// Import dce-commonkit
import {
  getTimeInfoInET,
  LogFunction,
  Log,
  LogType,
  LogTypeSpecificInfo,
  LogMainInfo,
  LogSourceSpecificInfo,
  LogBuiltInMetadata,
  LogAction,
  LogLevel,
  ParamType,
  CommonKitErrorCode,
  LogSource,
} from 'dce-commonkit';

// Import caccl
import { getLaunchInfo } from 'caccl/server';

// Import caccl functions
import initExpressKitCollections, { internalGetLogCollection, internalGetSelectAdminCollection } from './initExpressKitCollections';

// Import shared types
import ExpressKitErrorCode from '../types/ExpressKitErrorCode';

// Import helpers
import handleError from './handleError';
import handleSuccess from './handleSuccess';
import genErrorPage from '../html/genErrorPage';
import genInfoPage from '../html/genInfoPage';
import parseUserAgent from './parseUserAgent';
import { validateSignedRequest } from './dataSigner';

/**
 * Generate an express API route handler
 * @author Gabe Abrams
 * @param opts object containing all arguments
 * @param opts.paramTypes map containing the types for each parameter that is
 *   included in the request (map: param name => type)
 * @param opts.handler function that processes the request
 * @param [opts.crossServerScope] the scope associated with this endpoint.
 *   If defined, this is a cross-server endpoint, which will never
 *   have any launch data, will never check Canvas roles or launch status, and will
 *   instead use scopes and reactkit credentials to sign and validate requests.
 *   Never start the path with /api/ttm or /api/admin if the endpoint is a cross-server
 *   endpoint because those roles will not be validated
 * @param [opts.skipSessionCheck=true if crossServerScope defined] if true, skip
 *   the session check (allow users to not be logged in and launched via LTI).
 *   If crossServerScope is defined, this is always true
 * @param [opts.unhandledErrorMessagePrefix] if included, when an error that
 *   is not of type ErrorWithCode is thrown, the client will receive an error
 *   where the error message is prefixed with this string. For example,
 *   if unhandledErrorMessagePrefix is
 *   'While saving progress, we encountered an error:'
 *   and the error is 'progressInfo is not an object',
 *   the client will receive an error with the message
 *   'While saving progress, we encountered an error: progressInfo is not an object'
 * @returns express route handler that takes the following arguments:
 *   params (map: param name => value),
 *   req (express request object),
 *   next (express next function),
 *   send (a function that sends a string to the client),
 *   redirect (takes a url and redirects the user to that url),
 *   renderErrorPage (shows a static error page to the user),
 *   renderInfoPage (shows a static info page to the user),
 *   renderCustomHTML (renders custom html and sends it to the user),
 *   and returns the value to send to the client as a JSON API response, or
 *   calls next() or redirect(...) or send(...) or renderErrorPage(...).
 *   Note: params also has userId, userFirstName,
 *   userLastName, userEmail, userAvatarURL, isLearner, isTTM, isAdmin,
 *   and any other variables that
 *   are directly added to the session, if the user does have a session.
 */
const genRouteHandler = (
  opts: {
    paramTypes?: {
      [k: string]: ParamType
    },
    handler: (
      opts: {
        params: {
          [k: string]: any
        },
        req: any,
        next: () => void,
        redirect: (pathOrURL: string) => void,
        send: (text: string, status?: number) => void,
        renderErrorPage: (
          opts?: {
            title?: string,
            description?: string,
            code?: string,
            pageTitle?: string,
            status?: number,
          },
        ) => void,
        renderInfoPage: (
          opts: {
            title: string,
            body: string,
          },
        ) => void,
        renderCustomHTML: (
          opts: {
            html: string,
            status?: number,
          },
        ) => void,
        logServerEvent: LogFunction,
      },
    ) => any,
    crossServerScope?: string,
    skipSessionCheck?: boolean,
    unhandledErrorMessagePrefix?: string,
  },
) => {
  // Return a route handler
  return async (req: any, res: any, next: () => void) => {
    /*----------------------------------------*/
    /* ------------- Preparation ------------ */
    /*----------------------------------------*/

    // Output params
    const output: { [k in string]: any } = {};

    // Determine cross server scopes
    let crossServerScope: string | null = null;
    if (opts.crossServerScope) {
      crossServerScope = opts.crossServerScope ?? null;
    }

