// A RestWrite encapsulates everything we need to run an operation
// that writes to the database.
// This could be either a "create" or an "update".

var deepcopy = require('deepcopy');
var rack = require('hat').rack();

var Auth = require('./Auth');
var cache = require('./cache');
var Config = require('./Config');
var crypto = require('./crypto');
var facebook = require('./facebook');
var Parse = require('parse/node');
var triggers = require('./triggers');

// query and data are both provided in REST API format. So data
// types are encoded by plain old objects.
// If query is null, this is a "create" and the data in data should be
// created.
// Otherwise this is an "update" - the object matching the query
// should get updated with data.
// RestWrite will handle objectId, createdAt, and updatedAt for
// everything. It also knows to use triggers and special modifications
// for the _User class.
function RestWrite(config, auth, className, query, data, originalData) {
  this.config = config;
  this.auth = auth;
  this.className = className;
  this.storage = {};

  if (!query && data.objectId) {
    throw new Parse.Error(Parse.Error.INVALID_KEY_NAME, 'objectId ' +
                          'is an invalid field name.');
  }

  // When the operation is complete, this.response may have several
  // fields.
  // response: the actual data to be returned
  // status: the http status code. if not present, treated like a 200
  // location: the location header. if not present, no location header
  this.response = null;

  // Processing this operation may mutate our data, so we operate on a
  // copy
  this.query = deepcopy(query);
  this.data = deepcopy(data);
  // We never change originalData, so we do not need a deep copy
  this.originalData = originalData;

  // The timestamp we'll use for this whole operation
  this.updatedAt = Parse._encode(new Date()).iso;

  if (this.data) {
    // Add default fields
    this.data.updatedAt = this.updatedAt;
    if (!this.query) {
      this.data.createdAt = this.updatedAt;
      this.data.objectId = newObjectId();
    }
  }
}

// A convenient method to perform all the steps of processing the
// write, in order.
// Returns a promise for a {response, status, location} object.
// status and location are optional.
RestWrite.prototype.execute = function() {
  return Promise.resolve().then(() => {
    return this.validateSchema();
  }).then(() => {
    return this.handleInstallation();
  }).then(() => {
    return this.handleSession();
  }).then(() => {
    return this.runBeforeTrigger();
  }).then(() => {
    return this.validateAuthData();
  }).then(() => {
    return this.transformUser();
  }).then(() => {
    return this.runDatabaseOperation();
  }).then(() => {
    return this.handleFollowup();
  }).then(() => {
    return this.runAfterTrigger();
  }).then(() => {
    return this.response;
  });
};

// Validates this operation against the schema.
RestWrite.prototype.validateSchema = function() {
  return this.config.database.validateObject(this.className, this.data);
};

// Runs any beforeSave triggers against this operation.
// Any change leads to our data being mutated.
RestWrite.prototype.runBeforeTrigger = function() {
  // Cloud code gets a bit of extra data for its objects
  var extraData = {className: this.className};
  if (this.query && this.query.objectId) {
    extraData.objectId = this.query.objectId;
  }
  // Build the inflated object, for a create write, originalData is empty
  var inflatedObject = triggers.inflate(extraData, this.originalData);;
  inflatedObject._finishFetch(this.data);
  // Build the original object, we only do this for a update write
  var originalObject;
  if (this.query && this.query.objectId) {
    originalObject = triggers.inflate(extraData, this.originalData);
  }

  return Promise.resolve().then(() => {
    return triggers.maybeRunTrigger(
      'beforeSave', this.auth, inflatedObject, originalObject);
  }).then((response) => {
    if (response && response.object) {
      this.data = response.object;
      // We should delete the objectId for an update write
      if (this.query && this.query.objectId) {
        delete this.data.objectId
      }
    }
  });
};

