const LOAN_PAYMENT_FEE_ATOMIC = 1000000n;
let loanPaymentContracts = [];
let loanPaymentLoadPromise = null;
let loanPaymentContractsKey = "";

function setLoanPaymentMessage(message, type = "") {
  setScopedTransactionMessage("Loan Payment", loanPaymentMessage, message, type);
}

function selectedLoanPaymentContract() {
  const hash = String(loanPaymentContractSelect?.value || "");
  return loanPaymentContracts.find((contract) => contract.contract === hash) || null;
}

function loanPaymentPeriodLabel(period) {
  return {
    daily: "Daily",
    weekly: "Weekly",
    monthly: "Monthly"
  }[String(period || "").toLowerCase()] || String(period || "Payment");
}

function populateLoanPaymentContracts() {
  if (!loanPaymentContractSelect) {
    return;
  }
  const previous = loanPaymentContractSelect.value;
  loanPaymentContractSelect.innerHTML = "";
  if (loanPaymentContracts.length) {
    const placeholder = document.createElement("option");
    placeholder.value = "";
    placeholder.textContent = "Select an active loan";
    loanPaymentContractSelect.appendChild(placeholder);
  }
  loanPaymentContracts.forEach((contract) => {
    const option = document.createElement("option");
    option.value = contract.contract;
    const remaining = formatAtomicBalance(contract.remaining_after_pending || "0");
    option.textContent =
      `${contract.loan_asset} loan from ${truncateMiddle(contract.lender, 8, 8)} (${remaining} remaining)`;
    loanPaymentContractSelect.appendChild(option);
  });
  if (!loanPaymentContracts.length) {
    const option = document.createElement("option");
    option.value = "";
    option.textContent = "No active borrower loans";
    loanPaymentContractSelect.appendChild(option);
  } else if ([...loanPaymentContractSelect.options].some((option) => option.value === previous)) {
    loanPaymentContractSelect.value = previous;
  }
  updateLoanPaymentDerivedFields(true);
}

async function loadLoanPaymentContracts(force = false) {
  if (loanPaymentLoadPromise) {
    return loanPaymentLoadPromise;
  }
  const invoke = window.__TAURI__?.core?.invoke;
  const broadcastNode = activeBroadcastNode();
  if (!invoke || !broadcastNode || !walletLoaded || !registrationRegistered) {
    return;
  }
  const key = `${activeWalletAddressShort || activeWalletAddressHex}|${broadcastNode}`;
  if (!force && loanPaymentContractsKey === key) {
    populateLoanPaymentContracts();
    return;
  }

  loanPaymentLoadPromise = (async () => {
    setLoanPaymentMessage("Loading active loans...");
    const contracts = await invoke("active_loan_contracts", { broadcastNode });
    loanPaymentContracts = Array.isArray(contracts) ? contracts : [];
    loanPaymentContractsKey = key;
    populateLoanPaymentContracts();
    setLoanPaymentMessage(
      loanPaymentContracts.length ? "" : "No active loans require payment."
    );
  })().catch((error) => {
    loanPaymentContracts = [];
    populateLoanPaymentContracts();
    setLoanPaymentMessage(String(error), "error");
    throw error;
  }).finally(() => {
    loanPaymentLoadPromise = null;
  });
  return loanPaymentLoadPromise;
}

function expectedLoanPayment(contract) {
  if (!contract) {
    return 0n;
  }
  const scheduled = BigInt(contract.payment_amount || "0");
  const remaining = BigInt(contract.remaining_after_pending || "0");
  return scheduled < remaining ? scheduled : remaining;
}

function updateLoanPaymentWarning(contract, amount) {
  if (!loanPaymentWarning) {
    return;
  }
  const expected = expectedLoanPayment(contract);
  const show = contract && amount !== null && amount > 0n && amount < expected;
  loanPaymentWarning.classList.toggle("hidden", !show);
  loanPaymentWarning.textContent = show
    ? `This is less than the expected ${atomicToDecimal(expected)} ${contract.loan_asset} payment. Partial payments are allowed, but the unpaid amount still counts toward the loan's overdue balance.`
    : "";
}

