import { NextResponse } from "next/server"
import { z } from "zod"
import { getSessionUser } from "@/lib/session"
import { aiConfigured, AI_UNCONFIGURED_ERROR } from "@/lib/ai/client"
import { aiComplete } from "@/lib/ai/provider"
import { RENT_RECEIPT_PROMPT, dataBlock } from "@/lib/ai/prompts"
import { enforceAiQuota } from "@/lib/ai/usage"

// Whitelist only the fields the receipt needs. Never pass the raw request body
// into the prompt — tenant-controlled strings must not become instructions.
const ReceiptInput = z.object({
  payment_id: z.string().optional(),
  amount: z.number().optional(),
  tenant_name: z.string().max(200).optional(),
  property_name: z.string().max(200).optional(),
  property_address: z.string().max(300).optional(),
  unit_number: z.string().max(50).optional(),
  landlord_name: z.string().max(200).optional(),
  payment_method: z.string().max(100).optional(),
  due_date: z.string().max(50).optional(),
  paid_date: z.string().max(50).optional(),
  period: z.string().max(100).optional(),
})

export async function POST(request: Request) {
  const user = await getSessionUser()
  if (!user) return NextResponse.json({ error: "Unauthorized" }, { status: 401 })

  // Before the quota check so an unconfigured server never burns a call.
  if (!aiConfigured()) return NextResponse.json({ error: AI_UNCONFIGURED_ERROR }, { status: 503 })

  const quota = await enforceAiQuota(user.id, "ai_rent_receipt")
  if (!quota.ok) return NextResponse.json({ error: quota.error }, { status: quota.status })

  const parsed = ReceiptInput.safeParse(await request.json())
  if (!parsed.success) {
    return NextResponse.json({ error: "Invalid payment details" }, { status: 400 })
  }

  // Pass only the whitelisted, validated fields to the model.
  const { payment_id, ...receiptFields } = parsed.data

  const text = await aiComplete({
    messages: [
      { role: "system", content: RENT_RECEIPT_PROMPT },
      {
        role: "user",
        content: dataBlock("PAYMENT DETAILS", JSON.stringify(receiptFields, null, 2)),
      },
    ],
    maxTokens: 1024,
    json: true,
  })

  let receipt
  try {
    receipt = JSON.parse(text)
  } catch {
    return NextResponse.json({ error: "Failed to parse AI response" }, { status: 500 })
  }

  return NextResponse.json(receipt)
}
