<?php

namespace BookStack\Auth\Access;

use BookStack\Auth\User;
use BookStack\Exceptions\JsonDebugException;
use BookStack\Exceptions\LdapException;
use BookStack\Exceptions\LdapFailedBindException;
use BookStack\Uploads\UserAvatars;
use ErrorException;
use Illuminate\Support\Facades\Log;

/**
 * Class LdapService
 * Handles any app-specific LDAP tasks.
 */
class LdapService
{
    protected Ldap $ldap;
    protected GroupSyncService $groupSyncService;
    protected UserAvatars $userAvatars;

    protected array $config;
    protected bool $enabled;

    /**
     * LdapService constructor.
     */
    public function __construct(Ldap $ldap, UserAvatars $userAvatars, GroupSyncService $groupSyncService)
    {
        $this->ldap = $ldap;
        $this->userAvatars = $userAvatars;
        $this->groupSyncService = $groupSyncService;
        $this->config = config('services.ldap');
        $this->enabled = config('auth.method') === 'ldap';
    }

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

    /**
     * Search for attributes for a specific user on the ldap.
     *
     * @throws LdapException
     */
    protected function getUserWithAttributes(string $userName, array $attributes): ?array
    {
        $ldapConnection = $this->bindConnection();

        // Clean attributes
        foreach ($attributes as $index => $attribute) {
            if (strpos($attribute, 'BIN;') === 0) {
                $attributes[$index] = substr($attribute, strlen('BIN;'));
            }
        }

        // Find user
        $userFilter = $this->buildFilter($this->config['user_filter'], ['user' => $userName]);
        $baseDn = $this->config['base_dn'];

        $followReferrals = $this->config['follow_referrals'] ? 1 : 0;
        $this->ldap->setOption($ldapConnection, LDAP_OPT_REFERRALS, $followReferrals);
        $users = $this->ldap->searchAndGetEntries($ldapConnection, $baseDn, $userFilter, $attributes);
        if ($users['count'] === 0) {
            return null;
        }

        return $users[0];
    }

    /**
     * Get the details of a user from LDAP using the given username.
     * User found via configurable user filter.
     *
     * @throws LdapException
     */
    public function getUserDetails(string $userName): ?array
    {
        $idAttr = $this->config['id_attribute'];
        $emailAttr = $this->config['email_attribute'];
        $displayNameAttr = $this->config['display_name_attribute'];
        $thumbnailAttr = $this->config['thumbnail_attribute'];

        $user = $this->getUserWithAttributes($userName, array_filter([
            'cn', 'dn', $idAttr, $emailAttr, $displayNameAttr, $thumbnailAttr,
        ]));

        if (is_null($user)) {
            return null;
        }

        $userCn = $this->getUserResponseProperty($user, 'cn', null);
        $formatted = [
            'uid'   => $this->getUserResponseProperty($user, $idAttr, $user['dn']),
            'name'  => $this->getUserResponseProperty($user, $displayNameAttr, $userCn),
            'dn'    => $user['dn'],
            'email' => $this->getUserResponseProperty($user, $emailAttr, null),
            'avatar' => $thumbnailAttr ? $this->getUserResponseProperty($user, $thumbnailAttr, null) : null,
        ];

        if ($this->config['dump_user_details']) {
            throw new JsonDebugException([
                'details_from_ldap'        => $user,
                'details_bookstack_parsed' => $formatted,
            ]);
        }

        return $formatted;
    }

    /**
     * Get a property from an LDAP user response fetch.
     * Handles properties potentially being part of an array.
     * If the given key is prefixed with 'BIN;', that indicator will be stripped
     * from the key and any fetched values will be converted from binary to hex.
     */
    protected function getUserResponseProperty(array $userDetails, string $propertyKey, $defaultValue)
    {
        $isBinary = strpos($propertyKey, 'BIN;') === 0;
        $propertyKey = strtolower($propertyKey);
        $value = $defaultValue;

        if ($isBinary) {
            $propertyKey = substr($propertyKey, strlen('BIN;'));
        }

        if (isset($userDetails[$propertyKey])) {
            $value = (is_array($userDetails[$propertyKey]) ? $userDetails[$propertyKey][0] : $userDetails[$propertyKey]);
            if ($isBinary) {
                $value = bin2hex($value);
            }
        }

        return $value;
    }

    /**
     * Check if the given credentials are valid for the given user.
     *
     * @throws LdapException
     */
    public function validateUserCredentials(?array $ldapUserDetails, string $password): bool
    {
        if (is_null($ldapUserDetails)) {
            return false;
        }

        try {
            $this->bindConnection($ldapUserDetails['dn'], $password);
        } catch (LdapFailedBindException $e) {
            return false;
        } catch (LdapException $e) {
            throw $e;
        }

        return true;
    }


    /**
     * Attempted to start and bind to a new LDAP connection.
     * Will attempt against multiple defined fail-over hosts if set.
     *
     * Throws a LdapFailedBindException error if the bind connected but failed.
     * Otherwise, generic LdapException errors would be thrown.
     *
     * @return resource
     * @throws LdapException
     */
    protected function bindConnection(string $dn = null, string $password = null)
    {
        $systemBind = ($dn === null && $password === null);

