import { NextRequest, NextResponse } from 'next/server';
import { db, schema } from '@/lib/db';
import { eq, desc } from 'drizzle-orm';
import { getSession } from '@/lib/auth';
import { normalizeTier } from '@/lib/plan-access';
import { estimateConversionTokens } from '@/lib/conversion-pricing';

// GET /api/admin/stats — users enriched with project counts + token totals (admin only)
export async function GET(request: NextRequest) {
  try {
    const accessToken = request.cookies.get('scriba.access_token')?.value;
    const session = await getSession(accessToken);
    if (!session) return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });

    const currentUser = await db.query.users.findFirst({ where: eq(schema.users.id, session.user.id) });
    if (!currentUser || currentUser.role !== 'admin') {
      return NextResponse.json({ error: 'Forbidden' }, { status: 403 });
    }

    const users = await db.query.users.findMany({ orderBy: [desc(schema.users.createdAt)] });
    const companies = await db.query.companies.findMany({
      columns: { id: true, package: true },
    });
    const projects = await db.query.projects.findMany({
      columns: { id: true, userId: true, status: true, tokensUsed: true, totalLines: true, sourceLanguage: true, createdAt: true },
    });
    const companyPackageById = new Map(companies.map((company) => [company.id, company.package]));

    // Build per-user stats
    const enriched = users.map(u => {
      const userProjects = projects.filter(p => p.userId === u.id);
      const effectiveTier = normalizeTier(
        (u.companyId ? companyPackageById.get(u.companyId) : null) ?? u.tier
      );
      const totalTokens = userProjects.reduce((s, p) => {
        return s + estimateConversionTokens({
          tokensUsed: p.tokensUsed,
          totalLines: p.totalLines,
          sourceLanguage: p.sourceLanguage,
        });
      }, 0);
      return {
        ...u,
        tier: effectiveTier,
        projectCount: userProjects.length,
        activeProjects: userProjects.filter(p => ['analyzing', 'converting', 'validating'].includes(p.status ?? '')).length,
        completedProjects: userProjects.filter(p => p.status === 'completed').length,
        totalTokens,
      };
    });

    // Aggregate stats (clients only)
    const byTier = { starter: 0, professional: 0, enterprise: 0 };
    for (const u of users) {
      if (u.role !== 'client') continue;
      const effectiveTier = normalizeTier(
        (u.companyId ? companyPackageById.get(u.companyId) : null) ?? u.tier
      );
      byTier[effectiveTier] += 1;
    }

    return NextResponse.json({ users: enriched, byTier, totalProjects: projects.length });
  } catch (error) {
    console.error('Admin stats error:', error);
    return NextResponse.json({ error: 'Failed to fetch stats' }, { status: 500 });
  }
}