text: // This class handles schema validation, persistence, and modification.
  //
  // Each individual Schema object should be immutable. The helpers to
  // do things with the Schema just return a new schema when the schema
  // is changed.
  //
  // The canonical place to store this Schema is in the database itself,
  // in a _SCHEMA collection. This is not the right way to do it for an
  // open source framework, but it's backward compatible, so we're
  // keeping it this way for now.
  //
  // In API-handling code, you should only use the Schema class via the
  // DatabaseController. This will let us replace the schema logic for
  // different databases.
  // TODO: hide all schema logic inside the database adapter.
  const Parse = require('parse/node').Parse;
  
  const defaultColumns = Object.freeze({
    // Contain the default columns for every parse object type (except _Join collection)
    _Default: {
      "objectId":  {type:'String'},
      "createdAt": {type:'Date'},
      "updatedAt": {type:'Date'},
      "ACL":       {type:'ACL'},
    },
    // The additional default columns for the _User collection (in addition to DefaultCols)
    _User: {
      "username":      {type:'String'},
      "password":      {type:'String'},
      "email":         {type:'String'},
      "emailVerified": {type:'Boolean'},
      "authData":      {type:'Object'}
    },
    // The additional default columns for the _Installation collection (in addition to DefaultCols)
    _Installation: {
      "installationId":   {type:'String'},
      "deviceToken":      {type:'String'},
      "channels":         {type:'Array'},
      "deviceType":       {type:'String'},
      "pushType":         {type:'String'},
      "GCMSenderId":      {type:'String'},
      "timeZone":         {type:'String'},
      "localeIdentifier": {type:'String'},
      "badge":            {type:'Number'},
      "appVersion":       {type:'String'},
      "appName":          {type:'String'},
      "appIdentifier":    {type:'String'},
      "parseVersion":     {type:'String'},
    },
    // The additional default columns for the _Role collection (in addition to DefaultCols)
    _Role: {
      "name":  {type:'String'},
      "users": {type:'Relation', targetClass:'_User'},
      "roles": {type:'Relation', targetClass:'_Role'}
    },
    // The additional default columns for the _Session collection (in addition to DefaultCols)
    _Session: {
      "restricted":     {type:'Boolean'},
      "user":           {type:'Pointer', targetClass:'_User'},
      "installationId": {type:'String'},
      "sessionToken":   {type:'String'},
      "expiresAt":      {type:'Date'},
      "createdWith":    {type:'Object'}
    },
    _Product: {
      "productIdentifier":  {type:'String'},
      "download":           {type:'File'},
      "downloadName":       {type:'String'},
      "icon":               {type:'File'},
      "order":              {type:'Number'},
      "title":              {type:'String'},
      "subtitle":           {type:'String'},
    },
    _PushStatus: {
      "pushTime":     {type:'String'},
      "source":       {type:'String'}, // rest or webui
      "query":        {type:'String'}, // the stringified JSON query
      "payload":      {type:'String'}, // the stringified JSON payload,
      "title":        {type:'String'},
      "expiry":       {type:'Number'},
      "status":       {type:'String'},
      "numSent":      {type:'Number'},
      "numFailed":    {type:'Number'},
      "pushHash":     {type:'String'},
      "errorMessage": {type:'Object'},
      "sentPerType":  {type:'Object'},
      "failedPerType":{type:'Object'},
      "count":       {type:'Number'}
    },
    _JobStatus: {
      "jobName":    {type: 'String'},
      "source":     {type: 'String'},
      "status":     {type: 'String'},
      "message":    {type: 'String'},
      "params":     {type: 'Object'}, // params received when calling the job
      "finishedAt": {type: 'Date'}
    },
    _JobSchedule: {
      "jobName":      {type:'String'},
      "description":  {type:'String'},
      "params":       {type:'String'},
      "startAfter":   {type:'String'},
      "daysOfWeek":   {type:'Array'},
      "timeOfDay":    {type:'String'},
      "lastRun":      {type:'Number'},
      "repeatMinutes":{type:'Number'}
    },
    _Hooks: {
      "functionName": {type:'String'},
      "className":    {type:'String'},
      "triggerName":  {type:'String'},
      "url":          {type:'String'}
    },
    _GlobalConfig: {
      "objectId": {type: 'String'},
      "params": {type: 'Object'}
    },
    _Audience: {
      "objectId": {type:'String'},
      "name":   {type:'String'},
      "query": {type:'String'} //storing query as JSON string to prevent "Nested keys should not contain the '$' or '.' characters" error
    }
  });
  
  const requiredColumns = Object.freeze({
    _Product: ["productIdentifier", "icon", "order", "title", "subtitle"],
    _Role: ["name", "ACL"]
  });
  
  const systemClasses = Object.freeze(['_User', '_Installation', '_Role', '_Session', '_Product', '_PushStatus', '_JobStatus', '_JobSchedule', '_Audience']);
  
  const volatileClasses = Object.freeze(['_JobStatus', '_PushStatus', '_Hooks', '_GlobalConfig', '_JobSchedule', '_Audience']);
  
