import { createClient } from '@/lib/supabase/server'
import { NextResponse } from 'next/server'
import { ensureInitialized } from '@/lib/init'
import { validateBody } from '@/lib/api/validate'
import { AttachDocumentSchema } from '@/lib/api/schemas'
import { requireCompanyId } from '@/lib/company/context'
import { requireWritePermission } from '@/lib/auth/require-write'
import { appendProcessingHistory } from '@/lib/processing-history/append'

ensureInitialized()

/**
 * POST /api/transactions/[id]/attach-document
 *
 * Pin an unmatched document_attachments row to a bank transaction. Lets users
 * (or AI agents via MCP) bind a forwarded/uploaded invoice or receipt before
 * the transaction is categorized. When the transaction is later categorized,
 * the categorize route propagates the link to document_attachments.journal_entry_id.
 *
 * Idempotent — overwrites any existing link.
 */
export async function POST(
  request: Request,
  { params }: { params: Promise<{ id: string }> }
) {
  const supabase = await createClient()
  const { id: transactionId } = await params

  const { data: { user } } = await supabase.auth.getUser()
  if (!user) return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })

  const writeCheck = await requireWritePermission(supabase, user.id)
  if (!writeCheck.ok) return writeCheck.response

  const companyId = await requireCompanyId(supabase, user.id)

  const validation = await validateBody(request, AttachDocumentSchema)
  if (!validation.success) return validation.response
  const { document_id } = validation.data

  const { data: transaction, error: txError } = await supabase
    .from('transactions')
    .select('id, document_id')
    .eq('id', transactionId)
    .eq('company_id', companyId)
    .maybeSingle()

  if (txError || !transaction) {
    return NextResponse.json({ error: 'Transaction not found' }, { status: 404 })
  }

  const previousDocumentId = (transaction.document_id as string | null) ?? null

  const { data: document, error: docError } = await supabase
    .from('document_attachments')
    .select('id')
    .eq('id', document_id)
    .eq('company_id', companyId)
    .maybeSingle()

  if (docError || !document) {
    return NextResponse.json({ error: 'Document not found' }, { status: 404 })
  }

  const { error: updateError } = await supabase
    .from('transactions')
    .update({ document_id })
    .eq('id', transactionId)
    .eq('company_id', companyId)

  if (updateError) {
    const errMsg = (updateError as { message?: string }).message ?? ''
    if (errMsg.includes('BFL_DOCUMENT_IMMUTABILITY')) {
      return NextResponse.json(
        {
          error:
            'Bilagan är kopplad till en bokförd verifikation och kan inte ersättas. Storno verifikationen först.',
        },
        { status: 409 },
      )
    }
    console.error('[attach-document] Failed to attach:', updateError)
    return NextResponse.json({ error: 'Failed to attach document' }, { status: 500 })
  }

  // If this document came from an invoice_inbox_items row, mark that row
  // as matched so the inbox UI can show it as "Kopplad" + link back to the
  // transaction. Best-effort: a failure here must not roll back the
  // (compliant) document attach.
  //
  // The Supabase client resolves with { error } rather than rejecting on
  // RLS/DB errors, so we destructure rather than try/catch.
  const { error: inboxLinkErr } = await supabase
    .from('invoice_inbox_items')
    .update({ matched_transaction_id: transactionId })
    .eq('document_id', document_id)
    .eq('company_id', companyId)
    .is('matched_transaction_id', null)
    .is('created_supplier_invoice_id', null)
  if (inboxLinkErr) {
    console.error('[attach-document] Failed to link inbox item:', inboxLinkErr)
  }

  // Rättelse audit trail (BFL 5 kap 5 §): record swaps where a non-null doc
  // was replaced. Best-effort — a logging failure must not roll back the
  // (compliant) attach.
  if (previousDocumentId && previousDocumentId !== document_id) {
    try {
      await appendProcessingHistory({
        companyId,
        correlationId: transactionId,
        aggregateType: 'BankTransaction',
        aggregateId: transactionId,
        eventType: 'TransactionDocumentReplaced',
        payload: {
          transaction_id: transactionId,
          previous_document_id: previousDocumentId,
          new_document_id: document_id,
        },
        actor: { type: 'user', id: user.id },
        occurredAt: new Date(),
      })
    } catch (logErr) {
      console.error('[attach-document] Failed to append rättelse event:', logErr)
    }
  }

  return NextResponse.json({
    data: { transaction_id: transactionId, document_id, previous_document_id: previousDocumentId },
  })
}

/**
 * DELETE /api/transactions/[id]/attach-document
 *
 * Detach a document from a transaction.
 *
 * Blocked once the document has propagated into a journal entry (BFL 5 kap 6 §
 * räkenskapsinformation immutability) — at that point the doc is the
 * verifikation's underlag and can only be undone by reversing the entry.
 */
export async function DELETE(
  _request: Request,
  { params }: { params: Promise<{ id: string }> }
) {
  const supabase = await createClient()
  const { id: transactionId } = await params

  const { data: { user } } = await supabase.auth.getUser()
  if (!user) return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })

  const writeCheck = await requireWritePermission(supabase, user.id)
  if (!writeCheck.ok) return writeCheck.response

  const companyId = await requireCompanyId(supabase, user.id)

  const { data: tx, error: fetchError } = await supabase
    .from('transactions')
    .select('id, document_id')
    .eq('id', transactionId)
    .eq('company_id', companyId)
    .maybeSingle()

  if (fetchError || !tx) {
    return NextResponse.json({ error: 'Transaction not found' }, { status: 404 })
  }

  if (tx.document_id) {
    const { data: doc } = await supabase
      .from('document_attachments')
      .select('journal_entry_id')
      .eq('id', tx.document_id)
      .eq('company_id', companyId)
      .maybeSingle()
    if (doc?.journal_entry_id) {
      return NextResponse.json(
        {
          error:
            'Bilagan är kopplad till en bokförd verifikation och kan inte tas bort. Storno verifikationen först.',
        },
        { status: 409 },
      )
    }
  }

  const { error: updateError } = await supabase
    .from('transactions')
    .update({ document_id: null })
    .eq('id', transactionId)
    .eq('company_id', companyId)

  if (updateError) {
    // The enforce_transactions_document_immutability trigger raises a
    // P0001 exception with a stable BFL_DOCUMENT_IMMUTABILITY: prefix when the
    // previously-attached doc has already become räkenskapsinformation.
    // Match on the prefix (not on the generic SQLSTATE) so unrelated future
    // exceptions don't get translated into the Swedish underlag message.
    const errMsg = (updateError as { message?: string }).message ?? ''
    if (errMsg.includes('BFL_DOCUMENT_IMMUTABILITY')) {
      return NextResponse.json(
        {
          error:
            'Bilagan är kopplad till en bokförd verifikation och kan inte tas bort. Storno verifikationen först.',
        },
        { status: 409 },
      )
    }
    console.error('[attach-document] Failed to detach:', updateError)
    return NextResponse.json({ error: 'Failed to detach document' }, { status: 500 })
  }

  return NextResponse.json({ data: { transaction_id: transactionId, document_id: null } })
}