import { createClient } from '@/lib/supabase/server'
import { NextResponse } from 'next/server'
import { z } from 'zod'
import { requireCompanyId } from '@/lib/company/context'
import { requireWritePermission } from '@/lib/auth/require-write'

const RejectBodySchema = z.object({
  rejection_category: z
    .enum(['wrong_category', 'wrong_amount', 'duplicate', 'wrong_period', 'other'])
    .optional(),
  rejection_reason: z.string().max(2000).optional(),
})

/**
 * POST /api/pending-operations/:id/reject
 *
 * Reject a pending operation. Optionally accepts a JSON body with
 * `rejection_category` (fixed enum) and `rejection_reason` (free text). Both
 * are stored on the row so agents can fetch them via gnubok_get_recent_rejections
 * and learn from "no". The body is optional — bodyless POSTs from older
 * clients still mark the op rejected with NULL category/reason.
 */
export async function POST(
  request: Request,
  { params }: { params: Promise<{ id: string }> }
) {
  const supabase = await createClient()
  const { id } = 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)

  // Body is optional — accept empty/missing body without rejecting the request.
  // Old clients posted no body; the UI dialog will now post a body, but we
  // keep accepting both shapes to avoid coupling the API to the UI version.
  let rejectionCategory: string | undefined
  let rejectionReason: string | undefined
  const contentLength = request.headers.get('content-length')
  if (contentLength && contentLength !== '0') {
    try {
      const raw = await request.json()
      const parsed = RejectBodySchema.safeParse(raw)
      if (!parsed.success) {
        return NextResponse.json(
          { error: parsed.error.issues.map((i) => i.message).join('; ') },
          { status: 400 },
        )
      }
      rejectionCategory = parsed.data.rejection_category
      rejectionReason = parsed.data.rejection_reason?.trim() || undefined
    } catch {
      // Body present but unparseable — fail closed.
      return NextResponse.json({ error: 'Invalid JSON body' }, { status: 400 })
    }
  }

  const { data: op, error: fetchError } = await supabase
    .from('pending_operations')
    .select('id, status')
    .eq('id', id)
    .eq('company_id', companyId)
    .single()

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

  if (op.status !== 'pending') {
    // There is no auto-commit path (removed in 20260505190027), so a non-pending
    // status here means the op was resolved explicitly — almost always the user
    // pressed Godkänn in the /pending (Att göra) UI in parallel, or another
    // client already rejected it. Spell that out so an agent doesn't read the
    // generic 409 as "the system committed it behind my back".
    const explained =
      op.status === 'rejected'
        ? 'Operation already rejected.'
        : op.status === 'expired'
          ? 'Operation already expired and can no longer be rejected.'
          : `Operation already ${op.status} — it was approved explicitly (most likely via the ` +
            'Att göra / pending UI in parallel), not auto-committed. It can no longer be rejected; ' +
            'reverse or correct the resulting verifikat instead.'
    return NextResponse.json(
      { error: explained, status: op.status },
      { status: 409 }
    )
  }

  const { error: updateError } = await supabase
    .from('pending_operations')
    .update({
      status: 'rejected',
      resolved_at: new Date().toISOString(),
      ...(rejectionCategory ? { rejection_category: rejectionCategory } : {}),
      ...(rejectionReason ? { rejection_reason: rejectionReason } : {}),
    })
    .eq('id', id)

  if (updateError) {
    return NextResponse.json({ error: updateError.message }, { status: 500 })
  }

  return NextResponse.json({ data: { id, status: 'rejected' } })
}