  // 10 alpha numberic chars + uppercase
  const userIdRegex = /^[a-zA-Z0-9]{10}$/;
  // Anything that start with role
  const roleRegex = /^role:.*/;
  // * permission
  const publicRegex = /^\*$/
  
  const requireAuthenticationRegex = /^requiresAuthentication$/
  
  const permissionKeyRegex = Object.freeze([userIdRegex, roleRegex, publicRegex, requireAuthenticationRegex]);
  
  function verifyPermissionKey(key) {
    const result = permissionKeyRegex.reduce((isGood, regEx) => {
      isGood = isGood || key.match(regEx) != null;
      return isGood;
    }, false);
    if (!result) {
      throw new Parse.Error(Parse.Error.INVALID_JSON, `'${key}' is not a valid key for class level permissions`);
    }
  }
  
  const CLPValidKeys = Object.freeze(['find', 'count', 'get', 'create', 'update', 'delete', 'addField', 'readUserFields', 'writeUserFields']);
  function validateCLP(perms, fields) {
    if (!perms) {
      return;
    }
    Object.keys(perms).forEach((operation) => {
      if (CLPValidKeys.indexOf(operation) == -1) {
        throw new Parse.Error(Parse.Error.INVALID_JSON, `${operation} is not a valid operation for class level permissions`);
      }
  
      if (operation === 'readUserFields' || operation === 'writeUserFields') {
        if (!Array.isArray(perms[operation])) {
          throw new Parse.Error(Parse.Error.INVALID_JSON, `'${perms[operation]}' is not a valid value for class level permissions ${operation}`);
        } else {
          perms[operation].forEach((key) => {
            if (!fields[key] || fields[key].type != 'Pointer' || fields[key].targetClass != '_User') {
              throw new Parse.Error(Parse.Error.INVALID_JSON, `'${key}' is not a valid column for class level pointer permissions ${operation}`);
            }
          });
        }
        return;
      }
  
      Object.keys(perms[operation]).forEach((key) => {
        verifyPermissionKey(key);
        const perm = perms[operation][key];
        if (perm !== true) {
          throw new Parse.Error(Parse.Error.INVALID_JSON, `'${perm}' is not a valid value for class level permissions ${operation}:${key}:${perm}`);
        }
      });
    });
  }
  const joinClassRegex = /^_Join:[A-Za-z0-9_]+:[A-Za-z0-9_]+/;
  const classAndFieldRegex = /^[A-Za-z][A-Za-z0-9_]*$/;
  function classNameIsValid(className) {
    // Valid classes must:
    return (
      // Be one of _User, _Installation, _Role, _Session OR
      systemClasses.indexOf(className) > -1 ||
      // Be a join table OR
      joinClassRegex.test(className) ||
      // Include only alpha-numeric and underscores, and not start with an underscore or number
      fieldNameIsValid(className)
    );
  }
  
  // Valid fields must be alpha-numeric, and not start with an underscore or number
  function fieldNameIsValid(fieldName) {
    return classAndFieldRegex.test(fieldName);
  }
  
  // Checks that it's not trying to clobber one of the default fields of the class.
  function fieldNameIsValidForClass(fieldName, className) {
    if (!fieldNameIsValid(fieldName)) {
      return false;
    }
    if (defaultColumns._Default[fieldName]) {
      return false;
    }
    if (defaultColumns[className] && defaultColumns[className][fieldName]) {
      return false;
    }
    return true;
  }
  
  function invalidClassNameMessage(className) {
    return 'Invalid classname: ' + className + ', classnames can only have alphanumeric characters and _, and must start with an alpha character ';
  }
  
