"""Playwright 页面抓取工具。

对外仅暴露两个动作：
- open_page(url, wait_ms): 打开页面，返回 page_id
- query(page_id, selector): 选中节点并提取文字、图片 URL 与属性

实现上内部常驻一个 Browser；每次 open_page 创建独立 BrowserContext 和 Page，
query 完成后自动释放对应资源。
"""

from __future__ import annotations

import asyncio
import threading
import uuid
from dataclasses import dataclass

from playwright.async_api import Browser, BrowserContext, Page, async_playwright


@dataclass
class NodeSnapshot:
    """页面节点快照。"""

    tag: str
    text: str
    image_urls: list[str]
    attrs: dict[str, str]


@dataclass
class _PageSession:
    context: BrowserContext
    page: Page


class _BrowserRuntime:
    """在后台事件循环中管理 Playwright 生命周期。"""

    def __init__(self) -> None:
        self._thread: threading.Thread | None = None
        self._loop: asyncio.AbstractEventLoop | None = None
        self._ready = threading.Event()
        self._lock = threading.RLock()
        self._playwright = None
        self._browser: Browser | None = None
        self._pages: dict[str, _PageSession] = {}

    def _thread_main(self) -> None:
        loop = asyncio.new_event_loop()
        asyncio.set_event_loop(loop)
        self._loop = loop
        self._ready.set()
        loop.run_forever()

        pending = asyncio.all_tasks(loop)
        for task in pending:
            task.cancel()

        if pending:
            loop.run_until_complete(asyncio.gather(*pending, return_exceptions=True))

        if self._browser is not None:
            loop.run_until_complete(self._browser.close())
            self._browser = None

        if self._playwright is not None:
            loop.run_until_complete(self._playwright.stop())
            self._playwright = None

        loop.run_until_complete(loop.shutdown_asyncgens())
        loop.close()

    def _ensure_thread(self) -> None:
        with self._lock:
            if self._thread and self._thread.is_alive():
                return

            self._thread = threading.Thread(
                target=self._thread_main,
                name="offerpie-playwright",
                daemon=True,
            )
            self._thread.start()
            self._ready.wait()

    def _run(self, coro):
        self._ensure_thread()
        assert self._loop is not None
        future = asyncio.run_coroutine_threadsafe(coro, self._loop)
        return future.result()

    async def _ensure_browser(self) -> Browser:
        if self._browser is not None:
            return self._browser

        if self._playwright is None:
            self._playwright = await async_playwright().start()

        self._browser = await self._playwright.chromium.launch(headless=True)
        return self._browser

    async def _open_page(self, url: str, wait_ms: int) -> str:
        browser = await self._ensure_browser()
        context = await browser.new_context()
        page = await context.new_page()
        await page.goto(url, wait_until="domcontentloaded", timeout=30000)
        if wait_ms > 0:
            await page.wait_for_timeout(wait_ms)

        page_id = uuid.uuid4().hex
        self._pages[page_id] = _PageSession(context=context, page=page)
        return page_id

    async def _query(self, page_id: str, selector: str) -> list[NodeSnapshot]:
        session = self._pages.get(page_id)
        if session is None:
            raise KeyError(f"Unknown page_id: {page_id}")

        try:
            locator = session.page.locator(selector)
            payload = await locator.evaluate_all(
                r"""(elements) => elements.map((el) => {
                    const attrs = {};
                    for (const attr of Array.from(el.attributes || [])) {
                        attrs[attr.name] = attr.value;
                    }

                    const imageUrls = [];
                    const addImageUrl = (url) => {
                        if (!url) return;
                        try {
                            const absUrl = new URL(url, location.href).href;
                            if (
                                absUrl.startsWith('data:') ||
                                absUrl.startsWith('blob:') ||
                                absUrl === 'about:blank'
                            ) {
                                return;
                            }
                            imageUrls.push(absUrl);
                        } catch {
                            if (
                                url.startsWith('data:') ||
                                url.startsWith('blob:') ||
                                url === 'about:blank'
                            ) {
                                return;
                            }
                            imageUrls.push(url);
                        }
                    };

                    const resolveImageUrl = (img) => {
                        const candidates = [
                            img.getAttribute('data-src'),
                            img.getAttribute('data-original'),
                            img.getAttribute('data-croporisrc'),
                            img.currentSrc,
                            img.src,
                            img.getAttribute('src'),
                        ];

                        const srcset = img.getAttribute('srcset');
                        if (srcset) {
                            for (const part of srcset.split(',')) {
                                const candidate = part.trim().split(/\s+/)[0];
                                candidates.push(candidate);
                            }
                        }

                        for (const candidate of candidates) {
                            if (!candidate) continue;
                            if (
                                candidate.startsWith('data:') ||
                                candidate.startsWith('blob:') ||
                                candidate === 'about:blank'
                            ) {
                                continue;
                            }
                            try {
                                const absUrl = new URL(candidate, location.href).href;
                                if (
                                    absUrl.startsWith('data:') ||
                                    absUrl.startsWith('blob:') ||
                                    absUrl === 'about:blank'
                                ) {
                                    continue;
                                }
                                return absUrl;
                            } catch {
                                return candidate;
                            }
                        }

                        return null;
                    };

                    if (el.tagName === 'IMG') {
                        addImageUrl(resolveImageUrl(el));
                    }

                    for (const img of Array.from(el.querySelectorAll('img'))) {
                        addImageUrl(resolveImageUrl(img));
                    }

                    const text = (el.innerText || el.textContent || '').trim();

                    return {
                        tag: (el.tagName || '').toLowerCase(),
                        text,
                        image_urls: Array.from(new Set(imageUrls)),
                        attrs,
                    };
                })"""
            )
            return [
                NodeSnapshot(
                    tag=item.get("tag", ""),
                    text=item.get("text", ""),
                    image_urls=list(item.get("image_urls", [])),
                    attrs=dict(item.get("attrs", {})),
                )
                for item in payload
            ]
        finally:
            await session.page.close()
            await session.context.close()
            self._pages.pop(page_id, None)


_runtime = _BrowserRuntime()


def open_page(url: str, wait_ms: int = 3000) -> str:
    """打开页面并返回 page_id。"""
    return _runtime._run(_runtime._open_page(url, wait_ms))


def query(page_id: str, selector: str) -> list[NodeSnapshot]:
    """按选择器抓取节点，提取文本、图片 URL 与属性。"""
    items = _runtime._run(_runtime._query(page_id, selector))
    seen_urls: set[str] = set()

    for item in items:
        unique_urls: list[str] = []
        for url in item.image_urls:
            if url in seen_urls:
                continue
            seen_urls.add(url)
            unique_urls.append(url)
        item.image_urls = unique_urls

    return items