import { S3Client, GetObjectCommand } from "@aws-sdk/client-s3";
import { DynamoDBClient } from "@aws-sdk/client-dynamodb";
import { DynamoDBDocumentClient, PutCommand, UpdateCommand } from "@aws-sdk/lib-dynamodb";
import { parse } from "csv-parse/sync";

const s3 = new S3Client();
const ddb = DynamoDBDocumentClient.from(new DynamoDBClient());
const TABLE_NAME = process.env.TABLE_NAME;

export const handler = async (event) => {
  const record = event.Records[0];
  const bucket = record.s3.bucket.name;
  const key = decodeURIComponent(record.s3.object.key.replace(/\+/g, " "));

  // Download CSV from S3
  const { Body } = await s3.send(new GetObjectCommand({ Bucket: bucket, Key: key }));
  const csvText = await Body.transformToString("utf-8");

  // Parse CSV
  const rows = parse(csvText, {
    columns: true,
    skip_empty_lines: true,
    trim: true,
  });

  const normalizedRows = rows.map((row) => {
    const clean = {};
    for (const [k, v] of Object.entries(row)) {
      clean[String(k).trim()] = typeof v === "string" ? v.trim() : v;
    }
    return clean;
  });

  const parseAmount = (value) => {
    const num = parseFloat(String(value || "0").replace(/,/g, "").trim());
    return isNaN(num) ? 0 : num;
  };

  // Upsert each payment, preserving clear_status/bank_reference/cleared_date if they exist
  let count = 0;
  for (const row of normalizedRows) {
    const checkNumber = (row["Check Number"] || "").trim();
    const pk = `payment#${checkNumber}`;

    await ddb.send(
      new UpdateCommand({
        TableName: TABLE_NAME,
        Key: { pk },
        UpdateExpression: `
          SET #method = :method,
              payee = :payee,
              check_number = :check_number,
              invoice_numbers = :invoice_numbers,
              send_payment_on = :send_payment_on,
              amount_usd = :amount_usd,
              #status = :status,
              company_subsidiary = :company_subsidiary
        `,
        ExpressionAttributeNames: {
          "#method": "method",
          "#status": "status",
        },
        ExpressionAttributeValues: {
          ":method": (row["Method"] || "").trim(),
          ":payee": (row["Payee"] || "").trim(),
          ":check_number": checkNumber,
          ":invoice_numbers": (row["Invoice Numbers"] || "").trim(),
          ":send_payment_on": (row["Send Payment On"] || "").trim(),
          ":amount_usd": parseAmount(row["Amount in USD"]),
          ":status": (row["Status"] || "").trim(),
          ":company_subsidiary": (row["Company/Subsidiary"] || "").trim(),
        },
      })
    );
    count++;
  }

  // Update metadata record
  await ddb.send(
    new PutCommand({
      TableName: TABLE_NAME,
      Item: {
        pk: "metadata",
        file_name: key.split("/").pop(),
        last_updated: new Date().toISOString(),
        last_file_count: count,
      },
    })
  );

  console.log(`Upserted ${count} payments from ${key}`);
  return { statusCode: 200, body: `Upserted ${count} payments` };
};