  const invalidJsonError = new Parse.Error(Parse.Error.INVALID_JSON, "invalid JSON");
  const validNonRelationOrPointerTypes = [
    'Number',
    'String',
    'Boolean',
    'Date',
    'Object',
    'Array',
    'GeoPoint',
    'File',
    'Bytes'
  ];
  // Returns an error suitable for throwing if the type is invalid
  const fieldTypeIsInvalid = ({ type, targetClass }) => {
    if (['Pointer', 'Relation'].indexOf(type) >= 0) {
      if (!targetClass) {
        return new Parse.Error(135, `type ${type} needs a class name`);
      } else if (typeof targetClass !== 'string') {
        return invalidJsonError;
      } else if (!classNameIsValid(targetClass)) {
        return new Parse.Error(Parse.Error.INVALID_CLASS_NAME, invalidClassNameMessage(targetClass));
      } else {
        return undefined;
      }
    }
    if (typeof type !== 'string') {
      return invalidJsonError;
    }
    if (validNonRelationOrPointerTypes.indexOf(type) < 0) {
      return new Parse.Error(Parse.Error.INCORRECT_TYPE, `invalid field type: ${type}`);
    }
    return undefined;
  }
  
  const convertSchemaToAdapterSchema = schema => {
    schema = injectDefaultSchema(schema);
    delete schema.fields.ACL;
    schema.fields._rperm = { type: 'Array' };
    schema.fields._wperm = { type: 'Array' };
  
    if (schema.className === '_User') {
      delete schema.fields.password;
      schema.fields._hashed_password = { type: 'String' };
    }
  
    return schema;
  }
  
  const convertAdapterSchemaToParseSchema = ({...schema}) => {
    delete schema.fields._rperm;
    delete schema.fields._wperm;
  
    schema.fields.ACL = { type: 'ACL' };
  
    if (schema.className === '_User') {
      delete schema.fields.authData; //Auth data is implicit
      delete schema.fields._hashed_password;
      schema.fields.password = { type: 'String' };
    }
  
    return schema;
  }
  
  const injectDefaultSchema = ({className, fields, classLevelPermissions}) => ({
    className,
    fields: {
      ...defaultColumns._Default,
      ...(defaultColumns[className] || {}),
      ...fields,
    },
    classLevelPermissions,
  });
  
  const _HooksSchema =  {className: "_Hooks", fields: defaultColumns._Hooks};
  const _GlobalConfigSchema = { className: "_GlobalConfig", fields: defaultColumns._GlobalConfig }
  const _PushStatusSchema = convertSchemaToAdapterSchema(injectDefaultSchema({
    className: "_PushStatus",
    fields: {},
    classLevelPermissions: {}
  }));
  const _JobStatusSchema = convertSchemaToAdapterSchema(injectDefaultSchema({
    className: "_JobStatus",
    fields: {},
    classLevelPermissions: {}
  }));
  const _JobScheduleSchema = convertSchemaToAdapterSchema(injectDefaultSchema({
    className: "_JobSchedule",
    fields: {},
    classLevelPermissions: {}
  }));
  const _AudienceSchema = convertSchemaToAdapterSchema(injectDefaultSchema({
    className: "_Audience",
    fields: defaultColumns._Audience
  }));
  const VolatileClassesSchemas = [_HooksSchema, _JobStatusSchema, _JobScheduleSchema, _PushStatusSchema, _GlobalConfigSchema, _AudienceSchema];
  
  const dbTypeMatchesObjectType = (dbType, objectType) => {
    // console.log(typeof dbType.type);
    // console.log(typeof objectType.type);
    // console.log('dbtype ylol');
    if (dbType.type !== objectType.type) return false;
    if (dbType.targetClass !== objectType.targetClass) return false;
    if (dbType === objectType.type) return true;
    if (dbType.type === objectType.type) return true;
    return false;
  }
  
  const typeToString = (type) => {
    if (type.targetClass) {
      return `${type.type}<${type.targetClass}>`;
    }
    return `${type.type || type}`;
  }
  
  // Stores the entire schema of the app in a weird hybrid format somewhere between
  // the mongo format and the Parse format. Soon, this will all be Parse format.
  export default class SchemaController {
    _dbAdapter;
    data;
    perms;
  
    constructor(databaseAdapter, schemaCache) {
      this._dbAdapter = databaseAdapter;
      this._cache = schemaCache;
      // this.data[className][fieldName] tells you the type of that field, in mongo format
      this.data = {};
      // this.perms[className][operation] tells you the acl-style permissions
      this.perms = {};
    }
  
    reloadData(options = {clearCache: false}) {
      let promise = Promise.resolve();
      if (options.clearCache) {
        promise = promise.then(() => {
          return this._cache.clear();
        });
      }
      if (this.reloadDataPromise && !options.clearCache) {
        return this.reloadDataPromise;
      }
      this.reloadDataPromise = promise.then(() => {
        return this.getAllClasses(options);
      })
        .then(allSchemas => {
          const data = {};
          const perms = {};
          allSchemas.forEach(schema => {
            data[schema.className] = injectDefaultSchema(schema).fields;
            perms[schema.className] = schema.classLevelPermissions;
          });
  
