// GET /api/offline/search?q=...&types=mail,calendar&limit=20
//
// THE RETRIEVAL SURFACE. This is what an AI/RAG feature calls to gather
// relevant context from the user's own mail, calendar, contacts and files
// before prompting a model - hence the `snippet` on every hit and the
// `contextBlock` convenience field, which is the same information already
// flattened into text a prompt can carry directly.
//
// Read-only: it never touches the network and never writes. Gated identically
// to the reindex route.
import { NextRequest, NextResponse } from 'next/server';
import { logger } from '@/lib/logger';
import { isSqlcipherAvailable } from '@/lib/mail-index/binding';
import { hasKeyChannel, IndexKeyError, withIndexKey } from '@/lib/mail-index/key';
import { getStoreDir } from '@/lib/mail-index/paths';
import { IndexSessionError, resolveIndexSession } from '@/lib/mail-index/reindex';
import {
  isContentType, MailIndex, MailIndexUnavailableError, type ContentType, type SearchHit,
} from '@/lib/mail-index/store';

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

/**
 * One hit as a plain text block, ready to be concatenated into a prompt.
 * Kept server-side so every caller (a chat feature, a future agent, a test)
 * formats context the same way rather than each inventing its own.
 */
function toContextBlock(hit: SearchHit): string {
  const label: Record<ContentType, string> = {
    mail: 'EMAIL', calendar: 'CALENDAR EVENT', contact: 'CONTACT', file: 'FILE',
  };
  const lines = [`[${label[hit.contentType]}] ${hit.title}`];
  if (hit.occurredAt) lines.push(`Date: ${hit.occurredAt}`);
  if (hit.people) lines.push(`People: ${hit.people}`);
  const path = hit.metadata?.path;
  if (typeof path === 'string' && path) lines.push(`Path: ${path}`);
  if (hit.snippet) lines.push(`Excerpt: ${hit.snippet}`);
  return lines.join('\n');
}

export async function GET(request: NextRequest) {
  if (!getStoreDir()) {
    return new NextResponse(null, { status: 404 });
  }
  if (!hasKeyChannel() || !isSqlcipherAvailable()) {
    return NextResponse.json(
      { error: 'Encrypted local index is unavailable in this process.', code: 'unavailable' },
      { status: 503 },
    );
  }

  const params = request.nextUrl.searchParams;
  const query = (params.get('q') ?? '').trim();
  const wantStats = params.get('stats') === 'true';

  if (!query && !wantStats) {
    return NextResponse.json({ error: 'Missing q parameter' }, { status: 400 });
  }
  if (query.length > 512) {
    return NextResponse.json({ error: 'Query too long' }, { status: 400 });
  }

  const types = (params.get('types') ?? '')
    .split(',')
    .map((t) => t.trim())
    .filter(isContentType);

  const limitRaw = Number(params.get('limit') ?? '20');
  const limit = Number.isFinite(limitRaw) ? Math.min(Math.max(Math.trunc(limitRaw), 1), 100) : 20;

  try {
    const session = await resolveIndexSession(request);
    const storeDir = getStoreDir();
    if (!storeDir) return new NextResponse(null, { status: 404 });

    const payload = await withIndexKey(session.accountId, (key) => {
      const index = MailIndex.open({ storeDir, accountId: session.accountId, key });
      try {
        const stats = index.stats();
        if (!query) return { hits: [] as SearchHit[], stats };
        return { hits: index.search({ query, types, limit }), stats: wantStats ? stats : undefined };
      } finally {
        index.close();
      }
    });

    return NextResponse.json(
      {
        ok: true,
        query,
        types: types.length > 0 ? types : 'all',
        count: payload.hits.length,
        hits: payload.hits,
        // Everything a prompt needs, pre-joined in rank order.
        contextBlock: payload.hits.map(toContextBlock).join('\n\n---\n\n'),
        ...(payload.stats ? { stats: payload.stats } : {}),
      },
      { headers: { 'Cache-Control': 'no-store' } },
    );
  } catch (error) {
    if (error instanceof IndexSessionError) {
      return NextResponse.json({ error: error.message }, { status: error.status });
    }
    if (error instanceof IndexKeyError) {
      const status = error.code === 'no-secure-storage' ? 503 : 500;
      return NextResponse.json({ error: error.message, code: error.code }, { status });
    }
    if (error instanceof MailIndexUnavailableError) {
      return NextResponse.json({ error: error.message, code: 'unavailable' }, { status: 503 });
    }
    logger.error('mail-index search failed', {
      error: error instanceof Error ? error.message : String(error),
    });
    return NextResponse.json({ error: 'Search failed' }, { status: 500 });
  }
}