// Transforms auth data for a user object.
// Does nothing if this isn't a user object.
// Returns a promise for when we're done if it can't finish this tick.
RestWrite.prototype.validateAuthData = function() {
  if (this.className !== '_User') {
    return;
  }

  if (!this.query && !this.data.authData) {
    if (typeof this.data.username !== 'string') {
      throw new Parse.Error(Parse.Error.USERNAME_MISSING,
                            'bad or missing username');
    }
    if (typeof this.data.password !== 'string') {
      throw new Parse.Error(Parse.Error.PASSWORD_MISSING,
                            'password is required');
    }
  }

  if (!this.data.authData) {
    return;
  }

  var facebookData = this.data.authData.facebook;
  var anonData = this.data.authData.anonymous;

  if (anonData === null ||
    (anonData && anonData.id)) {
    return this.handleAnonymousAuthData();
  } else if (facebookData === null ||
    (facebookData && facebookData.id && facebookData.access_token)) {
    return this.handleFacebookAuthData();
  } else {
    throw new Parse.Error(Parse.Error.UNSUPPORTED_SERVICE,
                          'This authentication method is unsupported.');
  }
};

RestWrite.prototype.handleAnonymousAuthData = function() {
  var anonData = this.data.authData.anonymous;
  if (anonData === null && this.query) {
    // We are unlinking the user from the anonymous provider
    this.data._auth_data_anonymous = null;
    return;
  }

  // Check if this user already exists
  return this.config.database.find(
    this.className,
    {'authData.anonymous.id': anonData.id}, {})
  .then((results) => {
    if (results.length > 0) {
      if (!this.query) {
        // We're signing up, but this user already exists. Short-circuit
        delete results[0].password;
        this.response = {
          response: results[0],
          location: this.location()
        };
        return;
      }

      // If this is a PUT for the same user, allow the linking
      if (results[0].objectId === this.query.objectId) {
        // Delete the rest format key before saving
        delete this.data.authData;
        return;
      }

      // We're trying to create a duplicate account.  Forbid it
      throw new Parse.Error(Parse.Error.ACCOUNT_ALREADY_LINKED,
                            'this auth is already used');
    }

    // This anonymous user does not already exist, so transform it
    // to a saveable format
    this.data._auth_data_anonymous = anonData;

    // Delete the rest format key before saving
    delete this.data.authData;
  })

};

RestWrite.prototype.handleFacebookAuthData = function() {
  var facebookData = this.data.authData.facebook;
  if (facebookData === null && this.query) {
    // We are unlinking from Facebook.
    this.data._auth_data_facebook = null;
    return;
  }

  return facebook.validateUserId(facebookData.id,
                                 facebookData.access_token)
    .then(() => {
      return facebook.validateAppId(this.config.facebookAppIds,
                                    facebookData.access_token);
    }).then(() => {
      // Check if this user already exists
      // TODO: does this handle re-linking correctly?
      return this.config.database.find(
        this.className,
        {'authData.facebook.id': facebookData.id}, {});
    }).then((results) => {
      if (results.length > 0) {
        if (!this.query) {
          // We're signing up, but this user already exists. Short-circuit
          delete results[0].password;
          this.response = {
            response: results[0],
            location: this.location()
          };
          return;
        }

        // If this is a PUT for the same user, allow the linking
        if (results[0].objectId === this.query.objectId) {
          // Delete the rest format key before saving
          delete this.data.authData;
          return;
        }
        // We're trying to create a duplicate FB auth. Forbid it
        throw new Parse.Error(Parse.Error.ACCOUNT_ALREADY_LINKED,
                              'this auth is already used');
      }

      // This FB auth does not already exist, so transform it to a
      // saveable format
      this.data._auth_data_facebook = facebookData;

      // Delete the rest format key before saving
      delete this.data.authData;
    });
};

// The non-third-party parts of User transformation
RestWrite.prototype.transformUser = function() {
  if (this.response || this.className !== '_User') {
    return;
  }

  var promise = Promise.resolve();

  if (!this.query) {
    var token = 'r:' + rack();
    this.storage['token'] = token;
    promise = promise.then(() => {
      // TODO: Proper createdWith options, pass installationId
      var sessionData = {
        sessionToken: token,
        user: {
          __type: 'Pointer',
          className: '_User',
          objectId: this.objectId()
        },
        createdWith: {
          'action': 'login',
          'authProvider': 'password'
        },
        restricted: false,
        expiresAt: 0
      };
      var create = new RestWrite(this.config, Auth.master(this.config),
                                 '_Session', null, sessionData);
      return create.execute();
    });
  }

  return promise.then(() => {
    // Transform the password
    if (!this.data.password) {
      return;
    }
    if (this.query) {
      this.storage['clearSessions'] = true;
    }
    return crypto.hash(this.data.password).then((hashedPassword) => {
      this.data._hashed_password = hashedPassword;
      delete this.data.password;
    });

