n3/lib/N3StreamParser.js

Lightning fast, asynchronous, streaming Turtle / N3 / RDF library.

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = void 0;
var _readableStream = require("readable-stream");
var _N3Parser = _interopRequireDefault(require("./N3Parser"));
function _interopRequireDefault(e) { return e && e.__esModule ? e : { default: e }; }
// **N3StreamParser** parses a text stream into a quad stream.

// ## Constructor
class N3StreamParser extends _readableStream.Transform {
  constructor(options) {
    super({
      decodeStrings: true
    });
    this._readableState.objectMode = true;

    // Set up parser with dummy stream to obtain `data` and `end` callbacks
    const parser = new _N3Parser.default(options);
    let onData, onEnd;
    const callbacks = {
      // Handle quads by pushing them down the pipeline
      onQuad: (error, quad) => {
        error && this.emit('error', error) || quad && this.push(quad);
      },
      // Emit prefixes through the `prefix` event
      onPrefix: (prefix, uri) => {
        this.emit('prefix', prefix, uri);
      }
    };
    if (options && options.comments) callbacks.onComment = comment => {
      this.emit('comment', comment);
    };
    parser.parse({
      on: (event, callback) => {
        switch (event) {
          case 'data':
            onData = callback;
            break;
          case 'end':
            onEnd = callback;
            break;
        }
      }
    }, callbacks);

    // Implement Transform methods through parser callbacks
    this._transform = (chunk, encoding, done) => {
      onData(chunk);
      done();
    };
    this._flush = done => {
      onEnd();
      done();
    };
  }

  // ### Parses a stream of strings
  import(stream) {
    stream.on('data', chunk => {
      this.write(chunk);
    });
    stream.on('end', () => {
      this.end();
    });
    stream.on('error', error => {
      this.emit('error', error);
    });
    return this;
  }
}
exports.default = N3StreamParser;