import { Json2CsvTransform } from './transforms';

export declare namespace json2csv {
    export interface FieldValueCallbackInfo {
        label: string;
        default?: string;
    }

    export type FieldValueCallback<T> = FieldValueCallbackWithoutField<T> | FieldValueCallbackWithField<T>;

    export interface FieldValueCallbackWithoutField<T> {
        (row: T): any;
    }

    export interface FieldValueCallbackWithField<T> {
        (row: T, field: FieldValueCallbackInfo): any;
    }

    export interface FieldInfo<T> {
        label?: string;
        default?: string;
        value: string | FieldValueCallback<T>;
    }

    export interface NormalizedFieldInfo<T> {
        label: string;
        value: FieldValueCallback<T>;
    }

    export interface Options<T> {
        fields?: Array<string | FieldInfo<T>>;
        ndjson?: boolean;
        defaultValue?: string;
        quote?: string;
        escapedQuote?: string;
        delimiter?: string;
        eol?: string;
        excelStrings?: boolean;
        header?: boolean;
        includeEmptyRows?: boolean;
        withBOM?: boolean;
        transforms?: Array<Json2CsvTransform<any, any>>;
    }
}

declare abstract class JSON2CSVBase<T> {
    constructor(opts?: json2csv.Options<T>);

    /**
     * Check passing opts and set defaults.
     *
     * @param {json2csv.Options} opts Options object containing fields,
     * delimiter, default value, quote mark, header, etc.
     * @returns {json2csv.Options} preprocessed Options object
     */
    protected preprocessOpts(opts?: json2csv.Options<T>) : json2csv.Options<T>;

    /**
     * Check and normalize the fields configuration.
     *
     * @param {(string|json2csv.FieldInfo)[]} fields Fields configuration provided by the user
     * or inferred from the data
     * @returns {json2csv.NormalizedFieldInfo} preprocessed FieldsInfo array
     */
    preprocessFieldsInfo<T>(fields: Array<string | json2csv.FieldInfo<T>>): Array<json2csv.NormalizedFieldInfo<T>>;

    /**
     * Create the title row with all the provided fields as column headings
     *
     * @returns {string} titles as a string
     */
    protected getHeader(): string;

    /**
     * Preprocess each object according to the give opts (unwind, flatten, etc.).
     *
     * @param {object} row JSON object to be converted in a CSV row
     */
    protected preprocessRow(row: T): object;

    /**
     * Create the content of a specific CSV row
     *
     * @param {object} row JSON object to be converted in a CSV row
     * @returns {string} CSV string (row)
     */
    protected processRow(row: T): string;

    /**
     * Create the content of a specfic CSV row cell
     *
     * @param {object} row JSON object representing the  CSV row that the cell belongs to
     * @param {object} fieldInfo Details of the field to process to be a CSV cell
     * @returns {string} CSV string (cell)
     */
    protected processCell(row: T, fieldInfo: json2csv.NormalizedFieldInfo<T>) : string;

    /**
     * Create the content of a specfic CSV row cell
     *
     * @param {any} value Value to be included in a CSV cell
     * @returns {string} Value stringified and processed
     */
    protected processValue(value: any): string;
}

export default JSON2CSVBase;