'use strict';

var debug = require('debug')('plugin:oauth');
var url = require('url');
var jwt = require('jsonwebtoken');
var requestLib = require('request');
var _ = require('lodash');

const authHeaderRegex = /Bearer (.+)/;
const PRIVATE_JWT_VALUES = ['application_name', 'client_id', 'api_product_list', 'iat', 'exp'];
const SUPPORTED_DOUBLE_ASTERIK_PATTERN = "**";
const SUPPORTED_SINGLE_ASTERIK_PATTERN = "*";
const SUPPORTED_SINGLE_FORWARD_SLASH_PATTERN = "/";

module.exports.init = function (config, logger, stats) {

  var apiKeyCache = {};
  var request = config.request ? requestLib.defaults(config.request) : requestLib;

  var middleware = function (req, res, next) {

    var authHeaderName = config['authorization-header'] ? config['authorization-header'] : 'authorization';
    var apiKeyHeaderName = config['api-key-header'] ? config['api-key-header'] : 'x-api-key';
    var keepAuthHeader = config['keep-authorization-header'] || false;
    //support for enabling oauth or api key only
    var oauth_only = config['allowOAuthOnly'] || false;
    var apikey_only = config['allowAPIKeyOnly'] || false;
    //
    var apiKey;

    //support for enabling oauth or api key only
    if (oauth_only) {
      if (!req.headers['authorization']) {
        debug('missing_authorization');
        return sendError(req, res, next, logger, stats, 'missing_authorization', 'Missing Authorization header');
      } else {
        var header = authHeaderRegex.exec(req.headers['authorization']);
        if (!header || header.length < 2) {
          debug('Invalid Authorization Header');
          return sendError(req, res, next, logger, stats, 'invalid_request', 'Invalid Authorization header');
        }
      }
    }
    else if (apikey_only) {
      if (req.headers[authHeaderName]) {
        debug('Invalid Authorization Type');
        return sendError(req, res, next, logger, stats, 'invalid_auth', 'Invalid Authorization type');        
      }
    }
    //leaving rest of the code same to ensure backward compatibility
    if (!req.headers[authHeaderName]) {
      if (apiKey = req.headers[apiKeyHeaderName]) {
        exchangeApiKeyForToken(req, res, next, config, logger, stats, middleware, apiKey);
      } else if (req.reqUrl && req.reqUrl.query && (apiKey = req.reqUrl.query[apiKeyHeaderName])) {
        exchangeApiKeyForToken(req, res, next, config, logger, stats, middleware, apiKey);
      } else if (config.allowNoAuthorization) {
        return next();
      } else {
        debug('missing_authorization');
        return sendError(req, res, next, logger, stats, 'missing_authorization', 'Missing Authorization header');
      }
    } else {
      var header = authHeaderRegex.exec(req.headers[authHeaderName]);
      if (!header || header.length < 2) {
        debug('Invalid Authorization Header');
        return sendError(req, res, next, logger, stats, 'invalid_request', 'Invalid Authorization header');
      }

      var token = header[1];

      if (!keepAuthHeader) {
        delete (req.headers[authHeaderName]); // don't pass this header to target
      }

      verify(token, config, logger, stats, middleware, req, res, next);
    }
  }

  var exchangeApiKeyForToken = function (req, res, next, config, logger, stats, middleware, apiKey) {
    var cacheControl = req.headers['cache-control'];
    if (!cacheControl || (cacheControl && cacheControl.indexOf('no-cache') < 0)) { // caching is allowed
      var token = apiKeyCache[apiKey];
      if (token) {
        if (Date.now() / 1000 < token.exp) { // not expired yet (token expiration is in seconds)
          debug('api key cache hit', apiKey);
          return authorize(req, res, next, logger, stats, token);
        } else {
          delete apiKeyCache[apiKey];
          debug('api key cache expired', apiKey);
        }
      } else {
        debug('api key cache miss', apiKey);
      }
    }

    if (!config.verify_api_key_url) return sendError(req, res, next, logger, stats, 'invalid_request', 'API Key Verification URL not configured');
    request({
      url: config.verify_api_key_url,
      method: 'POST',
      json: { 'apiKey': apiKey },
      headers: { 'x-dna-api-key': apiKey }
    }, function (err, response, body) {
      if (err) {
        debug('verify apikey gateway timeout');
        return sendError(req, res, next, logger, stats, 'gateway_timeout', err.message);
      }
      if (response.statusCode !== 200) {
        debug('verify apikey access_denied');
        return sendError(req, res, next, logger, stats, 'access_denied', response.statusMessage);
      }
      verify(body, config, logger, stats, middleware, req, res, next, apiKey);
    });
  }

  var verify = function (token, config, logger, stats, middleware, req, res, next, apiKey) {
    var options = {
      algorithms: ['RS256'],
      ignoreExpiration: false,
      audience: undefined,
      issuer: undefined
    };

    jwt.verify(token && token.token ? token.token : token, config.public_key, options, function (err, decodedToken) {

      if (err) {

        if (config.allowInvalidAuthorization) {

          console.warn('ignoring err', err);
          return next();

