@pujansrt/data-genie/dist/writers/fixed-width-writer.d.ts

High performant ETL engine written in TypeScript

import { DataWriter, DataRecord } from '../core/interfaces';
/**
 * FixedWidthWriter class for writing data records to a file in a fixed-width format.
 * Each field's width is predefined, and values are padded or truncated to fit.
 */
export declare class FixedWidthWriter implements DataWriter {
    private readonly filePath;
    private outputStream;
    private fieldWidths;
    private fieldNames;
    private hasFieldNamesInFirstRow;
    private headerWritten;
    private initializedFieldNames;
    /**
     * Constructs a new FixedWidthWriter.
     * @param filePath The path to the output file.
     */
    constructor(filePath: string);
    /**
     * Sets the fixed widths for each field. This is mandatory before writing.
     * @param widths A list of numbers, where each number represents the width of a field.
     * @returns The current FixedWidthWriter instance for chaining.
     */
    setFieldWidths(...widths: number[]): this;
    /**
     * Sets the names of the fields. If `hasFieldNamesInFirstRow` is true, these names
     * will be used to write the header row. Otherwise, they define the order of data
     * extraction from `DataRecord` objects.
     * @param names A list of string names for the fields.
     * @returns The current FixedWidthWriter instance for chaining.
     */
    setFieldNames(...names: string[]): this;
    /**
     * Specifies whether the first row written should be a header row containing the field names.
     * If true, `setFieldNames` must be called before writing any records.
     * @param value True to write field names in the first row, false otherwise.
     * @returns The current FixedWidthWriter instance for chaining.
     */
    setFieldNamesInFirstRow(value: boolean): this;
    /**
     * Writes a single data record to the fixed-width file.
     * @param record The DataRecord object to write.
     * @returns A Promise that resolves when the record has been written.
     * @throws Error if field widths are not defined.
     * @throws Error if `hasFieldNamesInFirstRow` is true but field names are not set.
     * @throws Error if the number of field names does not match the number of field widths.
     */
    write(record: DataRecord): Promise<void>;
    /**
     * Writes all data records from an asynchronous iterable to the fixed-width file.
     * @param records An AsyncIterableIterator of DataRecord objects.
     * @returns A Promise that resolves when all records have been written.
     */
    writeAll(records: AsyncIterableIterator<DataRecord>): Promise<void>;
    /**
     * Closes the underlying write stream. This should be called when all data has been written.
     * @returns A Promise that resolves when the stream is closed.
     */
    close(): Promise<void>;
    /**
     * Formats a single field value to fit the specified width.
     * It truncates if the value is too long and pads with spaces to the right if too short.
     * @param value The value to format.
     * @param width The target width for the field.
     * @returns The formatted string.
     */
    private formatField;
}