// Pure reconciliation logic for fetchBoaTransactions (payments-dashboard#66).
// No AWS clients or environment access here so node:test can exercise the
// classifier, matcher, and state transitions directly.

import { toISODate } from "./dates.js";

// Untrusted values (bank descriptions, references) must be JSON-encoded
// before log interpolation — bank text can carry newlines, which would forge
// CloudWatch log lines (CWE-117). Same rule as processPaymentCsv's logSafe.
export const logSafe = (v) => JSON.stringify(String(v ?? "").slice(0, 128));

// Comma-tolerant amount parsing ("1,234.56" bank strings and stored values).
export const parseAmount = (value) => {
  const num = parseFloat(String(value ?? "0").replace(/,/g, "").trim());
  return isNaN(num) ? 0 : num;
};

const cents = (v) => Math.round(Math.abs(parseAmount(v)) * 100);

// Sign-insensitive cent equality; zero never matches (a blank amount must
// not pair with another blank amount).
export const amountsEqual = (a, b) => cents(a) > 0 && cents(a) === cents(b);

// BAI transaction-code -> event map. BoA's Previous Day feed uses standard
// BAI type codes; only 475 (check paid, debit) is empirically confirmed so
// far. The codes for ARP refer-to-maker return credits, return-of-posted-
// check credits (check-numbered and electronic variants), ACH CCD debits and
// return credits, and the true meaning of 255 (the old filter assumed
// "returned check", unverified) are pending the enumeration replay over
// known event dates (2/20, 3/31, 4/8, 6/16-6/23) — add them here as they
// are confirmed. Until then classification falls back to description text,
// and unmapped codes on check-shaped transactions are logged and counted,
// never silently dropped.
export const BAI_CODE_EVENTS = {
  475: { event: "check_paid", direction: "debit" },
};

// Standard BAI ranges: 100-399 are credit type codes, 400-699 are debit
// type codes. Used only when the feed carries no explicit indicator.
export function directionFromCode(code) {
  const n = parseInt(String(code ?? ""), 10);
  if (!Number.isInteger(n)) return null;
  if (n >= 100 && n < 400) return "credit";
  if (n >= 400 && n < 700) return "debit";
  return null;
}

export function directionOf(txn) {
  const indicator = String(
    txn.debitCreditIndicator ?? txn.creditDebitIndicator ?? ""
  ).toUpperCase();
  if (indicator.includes("DEBIT")) return "debit";
  if (indicator.includes("CREDIT")) return "credit";
  const fromCode = directionFromCode(txn.transactionCode);
  if (fromCode) return fromCode;
  const amt = parseAmount(txn.amount);
  if (amt < 0) return "debit";
  if (amt > 0) return "credit";
  return null;
}

// Statement description formats observed on the 2026-07-21 reconciliation.
const ARP_RETURN_RE = /^ARP RETURNED CHECK REFER TO MAKER CHECK #\s*(\d+)\b/i;
const POSTED_RETURN_CHECK_RE =
  /^RETURN OF POSTED CHECK \/ ITEM \(RECEIVED ON \d{2}-\d{2}\)\s*CHECK #\s*(\d+)\b/i;
const POSTED_RETURN_ELECTRONIC_RE =
  /^RETURN OF POSTED CHECK \/ ITEM \(RECEIVED ON \d{2}-\d{2}\)\s*ELECTRONIC TRANSACTION\b/i;
const ACH_PMT_RE = /DES:PAYMENTS\s+ID:PMT\s*(\d+)/i;
const PMT_INFO_RE = /PMT INFO:\s*(.*)$/i;
const CHECK_PAID_RE = /^CHECK\s*#?\s*(\d+)$/i;
// Trailing digit run at the end of PMT INFO — Stampli recently started
// embedding the payment number there, and the bank wraps it with arbitrary
// internal spaces ("21 222000108", "2122200 0256").
const EMBEDDED_NUMBER_RE = /(\d[\d ]{6,}\d)\s*$/;

const stripLeadingZeros = (s) => String(s ?? "").replace(/^0+(?=\d)/, "");

// Classify one Previous Day transaction into a reconciliation event.
// Precedence: confirmed BAI code map first, then description text. Anything
// unmapped that still looks check/payment-shaped comes back as "unknown" so
// the caller can log and count it — never silently drop it. Everything else
// (transfers, misc bank activity) is "ignored".
export function classifyTransaction(txn) {
  const code = String(txn.transactionCode ?? "").trim();
  const description = String(
    txn.text ?? txn.description ?? txn.transactionDescription ?? ""
  ).trim();
  const customerReference = stripLeadingZeros(String(txn.customerReference ?? "").trim());
  const bankReference = String(txn.bankReference ?? "").trim();
  const amount = Math.abs(parseAmount(txn.amount));
  const direction = BAI_CODE_EVENTS[code]?.direction ?? directionOf(txn);

  const base = {
    code,
    description,
    customerReference,
    bankReference,
    amount,
    direction,
    checkNumber: null,
    pmtId: null,
    embeddedPaymentNumber: null,
    vendorText: null,
    checkShaped: false,
  };