    // Determine whether we're skipping the session check
    const skipSessionCheck = !!(
      opts.skipSessionCheck
      || crossServerScope
    );

    // Get body from everywhere it can come from
    const requestBody: {
      [k: string]: any,
    } = {
      ...req.body,
      ...req.query,
      ...req.params,
    };

    /*----------------------------------------*/
    /* ------- Cross-Server Validation ------ */
    /*----------------------------------------*/

    if (crossServerScope) {
      try {
        // Create params to sign (specifically exclude path params)
        const paramsToSign = {
          ...req.body,
          ...req.query,
        };

        // Validate the request body
        await validateSignedRequest({
          method: req.method ?? 'GET',
          path: req.path,
          scope: crossServerScope,
          params: paramsToSign,
        });

        // Valid! Remove oauth values because they're no longer needed, and shouldn't be passed to the handler
        Object.keys(requestBody).forEach((key) => {
          if (key.startsWith('oauth_')) {
            delete requestBody[key];
          }
        });
      } catch (err) {
        return handleError(
          res,
          {
            message: `The authenticity of a cross-server request could not be validated because an error occurred: ${(err as any).message ?? 'unknown error'}`,
            code: ((err as any).code ?? ExpressKitErrorCode.UnknownCrossServerError),
            status: 401,
          },
        );
      }
    }

    /*----------------------------------------*/
    /* ------------ Parse Params ------------ */
    /*----------------------------------------*/

    // Process items one by one
    const paramList = Object.entries(opts.paramTypes ?? {});
    for (let i = 0; i < paramList.length; i++) {
      const [name, type] = paramList[i];

      // Find the value as a string
      const value = requestBody[name];

      // Parse
      if (type === ParamType.Boolean || type === ParamType.BooleanOptional) {
        // Boolean

        // Handle case where value doesn't exist
        if (value === undefined) {
          if (type === ParamType.BooleanOptional) {
            output[name] = undefined;
          } else {
            return handleError(
              res,
              {
                message: `Parameter ${name} is required, but it was not included.`,
                code: ExpressKitErrorCode.MissingParameter,
                status: 422,
              },
            );
          }
        } else {
          // Value exists

          // Simplify value
          const simpleVal = (
            String(value)
              .trim()
              .toLowerCase()
          );

          // Parse
          output[name] = (
            [
              'true',
              'yes',
              'y',
              '1',
              't',
            ].indexOf(simpleVal) >= 0
          );
        }
      } else if (type === ParamType.Float || type === ParamType.FloatOptional) {
        // Float

        // Handle case where value doesn't exist
        if (value === undefined) {
          if (type === ParamType.FloatOptional) {
            output[name] = undefined;
          } else {
            return handleError(
              res,
              {
                message: `Parameter ${name} is required, but it was not included.`,
                code: ExpressKitErrorCode.MissingParameter,
                status: 422,
              },
            );
          }
        } else if (!Number.isNaN(Number.parseFloat(String(value)))) {
          // Value is a number
          output[name] = Number.parseFloat(String(value));
        } else {
          // Issue!
          return handleError(
            res,
            {
              message: `Request data was malformed: ${name} was not a valid float.`,
              code: ExpressKitErrorCode.InvalidParameter,
              status: 422,
            },
          );
        }
      } else if (type === ParamType.Int || type === ParamType.IntOptional) {
        // Int

        // Handle case where value doesn't exist
        if (value === undefined) {
          if (type === ParamType.IntOptional) {
            output[name] = undefined;
          } else {
            return handleError(
              res,
              {
                message: `Parameter ${name} is required, but it was not included.`,
                code: ExpressKitErrorCode.MissingParameter,
                status: 422,
              },
            );
          }
        } else if (!Number.isNaN(Number.parseInt(String(value), 10))) {
          // Value is a number
          output[name] = Number.parseInt(String(value), 10);
        } else {
          // Issue!
          return handleError(
            res,
            {
              message: `Request data was malformed: ${name} was not a valid int.`,
              code: ExpressKitErrorCode.InvalidParameter,
              status: 422,
            },
          );
        }
      } else if (type === ParamType.JSON || type === ParamType.JSONOptional) {
        // Stringified JSON