function updateLoanPaymentDerivedFields(setSuggestedAmount = false) {
  const contract = selectedLoanPaymentContract();
  if (!contract) {
    loanPaymentLender.textContent = "--";
    loanPaymentAsset.textContent = "--";
    loanPaymentScheduled.textContent = "--";
    loanPaymentConfirmed.textContent = "--";
    loanPaymentPending.textContent = "--";
    loanPaymentRemaining.textContent = "--";
    loanPaymentTipInput.value = "";
    loanPaymentFeeInput.value = atomicToDecimal(LOAN_PAYMENT_FEE_ATOMIC);
    updateLoanPaymentWarning(null, null);
    return;
  }

  const expected = expectedLoanPayment(contract);
  if (setSuggestedAmount || !loanPaymentValueInput.value) {
    loanPaymentValueInput.value = atomicToDecimal(expected);
  }
  const amount = decimalToAtomic(loanPaymentValueInput.value);
  const tip = amount !== null && amount > 0n ? (amount + 99n) / 100n : 0n;

  loanPaymentLender.textContent = contract.lender;
  loanPaymentAsset.textContent = contract.loan_asset;
  loanPaymentScheduled.textContent =
    `${loanPaymentPeriodLabel(contract.payment_period)}: ${atomicToDecimal(BigInt(contract.payment_amount || "0"))} ${contract.loan_asset}`;
  loanPaymentConfirmed.textContent =
    `${atomicToDecimal(BigInt(contract.confirmed_paid || "0"))} ${contract.loan_asset}`;
  loanPaymentPending.textContent =
    `${atomicToDecimal(BigInt(contract.pending_paid || "0"))} ${contract.loan_asset}`;
  loanPaymentRemaining.textContent =
    `${atomicToDecimal(BigInt(contract.remaining_after_pending || "0"))} ${contract.loan_asset}`;
  loanPaymentTipInput.value = atomicToDecimal(tip);
  loanPaymentFeeInput.value = atomicToDecimal(LOAN_PAYMENT_FEE_ATOMIC);
  updateLoanPaymentWarning(contract, amount);
}

function loanPaymentBalance(asset) {
  return activeWalletBalances.find((balance) => {
    return String(balance.asset || "").trim().toLowerCase() === String(asset || "").trim().toLowerCase()
      && Number(balance.nft_series || 0) === 0;
  });
}

function validateLoanPaymentForm() {
  if (!walletLoaded) {
    return "Load a wallet before making a loan payment.";
  }
  if (!registrationRegistered) {
    return "Address registration is required before making a loan payment.";
  }
  const contract = selectedLoanPaymentContract();
  if (!contract) {
    return "Select an active loan.";
  }
  const amount = decimalToAtomic(loanPaymentValueInput?.value);
  if (amount === null || amount <= 0n) {
    return "Enter a valid payment amount.";
  }
  const remaining = BigInt(contract.remaining_after_pending || "0");
  if (amount > remaining) {
    return `Payment cannot exceed the remaining ${atomicToDecimal(remaining)} ${contract.loan_asset}.`;
  }
  const tip = (amount + 99n) / 100n;
  const available = balanceAtomicValue(loanPaymentBalance(contract.loan_asset));
  if (amount + tip > available) {
    return `This wallet cannot cover the payment and 1% miner tip in ${contract.loan_asset}.`;
  }
  const baseBalance = baseCoinBalanceAtomic();
  if (isBaseTransferAsset(contract.loan_asset)) {
    if (amount + tip + LOAN_PAYMENT_FEE_ATOMIC > available) {
      return `This wallet cannot cover the payment, tip, and ${atomicToDecimal(LOAN_PAYMENT_FEE_ATOMIC)} ${activeBaseCoin()} fee.`;
    }
  } else if (baseBalance < LOAN_PAYMENT_FEE_ATOMIC) {
    return `This payment requires ${atomicToDecimal(LOAN_PAYMENT_FEE_ATOMIC)} ${activeBaseCoin()} for the transaction fee.`;
  }
  return "";
}