        // Check LDAP extension in installed
        if (!function_exists('ldap_connect') && config('app.env') !== 'testing') {
            throw new LdapException(trans('errors.ldap_extension_not_installed'));
        }

        // Disable certificate verification.
        // This option works globally and must be set before a connection is created.
        if ($this->config['tls_insecure']) {
            $this->ldap->setOption(null, LDAP_OPT_X_TLS_REQUIRE_CERT, LDAP_OPT_X_TLS_NEVER);
        }

        $serverDetails = $this->parseMultiServerString($this->config['server']);
        $lastException = null;

        foreach ($serverDetails as $server) {
            try {
                $connection = $this->startServerConnection($server);
            } catch (LdapException $exception) {
                $lastException = $exception;
                continue;
            }

            try {
                if ($systemBind) {
                    $this->bindSystemUser($connection);
                } else {
                    $this->bindGivenUser($connection, $dn, $password);
                }
            } catch (LdapFailedBindException $exception) {
                // Rethrow simply to indicate the importance of handling this exception case
                // to indicate auth status. We skip past attempting fail-over hosts in this case since it's
                // likely the connection worked here but the bind was unauthorised.
                throw $exception;
            } catch (ErrorException $exception) {
                Log::error('LDAP bind error: ' . $exception->getMessage());
                $lastException = new LdapException('Encountered error during LDAP bind');
                continue;
            }

            return $connection;
        }

        throw $lastException;
    }

    /**
     * Bind to the given LDAP connection using the given credentials.
     * MUST throw an exception on failure.
     *
     * @param resource $connection
     *
     * @throws LdapFailedBindException
     */
    protected function bindGivenUser($connection, string $dn = null, string $password = null): void
    {
        $ldapBind = $this->ldap->bind($connection, $dn, $password);

        if (!$ldapBind) {
            throw new LdapFailedBindException('Failed to bind with given user details');
        }
    }

    /**
     * Bind the system user to the LDAP connection using the configured credentials  otherwise anonymous
     * access is attempted. MUST throw an exception on failure.
     *
     * @param resource $connection
     *
     * @throws LdapFailedBindException
     */
    protected function bindSystemUser($connection): void
    {
        $ldapDn = $this->config['dn'];
        $ldapPass = $this->config['pass'];

        $isAnonymous = ($ldapDn === false || $ldapPass === false);
        if ($isAnonymous) {
            $ldapBind = $this->ldap->bind($connection);
        } else {
            $ldapBind = $this->ldap->bind($connection, $ldapDn, $ldapPass);
        }

        if (!$ldapBind) {
            throw new LdapFailedBindException(($isAnonymous ? trans('errors.ldap_fail_anonymous') : trans('errors.ldap_fail_authed')));
        }
    }

    /**
     * Attempt to start a server connection from the provided details.
     *
     * @param array{host: string, port: int} $serverDetail
     * @return resource
     * @throws LdapException
     */
    protected function startServerConnection(array $serverDetail)
    {
        $ldapConnection = $this->ldap->connect($serverDetail['host'], $serverDetail['port']);

        if (!$ldapConnection) {
            throw new LdapException(trans('errors.ldap_cannot_connect'));
        }

        // Set any required options
        if ($this->config['version']) {
            $this->ldap->setVersion($ldapConnection, $this->config['version']);
        }

        // Start and verify TLS if it's enabled
        if ($this->config['start_tls']) {
            try {
                $tlsStarted = $this->ldap->startTls($ldapConnection);
            } catch (ErrorException $exception) {
                $tlsStarted = false;
            }

            if (!$tlsStarted) {
                throw new LdapException('Could not start TLS connection');
            }
        }

        return $ldapConnection;
    }

    /**
     * Parse a potentially multi-value LDAP server host string and return an array of host/port detail pairs.
     * Multiple hosts are separated with a semicolon, for example: 'ldap.example.com:8069;ldaps://ldap.example.com'
     *
     * @return array<array{host: string, port: int}>
     */
    protected function parseMultiServerString(string $serversString): array
    {
        $serverStringList = explode(';', $serversString);

        return array_map(fn ($serverStr) => $this->parseSingleServerString($serverStr), $serverStringList);
    }

    /**
     * Parse an LDAP server string and return the host and port for a connection.
     * Is flexible to formats such as 'ldap.example.com:8069' or 'ldaps://ldap.example.com'.
     *
     * @return array{host: string, port: int}
     */
    protected function parseSingleServerString(string $serverString): array
    {
        $serverNameParts = explode(':', $serverString);

