import { NextRequest, NextResponse } from 'next/server';
import { redis } from '@/lib/redis';
import { prisma } from '@/lib/prisma';
import { parseRedisInt, getCurrentPeriodKey } from '@/lib/quota-utils';

function verifyCronAuth(req: NextRequest): boolean {
  const cronSecret = process.env.CRON_SECRET;
  if (!cronSecret) {
    console.error('[sync-usage] CRON_SECRET env var is required but not set');
    return false;
  }
  const authHeader = req.headers.get('authorization');
  return authHeader === `Bearer ${cronSecret}`;
}

async function scanKeys(pattern: string): Promise<string[]> {
  const keys: string[] = [];
  let cursor = '0';
  do {
    const [nextCursor, batch] = await redis.scan(
      cursor,
      'MATCH',
      pattern,
      'COUNT',
      200,
    );
    cursor = nextCursor;
    keys.push(...batch);
  } while (cursor !== '0');
  return keys;
}

function parseUsageKey(key: string, period: string): { userId: string; feature: string } | null {
  const suffix = `:${period}`;
  if (!key.endsWith(suffix)) return null;
  if (key.endsWith(':tokens')) return null;

  const prefix = key.slice(0, key.length - suffix.length);
  const firstColon = prefix.indexOf(':');
  if (firstColon === -1) return null;

  const afterPrefix = prefix.slice(firstColon + 1);
  const lastColon = afterPrefix.lastIndexOf(':');
  if (lastColon === -1) return null;

  const userId = afterPrefix.slice(0, lastColon);
  const feature = afterPrefix.slice(lastColon + 1);

  if (!userId || !feature) return null;
  return { userId, feature };
}

export async function POST(req: NextRequest) {
  if (!verifyCronAuth(req)) {
    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
  }

  try {
    const period = getCurrentPeriodKey();
    const pattern = `usage:*:${period}`;
    const keys = await scanKeys(pattern);

    let synced = 0;
    let errors = 0;

    for (const key of keys) {
      if (key.endsWith(':tokens')) continue;

      try {
        const parsed = parseUsageKey(key, period);
        if (!parsed) continue;

        const { userId, feature } = parsed;

        const [counter, tokens] = await Promise.all([
          redis.get(key),
          redis.get(`${key}:tokens`),
        ]);

        const periodStart = new Date(`${period}-01`);
        const periodEnd = new Date(
          periodStart.getFullYear(),
          periodStart.getMonth() + 1,
          1,
        );

        await prisma.usageLog.upsert({
          where: {
            userId_feature_periodStart: {
              userId,
              feature,
              periodStart,
            },
          },
          create: {
            userId,
            feature,
            periodStart,
            periodEnd,
            requestsCount: parseRedisInt(counter),
            tokensUsed: parseRedisInt(tokens),
          },
          update: {
            requestsCount: parseRedisInt(counter),
            tokensUsed: parseRedisInt(tokens),
            syncedAt: new Date(),
          },
        });

        synced++;
      } catch (err) {
        errors++;
        console.error(`[sync-usage] Failed to sync key ${key}:`, err);
      }
    }

    return NextResponse.json({ synced, errors, total: keys.length });
  } catch (error) {
    console.error('[sync-usage] Error:', error);
    return NextResponse.json({ error: 'Sync failed' }, { status: 500 });
  }
}