/// !doc
/// ## JSON mappers
///
/// `import { simpleJsonParser, simpleJsonFormatter } from 'f-streams'`
///

/// * `mapper = simpleJsonParser(options)`
///   returns a mapper that parses JSON string.
///   It assumes that the stream has already been split on boundaries that delimit valid JSON strings,
///   with an optional separator at the end.
export interface ParserOptions {
    sep?: string;
    encoding?: string;
}

export function parse<T>(options?: ParserOptions) {
    const opts = options || {};
    const sep = opts.sep == null ? ',' : opts.sep;
    return (data: string | Buffer) => {
        let str: string;
        if (Buffer.isBuffer(data)) str = data.toString(opts.encoding || 'utf8');
        else str = data;
        if (str === '') return;
        // remove trailing separator, if any
        if (sep && str.substring(str.length - sep.length) === sep) str = str.substring(0, str.length - sep.length);
        return JSON.parse(str) as T;
    };
}
/// * `mapper = simpleJsonFormatter(options)`
///   returns a mapper that converts objects to JSON.
///   You can use a the `sep` option to specify a separator that will be added at the end of every item.
///   By default, `sep` is `,\n`.
export interface FormatterOptions {
    sep?: string;
    replacer?: (key: string, value: any) => any;
    space?: string;
}

export function stringify<T>(options?: FormatterOptions) {
    const opts = options || {};
    const sep = opts.sep == null ? ',\n' : opts.sep;
    return (data: T) => {
        return JSON.stringify(data, opts.replacer, opts.space) + sep;
    };
}