          // Inject the in-memory classes
          volatileClasses.forEach(className => {
            const schema = injectDefaultSchema({ className });
            data[className] = schema.fields;
            perms[className] = schema.classLevelPermissions;
          });
          this.data = data;
          this.perms = perms;
          delete this.reloadDataPromise;
        }, (err) => {
          this.data = {};
          this.perms = {};
          delete this.reloadDataPromise;
          throw err;
        });
      return this.reloadDataPromise;
    }
  
    getAllClasses(options = {clearCache: false}) {
      let promise = Promise.resolve();
      if (options.clearCache) {
        promise = this._cache.clear();
      }
      return promise.then(() => {
        return this._cache.getAllClasses()
      }).then((allClasses) => {
        if (allClasses && allClasses.length && !options.clearCache) {
          return Promise.resolve(allClasses);
        }
        return this._dbAdapter.getAllClasses()
          .then(allSchemas => allSchemas.map(injectDefaultSchema))
          .then(allSchemas => {
            return this._cache.setAllClasses(allSchemas).then(() => {
              return allSchemas;
            });
          })
      });
    }
  
    getOneSchema(className, allowVolatileClasses = false, options = {clearCache: false}) {
      let promise = Promise.resolve();
      if (options.clearCache) {
        promise = this._cache.clear();
      }
      return promise.then(() => {
        if (allowVolatileClasses && volatileClasses.indexOf(className) > -1) {
          return Promise.resolve({
            className,
            fields: this.data[className],
            classLevelPermissions: this.perms[className]
          });
        }
        return this._cache.getOneSchema(className).then((cached) => {
          if (cached && !options.clearCache) {
            return Promise.resolve(cached);
          }
          return this._dbAdapter.getClass(className)
            .then(injectDefaultSchema)
            .then((result) => {
              return this._cache.setOneSchema(className, result).then(() => {
                return result;
              })
            });
        });
      });
    }
  
    // Create a new class that includes the three default fields.
    // ACL is an implicit column that does not get an entry in the
    // _SCHEMAS database. Returns a promise that resolves with the
    // created schema, in mongo format.
    // on success, and rejects with an error on fail. Ensure you
    // have authorization (master key, or client class creation
    // enabled) before calling this function.
    addClassIfNotExists(className, fields = {}, classLevelPermissions) {
      var validationError = this.validateNewClass(className, fields, classLevelPermissions);
      if (validationError) {
        return Promise.reject(validationError);
      }
  
      return this._dbAdapter.createClass(className, convertSchemaToAdapterSchema({ fields, classLevelPermissions, className }))
        .then(convertAdapterSchemaToParseSchema)
        .then((res) => {
          return this._cache.clear().then(() => {
            return Promise.resolve(res);
          });
        })
        .catch(error => {
          if (error && error.code === Parse.Error.DUPLICATE_VALUE) {
            throw new Parse.Error(Parse.Error.INVALID_CLASS_NAME, `Class ${className} already exists.`);
          } else {
            throw error;
          }
        });
    }
  
    updateClass(className, submittedFields, classLevelPermissions, database) {
      return this.getOneSchema(className)
        .then(schema => {
          const existingFields = schema.fields;
          Object.keys(submittedFields).forEach(name => {
            const field = submittedFields[name];
            if (existingFields[name] && field.__op !== 'Delete') {
              throw new Parse.Error(255, `Field ${name} exists, cannot update.`);
            }
            if (!existingFields[name] && field.__op === 'Delete') {
              throw new Parse.Error(255, `Field ${name} does not exist, cannot delete.`);
            }
          });
  
          delete existingFields._rperm;
          delete existingFields._wperm;
          const newSchema = buildMergedSchemaObject(existingFields, submittedFields);
          const validationError = this.validateSchemaData(className, newSchema, classLevelPermissions, Object.keys(existingFields));
          if (validationError) {
            throw new Parse.Error(validationError.code, validationError.error);
          }
  