        // Handle case where value doesn't exist
        if (value === undefined) {
          if (type === ParamType.JSONOptional) {
            output[name] = undefined;
          } else {
            return handleError(
              res,
              {
                message: `Parameter ${name} is required, but it was not included.`,
                code: ExpressKitErrorCode.MissingParameter,
                status: 422,
              },
            );
          }
        } else {
          // Value exists

          // Parse
          try {
            output[name] = JSON.parse(String(value));
          } catch (err) {
            return handleError(
              res,
              {
                message: `Request data was malformed: ${name} was not a valid JSON payload.`,
                code: ExpressKitErrorCode.InvalidParameter,
                status: 422,
              },
            );
          }
        }
      } else if (type === ParamType.String || type === ParamType.StringOptional) {
        // String

        // Handle case where value doesn't exist
        if (value === undefined) {
          if (type === ParamType.StringOptional) {
            output[name] = undefined;
          } else {
            return handleError(
              res,
              {
                message: `Parameter ${name} is required, but it was not included.`,
                code: ExpressKitErrorCode.MissingParameter,
                status: 422,
              },
            );
          }
        } else {
          // Value exists

          // Leave as is
          output[name] = value;
        }
      } else {
        // No valid data type
        return handleError(
          res,
          {
            message: `An internal error occurred: we could not determine the type of ${name}.`,
            code: ExpressKitErrorCode.InvalidParameter,
            status: 422,
          },
        );
      }
    }

    /*----------------------------------------*/
    /* ------------- Launch Info ------------ */
    /*----------------------------------------*/

    // Get launch info
    const { launched, launchInfo } = getLaunchInfo(req);
    if (
      // Not launched
      (!launched || !launchInfo)
      // Not skipping the session check
      && !skipSessionCheck
    ) {
      return handleError(
        res,
        {
          message: 'Your session has expired. Please refresh the page and try again.',
          code: CommonKitErrorCode.SessionExpired,
          status: 401,
        },
      );
    }

    // Make sure students don't try to get/change data for other students
    if (
      // launchInfo is defined
      launchInfo
      // launched is true
      && launched
      // user is a student
      && launchInfo.isLearner
      // output.userId is defined
      && output.userId
      // the launchInfo userId is the "input" userId, check if the request
      // output userId differs from the launchInfo userId
      && (launchInfo.userId !== output.userId)
    ) {
      return handleError(
        res,
        {
          message: 'We encountered a student ID mismatch. Please refresh or try the action again. Contact support if this issue persists.',
          code: ExpressKitErrorCode.StudentIdMismatch,
          status: 401,
        },
      );
    }

    // Error if user info cannot be found
    if (
      // User information is incomplete
      (
        !launchInfo
        || !launchInfo.userId
        || !launchInfo.userFirstName
        || !launchInfo.userLastName
        || (
          launchInfo.notInCourse
          && !launchInfo.isAdmin
        )
        || (
          !launchInfo.isTTM
          && !launchInfo.isLearner
          && !launchInfo.isAdmin
        )
      )
      // Not skipping the session check
      && !skipSessionCheck
    ) {
      return handleError(
        res,
        {
          message: 'Your session was invalid. Please refresh the page and try again.',
          code: CommonKitErrorCode.SessionExpired,
          status: 401,
        },
      );
    }

    // Add launch info to output
    output.userId = (
      launchInfo
        ? (output.userId ?? launchInfo.userId)
        : (output.userId ?? undefined)
    );
    output.userFirstName = (
      launchInfo
        ? launchInfo.userFirstName
        : (output.userFirstName ?? undefined)
    );
    output.userLastName = (
      launchInfo
        ? launchInfo.userLastName
        : (output.userLastName ?? undefined)
    );
    output.userEmail = (
      launchInfo
        ? launchInfo.userEmail
        : (output.userEmail ?? undefined)
    );
    output.userAvatarURL = (
      launchInfo
        ? (
          launchInfo.userImage
          ?? 'http://www.gravatar.com/avatar/?d=identicon'
        )
        : (output.userAvatarURL ?? undefined)
    );
    output.isLearner = (
      launchInfo
        ? !!launchInfo.isLearner
        : (output.isLearner ?? undefined)
    );
    output.isTTM = (
      launchInfo
        ? !!launchInfo.isTTM
        : (output.isTTM ?? undefined)
    );
    output.isAdmin = (
      launchInfo
        ? !!launchInfo.isAdmin
        : (output.isAdmin ?? undefined)
    );
    output.courseId = (
      launchInfo
        ? (output.courseId ?? launchInfo.courseId)
        : (output.courseId ?? undefined)
    );
    output.courseName = (
      launchInfo
        ? launchInfo.contextLabel
        : (output.courseName ?? undefined)
    );

