gremlin-javascript/src/main/javascript/gremlin-javascript/lib/structure/io/binary/internals/EnumSerializer.js

/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 */

/**
 * @author Igor Ostapenko
 */

import { Buffer } from 'buffer';
import {
  barrier,
  cardinality,
  column,
  direction,
  dt,
  merge,
  operator,
  order,
  pick,
  pop,
  scope,
  t as _t,
  EnumValue,
} from '../../../../process/traversal.js';

export default class EnumSerializer {
  constructor(ioc) {
    this.ioc = ioc;

    const to_orig_enum = (obj) => {
      // process/traversal.js:toEnum() changes original element name (e.g. OUT => out) for end users' convenience
      // but we need original mapping as is w/o additional time spent on case-insensititive comparison
      const r = {};
      Object.values(obj).forEach((e) => (r[e.elementName] = e));
      return r;
    };
    const DT = ioc.DataType;
    this.types = [
      { name: 'Barrier', code: DT.BARRIER, enum: to_orig_enum(barrier) },
      { name: 'Cardinality', code: DT.CARDINALITY, enum: to_orig_enum(cardinality) },
      { name: 'Column', code: DT.COLUMN, enum: to_orig_enum(column) },
      { name: 'Direction', code: DT.DIRECTION, enum: to_orig_enum(direction) },
      { name: 'DT', code: DT.DT, enum: to_orig_enum(dt) },
      { name: 'Merge', code: DT.MERGE, enum: to_orig_enum(merge) },
      { name: 'Operator', code: DT.OPERATOR, enum: to_orig_enum(operator) },
      { name: 'Order', code: DT.ORDER, enum: to_orig_enum(order) },
      { name: 'Pick', code: DT.PICK, enum: to_orig_enum(pick) },
      { name: 'Pop', code: DT.POP, enum: to_orig_enum(pop) },
      { name: 'Scope', code: DT.SCOPE, enum: to_orig_enum(scope) },
      { name: 'T', code: DT.T, enum: to_orig_enum(_t) },
    ];
    this.byname = {};
    this.bycode = {};
    for (const type of this.types) {
      this.ioc.serializers[type.code] = this;
      this.byname[type.name] = type;
      this.bycode[type.code] = type;
    }
  }

  canBeUsedFor(value) {
    if (!(value instanceof EnumValue)) {
      return false;
    }
    if (!this.byname[value.typeName]) {
      throw new Error(`EnumSerializer.serialize: typeName=${value.typeName} is not supported.`);
    }

    return true;
  }

  serialize(item, fullyQualifiedFormat = true) {
    const type = this.byname[item.typeName];
    if (item.elementName === undefined || item.elementName === null) {
      if (fullyQualifiedFormat) {
        return Buffer.from([type.code, 0x01]);
      }
      return Buffer.from([this.ioc.DataType.STRING, 0x00, 0x00, 0x00, 0x00, 0x00]);
    }

    const bufs = [];
    if (fullyQualifiedFormat) {
      bufs.push(Buffer.from([type.code, 0x00]));
    }

    bufs.push(this.ioc.stringSerializer.serialize(item.elementName, true));

    return Buffer.concat(bufs);
  }

  deserialize(buffer, fullyQualifiedFormat = true) {
    let len = 0;
    let cursor = buffer;

    try {
      if (buffer === undefined || buffer === null || !(buffer instanceof Buffer)) {
        throw new Error('buffer is missing');
      }
      if (buffer.length < 1) {
        throw new Error('buffer is empty');
      }

      let type = undefined;
      if (fullyQualifiedFormat) {
        const type_code = cursor.readUInt8();
        len++;
        type = this.bycode[type_code];
        if (!type) {
          throw new Error(`unexpected {type_code}=${type_code}`);
        }
        cursor = cursor.slice(1);

        if (cursor.length < 1) {
          throw new Error('{value_flag} is missing');
        }
        const value_flag = cursor.readUInt8();
        len++;
        if (value_flag === 1) {
          return { v: null, len };
        }
        if (value_flag !== 0) {
          throw new Error('unexpected {value_flag}');
        }
        cursor = cursor.slice(1);
      }

      let elementName, elementName_len;
      try {
        ({ v: elementName, len: elementName_len } = this.ioc.stringSerializer.deserialize(cursor, true));
        len += elementName_len;
      } catch (err) {
        err.message = 'elementName: ' + err.message;
        throw err;
      }
      cursor = cursor.slice(elementName_len);

      let v;
      if (!type) {
        v = new EnumValue(undefined, elementName);
      } else {
        v = type.enum[elementName]; // users are expected to work with maps like Map.get(T.id), i.e. it must be exactly the same object
      }

      return { v, len };
    } catch (err) {
      throw this.ioc.utils.des_error({ serializer: this, args: arguments, cursor, err });
    }
  }
}