          // Finally we have checked to make sure the request is valid and we can start deleting fields.
          // Do all deletions first, then a single save to _SCHEMA collection to handle all additions.
          const deletedFields = [];
          const insertedFields = [];
          Object.keys(submittedFields).forEach(fieldName => {
            if (submittedFields[fieldName].__op === 'Delete') {
              deletedFields.push(fieldName);
            } else {
              insertedFields.push(fieldName);
            }
          });
  
          let deletePromise = Promise.resolve();
          if (deletedFields.length > 0) {
            deletePromise = this.deleteFields(deletedFields, className, database);
          }
  
          return deletePromise // Delete Everything
            .then(() => this.reloadData({ clearCache: true })) // Reload our Schema, so we have all the new values
            .then(() => {
              const promises = insertedFields.map(fieldName => {
                const type = submittedFields[fieldName];
                return this.enforceFieldExists(className, fieldName, type);
              });
              return Promise.all(promises);
            })
            .then(() => this.setPermissions(className, classLevelPermissions, newSchema))
          //TODO: Move this logic into the database adapter
            .then(() => ({
              className: className,
              fields: this.data[className],
              classLevelPermissions: this.perms[className]
            }));
        })
        .catch(error => {
          if (error === undefined) {
            throw new Parse.Error(Parse.Error.INVALID_CLASS_NAME, `Class ${className} does not exist.`);
          } else {
            throw error;
          }
        })
    }
  
    // Returns a promise that resolves successfully to the new schema
    // object or fails with a reason.
    enforceClassExists(className) {
      if (this.data[className]) {
        return Promise.resolve(this);
      }
      // We don't have this class. Update the schema
      return this.addClassIfNotExists(className)
      // The schema update succeeded. Reload the schema
        .then(() => this.reloadData({ clearCache: true }))
        .catch(() => {
        // The schema update failed. This can be okay - it might
        // have failed because there's a race condition and a different
        // client is making the exact same schema update that we want.
        // So just reload the schema.
          return this.reloadData({ clearCache: true });
        })
        .then(() => {
        // Ensure that the schema now validates
          if (this.data[className]) {
            return this;
          } else {
            throw new Parse.Error(Parse.Error.INVALID_JSON, `Failed to add ${className}`);
          }
        })
        .catch(() => {
        // The schema still doesn't validate. Give up
          throw new Parse.Error(Parse.Error.INVALID_JSON, 'schema class name does not revalidate');
        });
    }
  
    validateNewClass(className, fields = {}, classLevelPermissions) {
      if (this.data[className]) {
        throw new Parse.Error(Parse.Error.INVALID_CLASS_NAME, `Class ${className} already exists.`);
      }
      if (!classNameIsValid(className)) {
        return {
          code: Parse.Error.INVALID_CLASS_NAME,
          error: invalidClassNameMessage(className),
        };
      }
      return this.validateSchemaData(className, fields, classLevelPermissions, []);
    }
  
    validateSchemaData(className, fields, classLevelPermissions, existingFieldNames) {
      for (const fieldName in fields) {
        if (existingFieldNames.indexOf(fieldName) < 0) {
          if (!fieldNameIsValid(fieldName)) {
            return {
              code: Parse.Error.INVALID_KEY_NAME,
              error: 'invalid field name: ' + fieldName,
            };
          }
          if (!fieldNameIsValidForClass(fieldName, className)) {
            return {
              code: 136,
              error: 'field ' + fieldName + ' cannot be added',
            };
          }
          const error = fieldTypeIsInvalid(fields[fieldName]);
          if (error) return { code: error.code, error: error.message };
        }
      }
  
      for (const fieldName in defaultColumns[className]) {
        fields[fieldName] = defaultColumns[className][fieldName];
      }
  
      const geoPoints = Object.keys(fields).filter(key => fields[key] && fields[key].type === 'GeoPoint');
      if (geoPoints.length > 1) {
        return {
          code: Parse.Error.INCORRECT_TYPE,
          error: 'currently, only one GeoPoint field may exist in an object. Adding ' + geoPoints[1] + ' when ' + geoPoints[0] + ' already exists.',
        };
      }
      validateCLP(classLevelPermissions, fields);
    }
  
    // Sets the Class-level permissions for a given className, which must exist.
    setPermissions(className, perms, newSchema) {
      if (typeof perms === 'undefined') {
        return Promise.resolve();
      }
      validateCLP(perms, newSchema);
      return this._dbAdapter.setClassLevelPermissions(className, perms)
        .then(() => this.reloadData({ clearCache: true }));
    }
  