  }).then(() => {
    // Check for username uniqueness
    if (!this.data.username) {
      if (!this.query) {
        // TODO: what's correct behavior here
        this.data.username = '';
      }
      return;
    }
    return this.config.database.find(
      this.className, {
        username: this.data.username,
        objectId: {'$ne': this.objectId()}
      }, {limit: 1}).then((results) => {
        if (results.length > 0) {
          throw new Parse.Error(Parse.Error.USERNAME_TAKEN,
                                'Account already exists for this username');
        }
        return Promise.resolve();
      });
  }).then(() => {
    if (!this.data.email) {
      return;
    }
    // Validate basic email address format
    if (!this.data.email.match(/^.+@.+$/)) {
      throw new Parse.Error(Parse.Error.INVALID_EMAIL_ADDRESS,
                            'Email address format is invalid.');
    }
    // Check for email uniqueness
    return this.config.database.find(
      this.className, {
        email: this.data.email,
        objectId: {'$ne': this.objectId()}
      }, {limit: 1}).then((results) => {
        if (results.length > 0) {
          throw new Parse.Error(Parse.Error.EMAIL_TAKEN,
                                'Account already exists for this email ' +
                                'address');
        }
        return Promise.resolve();
      });
  });
};

// Handles any followup logic
RestWrite.prototype.handleFollowup = function() {
  if (this.storage && this.storage['clearSessions']) {
    var sessionQuery = {
      user: {
          __type: 'Pointer',
          className: '_User',
          objectId: this.objectId()
        }
    };
    delete this.storage['clearSessions'];
    return this.config.database.destroy('_Session', sessionQuery)
    .then(this.handleFollowup);
  }
};

// Handles the _Role class specialness.
// Does nothing if this isn't a role object.
RestWrite.prototype.handleRole = function() {
  if (this.response || this.className !== '_Role') {
    return;
  }

  if (!this.auth.user && !this.auth.isMaster) {
    throw new Parse.Error(Parse.Error.INVALID_SESSION_TOKEN,
                          'Session token required.');
  }

  if (!this.data.name) {
    throw new Parse.Error(Parse.Error.INVALID_ROLE_NAME,
                          'Invalid role name.');
  }
};

// Handles the _Session class specialness.
// Does nothing if this isn't an installation object.
RestWrite.prototype.handleSession = function() {
  if (this.response || this.className !== '_Session') {
    return;
  }

  if (!this.auth.user && !this.auth.isMaster) {
    throw new Parse.Error(Parse.Error.INVALID_SESSION_TOKEN,
                          'Session token required.');
  }

  // TODO: Verify proper error to throw
  if (this.data.ACL) {
    throw new Parse.Error(Parse.Error.INVALID_KEY_NAME, 'Cannot set ' +
                          'ACL on a Session.');
  }

  if (!this.query && !this.auth.isMaster) {
    var token = 'r:' + rack();
    var sessionData = {
      sessionToken: token,
      user: {
        __type: 'Pointer',
        className: '_User',
        objectId: this.auth.user.id
      },
      createdWith: {
        'action': 'create'
      },
      restricted: true,
      expiresAt: 0
    };
    for (var key in this.data) {
      if (key == 'objectId') {
        continue;
      }
      sessionData[key] = this.data[key];
    }
    var create = new RestWrite(this.config, Auth.master(this.config),
                               '_Session', null, sessionData);
    return create.execute().then((results) => {
      if (!results.response) {
        throw new Parse.Error(Parse.Error.INTERNAL_SERVER_ERROR,
                              'Error creating session.');
      }
      sessionData['objectId'] = results.response['objectId'];
      this.response = {
        status: 201,
        location: results.location,
        response: sessionData
      };
    });
  }
};