    // Add other session variables
    Object.keys(req.session).forEach((propName) => {
      // Skip if prop already in output
      if (output[propName] !== undefined) {
        return;
      }

      // Add to output
      const value = req.session[propName];
      if (
        typeof value === 'string'
        || typeof value === 'boolean'
        || typeof value === 'number'
      ) {
        output[propName] = value;
      }
    });

    /*----------------------------------------*/
    /* ----- Require Course Consistency ----- */
    /*----------------------------------------*/

    // Make sure the user actually launched from the appropriate course
    if (
      output.courseId
      && launchInfo
      && launchInfo.courseId
      && output.courseId !== launchInfo.courseId
      && !output.isTTM
      && !output.isAdmin
    ) {
      // Course of interest is not the launch course
      return handleError(
        res,
        {
          message: 'You switched sessions by opening this app in another tab. Please refresh the page and try again.',
          code: ExpressKitErrorCode.WrongCourse,
          status: 401,
        },
      );
    }

    /*----------------------------------------*/
    /*       Require Proper Permissions       */
    /*----------------------------------------*/

    // Add TTM endpoint security
    if (
      // This is a TTM endpoint
      req.path.startsWith('/api/ttm')
      // User is not a TTM
      && (
        // User is not a TTM
        !output.isTTM
        // User is not an admin
        && !output.isAdmin
      )
    ) {
      // User does not have access
      return handleError(
        res,
        {
          message: 'This action is only allowed if you are a teaching team member for the course. Please go back to Canvas, log in as a teaching team member, and try again.',
          code: ExpressKitErrorCode.NotTTM,
          status: 401,
        },
      );
    }

    // Add Admin endpoint security
    if (
      // This is an admin endpoint
      req.path.startsWith('/api/admin')
      // User is not an admin
      && !output.isAdmin
    ) {
      // User does not have access
      return handleError(
        res,
        {
          message: 'This action is only allowed if you are a Canvas admin. Please go back to Canvas, log in as an admin, and try again.',
          code: ExpressKitErrorCode.NotAdmin,
          status: 401,
        },
      );
    }

    // Add Select Admin endpoint security
    if (
      // This is a select admin endpoint
      req.path.startsWith('/api/admin/select')
    ) {
      // Get select admin collection
      const selectAdminCollection = await internalGetSelectAdminCollection();
      const id = output.userId;

      // Find match if exists in select admin collection
      const [match] = await selectAdminCollection.find({ id });

      // Check that user exists in select admin collection
      if (!match) {
        // User does not have access
        return handleError(
          res,
          {
            message: 'This action is only allowed for select Canvas admins. Please go back to Canvas, log in as a select admin, and try again.',
            code: ExpressKitErrorCode.NotSelectAdmin,
            status: 401,
          },
        );
      }
    }

    /*----------------------------------------*/
    /* ------------- Log Handler ------------ */
    /*----------------------------------------*/

    // Create a log handler function

    /**
     * Log an event on the server
     * @author Gabe Abrams
     */
    const logServerEvent: LogFunction = async (logOpts) => {
      // NOTE: internally, we slip through an opts.overrideAsClientEvent boolean
      // that indicates that this is actually a client event, but we don't
      // include that in the LogFunction type because this is internal and
      // hidden from users
      try {
        // Parse user agent
        const {
          browser,
          device,
        } = parseUserAgent(req.headers['user-agent']);

        // Get time info in ET
        const {
          timestamp,
          year,
          month,
          day,
          hour,
          minute,
        } = getTimeInfoInET();

