// ==UserScript==
// @name         超星学习通未答题任务标记
// @version      1.0
// @match        https://mooc2-ans.chaoxing.com/mooc2-ans/mycourse/*
// @grant        GM_xmlhttpRequest
// @connect      mobilelearn.chaoxing.
// @license      MIT
// @description  自动标记超星学习通中未答题任务标记
// @author       Kaesinol
// ==/UserScript==

(() => {
    const TTL = 7 * 24 * 60 * 60 * 1000;
    const log = (...args) => console.log('[CX Answer]', ...args);
    const queue = [];
    const pending = new Map();
    const seen = new WeakSet();
    const observedDocs = new WeakSet();
    const observedFrames = new WeakSet();
    let running = false;
    let stopped = false;

    const markRed = li => li.style.outline = '2px solid red';

    function cached(id) {
        const key = `cx-answer:${id}`;
        try {
            const value = JSON.parse(localStorage.getItem(key));
            if (value?.answered === true &&
                Date.now() - value.time >= 0 &&
                Date.now() - value.time < TTL) return true;
            if (value !== null) localStorage.removeItem(key);
        } catch {
            localStorage.removeItem(key);
        }
        return false;
    }

    function enqueue(li) {
        const id = li.getAttribute('activeid');
        if (!id || seen.has(li)) return;
        seen.add(li);

        if (cached(id)) {
            log('缓存命中:', id);
            return;
        }

        if (stopped) {
            markRed(li);
            return;
        }

        if (pending.has(id)) {
            pending.get(id).lis.add(li);
            return;
        }

        const item = { id, lis: new Set([li]) };
        pending.set(id, item);
        queue.push(item);
        pump();
    }

    function pump() {
        if (running || stopped || !queue.length) return;

        const item = queue.shift();
        const { id, lis } = item;
        running = true;
        log('请求:', id, '队列剩余:', queue.length);

        GM_xmlhttpRequest({
            method: 'GET',
            url: `https://mobilelearn.chaoxing.com/v2/apis/studentQuestion/getAnswerResult?activeId=${id}`,
            withCredentials: true,

            onload(r) {
                let json;

                try {
                    json = JSON.parse(r.responseText);
                } catch (e) {
                    console.error('[CX Answer] JSON 解析失败:', id, e, r.responseText);
                    lis.forEach(markRed);
                    finish(item);
                    return;
                }

                console.log('[CX Answer] JSON:', id, json);

                if (json?.result === 0 || json?.result === '0') {
                    stopped = true;
                    log('result=0，停止所有后续请求:', json.errorMsg);

                    lis.forEach(markRed);
                    queue.forEach(item => item.lis.forEach(markRed));
                    queue.length = 0;
                    pending.clear();
                    running = false;
                    return;
                }

                if (json?.data?.isAnswered === true) {
                    localStorage.setItem(`cx-answer:${id}`, JSON.stringify({
                        answered: true,
                        time: Date.now()
                    }));
                    log('已作答，缓存 7 天:', id);
                } else {
                    log('未作答或无法获取状态，标红:', id);
                    lis.forEach(markRed);
                }

                finish(item);
            },

            onerror(e) {
                console.error('[CX Answer] 请求失败:', id, e);
                lis.forEach(markRed);
                finish(item);
            }
        });
    }

    function finish(item) {
        pending.delete(item.id);
        running = false;
        pump();
    }

    function scan(doc) {
        const list = doc.querySelectorAll('li[activeid][activestatus="1"]:not(:has(div[aria-label="签到"]))');
        list.forEach(enqueue);

        doc.querySelectorAll('iframe').forEach(frame => {
            if (!observedFrames.has(frame)) {
                observedFrames.add(frame);
                frame.addEventListener('load', () => {
                    try {
                        observe(frame.contentDocument);
                    } catch {}
                });
            }

            try {
                if (frame.contentDocument) observe(frame.contentDocument);
            } catch {}
        });
    }

    function observe(doc) {
        if (!doc || observedDocs.has(doc)) return;

        if (!doc.documentElement) {
            doc.addEventListener('DOMContentLoaded', () => observe(doc), { once: true });
            return;
        }

        observedDocs.add(doc);
        scan(doc);

        new MutationObserver(() => scan(doc)).observe(doc.documentElement, {
            childList: true,
            subtree: true
        });
    }

    log('脚本启动:', location.href);
    observe(document);
})();