        // If we have a protocol just return the full string since PHP will ignore a separate port.
        if ($serverNameParts[0] === 'ldaps' || $serverNameParts[0] === 'ldap') {
            return ['host' => $serverString, 'port' => 389];
        }

        // Otherwise, extract the port out
        $hostName = $serverNameParts[0];
        $ldapPort = (count($serverNameParts) > 1) ? intval($serverNameParts[1]) : 389;

        return ['host' => $hostName, 'port' => $ldapPort];
    }

    /**
     * Build a filter string by injecting common variables.
     */
    protected function buildFilter(string $filterString, array $attrs): string
    {
        $newAttrs = [];
        foreach ($attrs as $key => $attrText) {
            $newKey = '${' . $key . '}';
            $newAttrs[$newKey] = $this->ldap->escape($attrText);
        }

        return strtr($filterString, $newAttrs);
    }

    /**
     * Get the groups a user is a part of on ldap.
     *
     * @throws LdapException
     * @throws JsonDebugException
     */
    public function getUserGroups(string $userName): array
    {
        $groupsAttr = $this->config['group_attribute'];
        $user = $this->getUserWithAttributes($userName, [$groupsAttr]);

        if ($user === null) {
            return [];
        }

        $userGroups = $this->groupFilter($user);
        $allGroups = $this->getGroupsRecursive($userGroups, []);

        if ($this->config['dump_user_groups']) {
            throw new JsonDebugException([
                'details_from_ldap'             => $user,
                'parsed_direct_user_groups'     => $userGroups,
                'parsed_recursive_user_groups'  => $allGroups,
            ]);
        }

        return $allGroups;
    }

    /**
     * Get the parent groups of an array of groups.
     *
     * @throws LdapException
     */
    private function getGroupsRecursive(array $groupsArray, array $checked): array
    {
        $groupsToAdd = [];
        foreach ($groupsArray as $groupName) {
            if (in_array($groupName, $checked)) {
                continue;
            }

            $parentGroups = $this->getGroupGroups($groupName);
            $groupsToAdd = array_merge($groupsToAdd, $parentGroups);
            $checked[] = $groupName;
        }

        $groupsArray = array_unique(array_merge($groupsArray, $groupsToAdd), SORT_REGULAR);

        if (empty($groupsToAdd)) {
            return $groupsArray;
        }

        return $this->getGroupsRecursive($groupsArray, $checked);
    }

    /**
     * Get the parent groups of a single group.
     *
     * @throws LdapException
     */
    private function getGroupGroups(string $groupName): array
    {
        $ldapConnection = $this->bindConnection();

        $followReferrals = $this->config['follow_referrals'] ? 1 : 0;
        $this->ldap->setOption($ldapConnection, LDAP_OPT_REFERRALS, $followReferrals);

        $baseDn = $this->config['base_dn'];
        $groupsAttr = strtolower($this->config['group_attribute']);

        $groupFilter = 'CN=' . $this->ldap->escape($groupName);
        $groups = $this->ldap->searchAndGetEntries($ldapConnection, $baseDn, $groupFilter, [$groupsAttr]);
        if ($groups['count'] === 0) {
            return [];
        }

        return $this->groupFilter($groups[0]);
    }

    /**
     * Filter out LDAP CN and DN language in a ldap search return.
     * Gets the base CN (common name) of the string.
     */
    protected function groupFilter(array $userGroupSearchResponse): array
    {
        $groupsAttr = strtolower($this->config['group_attribute']);
        $ldapGroups = [];
        $count = 0;

        if (isset($userGroupSearchResponse[$groupsAttr]['count'])) {
            $count = (int) $userGroupSearchResponse[$groupsAttr]['count'];
        }

        for ($i = 0; $i < $count; $i++) {
            $dnComponents = $this->ldap->explodeDn($userGroupSearchResponse[$groupsAttr][$i], 1);
            if (!in_array($dnComponents[0], $ldapGroups)) {
                $ldapGroups[] = $dnComponents[0];
            }
        }

        return $ldapGroups;
    }

    /**
     * Sync the LDAP groups to the user roles for the current user.
     *
     * @throws LdapException
     * @throws JsonDebugException
     */
    public function syncGroups(User $user, string $username)
    {
        $userLdapGroups = $this->getUserGroups($username);
        $this->groupSyncService->syncUserWithFoundGroups($user, $userLdapGroups, $this->config['remove_from_groups']);
    }

    /**
     * Save and attach an avatar image, if found in the ldap details, and attach
     * to the given user model.
     */
    public function saveAndAttachAvatar(User $user, array $ldapUserDetails): void
    {
        if (is_null(config('services.ldap.thumbnail_attribute')) || is_null($ldapUserDetails['avatar'])) {
            return;
        }

        try {
            $imageData = $ldapUserDetails['avatar'];
            $this->userAvatars->assignToUserFromExistingData($user, $imageData, 'jpg');
        } catch (\Exception $exception) {
            Log::info("Failed to use avatar image from LDAP data for user id {$user->id}");
        }
    }
}