        // Main log info
        const mainLogInfo: LogMainInfo = {
          id: `${launchInfo ? launchInfo.userId : 'unknown'}-${Date.now()}-${Math.floor(Math.random() * 100000)}-${Math.floor(Math.random() * 100000)}`,
          userFirstName: (launchInfo ? launchInfo.userFirstName : 'unknown'),
          userLastName: (launchInfo ? launchInfo.userLastName : 'unknown'),
          userEmail: (launchInfo ? launchInfo.userEmail : 'unknown'),
          userId: (launchInfo ? launchInfo.userId : -1),
          isLearner: (launchInfo && !!launchInfo.isLearner),
          isAdmin: (launchInfo && !!launchInfo.isAdmin),
          isTTM: (launchInfo && !!launchInfo.isTTM),
          courseId: (launchInfo ? launchInfo.courseId : -1),
          courseName: (launchInfo ? launchInfo.contextLabel : 'unknown'),
          browser,
          device,
          year,
          month,
          day,
          hour,
          minute,
          timestamp,
          context: (
            typeof logOpts.context === 'string'
              ? logOpts.context
              : (
                ((logOpts.context as any) ?? {})._
                ?? LogBuiltInMetadata.Context.Uncategorized
              )
          ),
          subcontext: (
            logOpts.subcontext
            ?? LogBuiltInMetadata.Context.Uncategorized
          ),
          tags: (logOpts.tags ?? []),
          level: (logOpts.level ?? LogLevel.Info),
          metadata: (logOpts.metadata ?? {}),
        };

        // Type-specific info
        const typeSpecificInfo: LogTypeSpecificInfo = (
          ('error' in logOpts && logOpts.error)
            ? {
              type: LogType.Error,
              errorMessage: (logOpts as any).error.message ?? 'Unknown message',
              errorCode: (logOpts as any).error.code ?? CommonKitErrorCode.NoCode,
              errorStack: (logOpts as any).error.stack ?? 'No stack',
            }
            : {
              type: LogType.Action,
              target: (
                (logOpts as any).target
                ?? LogBuiltInMetadata.Target.NoTarget
              ),
              action: (
                (logOpts as any).action
                ?? LogAction.Unknown
              ),
            }
        );

        // Source-specific info
        const sourceSpecificInfo: LogSourceSpecificInfo = (
          (logOpts as any).overrideAsClientEvent
            ? {
              source: LogSource.Client,
            }
            : {
              source: LogSource.Server,
              routePath: req.path,
              routeTemplate: req.route.path,
            }
        );

        // Build log event
        const log: Log = {
          ...mainLogInfo,
          ...typeSpecificInfo,
          ...sourceSpecificInfo,
        };

        // Either print to console or save to db
        const logCollection = await internalGetLogCollection();
        if (logCollection) {
          // Store to the log collection
          await logCollection.insert(log);
        } else if (log.type === LogType.Error) {
          // Print to console
          // eslint-disable-next-line no-console
          console.error('dce error log:', log);
        } else {
          // eslint-disable-next-line no-console
          console.log('dce action log:', log);
        }

        // Return log entry
        return log;
      } catch (err) {
        // Print because we cannot store the error
        // eslint-disable-next-line no-console
        console.error(
          'Could not log the following:',
          logOpts,
          'due to this error:',
          (err as any ?? {}).message,
          (err as any ?? {}).stack,
        );

        // Create a dummy log to return
        const dummyMainInfo: LogMainInfo = {
          id: '-1',
          userFirstName: 'Unknown',
          userLastName: 'Unknown',
          userEmail: 'unknown@harvard.edu',
          userId: 1,
          isLearner: false,
          isAdmin: false,
          isTTM: false,
          courseId: 1,
          courseName: 'Unknown',
          browser: {
            name: 'Unknown',
            version: 'Unknown',
          },
          device: {
            isMobile: false,
            os: 'Unknown',
          },
          year: 1,
          month: 1,
          day: 1,
          hour: 1,
          minute: 1,
          timestamp: Date.now(),
          tags: [],
          level: LogLevel.Warn,
          metadata: {},
          context: LogBuiltInMetadata.Context.Uncategorized,
          subcontext: LogBuiltInMetadata.Context.Uncategorized,
        };

        const dummyTypeSpecificInfo: LogTypeSpecificInfo = {
          type: LogType.Error,
          errorMessage: 'Unknown',
          errorCode: 'Unknown',
          errorStack: 'No Stack',
        };

        const dummySourceSpecificInfo: LogSourceSpecificInfo = {
          source: LogSource.Server,
          routePath: req.path,
          routeTemplate: req.route.path,
        };

        const log: Log = {
          ...dummyMainInfo,
          ...dummyTypeSpecificInfo,
          ...dummySourceSpecificInfo,
        };

        return log;
      }
    };

