'use strict';

var PromiseA = require('bluebird');
var crypto = require('crypto');
var OpErr = PromiseA.OperationalError;

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

function timespan(duration, max) {
  var timestamp = Math.floor(Date.now() / 1000);

  if (typeof duration === 'string') {
    duration = Math.floor(require('ms')(duration) / 1000);
  }
  if (typeof duration !== 'number') {
    return timestamp;
  }

  if (max && timestamp+duration > max) {
    return max - timestamp;
  }
  return duration;
}

module.exports.create = function (bigconf, deps, app) {
  var Jwks = { restful: {} };
  var Grants = { restful: {} };
  var Accounts = { 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 checkIsserToken(req, expectedSub) {
    if (!req.oauth3 || !req.oauth3.verifyAsync) {
      return PromiseA.reject(new OpErr("request requires a token for authorization"));
    }
    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 OpErr("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 (!expectedSub || !Array.isArray(token.axs) || !token.axs.length) {
          throw new OpErr("no account pairwise identifier");
        }

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

      if (expectedSub && expectedSub !== sub) {
        throw new OpErr("token does not allow access to resources for '"+expectedSub+"'");
      }
      return sub;
    });
  }
  function authorizeIssuer(req, res, next) {
    var promise = checkIsserToken(req, req.params.sub).then(function () {
      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) {
    // 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) {
      if (req.params.kid === req.experienceId) {
        return store.IssuerOauth3OrgPrivateKeys.get(req.experienceId);
      }

      return store.IssuerOauth3OrgGrants.find({ azpSub: req.params.sub }).then(function (results) {
        if (!results.length) {
          throw new OpErr("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 OpErr('PPID collision - unable to safely retrieve keys');
        }

        return store.IssuerOauth3OrgJwks.get(results[0].sub+'/'+req.params.kid);
      });
    }).then(function (jwk) {
      if (!jwk) {
        throw new OpErr("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 OpErr('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 OpErr('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 OpErr("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 OpErr("pre-existing PPID collision detected");
        } else if (existing[0].sub !== req.params.sub || existing[0].azp !== req.params.azp) {
          throw new OpErr("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');
  };


  Accounts.retrieveOtp = function (codeStore, codeId) {
    return codeStore.get(codeId).then(function (code) {
      if (!code) {
        return null;
      }

      var expires = (new Date(code.expires)).valueOf();
      if (!expires || Date.now() > expires) {
        return codeStore.destroy(codeId).then(function () {
          return null;
        });
      }

      return code;
    });
  };
  Accounts.validateOtp = function (codeStore, codeId, token) {
    if (!codeId) {
      return PromiseA.reject(new Error("Must provide authcode ID"));
    }
    if (!token) {
      return PromiseA.reject(new Error("Must provide authcode code"));
    }
    return codeStore.get(codeId).then(function (code) {
      if (!code) {
        throw new OpErr('authcode specified does not exist or has expired');
      }

      return PromiseA.resolve().then(function () {
        var attemptsLeft = 3 - (code.attempts && code.attempts.length || 0);
        if (attemptsLeft <= 0) {
          throw new OpErr('you have tried to authorize this code too many times');
        }
        if (code.code !== token) {
          throw new OpErr('you have entered the code incorrectly. '+attemptsLeft+' attempts remaining');
        }
        // TODO: maybe impose a rate limit, although going fast doesn't help you break the
        // system when you can only try 3 times total.
      }).then(function () {
        return codeStore.destroy(codeId).then(function () {
          return code;
        });
      }, function (err) {
        code.attempts = code.attempts || [];
        code.attempts.unshift(new Date());

        return codeStore.upsert(codeId, code).then(function () {
          return PromiseA.reject(err);
        }, function () {
          return PromiseA.reject(err);
        });
      });
    });
  };

  Accounts.getOrCreate = function (store, username) {
    return store.IssuerOauth3OrgAccounts.get(username).then(function (account) {
      if (account) {
        return account;
      }

      account = {
        username:  username,
        accountId: makeB64UrlSafe(crypto.randomBytes(32).toString('base64')),
      };
      return store.IssuerOauth3OrgAccounts.create(username, account).then(function () {
        // TODO: put sort sort of email notification to the server managers?
        return account;
      });
    });
  };
  Accounts.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;
      });
    });
  };