// Handles the _Installation class specialness.
// Does nothing if this isn't an installation object.
// If an installation is found, this can mutate this.query and turn a create
// into an update.
// Returns a promise for when we're done if it can't finish this tick.
RestWrite.prototype.handleInstallation = function() {
  if (this.response || this.className !== '_Installation') {
    return;
  }

  if (!this.query && !this.data.deviceToken && !this.data.installationId) {
    throw new Parse.Error(135,
                          'at least one ID field (deviceToken, installationId) ' +
                          'must be specified in this operation');
  }

  if (!this.query && !this.data.deviceType) {
    throw new Parse.Error(135,
                          'deviceType must be specified in this operation');
  }

  // If the device token is 64 characters long, we assume it is for iOS
  // and lowercase it.
  if (this.data.deviceToken && this.data.deviceToken.length == 64) {
    this.data.deviceToken = this.data.deviceToken.toLowerCase();
  }

  // TODO: We may need installationId from headers, plumb through Auth?
  //       per installation_handler.go

  // We lowercase the installationId if present
  if (this.data.installationId) {
    this.data.installationId = this.data.installationId.toLowerCase();
  }

  if (this.data.deviceToken && this.data.deviceType == 'android') {
    throw new Parse.Error(114,
                          'deviceToken may not be set for deviceType android');
  }

  var promise = Promise.resolve();

  if (this.query && this.query.objectId) {
    promise = promise.then(() => {
      return this.config.database.find('_Installation', {
        objectId: this.query.objectId
      }, {}).then((results) => {
        if (!results.length) {
          throw new Parse.Error(Parse.Error.OBJECT_NOT_FOUND,
                                'Object not found for update.');
        }
        var existing = results[0];
        if (this.data.installationId && existing.installationId &&
          this.data.installationId !== existing.installationId) {
          throw new Parse.Error(136,
                                'installationId may not be changed in this ' +
                                'operation');
        }
        if (this.data.deviceToken && existing.deviceToken &&
          this.data.deviceToken !== existing.deviceToken &&
          !this.data.installationId && !existing.installationId) {
          throw new Parse.Error(136,
                                'deviceToken may not be changed in this ' +
                                'operation');
        }
        if (this.data.deviceType && this.data.deviceType &&
          this.data.deviceType !== existing.deviceType) {
          throw new Parse.Error(136,
                                'deviceType may not be changed in this ' +
                                'operation');
        }
        return Promise.resolve();
      });
    });
  }

  // Check if we already have installations for the installationId/deviceToken
  var installationMatch;
  var deviceTokenMatches = [];
  promise = promise.then(() => {
    if (this.data.installationId) {
      return this.config.database.find('_Installation', {
        'installationId': this.data.installationId
      });
    }
    return Promise.resolve([]);
  }).then((results) => {
    if (results && results.length) {
      // We only take the first match by installationId
      installationMatch = results[0];
    }
    if (this.data.deviceToken) {
      return this.config.database.find(
        '_Installation',
        {'deviceToken': this.data.deviceToken});
    }
    return Promise.resolve([]);
  }).then((results) => {
    if (results) {
      deviceTokenMatches = results;
    }
    if (!installationMatch) {
      if (!deviceTokenMatches.length) {
        return;
      } else if (deviceTokenMatches.length == 1 &&
        (!deviceTokenMatches[0]['installationId'] || !this.data.installationId)
      ) {
        // Single match on device token but none on installationId, and either
        // the passed object or the match is missing an installationId, so we
        // can just return the match.
        return deviceTokenMatches[0]['objectId'];
      } else if (!this.data.installationId) {
        throw new Parse.Error(132,
                              'Must specify installationId when deviceToken ' +
                              'matches multiple Installation objects');
      } else {
        // Multiple device token matches and we specified an installation ID,
        // or a single match where both the passed and matching objects have
        // an installation ID. Try cleaning out old installations that match
        // the deviceToken, and return nil to signal that a new object should
        // be created.
        var delQuery = {
          'deviceToken': this.data.deviceToken,
          'installationId': {
            '$ne': this.data.installationId
          }
        };
        if (this.data.appIdentifier) {
          delQuery['appIdentifier'] = this.data.appIdentifier;
        }
        this.config.database.destroy('_Installation', delQuery);
        return;
      }
    } else {
      if (deviceTokenMatches.length == 1 &&
        !deviceTokenMatches[0]['installationId']) {
        // Exactly one device token match and it doesn't have an installation
        // ID. This is the one case where we want to merge with the existing
        // object.
        var delQuery = {objectId: installationMatch.objectId};
        return this.config.database.destroy('_Installation', delQuery)
          .then(() => {
            return deviceTokenMatches[0]['objectId'];
          });
      } else {
        if (this.data.deviceToken &&
          installationMatch.deviceToken != this.data.deviceToken) {
          // We're setting the device token on an existing installation, so
          // we should try cleaning out old installations that match this
          // device token.
          var delQuery = {
            'deviceToken': this.data.deviceToken,
            'installationId': {
              '$ne': this.data.installationId
            }
          };
          if (this.data.appIdentifier) {
            delQuery['appIdentifier'] = this.data.appIdentifier;
          }
          this.config.database.destroy('_Installation', delQuery);
        }
        // In non-merge scenarios, just return the installation match id
        return installationMatch.objectId;
      }
    }
  }).then((objId) => {
    if (objId) {
      this.query = {objectId: objId};
      delete this.data.objectId;
      delete this.data.createdAt;
    }
    // TODO: Validate ops (add/remove on channels, $inc on badge, etc.)
  });
  return promise;
};

