/**
 * Patch: make q=category return distinct tags from MongoDB posts collection.
 *
 * In queryController, line 28 rewrites q === "category" → "categories" before
 * the switch, so the new case label must be "categories" (not "category").
 * The default branch returns config.categories (always []) because
 * publication.categories is not configured. This patch inserts a
 * case "categories": before default: that queries the posts collection instead.
 *
 * postsCollection may be undefined (no MongoDB). The ternary provides a []
 * fallback consistent with the guard pattern used throughout query.js.
 */

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

const MARKER = "// [patch] micropub-category-from-posts";

const candidates = [
  "node_modules/@indiekit/endpoint-micropub/lib/controllers/query.js",
  "node_modules/@indiekit/indiekit/node_modules/@indiekit/endpoint-micropub/lib/controllers/query.js",
];

const OLD_SNIPPET = `        break;
      }

      default: {
        // Query configuration value (can be filtered, limited and offset)
        if (config[q]) {`;

const NEW_SNIPPET = `        break;
      }

      case "categories": { ${MARKER}
        const cats = postsCollection
          ? (await postsCollection.distinct("properties.category")).filter(Boolean).sort()
          : [];
        response.json({
          categories: queryConfig(cats, { filter: filter?.toLowerCase(), limit, offset }),
        });
        break;
      }

      default: {
        // Query configuration value (can be filtered, limited and offset)
        if (config[q]) {`;

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

let totalPatched = 0;
let totalChecked = 0;

for (const filePath of candidates) {
  if (!(await exists(filePath))) continue;
  totalChecked++;

  const source = await readFile(filePath, "utf8");
  if (source.includes(MARKER)) {
    console.log(`[postinstall] patch-micropub-category-from-posts: already applied to ${filePath}`);
    continue;
  }

  if (!source.includes(OLD_SNIPPET)) {
    console.warn(`[postinstall] patch-micropub-category-from-posts: snippet not found in ${filePath} (upstream changed?)`);
    continue;
  }

  const updated = source.replace(OLD_SNIPPET, NEW_SNIPPET);
  await writeFile(filePath, updated, "utf8");
  console.log(`[postinstall] Applied patch-micropub-category-from-posts to ${filePath}`);
  totalPatched++;
}

if (totalChecked === 0) {
  console.log("[postinstall] patch-micropub-category-from-posts: no target files found");
} else if (totalPatched === 0) {
  console.log("[postinstall] patch-micropub-category-from-posts: already up to date");
} else {
  console.log(`[postinstall] patch-micropub-category-from-posts: patched ${totalPatched} file(s)`);
}