marc4js/lib/transform/text_transformer.js

a node.js module for handling MARC data

'use strict';

var Transform = require('stream').Transform;
var util = require('util');
var os = require('os');
var Util = require('../util');
var Record = require('../marc/record');
var Leader = require('../marc/leader');
var ControlField = require('../marc/control_field');
var DataField = require('../marc/data_field');
var Subfield = require('../marc/subfield');

var TextTransformer = function (opts) {
    opts = opts || {};
    this.objectMode = opts.objectMode || false;
    this.encoding = opts.encoding || 'utf8';

    Transform.call(this, opts);
};

util.inherits(TextTransformer, Transform);

TextTransformer.prototype._transform = function (record, encoding, callback) {
    this.push(record);
    return callback();
};

TextTransformer.prototype.write = function(chunk, encoding, callback) {
    var record = chunk;
    var buffers = [];
    if (typeof encoding === 'undefined') {
        encoding = this.encoding;
    }
    try {
        buffers.push(new Buffer("LDR    ", encoding));
        buffers.push(new Buffer(record.leader.marshal(), encoding));
        buffers.push(new Buffer(os.EOL, encoding));

        // write directory
        record.variableFields.forEach(function (field) {
            buffers.push(new Buffer(field.tag + " ", encoding));
            if (field instanceof ControlField) {
                buffers.push(new Buffer("   ", encoding));
                buffers.push(new Buffer(field.data, encoding));
                buffers.push(new Buffer(os.EOL));
            } else {
                buffers.push(new Buffer(field.indicator1, encoding));
                buffers.push(new Buffer(field.indicator2, encoding));
                buffers.push(new Buffer(" ", encoding));
                field.subfields.forEach(function (subfield) {
                    buffers.push(new Buffer("$" + subfield.code, encoding));
                    buffers.push(new Buffer(subfield.data, encoding));
                });
                buffers.push(new Buffer(os.EOL));
            }
        });

        buffers.push(new Buffer(os.EOL));
        chunk = Buffer.concat(buffers);
    } catch (err) {
        console.log('error', err.stack);
        callback(err);
    }
    return Transform.prototype.write.call(this, chunk, encoding, callback);
};

module.exports = TextTransformer;