RestWrite.prototype.runDatabaseOperation = function() {
  if (this.response) {
    return;
  }

  if (this.className === '_User' &&
      this.query &&
      !this.auth.couldUpdateUserId(this.query.objectId)) {
    throw new Parse.Error(Parse.Error.SESSION_MISSING,
                          'cannot modify user ' + this.objectId);
  }

  // TODO: Add better detection for ACL, ensuring a user can't be locked from
  //       their own user record.
  if (this.data.ACL && this.data.ACL['*unresolved']) {
    throw new Parse.Error(Parse.Error.INVALID_ACL, 'Invalid ACL.');
  }

  var options = {};
  if (!this.auth.isMaster) {
    options.acl = ['*'];
    if (this.auth.user) {
      options.acl.push(this.auth.user.id);
    }
  }

  if (this.query) {
    // Run an update
    return this.config.database.update(
      this.className, this.query, this.data, options).then((resp) => {
        this.response = resp;
        this.response.updatedAt = this.updatedAt;
      });
  } else {
    // Run a create
    return this.config.database.create(this.className, this.data, options)
      .then(() => {
        var resp = {
          objectId: this.data.objectId,
          createdAt: this.data.createdAt
        };
        if (this.storage['token']) {
          resp.sessionToken = this.storage['token'];
        }
        this.response = {
          status: 201,
          response: resp,
          location: this.location()
        };
      });
  }
};

// Returns nothing - doesn't wait for the trigger.
RestWrite.prototype.runAfterTrigger = function() {
  var extraData = {className: this.className};
  if (this.query && this.query.objectId) {
    extraData.objectId = this.query.objectId;
  }

  // Build the inflated object, different from beforeSave, originalData is not empty
  // since developers can change data in the beforeSave.
  var inflatedObject = triggers.inflate(extraData, this.originalData);
  inflatedObject._finishFetch(this.data);
  // Build the original object, we only do this for a update write.
  var originalObject;
  if (this.query && this.query.objectId) {
    originalObject = triggers.inflate(extraData, this.originalData);
  }

  triggers.maybeRunTrigger('afterSave', this.auth, inflatedObject, originalObject);
};

// A helper to figure out what location this operation happens at.
RestWrite.prototype.location = function() {
  var middle = (this.className === '_User' ? '/users/' :
                '/classes/' + this.className + '/');
  return this.config.mount + middle + this.data.objectId;
};

// A helper to get the object id for this operation.
// Because it could be either on the query or on the data
RestWrite.prototype.objectId = function() {
  return this.data.objectId || this.query.objectId;
};

// Returns a string that's usable as an object id.
// Probably unique. Good enough? Probably!
function newObjectId() {
  var chars = ('ABCDEFGHIJKLMNOPQRSTUVWXYZ' +
               'abcdefghijklmnopqrstuvwxyz' +
               '0123456789');
  var objectId = '';
  for (var i = 0; i < 10; ++i) {
    objectId += chars[Math.floor(Math.random() * chars.length)];
  }
  return objectId;
}

module.exports = RestWrite;