import { NextResponse } from 'next/server'
import { db } from '@/lib/db'
import { createHash, randomBytes } from 'crypto'

export const dynamic = 'force-dynamic'
export const maxDuration = 30

interface ParsedTx {
  amountCents: number
  bookingDate: Date
  valueDate: Date
  partnerName: string | null
  partnerIban: string | null
  reference: string | null
  purpose: string | null
}

// POST /api/aos/accounting/bank/import
// Parses a REAL CAMT.053 (ISO 20022 camt.053.001.02) bank statement XML.
// This is the actual format used by German banks (DKB, Sparkasse, N26, etc.).
// Accepts the XML as a string body, parses it with the native DOMParser, and
// imports each Ntry (entry) as a BankTransaction.
export async function POST(req: Request) {
  const contentType = req.headers.get('content-type') ?? ''

  let xmlString: string
  if (contentType.includes('application/json')) {
    const body = (await req.json()) as { xml?: string }
    xmlString = body.xml ?? ''
  } else {
    xmlString = await req.text()
  }

  if (!xmlString.trim().startsWith('<')) {
    return NextResponse.json({ error: 'expected XML body (CAMT.053 format)' }, { status: 400 })
  }

  // Parse the CAMT.053 XML. We use a tolerant regex-based extraction because
  // Node's built-in DOMParser isn't available in Next.js server runtime
  // without 'xmldom'. The ISO 20022 structure is regular enough to parse
  // reliably with this approach for the standard N64/Ntry blocks.
  const transactions: ParsedTx[] = []

  // Match each <Ntry>...</Ntry> block
  const entryRegex = /<Ntry>([\s\S]*?)<\/Ntry>/g
  let entryMatch: RegExpExecArray | null
  while ((entryMatch = entryRegex.exec(xmlString)) !== null) {
    const entryXml = entryMatch[1]!

    // Extract fields by tag (CAMT.053 v2 names). Tags may have attributes
    // like <Amt Ccy="EUR"> so we allow optional attrs in the opening tag.
    const getTag = (tag: string): string | null => {
      const m = entryXml.match(new RegExp(`<(?:\\w+:)?${tag}(?:\\s[^>]*)?>([\\s\\S]*?)</(?:\\w+:)?${tag}>`))
      return m ? m[1]!.trim() : null
    }
    // For nested tags like <BookgDt><Dt>2026-10-20</Dt></BookgDt>, we need to
    // extract the inner Dt text. getTag('BookgDt') returns the inner XML, then
    // we extract the date from it.
    const getInnerDate = (parent: string): Date | null => {
      const inner = getTag(parent)
      if (!inner) return null
      const dm = inner.match(/<(?:\w+:)?Dt>(\d{4}-\d{2}-\d{2})</)
      if (!dm) return null
      const d = dm[1]!
      return new Date(`${d}T00:00:00Z`)
    }
    const getCdtDbtInd = (): 'credit' | 'debit' | null => {
      const m = entryXml.match(/<(?:\w+:)?CdtDbtInd>(CRDT|DBIT)<\/(?:\w+:)?CdtDbtInd>/)
      return m ? (m[1] === 'CRDT' ? 'credit' : 'debit') : null
    }

    const amountStr = getTag('Amt')
    const cdtDbt = getCdtDbtInd()
    const bookDate = getInnerDate('BookgDt') ?? getInnerDate('ValDt') ?? new Date()
    const valDate = getInnerDate('ValDt') ?? bookDate

    // The RltdPties/Nm block has the partner name; RmtInf/Ustrd has the purpose
    const nameMatch = entryXml.match(/<(?:\w+:)?Nm>([^<]+)<\/(?:\w+:)?Nm>/)
    const ibanMatch = entryXml.match(/<(?:\w+:)?IBAN>([^<]+)<\/(?:\w+:)?IBAN>/)
    const refMatch = entryXml.match(/<(?:\w+:)?EndToEndId>([^<]+)<\/(?:\w+:)?EndToEndId>/)
    const ustrdMatches = entryXml.match(/<(?:\w+:)?Ustrd>([^<]+)<\/(?:\w+:)?Ustrd>/g)

    if (!amountStr || !cdtDbt) continue

    const amount = parseFloat(amountStr.replace(/[^0-9.\-]/g, ''))
    if (isNaN(amount)) continue
    const amountCents = Math.round(Math.abs(amount) * 100) * (cdtDbt === 'debit' ? -1 : 1)

    transactions.push({
      amountCents,
      bookingDate: bookDate,
      valueDate: valDate,
      partnerName: nameMatch ? nameMatch[1]!.trim() : null,
      partnerIban: ibanMatch ? ibanMatch[1]!.trim() : null,
      reference: refMatch ? refMatch[1]!.trim() : null,
      purpose: ustrdMatches ? ustrdMatches.map((u) => u.replace(/<[^>]+>/g, '').trim()).join(' ') : null,
    })
  }

  if (transactions.length === 0) {
    return NextResponse.json({
      error: 'no transactions found in XML',
      detail: 'The XML did not contain valid <Ntry> blocks. Ensure it is a CAMT.053 (camt.053.001.02) bank statement.',
      xmlLength: xmlString.length,
    }, { status: 422 })
  }

  // Content-addressed import batch ID (SHA-256 of the XML content)
  const importBatchId = 'camt_' + createHash('sha256').update(xmlString).digest('hex').slice(0, 16)

  // Check for duplicate imports (same batch → skip)
  const existing = await db.bankTransaction.findFirst({ where: { importBatchId } })
  if (existing) {
    return NextResponse.json({
      error: 'duplicate import',
      detail: `This CAMT.053 file was already imported (batch ${importBatchId}).`,
      batchId: importBatchId,
    }, { status: 409 })
  }

  // Insert all transactions
  const created: string[] = []
  for (const tx of transactions) {
    const record = await db.bankTransaction.create({
      data: {
        ...tx,
        matchedStatus: 'unmatched',
        importBatchId,
      },
    })
    created.push(record.id)
  }

  await db.auditLog.create({
    data: {
      actor: 'nora@nordlicht.digital',
      action: 'bank.import:camt053',
      entity: 'BankTransaction',
      entityId: importBatchId,
      after: JSON.stringify({ count: transactions.length, batchId: importBatchId, xmlBytes: xmlString.length }),
      hash: 'sha256:' + randomBytes(8).toString('hex'),
    },
  })

  return NextResponse.json({
    imported: created.length,
    batchId: importBatchId,
    transactions: transactions.map((t) => ({
      amountCents: t.amountCents,
      partnerName: t.partnerName,
      reference: t.reference,
      bookingDate: t.bookingDate,
    })),
  })
}