  Accounts.restful.sendOtp = function (req, res) {
    var params = req.body;
    var promise = PromiseA.resolve().then(function () {
      if (!params || !params.username) {
        throw new OpErr("must provide the email address as 'username' in the body");
      }
      if ((params.username_type && 'email' !== params.username_type) || !/@/.test(params.username)) {
        throw new OpErr("only email one-time login codes are supported at this time");
      }
      params.username_type = 'email';

      return req.getSiteStore();
    }).then(function (store) {
      var codeStore = store.IssuerOauth3OrgCodes;
      var codeId = crypto.createHash('sha256').update(params.username_type+':'+params.username).digest('base64');
      codeId = makeB64UrlSafe(codeId);

      return Accounts.retrieveOtp(codeStore, codeId).then(function (code) {
        if (code) {
          return code;
        }

        var token = '';
        while (!/^\d{4}-\d{4}-\d{4}$/.test(token)) {
          // Most of the number we can generate this was start with 1 (and no matter what can't
          // start with 0), so we don't use the very first digit. Also basically all of the
          // numbers are too big to accurately store in JS floats, so we limit the trailing 0's.
          token = (parseInt(crypto.randomBytes(8).toString('hex'), 16)).toString()
            .replace(/0+$/, '0').replace(/\d(\d{4})(\d{4})(\d{4}).*/, '$1-$2-$3');
        }
        code = {
          id: codeId,
          code: token,
          expires: new Date(Date.now() + 20*60*1000),
        };
        return codeStore.upsert(codeId, code).then(function (){
          return code;
        });
      });
    }).then(function (code) {
      var emailParams = {
        to:      params.username,
        from:    'login@daplie.com',   // opts.mailer.defaults.system
        replyTo: 'hello@daplie.com',
        subject: "Use " + code.code + " as your Login Code",  // message.Subject
        text:    code.code + " is your Login Code."        // message['stripped-html']
      };
      emailParams['h:Reply-To'] = emailParams.replyTo;

      return req.getSiteMailer().sendMailAsync(emailParams).then(function () {
        return {
          code_id: code.id,
          expires: code.expires,
          created: new Date(parseInt(code.createdAt, 10) || code.createdAt),
        };
      });
    });

    app.handlePromise(req, res, promise, '[issuer@oauth3.org] send one-time-password');
  };

  Accounts.restful.createToken = function (req, res) {
    var store;
    var promise = req.getSiteStore().then(function (_store) {
      store = _store;
      if (!req.body || !req.body.grant_type) {
        throw new OpErr("missing 'grant_type' from the body");
      }

      if (req.body.grant_type === 'password') {
        return Accounts.restful.createToken.password(req);
      }
      if (req.body.grant_type === 'issuer_token') {
        return Accounts.restful.createToken.issuerToken(req);
      }
      if (req.body.grant_type === 'refresh_token') {
        return Accounts.restful.createToken.refreshToken(req);
      }

      throw new OpErr("unknown or un-implemented grant_type '"+req.body.grant_type+"'");
    }).then(function (token_info) {
      token_info.iss = req.experienceId;
      if (!token_info.aud) {
        throw new OpErr("missing required token field 'aud'");
      }
      if (!token_info.azp) {
        throw new OpErr("missing required token field 'azp'");
      }

      if (token_info.iss === token_info.azp) {
        // We don't have normal grants for the issuer, so we don't need to look the
        // azpSub or the grants up in the database.
        token_info.azpSub = token_info.sub;
        token_info.scope = '';
        return token_info;
      }

