import { NextRequest, NextResponse } from 'next/server';
import OpenAI from 'openai';
import { z } from 'zod';
import { zodResponseFormat } from 'openai/helpers/zod';

const openai = new OpenAI();

// Define the schema for individual items
const ItemSchema = z.object({
  item: z.string().describe('name of item, transaction description, or entry'),
  unit_price: z.number().describe('unit price, transaction amount, or individual cost'),
  quantity: z.number().describe('quantity, count of items, or number of transactions (use 1 for single transactions)'),
  sum: z.number().describe('total amount for this item, transaction total, or entry amount')
});

// Define the main extraction schema
const ExtractionSchema = z.object({
  company: z.string().describe('name of company, bank, or organization'),
  address: z.string().describe('address, location, or branch information'),
  total_sum: z.number().describe('total amount, sum of transactions, total paid, or final balance'),
  items: z.array(ItemSchema).describe('list of items, transactions, or entries')
});

export async function POST(request: NextRequest) {
  try {
    const { text, schema } = await request.json();

    if (!text) {
      return NextResponse.json(
        { error: 'No text provided' },
        { status: 400 }
      );
    }

    const completion = await openai.beta.chat.completions.parse({
      model: 'gpt-4o-2024-08-06',
      messages: [
        {
          role: 'system',
          content: `You are an expert at extracting structured data from documents. 
          You will be given text from a PDF document (likely an invoice or bank statement) 
          and should extract the required information into the given structure.

          For bank statements:
          - Treat transaction descriptions as items
          - Use transaction amounts as unit prices
          - Use 1 as quantity for single transactions
          - Total amount can be total deposits, total checks, or final balance

          For invoices:
          - Extract traditional invoice fields
          - Calculate missing values if possible (e.g., sum = unit_price * quantity)

          For any document type:
          - Look for organization names in headers or footers
          - Find address or location information
          - Identify itemized lists or transactions
          - Look for total amounts or summaries

          Be precise with numerical values, extract them as numbers, not strings.
          If a value is missing but can be calculated, calculate it.
          Ensure all required fields are filled with meaningful values.`
        },
        {
          role: 'user',
          content: text
        }
      ],
      response_format: zodResponseFormat(ExtractionSchema, 'document_extraction')
    });

    const extractedData = completion.choices[0].message.parsed;

    return NextResponse.json(extractedData);
  } catch (error) {
    console.error('Error processing text:', error);
    return NextResponse.json(
      { error: 'Error processing text' },
      { status: 500 }
    );
  }
}