/**
 * Patch: replace countDocuments() with estimatedDocumentCount() in
 * federation-setup.js followers/following collection dispatchers.
 *
 * All four calls are already wrapped in cachedQuery(), but on cache miss
 * countDocuments() runs a full aggregate scan. estimatedDocumentCount()
 * reads collection metadata — O(1).
 *
 * Covers: ap_followers (×2) and ap_following (×2) in collection pagination
 * and counter dispatchers.
 */

import { access, readFile, writeFile } from "node:fs/promises";

const candidates = [
  "node_modules/@rmdes/indiekit-endpoint-activitypub/lib/federation-setup.js",
  "node_modules/@indiekit/indiekit/node_modules/@rmdes/indiekit-endpoint-activitypub/lib/federation-setup.js",
];

const MARKER = "// [patch] collection-count-estimate";

const replacements = [
  {
    old: `          const t = await collections.ap_followers.countDocuments();
          return [d, t];`,
    new: `          const t = await collections.ap_followers.estimatedDocumentCount(); ${MARKER}
          return [d, t];`,
  },
  {
    old: `        return await collections.ap_followers.countDocuments();`,
    new: `        return await collections.ap_followers.estimatedDocumentCount(); ${MARKER}`,
  },
  {
    old: `          const t = await collections.ap_following.countDocuments();
          return [d, t];`,
    new: `          const t = await collections.ap_following.estimatedDocumentCount(); ${MARKER}
          return [d, t];`,
  },
  {
    old: `        return await collections.ap_following.countDocuments();`,
    new: `        return await collections.ap_following.estimatedDocumentCount(); ${MARKER}`,
  },
];

async function exists(p) {
  try { await access(p); return true; } catch { return false; }
}

let patched = false;
for (const filePath of candidates) {
  if (!(await exists(filePath))) continue;
  let src = await readFile(filePath, "utf8");
  if (src.includes(MARKER)) {
    console.log(`[postinstall] patch-ap-collection-count-estimate: already applied in ${filePath}`);
    patched = true;
    break;
  }
  let changed = 0;
  for (const { old, new: replacement } of replacements) {
    if (src.includes(old)) {
      src = src.replace(old, replacement);
      changed++;
    }
  }
  if (changed === 0) {
    console.log(`[postinstall] patch-ap-collection-count-estimate: target snippets not found in ${filePath}`);
    continue;
  }
  await writeFile(filePath, src, "utf8");
  console.log(`[postinstall] patch-ap-collection-count-estimate: applied ${changed}/4 replacements in ${filePath}`);
  patched = true;
  break;
}

if (!patched) {
  console.log("[postinstall] patch-ap-collection-count-estimate: no target file found");
}