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

export const dynamic = 'force-dynamic'

const createAnlageSchema = z.object({
  name: z.string().min(1),
  category: z.string().optional().default('hardware'),
  purchaseDate: z.string().min(1),
  purchaseCostCents: z.number().int().positive(),
  usefulLifeYears: z.number().int().min(1).optional(),
  afaMethod: z.string().optional(),
})

// GET /api/aos/anlagen — list asset register with AfA
export async function GET() {
  try {
    const anlagen = await db.anlage.findMany({ orderBy: { purchaseDate: 'desc' } })
    const stats = {
      total: anlagen.length,
      totalPurchaseCents: anlagen.reduce((s, a) => s + a.purchaseCostCents, 0),
      totalBookValueCents: anlagen.reduce((s, a) => s + a.bookValueCents, 0),
      totalAnnualAfaCents: anlagen.reduce((s, a) => s + a.annualAfaCents, 0),
      gwgCount: anlagen.filter((a) => a.isGWG).length,
      sammelpostenCount: anlagen.filter((a) => a.isSammelposten).length,
      activeCount: anlagen.filter((a) => a.status === 'active').length,
    }
    return NextResponse.json({ anlagen, stats })
  } catch (err) {
    const msg = err instanceof Error ? err.message : 'internal server error'
    return NextResponse.json({ error: msg }, { status: 500 })
  }
}

// POST /api/aos/anlagen — create an asset with AfA computation
export async function POST(req: Request) {
  try {
    const parsed = createAnlageSchema.safeParse(await req.json())
    if (!parsed.success) {
      return NextResponse.json({ error: 'validation failed', details: parsed.error.flatten() }, { status: 400 })
    }
    const { name, category, purchaseDate, purchaseCostCents, usefulLifeYears, afaMethod } = parsed.data

    const cost = Math.round(purchaseCostCents)
    const years = usefulLifeYears ?? 3

    // GWG (Geringwertiger Wirtschaftsgüter): ≤ €800 net → Sofortabschreibung (§ 6 Abs. 2 EStG)
    const isGWG = cost <= 80000 // €800.00 in cents
    // Sammelposten: €251-€1000 net → Sammelabschreibung über 5 Jahre (§ 6 Abs. 2a EStG)
    const isSammelposten = !isGWG && cost > 80000 && cost <= 100000

    // Compute AfA
    let annualAfaCents = 0
    let bookValueCents = cost

    if (isGWG) {
      // Sofortabschreibung: full cost in year 1
      annualAfaCents = cost
      bookValueCents = 0
    } else if (isSammelposten) {
      // Sammelabschreibung: 1/5 per year over 5 years
      annualAfaCents = Math.round(cost / 5)
      bookValueCents = cost - annualAfaCents // after year 1
    } else {
      // Lineare AfA: cost / usefulLifeYears
      annualAfaCents = Math.round(cost / years)
      bookValueCents = cost - annualAfaCents // after year 1
    }

    const count = await db.anlage.count()
    const number = `ANL-2026-${String(count + 1).padStart(4, '0')}`

    const anlage = await db.anlage.create({
      data: {
        number, name: name.trim(), category: category || 'hardware',
        purchaseDate: new Date(purchaseDate),
        purchaseCostCents: cost,
        afaMethod: afaMethod ?? 'linear',
        usefulLifeYears: isGWG ? 1 : isSammelposten ? 5 : years,
        isGWG, isSammelposten,
        annualAfaCents,
        accumulatedAfaCents: annualAfaCents, // year 1
        bookValueCents,
      },
    })

    await db.auditLog.create({
      data: {
        actor: 'nora@nordlicht.digital', action: 'anlage.create', entity: 'Anlage', entityId: anlage.id,
        after: JSON.stringify({ number, name, cost, isGWG, annualAfaCents, bookValueCents }),
        hash: 'sha256:' + Math.random().toString(36).slice(2),
      },
    })

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