    // Returns a promise that resolves successfully to the new schema
    // object if the provided className-fieldName-type tuple is valid.
    // The className must already be validated.
    // If 'freeze' is true, refuse to update the schema for this field.
    enforceFieldExists(className, fieldName, type) {
      if (fieldName.indexOf(".") > 0) {
        // subdocument key (x.y) => ok if x is of type 'object'
        fieldName = fieldName.split(".")[ 0 ];
        type = 'Object';
      }
      if (!fieldNameIsValid(fieldName)) {
        throw new Parse.Error(Parse.Error.INVALID_KEY_NAME, `Invalid field name: ${fieldName}.`);
      }
  
      // If someone tries to create a new field with null/undefined as the value, return;
      if (!type) {
        return Promise.resolve(this);
      }
  
      return this.reloadData().then(() => {
        const expectedType = this.getExpectedType(className, fieldName);
        if (typeof type === 'string') {
          type = { type };
        }
  
        if (expectedType) {
          if (!dbTypeMatchesObjectType(expectedType, type)) {
            throw new Parse.Error(
              Parse.Error.INCORRECT_TYPE,
              `schema mismatch for ${className}.${fieldName}; expected ${typeToString(expectedType)} but got ${typeToString(type)}`
            );
          }
          return this;
        }
  
        return this._dbAdapter.addFieldIfNotExists(className, fieldName, type).then(() => {
          // The update succeeded. Reload the schema
          return this.reloadData({ clearCache: true });
        }, () => {
          //TODO: introspect the error and only reload if the error is one for which is makes sense to reload
  
          // The update failed. This can be okay - it might have been a race
          // condition where another client updated the schema in the same
          // way that we wanted to. So, just reload the schema
          return this.reloadData({ clearCache: true });
        }).then(() => {
          // Ensure that the schema now validates
          if (!dbTypeMatchesObjectType(this.getExpectedType(className, fieldName), type)) {
            throw new Parse.Error(Parse.Error.INVALID_JSON, `Could not add field ${fieldName}`);
          }
          // Remove the cached schema
          this._cache.clear();
          return this;
        });
      });
    }
  
    // maintain compatibility
    deleteField(fieldName, className, database) {
      return this.deleteFields([fieldName], className, database);
    }
  
    // Delete fields, and remove that data from all objects. This is intended
    // to remove unused fields, if other writers are writing objects that include
    // this field, the field may reappear. Returns a Promise that resolves with
    // no object on success, or rejects with { code, error } on failure.
    // Passing the database and prefix is necessary in order to drop relation collections
    // and remove fields from objects. Ideally the database would belong to
    // a database adapter and this function would close over it or access it via member.
    deleteFields(fieldNames, className, database) {
      if (!classNameIsValid(className)) {
        throw new Parse.Error(Parse.Error.INVALID_CLASS_NAME, invalidClassNameMessage(className));
      }
  
      fieldNames.forEach(fieldName => {
        if (!fieldNameIsValid(fieldName)) {
          throw new Parse.Error(Parse.Error.INVALID_KEY_NAME, `invalid field name: ${fieldName}`);
        }
        //Don't allow deleting the default fields.
        if (!fieldNameIsValidForClass(fieldName, className)) {
          throw new Parse.Error(136, `field ${fieldName} cannot be changed`);
        }
      });
  
      return this.getOneSchema(className, false, {clearCache: true})
        .catch(error => {
          if (error === undefined) {
            throw new Parse.Error(Parse.Error.INVALID_CLASS_NAME, `Class ${className} does not exist.`);
          } else {
            throw error;
          }
        })
        .then(schema => {
          fieldNames.forEach(fieldName => {
            if (!schema.fields[fieldName]) {
              throw new Parse.Error(255, `Field ${fieldName} does not exist, cannot delete.`);
            }
          });
  
          const schemaFields = { ...schema.fields };
          return database.adapter.deleteFields(className, schema, fieldNames)
            .then(() => {
              return Promise.all(fieldNames.map(fieldName => {
                const field = schemaFields[fieldName];
                if (field && field.type === 'Relation') {
                //For relations, drop the _Join table
                  return database.adapter.deleteClass(`_Join:${fieldName}:${className}`);
                }
                return Promise.resolve();
              }));
            });
        }).then(() => {
          this._cache.clear();
        });
    }
  