  // Description facts, extracted regardless of code so a code-mapped event
  // still carries the check number / PMT id it references.
  let descriptionEvent = null;
  let m;
  if ((m = ARP_RETURN_RE.exec(description))) {
    descriptionEvent = "check_return";
    base.checkNumber = stripLeadingZeros(m[1]);
  } else if ((m = POSTED_RETURN_CHECK_RE.exec(description))) {
    descriptionEvent = "check_return";
    base.checkNumber = stripLeadingZeros(m[1]);
  } else if (POSTED_RETURN_ELECTRONIC_RE.test(description)) {
    descriptionEvent = "electronic_return";
  } else if ((m = ACH_PMT_RE.exec(description))) {
    base.pmtId = m[1];
    const info = PMT_INFO_RE.exec(description);
    if (info) {
      let vendorText = info[1].trim();
      const embedded = EMBEDDED_NUMBER_RE.exec(vendorText);
      if (embedded && embedded[1].replace(/ /g, "").length >= 8) {
        base.embeddedPaymentNumber = embedded[1].replace(/ /g, "");
        vendorText = vendorText.slice(0, embedded.index).trim();
      }
      base.vendorText = vendorText || null;
    }
    if (direction === "debit") descriptionEvent = "ach_debit";
    else if (direction === "credit") descriptionEvent = "ach_return";
    // direction unknown -> leave null; falls through to "unknown" below.
  } else if ((m = CHECK_PAID_RE.exec(description))) {
    descriptionEvent = "check_paid";
    base.checkNumber = stripLeadingZeros(m[1]);
  }

  const event = BAI_CODE_EVENTS[code]?.event ?? descriptionEvent;

  if (event === "check_paid" && !base.checkNumber) {
    base.checkNumber = customerReference || null;
  }
  if (event === "check_return" && !base.checkNumber) {
    base.checkNumber = customerReference || null;
  }

  if (event) return { ...base, event };

  base.checkShaped =
    Boolean(customerReference) || /CHECK/i.test(description) || Boolean(base.pmtId);
  return { ...base, event: base.checkShaped ? "unknown" : "ignored" };
}

// Days from a stored Stampli send date (canonical MM/DD/YYYY) to an ISO
// reference date; null when the stored date does not parse.
function daysSinceIssue(payment, refISO) {
  const iso = toISODate(payment.send_payment_on);
  if (!iso) return null;
  return Math.round((Date.parse(refISO) - Date.parse(iso)) / 86400000);
}

const issuedWithinDays = (payment, refISO, days) => {
  const d = daysSinceIssue(payment, refISO);
  return d !== null && d >= 0 && d <= days;
};

// Match a check event (paid debit or return credit) against payment records.
// Match on check number AND amount, evaluating all candidates — never
// first-match on number alone: bank postings drop/collapse digits on long
// check numbers, so a posting under one number can belong to another check
// (or to a number we never issued). When the number matches but the amount
// does not — or the number is unknown — fall back to an exact-amount match
// within checks issued in the last 120 days. Anything but a single fallback
// candidate is unmatched: no write on ambiguity.
export function matchCheckTransaction(classified, payments, refDateISO) {
  const { checkNumber, amount } = classified;
  const checks = payments.filter((p) => p.method === "Check" && p.check_number);

  const numberMatches = checkNumber
    ? checks.filter((p) => p.check_number === checkNumber)
    : [];
  const exact = numberMatches.filter((p) => amountsEqual(p.amount_usd, amount));
  if (exact.length === 1) return { payment: exact[0], matchedBy: "number+amount" };
  if (exact.length > 1) return { unmatched: "multiple number+amount matches" };

  const fallback = checks.filter(
    (p) => amountsEqual(p.amount_usd, amount) && issuedWithinDays(p, refDateISO, 120)
  );
  if (fallback.length === 1) return { payment: fallback[0], matchedBy: "amount" };
  if (fallback.length > 1) {
    return { unmatched: `amount fallback ambiguous (${fallback.length} candidates)` };
  }
  return {
    unmatched: numberMatches.length
      ? "number matched with wrong amount; no unique amount fallback"
      : "no number match; no unique amount fallback",
  };
}