        } else {

          if (err.name === 'TokenExpiredError') {
            debug('Token expired error');
            return sendError(req, res, next, logger, stats, 'access_denied');
          }

          // todo: check other properties and/or give client more info?
          debug('invalid token');
          return sendError(req, res, next, logger, stats, 'invalid_token');
        }
      }

      authorize(req, res, next, logger, stats, decodedToken, apiKey);
    });
  };

  return {

    onrequest: function (req, res, next) {
      middleware(req, res, next);
    },

    api_key_cache_size: function () {
      return Object.keys(apiKeyCache).length;
    },

    api_key_cache_clear: function () {
      var deleted = 0;
      Object.keys(apiKeyCache).forEach(function (key) {
        delete apiKeyCache[key];
        deleted++;
      });
      return deleted;
    }

  };

  function authorize(req, res, next, logger, stats, decodedToken, apiKey) {
    if (checkIfAuthorized(config, req.reqUrl.path, res.proxy, decodedToken)) {
      req.token = decodedToken;

      var authClaims = _.omit(decodedToken, PRIVATE_JWT_VALUES);
      req.headers['x-authorization-claims'] = new Buffer(JSON.stringify(authClaims)).toString('base64');

      if (apiKey) {
        var cacheControl = req.headers['cache-control'];
        if (!cacheControl || (cacheControl && cacheControl.indexOf('no-cache') < 0)) { // caching is allowed
          // default to now (in seconds) + 30m if not set
          decodedToken.exp = decodedToken.exp || +(((Date.now() / 1000) + 1800).toFixed(0));
          apiKeyCache[apiKey] = decodedToken;
          debug('api key cache store', apiKey);
        } else {
          debug('api key cache skip', apiKey);
        }
      }

      next();
    } else {
      return sendError(req, res, next, logger, stats, 'access_denied');
    }
  }

}

// from the product name(s) on the token, find the corresponding proxy
// then check if that proxy is one of the authorized proxies in bootstrap
const checkIfAuthorized = module.exports.checkIfAuthorized = function checkIfAuthorized(config, urlPath, proxy, decodedToken) {

  if (!decodedToken.api_product_list) { debug('no api product list'); return false; }

  return decodedToken.api_product_list.some(function (product) {

    const validProxyNames = config.product_to_proxy[product];
    if (!validProxyNames) { debug('no proxies found for product'); return false; }

    const apiproxies = config.product_to_api_resource[product];
    var matchesProxyRules = false;
    if(apiproxies && apiproxies.length){
      apiproxies.forEach(function (tempApiProxy) {
          if(matchesProxyRules){
            //found one
            debug('found matching proxy rule');
            return;
          }
          const apiproxy = tempApiProxy.includes(proxy.base_path)
            ? tempApiProxy
            : proxy.base_path + (tempApiProxy.startsWith("/") ? "" : "/") +  tempApiProxy
          if (apiproxy.endsWith("/") && !urlPath.endsWith("/")) {
              urlPath = urlPath + "/";
          }

          if(apiproxy.includes(SUPPORTED_DOUBLE_ASTERIK_PATTERN)){
            const regex = apiproxy.replace(/\*\*/gi,".*")
            matchesProxyRules =  urlPath.match(regex)
          }else{
            if(apiproxy.includes(SUPPORTED_SINGLE_ASTERIK_PATTERN)){
              const regex = apiproxy.replace(/\*/gi,"[^/]+");
              matchesProxyRules =  urlPath.match(regex)
            }else{
              // if(apiproxy.includes(SUPPORTED_SINGLE_FORWARD_SLASH_PATTERN)){
              // }
              matchesProxyRules = urlPath == apiproxy;
            }
          }
      })

    }else{
      matchesProxyRules = true
    }

    //add pattern matching here

    return matchesProxyRules &&  validProxyNames.indexOf(proxy.name) >= 0;
  });
}

function sendError(req, res, next, logger, stats, code, message) {

  switch (code) {
    case 'invalid_request':
      res.statusCode = 400;
      break;
    case 'access_denied':
      res.statusCode = 403;
      break;
    case 'invalid_token':
    case 'missing_authorization':
    case 'invalid_authorization':
      res.statusCode = 401;
      break;
    case 'gateway_timeout':
      res.statusCode = 504;
      break;
    default:
      res.statusCode = 500;
  }

  var response = {
    error: code,
    error_description: message
  };

  debug('auth failure', res.statusCode, code, message ? message : '', req.headers, req.method, req.url);
  logger.error({ req: req, res: res }, 'oauth');

  if (!res.finished) res.setHeader('content-type', 'application/json');
  res.end(JSON.stringify(response));
  stats.incrementStatusCount(res.statusCode);
  next(code, message);
  return code;
}