@csvw-rdf-convertor/core/dist/lib/transformation-stream.js

This library was generated with [Nx](https://nx.dev).

import { Readable } from 'stream';
import { convertColumnToDateFormattedColumn, formatDate, isDateFormatedColumn } from './utils/date-formatting.js';
import { convertColumnToNumberFormattedColumn, isNumberColumn, transformNumber } from './utils/number-formating.js';
import { DataFactory } from 'rdf-data-factory';
import { trimUrl } from './utils/url-trimming.js';
const factory = new DataFactory();
export function transformStream(stream, tableDescription, columns, table, issueTracker) {
    const transformedStream = new Readable({
        objectMode: true,
        read () {
        // no-op
        }
    });
    //This part is called when the stream is piped to another stream and gets data.
    stream.on('data', (bindings)=>{
        for(let i = 0; i < tableDescription.tableSchema.columns.length && !tableDescription.tableSchema.columns[i].virtual; i++){
            const columnDescription = tableDescription.tableSchema.columns[i];
            if (!bindings.get(columns[i].queryVariable)) {
                if (columnDescription.null) {
                    if (columnDescription.null instanceof Array) {
                        bindings = bindings.set(columns[i].queryVariable, factory.literal(columnDescription.null[0]));
                    } else {
                        bindings = bindings.set(columns[i].queryVariable, factory.literal(columnDescription.null));
                    }
                } else {
                    continue;
                }
            }
            const value = bindings.get(columns[i].queryVariable).value;
            if (isDateFormatedColumn(columnDescription)) {
                const convertedDateColumn = convertColumnToDateFormattedColumn(columnDescription);
                if (convertedDateColumn) {
                    const formattedValue = formatDate(value, convertedDateColumn.datatype.format);
                    bindings = bindings.set(columns[i].queryVariable, factory.literal(formattedValue));
                }
            } else if (isNumberColumn(columnDescription)) {
                const convertedNumberColumn = convertColumnToNumberFormattedColumn(columnDescription);
                if (convertedNumberColumn) {
                    const formattedValue = transformNumber(value, convertedNumberColumn, issueTracker);
                    bindings = bindings.set(columns[i].queryVariable, factory.literal(formattedValue));
                }
            } else if (columnDescription.valueUrl) {
                const formattedValue = trimUrl(value, columnDescription.valueUrl, columns[i].name, issueTracker);
                bindings = bindings.set(columns[i].queryVariable, factory.literal(formattedValue));
            } else if (table.aboutUrl) {
                const formattedValue = trimUrl(value, table.aboutUrl, columns[i].name, issueTracker);
                bindings = bindings.set(columns[i].queryVariable, factory.literal(formattedValue));
            }
        }
        transformedStream.push(bindings);
    });
    stream.on('end', ()=>{
        transformedStream.push(null);
    });
    stream.on('error', (err)=>{
        transformedStream.destroy(err);
    });
    return transformedStream;
}

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