import {parseString} from 'xml2js';
import {promises} from 'fs';

const {readdir, readFile} = promises;

export async function* eachVestnik (prefix) {
    const xmlFileNames = (await readdir(prefix)).filter(each => each.endsWith('.xml'));
    for (let xmlFileName of xmlFileNames) {
        const contents = await readFile(`${prefix}/${xmlFileName}`, {encoding: 'utf8'});
        const object = await new Promise((resolve, reject) =>
            parseString(contents, (err, result) => err ? reject(err) : resolve(result)));
        yield object.vestnik;
    }
}

export function* eachItem (vestnik) {
    for (let obsah of vestnik.obsah)
        for (let oznamenia_vo of obsah.oznamenia_vo) {
            yield* eachItemInTree(oznamenia_vo);
        }
}

function* eachItemInTree (folder) {
    for (let subFolder of folder.folder || []) yield* eachItemInTree(subFolder);
    yield* folder.item;
}

export function* eachFormElement (item) {
    for (let content of item.content)
        for (let form of content.ZovoForm || [])
            yield* eachFormElementInTree(form);
}

const DIVE_TAGS = {Part: true, Repeater: true, RepeatingPart: true};
const IGNORE_TAGS = {SubTitle: true, $: true, _: true};

function* eachFormElementInTree (form) {
    for (let tag of Object.keys(form)) {
        if (IGNORE_TAGS[tag]) continue;
        for (let value of form[tag]) {
            let shouldCancel = false;
            const cancel = () => shouldCancel = true;
            const dive = () => eachFormElementInTree(value);
            yield {tag, value, cancel, dive};
            if (DIVE_TAGS[tag] && !shouldCancel) yield* dive();
        }
    }
}