import { Reader } from '../reader';
import { nextTick } from '../util';
import { Writer } from '../writer';

/// !doc
/// ## In-memory string streams
///
/// `import { stringReader, stringWriter } from 'f-streams'`
///

export interface Options {
    sync?: boolean;
    chunkSize?: number | (() => number);
}

export class StringWriter extends Writer<string> {
    buf: string;
    constructor(options: Options) {
        super((value: string) => {
            if (!options.sync) nextTick();
            if (value !== undefined) this.buf += value;
            return this;
        });
        this.buf = '';
    }
    toString() {
        return this.buf;
    }
    get result() {
        return this.buf;
    }
}

/// * `reader = stringReader(text, options)`
///   creates a reader that reads its chunks from `text`.
///   `reader.read()` will return the chunks asynchronously by default.
///   You can force synchronous delivery by setting `options.sync` to `true`.
///   The default chunk size is 1024. You can override it by passing
///   a `chunkSize` option.
export function reader(text: string, options?: Options | number) {
    let opts: Options;
    if (typeof options === 'number') {
        opts = {
            chunkSize: options,
        };
    } else opts = options || {};
    const chunkSize = opts.chunkSize || 1024;
    let pos = 0;
    return new Reader(function read() {
        if (!opts.sync) nextTick();
        if (pos >= text.length) return;
        const len = typeof chunkSize === 'function' ? chunkSize() : chunkSize;
        const s = text.substring(pos, pos + len);
        pos += len;
        return s;
    });
}
/// * `writer = stringWriter(options)`
///   creates a writer that collects strings into a text buffer.
///   `writer.write(data)` will write asynchronously by default.
///   You can force synchronous write by setting `options.sync` to `true`.
///   `writer.toString()` returns the internal text buffer into which the
///   strings have been collected.
export function writer(options?: Options) {
    return new StringWriter(options || {});
}

export function factory(url: string) {
    return {
        /// * `reader = factory.reader()`
        reader: () => {
            return module.exports.reader(url.substring(url.indexOf(':') + 1));
        },
        /// * `writer = factory.writer()`
        writer: () => {
            return module.exports.writer();
        },
    };
}