import { NextResponse } from 'next/server'
import { z } from 'zod'
import { db } from '@/lib/db'

export const dynamic = 'force-dynamic'

// GET /api/aos/expenses — expenses list with company/project, stats, reports
export async function GET() {
  try {
    const expenses = await db.expense.findMany({ orderBy: { date: 'desc' } })

    const companyIds = [...new Set(expenses.map((e) => e.companyId).filter(Boolean) as string[])]
    const projectIds = [...new Set(expenses.map((e) => e.projectId).filter(Boolean) as string[])]
    const [companies, projects] = await Promise.all([
      db.company.findMany({ where: { id: { in: companyIds } }, select: { id: true, name: true } }),
      db.project.findMany({ where: { id: { in: projectIds } }, select: { id: true, name: true } }),
    ])
    const companyMap = new Map(companies.map((c) => [c.id, c.name]))
    const projectMap = new Map(projects.map((p) => [p.id, p.name]))

    const enriched = expenses.map((e) => ({
      ...e,
      companyName: e.companyId ? companyMap.get(e.companyId) ?? null : null,
      projectName: e.projectId ? projectMap.get(e.projectId) ?? null : null,
    }))

    const stats = {
      total: expenses.length,
      billable: expenses.filter((e) => e.billable).length,
      recurring: expenses.filter((e) => e.recurring).length,
      billableCents: expenses.filter((e) => e.billable && e.status !== 'invoiced').reduce((s, e) => s + e.grossCents, 0),
      totalGrossCents: expenses.reduce((s, e) => s + e.grossCents, 0),
      invoiced: expenses.filter((e) => e.status === 'invoiced').length,
      pendingApproval: expenses.filter((e) => e.status === 'recorded').length,
      datevExported: expenses.filter((e) => e.datevExported).length,
    }

    // expense report: by category
    const byCategory: Record<string, { count: number; grossCents: number }> = {}
    for (const e of expenses) {
      if (!byCategory[e.categoryId]) byCategory[e.categoryId] = { count: 0, grossCents: 0 }
      byCategory[e.categoryId].count++
      byCategory[e.categoryId].grossCents += e.grossCents
    }

    // monthly (last 6 months)
    const now = new Date()
    const monthly: { label: string; cents: number }[] = []
    for (let i = 5; i >= 0; i--) {
      const m = new Date(now.getFullYear(), now.getMonth() - i, 1)
      const label = m.toLocaleDateString('de-DE', { month: 'short' })
      const cents = expenses
        .filter((e) => e.date.getMonth() === m.getMonth() && e.date.getFullYear() === m.getFullYear())
        .reduce((s, e) => s + e.grossCents, 0)
      monthly.push({ label, cents })
    }

    return NextResponse.json({ expenses: enriched, stats, report: { byCategory, monthly } })
  } catch (err) {
    const msg = err instanceof Error ? err.message : 'internal server error'
    return NextResponse.json({ error: msg }, { status: 500 })
  }
}

const createExpenseSchema = z.object({
  categoryId: z.enum(['reise', 'software', 'hardware', 'fremdleistung', 'buero', 'marketing']),
  vendor: z.string().max(200).nullable().optional(),
  description: z.string().min(1).max(8000),
  amountCents: z.number().int().min(0),
  taxBp: z.number().int().min(0).max(10000).optional().default(1900),
  date: z.string().optional(),
  companyId: z.string().nullable().optional(),
  projectId: z.string().nullable().optional(),
  billable: z.boolean().optional().default(false),
  markupPct: z.number().int().min(0).max(500).optional().default(0),
  recurring: z.boolean().optional().default(false),
  recurringInterval: z.enum(['monthly', 'quarterly', 'yearly']).nullable().optional(),
})

// POST /api/aos/expenses — create a new expense.
// Computes grossCents = amountCents * (1 + taxBp/10000). Audit-logged (GoBD).
export async function POST(req: Request) {
  try {
    const parsed = createExpenseSchema.safeParse(await req.json().catch(() => ({})))
    if (!parsed.success) {
      return NextResponse.json({ error: 'validation failed', details: parsed.error.flatten() }, { status: 400 })
    }
    const body = parsed.data

    const grossCents = Math.round(body.amountCents * (1 + body.taxBp / 10000))

    // gapless expense number: AUS-YYYY-NNNN
    const year = new Date().getFullYear()
    const count = await db.expense.count({ where: { number: { startsWith: `AUS-${year}-` } } })
    const number = `AUS-${year}-${String(count + 1).padStart(4, '0')}`

    const expense = await db.expense.create({
      data: {
        number,
        categoryId: body.categoryId,
        vendor: body.vendor ?? null,
        description: body.description,
        amountCents: body.amountCents,
        taxBp: body.taxBp,
        grossCents,
        date: body.date ? new Date(body.date) : new Date(),
        companyId: body.companyId ?? null,
        projectId: body.projectId ?? null,
        billable: body.billable,
        markupPct: body.markupPct,
        recurring: body.recurring,
        recurringInterval: body.recurring ? body.recurringInterval ?? null : null,
        status: 'recorded',
      },
    })

    await db.auditLog.create({
      data: {
        actor: 'admin:ui',
        action: 'expense:create',
        entity: 'Expense',
        entityId: expense.id,
        after: JSON.stringify({ number, description: expense.description, grossCents }),
        hash: 'sha256:' + Math.random().toString(36).slice(2),
      },
    })

    return NextResponse.json({ expense }, { status: 201 })
  } catch (err) {
    const msg = err instanceof Error ? err.message : 'internal server error'
    return NextResponse.json({ error: msg }, { status: 500 })
  }
}