// Electronic return credits carry no check number at all. Match by exact
// amount among bank-confirmed payments issued in the last 120 days
// (clear_status Cleared, or Returned so replays of an already-applied
// return dedupe to a noop instead of alerting). Ambiguity is unmatched.
export function matchElectronicReturn(classified, payments, refDateISO) {
  const candidates = payments.filter(
    (p) =>
      (p.clear_status === "Cleared" || p.clear_status === "Returned") &&
      amountsEqual(p.amount_usd, classified.amount) &&
      issuedWithinDays(p, refDateISO, 120)
  );
  if (candidates.length === 1) return { payment: candidates[0], matchedBy: "amount+cleared" };
  if (candidates.length > 1) {
    return { unmatched: `electronic return ambiguous (${candidates.length} candidates)` };
  }
  return { unmatched: "no bank-confirmed payment with this amount" };
}

const CANCEL_STATUSES = ["voided", "cancelled", "canceled", "marked as void"];
export const isCancelStatus = (s) => CANCEL_STATUSES.includes(String(s ?? "").toLowerCase());

// Decide the DDB write for a matched bank event. Pure: returns the fields
// to set plus the history entry; the handler turns it into an UpdateCommand
// and mirrors the fields onto its in-memory copy.
//
// Invariant: every non-noop result sets BOTH status and clear_status — the
// 2026-07-21 reconciliation traced five missed returns ($5,256.62) to
// writers touching one field but not the other.
//
// Status semantics (documented decision, #66): `clear_status` is bank truth
// ("Cleared without a subsequent return is permanent" keys off it). `status`
// stays on the CSV lifecycle ladder, which has no "Returned" rung, so on a
// return it is re-written with its current value to keep the both-fields
// invariant; consumers that need bounce visibility read clear_status. On a
// paid debit against a canceled record (a voided check the bank paid —
// expected without Positive Pay), the cancel status is likewise preserved:
// the ARP return that follows lands as terminal voided-and-bounced.
export function applyEvent(payment, classified, eventDateISO) {
  const { event, amount, bankReference } = classified;
  const canceled = isCancelStatus(payment.status);
  const historyEvent = {
    event,
    date: eventDateISO,
    bankRef: bankReference,
    amount,
  };

  // Replay idempotence: an identical event already recorded in history is a
  // noop, so re-running a date range never double-applies transitions.
  const alreadyApplied = (payment.history || []).some(
    (h) =>
      h.event === historyEvent.event &&
      h.date === historyEvent.date &&
      h.bankRef === historyEvent.bankRef &&
      amountsEqual(h.amount, amount)
  );
  if (alreadyApplied) return { kind: "noop", updates: null, historyEvent: null };

  if (event === "check_paid" || event === "ach_debit") {
    const redeposit = payment.clear_status === "Returned";
    const updates = {
      status: canceled ? payment.status : "Cleared",
      clear_status: "Cleared",
      paid_date: eventDateISO,
      cleared_date: eventDateISO,
      bank_reference: bankReference,
    };
    if (event === "ach_debit" && classified.pmtId) updates.pmt_id = classified.pmtId;
    return {
      kind: redeposit ? "redeposit" : canceled ? "cleared_on_canceled" : "cleared",
      updates,
      historyEvent,
    };
  }

  if (event === "check_return" || event === "electronic_return" || event === "ach_return") {
    const updates = {
      status: payment.status ?? "",
      clear_status: "Returned",
      returned_date: eventDateISO,
      bank_reference: bankReference,
    };
    if (event === "ach_return" && classified.pmtId) updates.pmt_id = classified.pmtId;
    return {
      // A return against a canceled record is the expected void-then-bounce
      // ARP cycle: terminal voided-and-bounced, counted separately.
      kind: canceled ? "voided_and_bounced" : "returned",
      updates,
      historyEvent,
    };
  }

  return { kind: "noop", updates: null, historyEvent: null };
}

const ISO_DATE_RE = /^\d{4}-\d{2}-\d{2}$/;

export function isValidISODate(s) {
  if (typeof s !== "string" || !ISO_DATE_RE.test(s)) return false;
  const [y, mo, d] = s.split("-").map(Number);
  const dt = new Date(Date.UTC(y, mo - 1, d));
  return (
    dt.getUTCFullYear() === y && dt.getUTCMonth() === mo - 1 && dt.getUTCDate() === d
  );
}

// Optional {fromDate, toDate} replay payload; the default stays yesterday,
// matching the previous-day inquiry cadence. Strings are validated strictly
// so a malformed payload fails loudly instead of querying a garbage range.
export function resolveDateRange(event, now = new Date()) {
  const hasFrom = event?.fromDate != null;
  const hasTo = event?.toDate != null;
  if (!hasFrom && !hasTo) {
    const yesterday = new Date(now.getTime() - 24 * 60 * 60 * 1000);
    const d = yesterday.toISOString().split("T")[0];
    return { fromDate: d, toDate: d };
  }
  const fromDate = hasFrom ? event.fromDate : event.toDate;
  const toDate = hasTo ? event.toDate : event.fromDate;
  if (!isValidISODate(fromDate) || !isValidISODate(toDate)) {
    throw new Error("fromDate/toDate must be valid YYYY-MM-DD strings");
  }
  if (fromDate > toDate) {
    throw new Error("fromDate must be <= toDate");
  }
  return { fromDate, toDate };
}