    // Validates an object provided in REST format.
    // Returns a promise that resolves to the new schema if this object is
    // valid.
    validateObject(className, object, query) {
      let geocount = 0;
      let promise = this.enforceClassExists(className);
      for (const fieldName in object) {
        if (object[fieldName] === undefined) {
          continue;
        }
        const expected = getType(object[fieldName]);
        if (expected === 'GeoPoint') {
          geocount++;
        }
        if (geocount > 1) {
          // Make sure all field validation operations run before we return.
          // If not - we are continuing to run logic, but already provided response from the server.
          return promise.then(() => {
            return Promise.reject(new Parse.Error(Parse.Error.INCORRECT_TYPE,
              'there can only be one geopoint field in a class'));
          });
        }
        if (!expected) {
          continue;
        }
        if (fieldName === 'ACL') {
          // Every object has ACL implicitly.
          continue;
        }
  
        promise = promise.then(schema => schema.enforceFieldExists(className, fieldName, expected));
      }
      promise = thenValidateRequiredColumns(promise, className, object, query);
      return promise;
    }
  
    // Validates that all the properties are set for the object
    validateRequiredColumns(className, object, query) {
      const columns = requiredColumns[className];
      if (!columns || columns.length == 0) {
        return Promise.resolve(this);
      }
  
      const missingColumns = columns.filter(function(column){
        if (query && query.objectId) {
          if (object[column] && typeof object[column] === "object") {
            // Trying to delete a required column
            return object[column].__op == 'Delete';
          }
          // Not trying to do anything there
          return false;
        }
        return !object[column]
      });
  
      if (missingColumns.length > 0) {
        throw new Parse.Error(
          Parse.Error.INCORRECT_TYPE,
          missingColumns[0] + ' is required.');
      }
      return Promise.resolve(this);
    }
  
    // Validates the base CLP for an operation
    testBaseCLP(className, aclGroup, operation) {
      if (!this.perms[className] || !this.perms[className][operation]) {
        return true;
      }
      const classPerms = this.perms[className];
      const perms = classPerms[operation];
      // Handle the public scenario quickly
      if (perms['*']) {
        return true;
      }
      // Check permissions against the aclGroup provided (array of userId/roles)
      if (aclGroup.some(acl => { return perms[acl] === true })) {
        return true;
      }
      return false;
    }
  
    // Validates an operation passes class-level-permissions set in the schema
    validatePermission(className, aclGroup, operation) {
  
      if (this.testBaseCLP(className, aclGroup, operation)) {
        return Promise.resolve();
      }
  
      if (!this.perms[className] || !this.perms[className][operation]) {
        return true;
      }
      const classPerms = this.perms[className];
      const perms = classPerms[operation];
  
      // If only for authenticated users
      // make sure we have an aclGroup
      if (perms['requiresAuthentication']) {
        // If aclGroup has * (public)
        if (!aclGroup || aclGroup.length == 0) {
          throw new Parse.Error(Parse.Error.OBJECT_NOT_FOUND,
            'Permission denied, user needs to be authenticated.');
        } else if (aclGroup.indexOf('*') > -1 && aclGroup.length == 1) {
          throw new Parse.Error(Parse.Error.OBJECT_NOT_FOUND,
            'Permission denied, user needs to be authenticated.');
        }
        // requiresAuthentication passed, just move forward
        // probably would be wise at some point to rename to 'authenticatedUser'
        return Promise.resolve();
      }
  
      // No matching CLP, let's check the Pointer permissions
      // And handle those later
      const permissionField = ['get', 'find', 'count'].indexOf(operation) > -1 ? 'readUserFields' : 'writeUserFields';
  
      // Reject create when write lockdown
      if (permissionField == 'writeUserFields' && operation == 'create') {
        throw new Parse.Error(Parse.Error.OPERATION_FORBIDDEN,
          `Permission denied for action ${operation} on class ${className}.`);
      }
  
      // Process the readUserFields later
      if (Array.isArray(classPerms[permissionField]) && classPerms[permissionField].length > 0) {
        return Promise.resolve();
      }
      throw new Parse.Error(Parse.Error.OPERATION_FORBIDDEN,
        `Permission denied for action ${operation} on class ${className}.`);
    }
  
    // Returns the expected type for a className+key combination
    // or undefined if the schema is not set
    getExpectedType(className, fieldName) {
      // console.log(className);
      // console.log(fieldName);
      // console.log(this.data);
      // console.log('expected');
      if (this.data && this.data[className]) {
        const expectedType = this.data[className][fieldName];
        return expectedType === 'map' ? 'Object' : expectedType;
      }
      return undefined;
    }
  
    // Checks if a given class is in the schema.
    hasClass(className) {
      return this.reloadData().then(() => !!(this.data[className]));
    }
  }
  
  // Returns a promise for a new Schema.
  const load = (dbAdapter, schemaCache, options) => {
    const schema = new SchemaController(dbAdapter, schemaCache);
    return schema.reloadData(options).then(() => schema);
  }
  
