import { _isIterable } from './_guards.js';
import type { Series, SyncSeries } from './types.js';

export function* flattenSync<T>(input: SyncSeries<SyncSeries<T>>): Generator<T> {
    for (const pool of input) {
        for (const value of pool) {
            yield value;
        }
    }
}

export async function* flattenAsync<T>(input: Series<Series<T>>): AsyncGenerator<Awaited<T>> {
    const awaited = await input;
    if (_isIterable(awaited)) {
        for (const pool of awaited) {
            const innerAwaited = await pool;
            if (_isIterable(innerAwaited)) {
                for (const value of innerAwaited) {
                    yield value;
                }
            } else {
                for await (const value of innerAwaited) {
                    yield value;
                }
            }
        }
    } else {
        for await (const pool of awaited) {
            if (_isIterable(pool)) {
                for (const value of pool) {
                    yield value;
                }
            } else {
                for await (const value of pool) {
                    yield value;
                }
            }
        }
    }
}

/** Flattens a series of series by one level deep. */
export namespace flatten {
    export const sync = flattenSync;
    export const async = flattenAsync;
}