'use strict';

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

function makeB64UrlSafe(b64) {
  return b64.replace(/\+/g, '-').replace(/\//g, '_').replace(/=*$/, '');
}

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

  // This tablename is based on the tablename found in the objects in model.js.
  // Instead of the snake_case the name with be UpperCammelCase, converted by masterquest-sqlite3.
  function attachSiteStore(tablename, req, res, next) {
    return req.getSiteStore().then(function (store) {
      req.Store = store[tablename];
      next();
    });
  }
  function detachSiteStore(req, res, next) {
    delete req.Store;
    next();
  }


  function authorizeIssuer(req, res, next) {
    var promise = PromiseA.resolve().then(function () {
      // It might seem unnecessary to wrap a promise in another promise, but this way it will
      // catch the error thrown when a token isn't provided and verifyAsync isn't a function.
      return req.oauth3.verifyAsync();
    }).then(function (token) {
      // Now that we've confirmed the token is valid we also need to make sure the issuer, audience,
      // and authorized party are all us, because no other app should be managing user identity.
      if (token.iss !== req.experienceId || token.aud !== token.iss || token.azp !== token.iss) {
        throw new Error("token does not allow access to requested resource");
      }

      var sub = token.sub || token.ppid || (token.acx && (token.acx.id || token.acx.appScopedId));
      if (!sub) {
        if (!Array.isArray(token.axs) || !token.axs.length) {
          throw new Error("no account pairwise identifier");
        }

        var allowed = token.axs.some(function (acc) {
          return req.params.sub === (acc.id || acc.ppid || acc.appScopedId);
        });
        if (!allowed) {
          throw new Error("no account pairwise identifier matching '" + req.params.sub + "'");
        }
        sub = req.params.sub;
      }

      if (req.params.sub !== sub) {
        throw new Error("token does not allow access to resources for '"+req.params.sub+"'");
      }
      next();
    });

    app.handleRejection(req, res, promise, '[issuer@oauth3.org] authorize req as issuer');
  }


  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(makeB64UrlSafe(hash));
  };

  Jwks.restful.get = function (req, res) {
    var store;
    // The sub in params is the 3rd party PPID, but the keys are stored by the issuer PPID, so
    // we need to look up the issuer PPID using the 3rd party PPID.
    var promise = req.getSiteStore().then(function (_store) {
      store = _store;
      return store.IssuerOauth3OrgGrants.find({ azpSub: req.params.sub });
    }).then(function (results) {
      if (!results.length) {
        throw new Error("unknown PPID '"+req.params.sub+"'");
      }
      if (results.length > 1) {
        // This should not ever happen since there is a check for PPID collisions when saving
        // grants, but it's probably better to have this check anyway just incase something
        // happens that isn't currently accounted for.
        throw new Error('PPID collision - unable to safely retrieve keys');
      }

      return store.IssuerOauth3OrgJwks.get(results[0].sub+'/'+req.params.kid);
    }).then(function (jwk) {
      if (!jwk) {
        throw new Error("no keys stored with kid '"+req.params.kid+"' for PPID "+req.params.sub);
      }

      // 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. We also don't
      // want to deliver the sub or any other PPIDs.
      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;
      jwk.sub = req.params.sub;

      return req.Store.upsert(jwk.sub+'/'+jwk.kid, jwk);
    }).then(function () {
      return { success: true };
    });

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


  Grants.trim = function (grant) {
    return {
      sub:   grant.sub,
      azp:   grant.azp,
      // azpSub: grant.azpSub,
      scope: grant.scope,
      updatedAt: parseInt(grant.updatedAt, 10),
    };
  };

  Grants.restful.getOne = function (req, res) {
    var promise = req.Store.get(req.params.sub+'/'+req.params.azp).then(function (grant) {
      if (!grant) {
        throw new Error('no grants found');
      }
      return Grants.trim(grant);
    });

    app.handlePromise(req, res, promise, "[issuer@oauth3.org] retrieve grants");
  };
  Grants.restful.getAll = function (req, res) {
    var promise = req.Store.find({ sub: req.params.sub }).then(function (results) {
      return results.map(Grants.trim).sort(function (grantA, grantB) {
        return (grantA.azp < grantB.azp) ? -1 : 1;
      });
    });

