const { DynamoDBClient } = require("@aws-sdk/client-dynamodb");
const { DynamoDBDocumentClient, ScanCommand } = require("@aws-sdk/lib-dynamodb");
const { parse } = require("csv-parse/sync");
const fs = require("fs");

const ddb = DynamoDBDocumentClient.from(new DynamoDBClient({ region: "us-east-1" }));

function toISODate(mdyDate) {
  const parts = String(mdyDate).split("/");
  if (parts.length !== 3) return null;
  const [mm, dd, yyyy] = parts;
  return `${yyyy}-${mm.padStart(2, "0")}-${dd.padStart(2, "0")}`;
}

const cancelStatuses = ["voided", "cancelled", "canceled", "marked as void"];

(async () => {
  // Load all existing payments from DB
  const dbPayments = {};
  let lastKey;
  do {
    const result = await ddb.send(
      new ScanCommand({
        TableName: "PaymentsDashboard",
        FilterExpression: "begins_with(pk, :prefix)",
        ExpressionAttributeValues: { ":prefix": "payment#" },
        ExclusiveStartKey: lastKey,
      })
    );
    for (const item of result.Items) {
      dbPayments[item.pk] = item;
    }
    lastKey = result.LastEvaluatedKey;
  } while (lastKey);

  // Read CSV from stdin
  const csvText = fs.readFileSync(0, "utf-8");
  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;
  };

  const statusRank = {
    "scheduled": 1,
    "payment submitted": 2,
    "issued": 3,
    "outstanding": 4,
    "cleared": 5,
  };

  const newRecords = [];
  const statusChanges = [];
  const bankProtected = [];
  const statusProtected = [];
  const newCheckIssues = [];
  const cancelCheckIssues = [];
  let noChangeCount = 0;
  const today = new Date().toISOString().slice(0, 10);

  for (const row of normalizedRows) {
    const checkNumber = (row["Check Number"] || "").trim();
    if (!checkNumber) continue;

    const method = (row["Method"] || "").trim();
    let status = (row["Status"] || "").trim();
    const sendOn = (row["Send Payment On"] || "").trim();
    const payee = (row["Payee"] || "").trim();
    const amount = parseAmount(row["Amount in USD"]);

    // ACH auto-clear logic
    if (method === "ACH" && !cancelStatuses.includes(status.toLowerCase())) {
      const sendDate = toISODate(sendOn);
      if (sendDate && sendDate <= today) {
        status = "Cleared";
      }
    }

    const pk = "payment#" + checkNumber;
    const existing = dbPayments[pk];

    // Bank-confirmed protection
    const bankConfirmed = existing?.clear_status === "Cleared";
    let originalCsvStatus = status;
    if (bankConfirmed) {
      status = "Cleared";
    }

    // Status progression protection
    if (existing) {
      const oldRank = statusRank[(existing.status || "").toLowerCase()] || 0;
      const newRank = statusRank[status.toLowerCase()] || 0;

      if (oldRank === 5) {
        // Cleared is permanent — cannot be voided, cancelled, or anything else
        if (status !== existing.status) {
          statusProtected.push({ checkNumber, payee, csvStatus: originalCsvStatus, dbStatus: existing.status, reason: "Cleared is permanent" });
        }
        status = existing.status;
      } else if (newRank < oldRank && !cancelStatuses.includes(status.toLowerCase())) {
        // Non-cancel status regression — keep the existing (higher) status
        statusProtected.push({ checkNumber, payee, csvStatus: originalCsvStatus, dbStatus: existing.status, reason: "would regress status" });
        status = existing.status;
      }
    }

    if (!existing) {
      newRecords.push({ checkNumber, payee, method, status, amount, sendOn });
      if (method === "Check") {
        newCheckIssues.push({ checkNumber, payee, amount: amount.toFixed(2), issueDate: toISODate(sendOn) });
      }
    } else {
      const oldStatus = existing.status || "";

      if (bankConfirmed && originalCsvStatus !== "Cleared") {
        bankProtected.push({ checkNumber, payee, csvStatus: originalCsvStatus, dbStatus: oldStatus });
      }

      if (oldStatus !== status) {
        statusChanges.push({ checkNumber, payee, method, oldStatus, newStatus: status, amount });
      } else {
        noChangeCount++;
      }

