/**
 * @typedef {function(string): boolean} GlyphCheck
 */

/**
 * @type {GlyphCheck}
 */
const isAlphaLike = (inGlyph) => {
    const inCode = inGlyph.charCodeAt(0);

    if (inCode >= 97 && inCode <= 122) {
        return true;
    }

    if (inCode >= 65 && inCode <= 90) {
        return true;
    }

    return `$_.`.includes(inGlyph);
};

/**
 * @type {GlyphCheck}
 */
const isWhiteSpace = (inGlyph) => `\n\r\t `.includes(inGlyph);

/**
 * @type {GlyphCheck}
 */
const isQuote = (inGlyph) => `"'\``.includes(inGlyph);

/**
 * @param {GlyphCheck} inCheck
 * @returns {GlyphCheck}
 */
const isNot = (inCheck) => (inGlyph) => !inCheck(inGlyph);

/**
 * @param {string} inText
 * @param {number} inStart
 * @param {GlyphCheck} inTest
 * @returns {number}
 */
const contiguous = (inText, inStart, inTest) => {
    let ok = true;
    let index = inStart;
    let count = 0;
    while (ok && count < inText.length) {
        count++;
        ok = inTest(inText.charAt(index++));
    }
    return index - 1;
};

/**
 * @param {string} inFile
 * @param {number} [inIndex=0]
 * @param {Array<{internal: string, external: string}>} inLocal
 * @param {Array<string>} inForeign
 * @returns {number|boolean}
 */
const findNextExport = (inFile, inIndex = 0, inLocal, inForeign) => {
    const pos = inFile.indexOf("export", inIndex);
    if (pos !== -1) {
        if (!isAlphaLike(inFile.charAt(pos - 1)) || !isAlphaLike(inFile.charAt(pos + 6))) {
            const nextCharInd = contiguous(inFile, pos + 6, isWhiteSpace);
            const nextChar = inFile[nextCharInd];

            if (nextChar === "*") {
                const firstQuoteInd = contiguous(inFile, nextCharInd + 1, isNot(isQuote));
                const secondQuoteInd = contiguous(inFile, firstQuoteInd + 1, isNot(isQuote));
                inForeign.push(inFile.substring(nextCharInd, secondQuoteInd + 1));
            } else if (nextChar == "{") {
                const endBracketInd = contiguous(inFile, nextCharInd, (inGlyph) => inGlyph !== "}");
                const nextLetterInd = contiguous(inFile, endBracketInd + 1, isWhiteSpace);
                if (inFile.substring(nextLetterInd, nextLetterInd + 4) == "from") {
                    const firstQuoteInd = contiguous(inFile, nextLetterInd + 4, isNot(isQuote));
                    const secondQuoteInd = contiguous(inFile, firstQuoteInd + 1, isNot(isQuote));
                    inForeign.push(inFile.substring(nextCharInd, secondQuoteInd + 1));
                } else {
                    const members = inFile.substring(nextCharInd + 1, endBracketInd).replaceAll(" as ", "|||").replace(/\s/g, '');
                    members.split(",").forEach(part => {
                        const renamed = part.split("|||");
                        inLocal.push({ internal: renamed, external: renamed || renamed });
                    });
                }
            } else if (isAlphaLike(nextChar)) {
                const keywordEndInd = contiguous(inFile, nextCharInd, isAlphaLike);
                const keyword = inFile.substring(nextCharInd, keywordEndInd);
                if (keyword === "default") {
                    inLocal.push({ internal: keyword, external: keyword });
                } else if (["const", "let", "var", "function", "class"].includes(keyword)) {
                    const varStartInd = contiguous(inFile, keywordEndInd + 1, isWhiteSpace);
                    const varEndInd = contiguous(inFile, varStartInd + 1, isAlphaLike);
                    const keyword = inFile.substring(varStartInd, varEndInd);
                    inLocal.push({ internal: keyword, external: keyword });
                }
            }
        }

        return pos + 7;
    } else {
        return false;
    }
};

/**
 * @param {string} inFile
 * @returns {[local: string[], foreign: string[]]}
 */
export const Exports = (inFile) => {
    let match = /** @type {number|boolean} */ (0);
    let count = 0;
    const local = /** @type {string[]} */ ([]);
    const foreign = /** @type {string[]} */ ([]);
    while (match !== false && count < 200) {
        count++;
        match = findNextExport(inFile, match, local, foreign);
    }
    return [local, foreign];
};

/**
 * @param {string|URL} inURL
 * @returns {Promise<[local: string[], foreign: string[]]>}
 */
export const FileExports = async (inURL) => {
    const resp = await fetch(inURL);
    const text = await resp.text();
    return Exports(text);
};