'use strict';

var PromiseA = require('bluebird');
var crypto = require('crypto');

module.exports.create = function (bigconf, deps, app) {
  var Jwks = { restful: {} };

  function attachModels(req, res, next) {
    return req.getSiteStore().then(function (models) {
      req.Models = models;
      next();
    });
  }

  Jwks.thumbprint = function (jwk) {
    // To produce a thumbprint we need to create a JSON string with only the required keys for
    // the key type, with the keys sorted lexicographically and no white space. We then need
    // run it through a SHA-256 and encode the result in url safe base64.
    // https://stackoverflow.com/questions/42588786/how-to-fingerprint-a-jwk
    var keys;
    if (jwk.kty === 'EC') {
      keys = ['crv', 'x', 'y'];
    } else if (jwk.kty === 'RSA') {
      keys = ['e', 'n'];
    } else {
      return PromiseA.reject(new Error('invalid JWK key type ' + jwk.kty));
    }
    keys.push('kty');
    keys.sort();

    var missing = keys.filter(function (name) { return !jwk.hasOwnProperty(name); });
    if (missing.length > 0) {
      return PromiseA.reject(new Error('JWK of type '+jwk.kty+' missing fields ' + missing));
    }

    // I'm not 100% sure this behavior is guaranteed by a real standard, but when we use an array
    // as the replacer argument the keys are always in the order they appeared in the array.
    var jwkStr = JSON.stringify(jwk, keys);
    var hash = crypto.createHash('sha256').update(jwkStr).digest('base64');
    return PromiseA.resolve(hash.replace(/\+/g, '-').replace(/\//g, '_').replace(/=+/g, ''));
  };

  Jwks.restful.get = function (req, res) {
    var promise = req.Models.IssuerOauth3OrgJwks.find({ kid: req.params.kid }, { limit: 1 }).then(function (jwkArr) {
      var jwk = jwkArr[0];
      // We need to sanitize the key to make sure we don't deliver any private keys fields if
      // we were given a key we could use to sign tokens on behalf of the user.
      var whitelist = [ 'kty', 'alg', 'kid', 'use' ];
      if (jwk.kty === 'EC') {
        whitelist = whitelist.concat([ 'crv', 'x', 'y' ]);
      } else if (jwk.kty === 'RSA') {
        whitelist = whitelist.concat([ 'e', 'n' ]);
      }

      var result = {};
      whitelist.forEach(function (key) {
        result[key] = jwk[key];
      });
      return result;
    });

    app.handlePromise(req, res, promise, "[issuer@oauth3.org] retrieve JWK");
  };
  Jwks.restful.saveNew = function (req, res) {
    var jwk = req.body;
    var promise = Jwks.thumbprint(jwk).then(function (kid) {
      if (jwk.kid && jwk.kid !== kid) {
        throw new Error('provided kid "'+jwk.kid+'" does not match calculated "'+kid+'"');
      }
      jwk.kid = kid;

      return req.Models.IssuerOauth3OrgJwks.upsert(req.params.sub, jwk);
    }).then(function () {
      return { success: true };
    });

    app.handlePromise(req, res, promise, "[issuer@oauth3.org] create JWK");
  };

  app.use(   '/jwks', attachModels);
  app.get(   '/jwks/:kid.json', Jwks.restful.get);
  app.post(  '/jwks/:sub', Jwks.restful.saveNew);
};