function loanPaymentPayload() {
  const contract = selectedLoanPaymentContract();
  return {
    broadcastNode: activeBroadcastNode(),
    contractHash: contract.contract,
    paybackAmount: String(decimalToAtomic(loanPaymentValueInput.value))
  };
}

function setLoanPaymentButtonsDisabled(disabled) {
  document.querySelector("[data-loan-payment-save]")?.toggleAttribute("disabled", disabled);
  document.querySelector("[data-loan-payment-broadcast]")?.toggleAttribute("disabled", disabled);
}

function clearLoanPaymentForm() {
  loanPaymentContractSelect.value = "";
  loanPaymentValueInput.value = "";
  updateLoanPaymentDerivedFields(false);
}

async function handleLoanPaymentAction(action) {
  const validationError = validateLoanPaymentForm();
  if (validationError) {
    setLoanPaymentMessage(validationError, "error");
    return;
  }
  const invoke = window.__TAURI__?.core?.invoke;
  if (!invoke) {
    setLoanPaymentMessage("Wallet bridge is not available.", "error");
    return;
  }
  const walletKey = await requestSigningWalletKey();
  if (guiRuntimeSettings.require_key_before_signing !== false && !walletKey) {
    setLoanPaymentMessage("Signing cancelled.");
    return;
  }

  setLoanPaymentButtonsDisabled(true);
  try {
    if (action === "save") {
      setLoanPaymentMessage("Saving loan payment transaction...");
      const review = await invoke("save_loan_payment_transaction", {
        ...loanPaymentPayload(),
        walletKey
      });
      clearLoanPaymentForm();
      setLoanPaymentMessage(`Loan payment saved: ${review.file_name}`, "success");
      if (typeof refreshUnbroadcastTransactions === "function") {
        refreshUnbroadcastTransactions();
      }
    } else {
      setLoanPaymentMessage("Broadcasting loan payment...");
      const result = await invoke("broadcast_loan_payment_transaction", {
        ...loanPaymentPayload(),
        walletKey
      });
      await loadLoanPaymentContracts(true);
      clearLoanPaymentForm();
      setLoanPaymentMessage(result.response || "Loan payment broadcast.", "success");
    }
  } catch (error) {
    setLoanPaymentMessage(String(error), "error");
    await loadLoanPaymentContracts(true).catch(() => {});
  } finally {
    setLoanPaymentButtonsDisabled(false);
  }
}

function prepareLoanPaymentForm() {
  setLoanPaymentMessage("");
  loadLoanPaymentContracts(false).catch(() => {
    // The form displays the lookup error.
  });
}

function resetLoanPaymentSession() {
  loanPaymentContracts = [];
  loanPaymentLoadPromise = null;
  loanPaymentContractsKey = "";
  loanPaymentContractSelect.innerHTML = "";
  loanPaymentValueInput.value = "";
  updateLoanPaymentDerivedFields(false);
  setLoanPaymentMessage("");
}

loanPaymentContractSelect?.addEventListener("change", () => {
  setLoanPaymentMessage("");
  updateLoanPaymentDerivedFields(true);
});
loanPaymentValueInput?.addEventListener("input", () => {
  setLoanPaymentMessage("");
  updateLoanPaymentDerivedFields(false);
});
document
  .querySelector("[data-loan-payment-save]")
  ?.addEventListener("click", () => handleLoanPaymentAction("save"));
document
  .querySelector("[data-loan-payment-broadcast]")
  ?.addEventListener("click", () => handleLoanPaymentAction("broadcast"));