#!/usr/bin/env node
/**
 * cdp_shot.js —— 用 CDP 对**已经在跑的** Chrome 某个标签页截图存成 PNG。
 * 零依赖 (Node >= 22 内置 WebSocket/fetch)。
 *
 * 用法:
 *   node tools/cdp_shot.js --match drag_ele --out /tmp/a.png            # 整页
 *   node tools/cdp_shot.js --match drag_ele --out /tmp/a.png --clip 10,68,340,243
 *   node tools/cdp_shot.js --list
 *
 * 选项:
 *   --port N         调试端口 (默认 9222)
 *   --match SUBSTR   选 url 含该子串的 page/iframe 标签页 (默认第一个)
 *   --out PATH       输出 PNG 路径 (默认 /tmp/cdp_shot.png)
 *   --clip x,y,w,h   只截该区域 (CSS px, 相对该标签页视口)
 *   --scale N        设备像素比 (默认 1)
 */
const fs = require('fs');

function arg(name, def) {
    const i = process.argv.indexOf('--' + name);
    if (i < 0) return def;
    const v = process.argv[i + 1];
    return (v === undefined || v.startsWith('--')) ? true : v;
}

class Cdp {
    constructor(ws) { this.ws = ws; this.id = 0; this.waits = new Map(); }
    static async connect(url) {
        const ws = new WebSocket(url);
        await new Promise((res, rej) => { ws.onopen = res; ws.onerror = rej; });
        const c = new Cdp(ws);
        ws.onmessage = ev => {
            const m = JSON.parse(ev.data);
            if (m.id && c.waits.has(m.id)) {
                const { res, rej } = c.waits.get(m.id);
                c.waits.delete(m.id);
                m.error ? rej(new Error(JSON.stringify(m.error))) : res(m.result);
            }
        };
        return c;
    }
    send(method, params = {}) {
        const id = ++this.id;
        this.ws.send(JSON.stringify({ id, method, params }));
        return new Promise((res, rej) => this.waits.set(id, { res, rej }));
    }
    close() { try { this.ws.close(); } catch (e) {} }
}

(async () => {
    const port = parseInt(arg('port', '9222'), 10);
    if (arg('list', false)) {
        const t = await (await fetch(`http://127.0.0.1:${port}/json/list`)).json();
        for (const x of t) console.log(`${x.type}\t${(x.url || '').slice(0, 120)}\t${x.id}`);
        return;
    }
    const match = arg('match', null);
    const targets = (await (await fetch(`http://127.0.0.1:${port}/json/list`)).json())
        .filter(t => t.type === 'page' || t.type === 'iframe');
    let target = match ? targets.find(t => (t.url || '').includes(match)) : null;
    if (!target) target = targets[0];
    if (!target) throw new Error('没有可用标签页');

    const cdp = await Cdp.connect(target.webSocketDebuggerUrl);
    const params = { format: 'png', captureBeyondViewport: !!arg('clip', false) };
    const clipRaw = arg('clip', null);
    if (clipRaw) {
        const [x, y, w, h] = String(clipRaw).split(',').map(Number);
        params.clip = { x, y, width: w, height: h, scale: parseFloat(arg('scale', '1')) };
    }
    const r = await cdp.send('Page.captureScreenshot', params);
    const out = arg('out', '/tmp/cdp_shot.png');
    fs.writeFileSync(out, Buffer.from(r.data, 'base64'));
    console.log(JSON.stringify({ ok: true, out, target: { url: target.url, id: target.id } }));
    cdp.close();
})().catch(e => { console.error(String(e)); process.exit(1); });