    app.handlePromise(req, res, promise, "[issuer@oauth3.org] retrieve grants");
  };
  Grants.restful.saveNew = function (req, res) {
    var promise = PromiseA.resolve().then(function () {
      if (typeof req.body.scope !== 'string' || typeof req.body.sub !== 'string') {
        throw new Error("malformed request: 'sub' and 'scope' must be strings");
      }
      return req.Store.find({ azpSub: req.body.sub });
    }).then(function (existing) {
      if (existing.length) {
        if (existing.length > 1) {
          throw new Error("pre-existing PPID collision detected");
        } else if (existing[0].sub !== req.params.sub || existing[0].azp !== req.params.azp) {
          throw new Error("PPID collision detected, cannot save authorized party's sub");
        }
      }

      var grant = {
        sub:    req.params.sub,
        azp:    req.params.azp,
        azpSub: req.body.sub,
        scope:  req.body.scope.split(/[+ ,]+/g).join(','),
      };
      return req.Store.upsert(grant.sub+'/'+grant.azp, grant);
    }).then(function () {
      return {success: true};
    });

    app.handlePromise(req, res, promise, '[issuer@oauth3.org] save grants');
  };

  Tokens.getPrivKey = function (store, experienceId) {
    return store.IssuerOauth3OrgPrivateKeys.get(experienceId).then(function (jwk) {
      if (jwk) {
        return jwk;
      }

      var keyPair = require('elliptic').ec('p256').genKeyPair();
      jwk = {
        kty: 'EC',
        crv: 'P-256',
        alg: 'ES256',
        kid: experienceId,
        x: makeB64UrlSafe(keyPair.getPublic().getX().toArrayLike(Buffer).toString('base64')),
        y: makeB64UrlSafe(keyPair.getPublic().getY().toArrayLike(Buffer).toString('base64')),
        d: makeB64UrlSafe(keyPair.getPrivate().toArrayLike(Buffer).toString('base64')),
      };

      return store.IssuerOauth3OrgPrivateKeys.upsert(experienceId, jwk).then(function () {
        return jwk;
      });
    });
  };

  Tokens.restful.create = function (req, res) {
    var store;
    var promise = req.getSiteStore().then(function (_store) {
      store = _store;
      return store.IssuerOauth3OrgGrants.get(req.params.sub+'/'+req.params.azp);
    }).then(function (grant) {
      if (!grant) {
        throw new Error("'"+req.params.azp+"' not given any grants from '"+req.params.sub+"'");
      }
      return Tokens.getPrivKey(store, req.experienceId).then(function (jwk) {
        var pem = require('jwk-to-pem')(jwk, { private: true });
        var payload = {
          // standard
          iss: req.experienceId, // https://tools.ietf.org/html/draft-ietf-oauth-json-web-token-32#section-4.1.1
          aud: req.params.aud,   // https://tools.ietf.org/html/draft-ietf-oauth-json-web-token-32#section-4.1.3
          azp: grant.azp,
          sub: grant.azpSub,     // https://tools.ietf.org/html/draft-ietf-oauth-json-web-token-32#section-4.1.2
          // extended
          scp: grant.scope,
        };
        var opts = {
          algorithm: jwk.alg,
          header: {
            kid: jwk.kid
          }
        };

        return {
          access_token: require('jsonwebtoken').sign(payload, pem, Object.assign({expiresIn: '1d'}, opts)),
          refresh_token: require('jsonwebtoken').sign(payload, pem, opts),
          scope: grant.scope,
        };
      });
    });

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

  app.get(   '/jwks/:sub/:kid.json', Jwks.restful.get);
  // Everything but getting keys is only for the issuer
  app.use(   '/jwks/:sub', authorizeIssuer, attachSiteStore.bind(null, 'IssuerOauth3OrgJwks'));
  app.post(  '/jwks/:sub', Jwks.restful.saveNew);

  // Everything regarding grants is only for the issuer
  app.use(   '/grants/:sub', authorizeIssuer, attachSiteStore.bind(null, 'IssuerOauth3OrgGrants'));
  app.get(   '/grants/:sub', Grants.restful.getAll);
  app.get(   '/grants/:sub/:azp', Grants.restful.getOne);
  app.post(  '/grants/:sub/:azp', Grants.restful.saveNew);

  app.use(   '/access_token/:sub', authorizeIssuer);
  app.post(  '/access_token/:sub/:aud/:azp', Tokens.restful.create);

  app.use(detachSiteStore);
};