(function() {
    let playerContainer = null;

    function createPlayer() {
        if (playerContainer) return;

        playerContainer = document.createElement('div');
        playerContainer.id = 'readvox-player';

        const playerIframe = document.createElement('iframe');
        playerIframe.src = chrome.runtime.getURL('popup.html');
        playerIframe.className = 'player-iframe';

        playerContainer.appendChild(playerIframe);
        document.body.appendChild(playerContainer);

        makeDraggable(playerContainer);
    }

    function removePlayer() {
        if (playerContainer) {
            playerContainer.remove();
            playerContainer = null;
        }
    }

    function makeDraggable(element) {
        let pos1 = 0, pos2 = 0, pos3 = 0, pos4 = 0;

        const dragMouseDown = (e) => {
            e = e || window.event;

            pos3 = e.clientX;
            pos4 = e.clientY;
            document.onmouseup = closeDragElement;
            document.onmousemove = elementDrag;
        };

        const elementDrag = (e) => {
            e = e || window.event;
            e.preventDefault();

            pos1 = pos3 - e.clientX;
            pos2 = pos4 - e.clientY;
            pos3 = e.clientX;
            pos4 = e.clientY;

            element.style.top = (element.offsetTop - pos2) + "px";
            element.style.left = (element.offsetLeft - pos1) + "px";
        };

        const closeDragElement = () => {
            document.onmouseup = null;
            document.onmousemove = null;
        };

        element.addEventListener('mousedown', dragMouseDown);
    }

    // ---------- Grammar Highlight Logic ----------

    const PARAGRAPH_SELECTORS = 'p, article p, section p, div';

    function callBackend(payload) {
        return new Promise((resolve, reject) => {
            chrome.runtime.sendMessage(
                { type: 'GRAMMAR_API_REQUEST', ...payload },
                (response) => {
                    if (chrome.runtime.lastError) {
                        reject(new Error(chrome.runtime.lastError.message));
                        return;
                    }
                    if (!response) {
                        reject(new Error('后台未返回数据。'));
                        return;
                    }
                    if (response.error) {
                        reject(new Error(response.error));
                        return;
                    }
                    resolve(response);
                }
            );
        });
    }

    function isParagraphElement(node) {
        return (
            node &&
            node.nodeType === Node.ELEMENT_NODE &&
            node.matches &&
            node.matches(PARAGRAPH_SELECTORS)
        );
    }

    function collectParagraphNodes(container) {
        if (!container || container.nodeType !== Node.ELEMENT_NODE) return [];
        const paragraphs = Array.from(container.querySelectorAll('p')).filter(
            (el) => el.innerText.trim()
        );
        if (paragraphs.length > 0) return paragraphs;
        return [container];
    }

    function buildParagraphTarget(nodes) {
        const usableNodes = nodes.filter(
            (node) => node && node.innerText && node.innerText.trim()
        );
        if (usableNodes.length === 0) {
            throw new Error('未找到可用段落文本。');
        }

        const originals = usableNodes.map((node) => node.innerHTML);
        const paragraphs = usableNodes.map((node) => node.innerText.trim());

        return {
            payload: { paragraphs },
            apply(htmlList) {
                const list = Array.isArray(htmlList) ? htmlList : [];
                usableNodes.forEach((node, idx) => {
                    const html = list[idx];
                    if (typeof html === 'string' && html.trim()) {
                        node.innerHTML = html;
                    }
                });
            },
            restore() {
                usableNodes.forEach((node, idx) => {
                    node.innerHTML = originals[idx];
                });
            }
        };
    }

    function getSelectionTarget() {
        const selection = window.getSelection();
        if (!selection || selection.rangeCount === 0) {
            throw new Error('请先在页面中选择一段文本。');
        }
        const range = selection.getRangeAt(0);
        if (range.collapsed) {
            throw new Error('所选文本为空。');
        }

        const root =
            range.commonAncestorContainer.nodeType === Node.ELEMENT_NODE
                ? range.commonAncestorContainer
                : range.commonAncestorContainer.parentElement || document.body;

        const walker = document.createTreeWalker(root, NodeFilter.SHOW_ELEMENT, {
            acceptNode(node) {
                if (!(node instanceof HTMLElement)) return NodeFilter.FILTER_SKIP;
                return isParagraphElement(node) && range.intersectsNode(node)
                    ? NodeFilter.FILTER_ACCEPT
                    : NodeFilter.FILTER_SKIP;
            }
        });

        const nodes = [];
        let current = walker.nextNode();
        while (current) {
            nodes.push(current);
            current = walker.nextNode();
        }

        if (nodes.length === 0) {
            const fallback =
                (range.commonAncestorContainer.nodeType === Node.ELEMENT_NODE
                    ? range.commonAncestorContainer
                    : range.commonAncestorContainer.parentElement) || document.body;
            nodes.push(fallback.closest(PARAGRAPH_SELECTORS) || fallback);
        }

        return buildParagraphTarget(nodes);
    }

    function getParagraphTarget() {
        const selection = window.getSelection();
        let node =
            selection && selection.rangeCount > 0
                ? selection.getRangeAt(0).commonAncestorContainer
                : document.activeElement;

        if (!node) {
            node = document.body;
        }

        if (node.nodeType === Node.TEXT_NODE) {
            node = node.parentElement;
        }

        const paragraph =
            node.closest(PARAGRAPH_SELECTORS) || document.querySelector('p') || document.body;

        return buildParagraphTarget([paragraph]);
    }

    function getArticleTarget() {
        const container =
            document.querySelector('article') ||
            document.querySelector('main') ||
            document.body;

        const nodes = collectParagraphNodes(container).filter(
            (node) => node.innerText.trim()
        );

        return buildParagraphTarget(nodes);
    }

    async function handleAnalyze(mode) {
        let targetGetter;
        switch (mode) {
            case 'selection':
                targetGetter = getSelectionTarget;
                break;
            case 'paragraph':
                targetGetter = getParagraphTarget;
                break;
            case 'page':
            case 'article':
                targetGetter = getArticleTarget;
                break;
            default:
                throw new Error('未知的分析模式。');
        }

        const target = targetGetter();
        try {
            const response = await callBackend(target.payload);
            const htmlList =
                response.highlightedHtmls ||
                (response.highlightedHtml ? [response.highlightedHtml] : []);
            if (!htmlList || htmlList.length === 0) {
                throw new Error('后台未返回数据。');
            }
            target.apply(htmlList);
            return {};
        } catch (error) {
            target.restore?.();
            throw error;
        }
    }

    // ---------- Message Handler ----------

    chrome.runtime.onMessage.addListener((request, sender, sendResponse) => {
        if (request.action === "activatePlayer") {
            createPlayer();
        } else if (request.action === "deactivatePlayer") {
            removePlayer();
        } else if (request.type === 'EXECUTE_GRAMMAR') {
            handleAnalyze(request.mode)
                .then(() => sendResponse({ success: true }))
                .catch((error) => {
                    sendResponse({ error: error.message || '未知错误' });
                });
            return true;
        }
    });
})();