    /*------------------------------------------------------------------------*/
    /*                              Call handler                              */
    /*------------------------------------------------------------------------*/

    // Keep track of whether a response was already sent
    let responseSent = false;

    /**
     * Redirect the user to another path or url
     * @author Gabe Abrams
     * @param pathOrURL the path or url to redirect to
     */
    const redirect = (pathOrURL: string) => {
      responseSent = true;
      res.redirect(pathOrURL);
    };

    /**
     * Send text to the client (with an optional status code)
     * @author Gabe Abrams
     * @param text the text to send to the client
     * @parm [status=200] the http status code to send
     */
    const send = (text: string, status: number = 200) => {
      responseSent = true;
      res.status(status).send(text);
    };

    /**
     * Render an error page
     * @author Gabe Abrams
     * @param renderOpts object containing all arguments
     * @param [renderOpts.title=An Error Occurred] title of the error box
     * @param [renderOpts.description=An unknown server error occurred. Please contact support.]
     *   a human-readable description of the error
     * @param [renderOpts.code=CommonKitErrorCode.NoCode] error code to show
     * @param [renderOpts.pageTitle=renderOpts.title] title of the page/tab if it differs from
     *   the title of the error
     * @param [renderOpts.status=500] http status code
     */
    const renderErrorPage = (
      renderOpts: {
        title?: string,
        description?: string,
        code?: string,
        pageTitle?: string,
        status?: number,
      } = {},
    ) => {
      const html = genErrorPage(renderOpts);
      send(html, renderOpts.status ?? 500);

      // Log server-side error if not a session expired error or 404
      if (renderOpts.status && renderOpts.status === 404) {
        return;
      }
      if (renderOpts.title?.toLowerCase().includes('session expired')) {
        return;
      }
      logServerEvent({
        context: LogBuiltInMetadata.Context.ServerRenderedErrorPage,
        error: {
          message: `${renderOpts.title}: ${renderOpts.description}`,
          code: renderOpts.code,
        },
        metadata: {
          title: renderOpts.title,
          description: renderOpts.description,
          code: renderOpts.code,
          pageTitle: renderOpts.pageTitle,
          status: renderOpts.status ?? 500,
        },
      });
    };

    /**
     * Render an info page
     * @author Gabe Abrams
     * @param renderOpts object containing all arguments
     * @param renderOpts.title title of the info box
     * @param renderOpts.body a human-readable text body for the info alert
     */
    const renderInfoPage = (
      renderOpts: {
        title: string,
        body: string,
      },
    ) => {
      const html = genInfoPage(renderOpts);
      send(html, 200);
    };

    /**
     * Render custom HTML
     * @author Gabe Abrams
     * @param htmlOpts object containing all arguments
     * @param htmlOpts.html the HTML to send to the client
     * @param [ejsOpts.status=200] the http status code to send
     */
    const renderCustomHTML = (
      htmlOpts: {
        html: string,
        status?: number,
      },
    ) => {
      send(htmlOpts.html, htmlOpts.status ?? 200);
    };

    // Call the handler
    try {
      const results = await opts.handler({
        params: output,
        req,
        send,
        next: () => {
          responseSent = true;
          next();
        },
        redirect,
        renderErrorPage,
        renderInfoPage,
        renderCustomHTML,
        logServerEvent,
      });

      // Send results to client (only if next wasn't called)
      if (!responseSent) {
        return handleSuccess(res, results ?? undefined);
      }
    } catch (err) {
      // Prefix error message if needed
      if (
        opts.unhandledErrorMessagePrefix
        && err instanceof Error
        && err.message
        && err.name !== 'ErrorWithCode'
      ) {
        err.message = `${opts.unhandledErrorMessagePrefix.trim()} ${err.message.trim()}`;
      }

      // Send error to client (only if next wasn't called)
      if (!responseSent) {
        handleError(res, err);

        // Log server-side error
        logServerEvent({
          context: LogBuiltInMetadata.Context.ServerEndpointError,
          error: err,
        });

        return;
      }

      // Log error that was not responded with
      // eslint-disable-next-line no-console
      console.log('Error occurred but could not be sent to client because a response was already sent:', err);
    }
  };
};

export default genRouteHandler;