      var search = {};
      ['sub', 'azp', 'azpSub'].forEach(function (key) {
        if (token_info[key]) {
          search[key] = token_info[key];
        }
      });
      return store.IssuerOauth3OrgGrants.find(search).then(function (grants) {
        if (!grants.length) {
          throw new OpErr("'"+token_info.azp+"' not given any grants from '"+(token_info.sub || token_info.azpSub)+"'");
        }
        if (grants.length > 1) {
          throw new Error("unexpected resource collision: too many relevant grants");
        }
        var grant = grants[0];
        Object.keys(grant).forEach(function (key) {
          token_info[key] = grant[key];
        });
        return token_info;
      });
    }).then(function (token_info) {
      return Accounts.getPrivKey(store, req.experienceId).then(function (jwk) {
        var pem = require('jwk-to-pem')(jwk, { private: true });
        var payload =  {
          // standard
          iss: token_info.iss,    // https://tools.ietf.org/html/draft-ietf-oauth-json-web-token-32#section-4.1.1
          aud: token_info.aud,    // https://tools.ietf.org/html/draft-ietf-oauth-json-web-token-32#section-4.1.3
          azp: token_info.azp,
          sub: token_info.azpSub, // https://tools.ietf.org/html/draft-ietf-oauth-json-web-token-32#section-4.1.2
          // extended
          scp: token_info.scope,
        };
        var opts = {
          algorithm: jwk.alg,
          header: {
            kid: jwk.kid
          }
        };
        var accessOpts  = {expiresIn: timespan(req.body.exp || '1d', token_info.exp)};
        var refreshOpts = {expiresIn: timespan(req.body.refresh_exp, token_info.exp)};

        var jwt = require('jsonwebtoken');
        var result = {};
        result.scope = token_info.scope;
        result.access_token = jwt.sign(payload, pem, Object.assign(accessOpts, opts));
        if (req.body.refresh_token) {
          if (token_info.refresh_token) {
            result.refresh_token = token_info.refresh_token;
          } else {
            result.refresh_token = jwt.sign(payload, pem, Object.assign(refreshOpts, opts));
          }
        }
        return result;
      });
    });

    app.handlePromise(req, res, promise, '[issuer@oauth3.org] create tokens');
  };
  Accounts.restful.createToken.password = function (req) {
    var params = req.body;
    if (!params || !params.username) {
      return PromiseA.reject(PromiseA.OperationalError("must provide the email address as 'username' in the body"));
    }
    if ((params.username_type && 'email' !== params.username_type) || !/@/.test(params.username)) {
      return PromiseA.reject(PromiseA.OperationalError("only email one-time login codes are supported at this time"));
    }
    params.username_type = 'email';
    if (!params.password) {
      return PromiseA.reject(new OpErr("request missing 'password'"));
    }

    var codeId = crypto.createHash('sha256').update(params.username_type+':'+params.username).digest('base64');
    codeId = makeB64UrlSafe(codeId);
    return req.getSiteStore().then(function (store) {
      return Accounts.validateOtp(store.IssuerOauth3OrgCodes, codeId, params.password)
      .then(function () {
        return Accounts.getOrCreate(store, params.username);
      }).then(function (account) {
        return {
          sub: account.accountId,
          aud: req.params.aud || req.body.aud || req.experienceId,
          azp: req.params.azp || req.body.azp || req.experienceId,
        };
      });
    });
  };
  Accounts.restful.createToken.issuerToken = function (req) {
    return checkIsserToken(req, req.params.sub || req.body.sub).then(function (sub) {
      return {
        sub: sub,
        aud: req.params.aud || req.body.aud,
        azp: req.params.azp || req.body.azp,
        exp: req.oauth3.token.exp,
      };
    });
  };
  Accounts.restful.createToken.refreshToken = function (req) {
    return PromiseA.resolve().then(function () {
      if (!req.body.refresh_token) {
        throw new OpErr("missing refresh token");
      }

      return req.oauth3.verifyAsync(req.body.refresh_token).then(function (token) {
        return {
          sub: token.sub,
          aud: token.aud,
          azp: token.azp,
          exp: token.exp,
          refresh_token: req.body.refresh_token,
        };
      });
    });
  };


  app.get(   '/jwks/:sub/:kid.json', Jwks.restful.get);
  app.get(   '/jwks/:sub/:kid',      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.post(  '/access_token/send_otp', Accounts.restful.sendOtp);
  app.post(  '/access_token/:sub/:aud/:azp', Accounts.restful.createToken);
  app.post(  '/access_token',                Accounts.restful.createToken);

  app.use(detachSiteStore);
};