  // Builds a new schema (in schema API response format) out of an
  // existing mongo schema + a schemas API put request. This response
  // does not include the default fields, as it is intended to be passed
  // to mongoSchemaFromFieldsAndClassName. No validation is done here, it
  // is done in mongoSchemaFromFieldsAndClassName.
  function buildMergedSchemaObject(existingFields, putRequest) {
    const newSchema = {};
    const sysSchemaField = Object.keys(defaultColumns).indexOf(existingFields._id) === -1 ? [] : Object.keys(defaultColumns[existingFields._id]);
    for (const oldField in existingFields) {
      if (oldField !== '_id' && oldField !== 'ACL' &&  oldField !== 'updatedAt' && oldField !== 'createdAt' && oldField !== 'objectId') {
        if (sysSchemaField.length > 0 && sysSchemaField.indexOf(oldField) !== -1) {
          continue;
        }
        const fieldIsDeleted = putRequest[oldField] && putRequest[oldField].__op === 'Delete'
        if (!fieldIsDeleted) {
          newSchema[oldField] = existingFields[oldField];
        }
      }
    }
    for (const newField in putRequest) {
      if (newField !== 'objectId' && putRequest[newField].__op !== 'Delete') {
        if (sysSchemaField.length > 0 && sysSchemaField.indexOf(newField) !== -1) {
          continue;
        }
        newSchema[newField] = putRequest[newField];
      }
    }
    return newSchema;
  }
  
  // Given a schema promise, construct another schema promise that
  // validates this field once the schema loads.
  function thenValidateRequiredColumns(schemaPromise, className, object, query) {
    return schemaPromise.then((schema) => {
      return schema.validateRequiredColumns(className, object, query);
    });
  }
  
  // Gets the type from a REST API formatted object, where 'type' is
  // extended past javascript types to include the rest of the Parse
  // type system.
  // The output should be a valid schema value.
  // TODO: ensure that this is compatible with the format used in Open DB
  function getType(obj) {
    const type = typeof obj;
    switch(type) {
    case 'boolean':
      return 'Boolean';
    case 'string':
      return 'String';
    case 'number':
      return 'Number';
    case 'map':
    case 'object':
      if (!obj) {
        return undefined;
      }
      return getObjectType(obj);
    case 'function':
    case 'symbol':
    case 'undefined':
    default:
      throw 'bad obj: ' + obj;
    }
  }
  
  // This gets the type for non-JSON types like pointers and files, but
  // also gets the appropriate type for $ operators.
  // Returns null if the type is unknown.
  function getObjectType(obj) {
    if (obj instanceof Array) {
      return 'Array';
    }
    if (obj.__type){
      switch(obj.__type) {
      case 'Pointer' :
        if(obj.className) {
          return {
            type: 'Pointer',
            targetClass: obj.className
          }
        }
        break;
      case 'Relation' :
        if(obj.className) {
          return {
            type: 'Relation',
            targetClass: obj.className
          }
        }
        break;
      case 'File' :
        if(obj.name) {
          return 'File';
        }
        break;
      case 'Date' :
        if(obj.iso) {
          return 'Date';
        }
        break;
      case 'GeoPoint' :
        if(obj.latitude != null && obj.longitude != null) {
          return 'GeoPoint';
        }
        break;
      case 'Bytes' :
        if(obj.base64) {
          return 'Bytes';
        }
        break;
      }
      throw new Parse.Error(Parse.Error.INCORRECT_TYPE, "This is not a valid " + obj.__type);
    }
    if (obj['$ne']) {
      return getObjectType(obj['$ne']);
    }
    if (obj.__op) {
      switch(obj.__op) {
      case 'Increment':
        return 'Number';
      case 'Delete':
        return null;
      case 'Add':
      case 'AddUnique':
      case 'Remove':
        return 'Array';
      case 'AddRelation':
      case 'RemoveRelation':
        return {
          type: 'Relation',
          targetClass: obj.objects[0].className
        }
      case 'Batch':
        return getObjectType(obj.ops[0]);
      default:
        throw 'unexpected op: ' + obj.__op;
      }
    }
    return 'Object';
  }
  
  export {
    load,
    classNameIsValid,
    fieldNameIsValid,
    invalidClassNameMessage,
    buildMergedSchemaObject,
    systemClasses,
    defaultColumns,
    convertSchemaToAdapterSchema,
    VolatileClassesSchemas,
  };
  