/**
 * /api/admin/indexer — Status of the Postgres indexing layer.
 *
 * Compares:
 *   - docs on disk      → raw/<doc>--subagent/_index.json exists
 *   - docs in DB        → public.documents rows
 *   - chunks on disk    → sum of raw/<doc>--subagent/chunks/*.md
 *   - chunks in DB      → COUNT(*) FROM public.chunks
 *   - chunks embedded   → COUNT(*) FROM public.chunks WHERE embedding IS NOT NULL
 *   - entity_mentions   → COUNT(*) FROM public.entity_mentions
 */
import fs from "node:fs/promises";
import path from "node:path";
import { UFO_ROOT } from "@/lib/wiki";
import { pgQuery } from "@/lib/retrieval/db";

export const runtime = "nodejs";
export const dynamic = "force-dynamic";

interface DbStat {
  documents_count: number;
  chunks_count: number;
  chunks_with_embedding: number;
  entities_count: number;
  entity_mentions_count: number;
}

function json(data: unknown, status = 200) {
  return new Response(JSON.stringify(data), {
    status,
    headers: { "content-type": "application/json", "cache-control": "no-cache" },
  });
}

async function diskStats() {
  const rawRoot = path.join(UFO_ROOT, "raw");
  let docsOnDisk: string[] = [];
  try {
    const entries = await fs.readdir(rawRoot);
    docsOnDisk = entries.filter((e) => e.endsWith("--subagent"));
  } catch {
    /* missing dir */
  }
  let chunksOnDisk = 0;
  for (const d of docsOnDisk) {
    try {
      const dir = await fs.readdir(path.join(rawRoot, d, "chunks"));
      chunksOnDisk += dir.filter((f) => f.startsWith("c") && f.endsWith(".md")).length;
    } catch {
      /* missing */
    }
  }
  return { docs_on_disk: docsOnDisk.length, chunks_on_disk: chunksOnDisk };
}

export async function GET() {
  const disk = await diskStats();
  let db: DbStat | null = null;
  let dbError: string | null = null;

  try {
    const rows = await pgQuery<DbStat>(
      `SELECT
         (SELECT COUNT(*) FROM public.documents)::INT      AS documents_count,
         (SELECT COUNT(*) FROM public.chunks)::INT         AS chunks_count,
         (SELECT COUNT(*) FROM public.chunks WHERE embedding IS NOT NULL)::INT AS chunks_with_embedding,
         (SELECT COUNT(*) FROM public.entities)::INT       AS entities_count,
         (SELECT COUNT(*) FROM public.entity_mentions)::INT AS entity_mentions_count`,
      [],
    );
    db = rows[0] ?? null;
  } catch (e) {
    dbError = (e as Error).message;
  }

  return json({
    disk,
    db,
    db_error: dbError,
    gap: db
      ? {
          docs_to_index: Math.max(0, disk.docs_on_disk - db.documents_count),
          chunks_to_index: Math.max(0, disk.chunks_on_disk - db.chunks_count),
          chunks_without_embedding: Math.max(0, db.chunks_count - db.chunks_with_embedding),
          ready_for_retrieval: db.chunks_with_embedding > 0,
        }
      : null,
  });
}