import { assertArgument } from "../utils/index.js";


const subsChrs = " !#$%&'()*+,-./<=>?@[]^_`{|}~";
const Word = /^[a-z]*$/i;

function unfold(words: Array<string>, sep: string): Array<string> {
    let initial = 97;
    return words.reduce((accum, word) => {
        if (word === sep) {
            initial++;
        } else if (word.match(Word)) {
            accum.push(String.fromCharCode(initial) + word);
        } else {
            initial = 97;
            accum.push(word);
        }
        return accum;
    }, <Array<string>>[]);
}

export function decode(data: string, subs: string): Array<string> {

    // Replace all the substitutions with their expanded form
    for (let i = subsChrs.length - 1; i >= 0; i--) {
        data = data.split(subsChrs[i]).join(subs.substring(2 * i, 2 * i + 2));
    }

    // Get all tle clumps; each suffix, first-increment and second-increment
    const clumps: Array<string> = [ ];
    const leftover = data.replace(/(:|([0-9])|([A-Z][a-z]*))/g, (all, item, semi, word) => {
        if (semi) {
            for (let i = parseInt(semi); i >= 0; i--) { clumps.push(";"); }
        } else {
            clumps.push(item.toLowerCase());
        }
        return "";
    });
    /* c8 ignore start */
    if (leftover) { throw new Error(`leftovers: ${ JSON.stringify(leftover) }`); }
    /* c8 ignore stop */

    return unfold(unfold(clumps, ";"), ":");
}

export function decodeOwl(data: string): Array<string> {
    assertArgument(data[0] === "0", "unsupported auwl data", "data", data);

    return decode(
        data.substring(1 + 2 * subsChrs.length),
        data.substring(1, 1 + 2 * subsChrs.length));
}