ID token validate failed with error: {$exception->getMessage()}");
        }

        $userDetails = $this->getUserDetails($idToken);
        $isLoggedIn = auth()->check();

        if (empty($userDetails['email'])) {
            throw new OidcException(trans('errors.oidc_no_email_address'));
        }

        if ($isLoggedIn) {
            throw new OidcException(trans('errors.oidc_already_logged_in'));
        }

        try {
            $user = $this->registrationService->findOrRegister(
                $userDetails['name'],
                $userDetails['email'],
                $userDetails['external_id']
            );
        } catch (UserRegistrationException $exception) {
            throw new OidcException($exception->getMessage());
        }

        if ($this->shouldSyncGroups()) {
            $groups = $userDetails['groups'];
            $detachExisting = $this->config()['remove_from_groups'];
            $this->groupService->syncUserWithFoundGroups($user, $groups, $detachExisting);
        }

        $this->loginService->login($user, 'oidc');

        return $user;
    }

    /**
     * Get the OIDC config from the application.
     */
    protected function config(): array
    {
        return config('oidc');
    }

    /**
     * Check if groups should be synced.
     */
    protected function shouldSyncGroups(): bool
    {
        return $this->config()['user_to_groups'] !== false;
    }

    /**
     * Start the RP-initiated logout flow if active, otherwise start a standard logout flow.
     * Returns a post-app-logout redirect URL.
     * Reference: https://openid.net/specs/openid-connect-rpinitiated-1_0.html
     * @throws OidcException
     */
    public function logout(): string
    {
        $oidcToken = session()->pull("oidc_id_token");
        $defaultLogoutUrl = url($this->loginService->logout());
        $oidcSettings = $this->getProviderSettings();

        if (!$oidcSettings->endSessionEndpoint) {
            return $defaultLogoutUrl;
        }

        $endpointParams = [
            'id_token_hint' => $oidcToken,
            'post_logout_redirect_uri' => $defaultLogoutUrl,
        ];

        $joiner = str_contains($oidcSettings->endSessionEndpoint, '?') ? '&' : '?';

        return $oidcSettings->endSessionEndpoint . $joiner . http_build_query($endpointParams);
    }
}