      // Check for new cancel (only if not bank-confirmed and not cleared)
      if (method === "Check" && !bankConfirmed && (statusRank[(oldStatus).toLowerCase()] || 0) < 5 && cancelStatuses.includes(status.toLowerCase()) && !cancelStatuses.includes(oldStatus.toLowerCase())) {
        cancelCheckIssues.push({ checkNumber, payee, amount: amount.toFixed(2), issueDate: toISODate(sendOn) });
      }
    }
  }

  console.log("=== DRY RUN SUMMARY ===");
  console.log("CSV rows: " + normalizedRows.length);
  console.log("Existing DB records: " + Object.keys(dbPayments).length);
  console.log("");

  if (newRecords.length) {
    console.log("--- NEW RECORDS (" + newRecords.length + ") ---");
    for (const r of newRecords) {
      console.log("  + " + r.checkNumber + " | " + r.payee + " | " + r.method + " | " + r.status + " | $" + r.amount);
    }
    console.log("");
  }

  if (statusChanges.length) {
    console.log("--- STATUS CHANGES (" + statusChanges.length + ") ---");
    for (const r of statusChanges) {
      console.log("  ~ " + r.checkNumber + " | " + r.payee + " | " + r.method + " | \"" + r.oldStatus + "\" -> \"" + r.newStatus + "\" | $" + r.amount);
    }
    console.log("");
  }

  if (statusProtected.length) {
    console.log("--- STATUS PROGRESSION PROTECTED (" + statusProtected.length + ") ---");
    console.log("  (CSV tried to regress status — blocked by progression guard)");
    for (const r of statusProtected) {
      console.log("  # " + r.checkNumber + " | " + r.payee + " | CSV: \"" + r.csvStatus + "\" | Kept: \"" + r.dbStatus + "\" | " + r.reason);
    }
    console.log("");
  }

  if (bankProtected.length) {
    console.log("--- BANK-CONFIRMED PROTECTED (" + bankProtected.length + ") ---");
    console.log("  (CSV tried to change status but bank already confirmed Cleared)");
    for (const r of bankProtected) {
      console.log("  ! " + r.checkNumber + " | " + r.payee + " | CSV: \"" + r.csvStatus + "\" | Kept: Cleared");
    }
    console.log("");
  }

  if (newCheckIssues.length) {
    console.log("--- BOA: CHECK ISSUES / add_Issue (" + newCheckIssues.length + ") ---");
    for (const r of newCheckIssues) {
      console.log("  >> " + r.checkNumber + " | " + r.payee + " | $" + r.amount + " | " + r.issueDate);
    }
    console.log("");
  }

  if (cancelCheckIssues.length) {
    console.log("--- BOA: CHECK CANCELS / cancel_Issue (" + cancelCheckIssues.length + ") ---");
    for (const r of cancelCheckIssues) {
      console.log("  XX " + r.checkNumber + " | " + r.payee + " | $" + r.amount + " | " + r.issueDate);
    }
    console.log("");
  }

  console.log("=== TOTALS ===");
  console.log("New DB records:      " + newRecords.length);
  console.log("Status updates:      " + statusChanges.length);
  console.log("Status-protected:    " + statusProtected.length);
  console.log("Bank-protected:      " + bankProtected.length);
  console.log("BoA add_Issue:       " + newCheckIssues.length);
  console.log("BoA cancel_Issue:    " + cancelCheckIssues.length);
  console.log("Unchanged:           " + noChangeCount);
})();