#!/usr/bin/env node
/**
 * Pull the CSV from the headless browser via CDP and assemble it on disk.
 *
 * Usage:
 *   tsx scripts/_dump-browser-csv.ts <viewId> <expression> <out-path>
 *
 * Example:
 *   tsx scripts/_dump-browser-csv.ts stable-browser-session/xxx 'window.__hbCsv' scripts/nss-hex-bolts.csv
 */
import { writeFileSync } from "node:fs";

const [, , viewIdExpr, expression, outPath] = process.argv;
if (!viewIdExpr || !expression || !outPath) {
  console.error("Usage: tsx _dump-browser-csv.ts <viewId> <expr> <out>");
  process.exit(1);
}

const port = 9222;
const host = "127.0.0.1";

// Discover the page WebSocket URL.
async function getWsUrl(): Promise<string> {
  const r = await fetch(`http://${host}:${port}/json`);
  const tabs = (await r.json()) as Array<{ id: string; webSocketDebuggerUrl: string }>;
  const target = tabs.find((t) => t.id.startsWith(viewIdExpr));
  if (!target) throw new Error(`tab not found for viewId prefix ${viewIdExpr}`);
  return target.webSocketDebuggerUrl;
}

async function evalChunked(ws: WebSocket, expression: string): Promise<string> {
  const CHUNK = 6000;
  const full = await evalOnce(ws, expression);
  const out: string[] = [];
  for (let i = 0; i < full.length; i += CHUNK) {
    out.push(full.substring(i, i + CHUNK));
  }
  return out.join("");
}

function evalOnce(
  ws: WebSocket,
  expression: string,
): Promise<string> {
  return new Promise((resolve, reject) => {
    const id = Math.floor(Math.random() * 1e9);
    const onMsg = (ev: MessageEvent) => {
      const msg = JSON.parse(ev.data);
      if (msg.id !== id) return;
      ws.removeEventListener("message", onMsg);
      if (msg.error) reject(new Error(msg.error.message));
      else resolve(msg.result?.value ?? "");
    };
    ws.addEventListener("message", onMsg);
    ws.send(
      JSON.stringify({
        id,
        method: "Runtime.evaluate",
        params: { expression, returnByValue: true },
      }),
    );
  });
}

async function main() {
  const wsUrl = await getWsUrl();
  const ws = new WebSocket(wsUrl);
  await new Promise<void>((resolve, reject) => {
    ws.addEventListener("open", () => resolve());
    ws.addEventListener("error", (e) => reject(new Error(String(e))));
  });
  const csv = await evalChunked(ws, expression);
  writeFileSync(outPath, csv);
  console.log(`Wrote ${csv.length} bytes to ${outPath}`);
  ws.close();
}

main().catch((e) => {
  console.error("FATAL:", e);
  process.exit(1);
});