import { useEffect, useState } from "react";
import { InlineNotification, Modal, Select, SelectItem, TextInput } from "@carbon/react";
import { api } from "../lib/api";
import { todayIst } from "../lib/fiscal";
import { formatPaise, paiseToInput, parseRupeesToPaise } from "../lib/money";
import { PAYMENT_MODES, type Payment, type PaymentMode } from "../lib/payments";
import { useReturnFocus } from "../hooks/useReturnFocus";

interface Props {
  open: boolean;
  invoiceId: number;
  invoiceNumber: string;
  /** What is still owed, in paise. */
  balancePaise: number;
  onClose: () => void;
  onRecorded: (payment: Payment) => void;
}

/** "Record payment": cash received plus TDS deducted, validated against the balance before it is sent. */
export default function RecordPaymentModal({ open, invoiceId, invoiceNumber, balancePaise, onClose, onRecorded }: Props) {
  const [paidOn, setPaidOn] = useState(todayIst());
  const [amount, setAmount] = useState("");
  const [tds, setTds] = useState("");
  const [mode, setMode] = useState<PaymentMode>("bank_transfer");
  const [reference, setReference] = useState("");
  const [notes, setNotes] = useState("");
  const [error, setError] = useState<string | null>(null);
  const [busy, setBusy] = useState(false);
  useReturnFocus(open);

  // Each opening starts from the balance, so the common case (paid in full) is one click.
  useEffect(() => {
    if (!open) return;
    setPaidOn(todayIst());
    setAmount(paiseToInput(balancePaise));
    setTds("");
    setMode("bank_transfer");
    setReference("");
    setNotes("");
    setError(null);
    setBusy(false);
  }, [open, balancePaise]);

  const amountPaise = parseRupeesToPaise(amount);
  const tdsPaise = parseRupeesToPaise(tds);
  const amountInvalid = amountPaise === null;
  const tdsInvalid = tdsPaise === null;
  const total = (amountPaise ?? 0) + (tdsPaise ?? 0);
  const overBalance = !amountInvalid && !tdsInvalid && total > balancePaise;
  const empty = !amountInvalid && !tdsInvalid && total === 0;
  const dateInvalid = !/^\d{4}-\d{2}-\d{2}$/.test(paidOn);
  const canSubmit = !busy && !amountInvalid && !tdsInvalid && !overBalance && !empty && !dateInvalid;

  const submit = async () => {
    if (!canSubmit || amountPaise === null || tdsPaise === null) return;
    setBusy(true);
    setError(null);
    try {
      const payment = await api.recordPayment({ invoiceId, paidOn, amountPaise, tdsPaise, mode, reference, notes });
      onRecorded(payment);
    } catch (e) {
      setError(String(e));
      setBusy(false);
    }
  };

  return (
    <Modal
      open={open}
      modalHeading={`Record payment for ${invoiceNumber}`}
      primaryButtonText={busy ? "Saving…" : "Record payment"}
      secondaryButtonText="Cancel"
      primaryButtonDisabled={!canSubmit}
      onRequestClose={onClose}
      onRequestSubmit={() => void submit()}
    >
      <div className="voiced-stack">
        <p>
          Balance due: <strong>{formatPaise(balancePaise)}</strong>
        </p>
        {error ? <InlineNotification kind="error" lowContrast hideCloseButton title="Could not record the payment" subtitle={error} /> : null}
        <TextInput
          id="payDate"
          type="date"
          labelText="Date received"
          value={paidOn}
          invalid={dateInvalid}
          invalidText="Enter a date"
          onChange={(e) => setPaidOn(e.target.value)}
        />
        <TextInput
          id="payAmount"
          inputMode="decimal"
          labelText="Amount received (₹)"
          helperText="Cash that reached your account"
          value={amount}
          invalid={amountInvalid || overBalance || empty}
          invalidText={
            amountInvalid
              ? "Enter an amount like 1250.50"
              : overBalance
                ? `Amount plus TDS is more than the balance of ${formatPaise(balancePaise)}`
                : "Enter an amount received or TDS deducted"
          }
          onChange={(e) => setAmount(e.target.value)}
        />
        <TextInput
          id="payTds"
          inputMode="decimal"
          labelText="TDS deducted by client (₹)"
          helperText="Counts towards settling the invoice; leave empty if none"
          value={tds}
          invalid={tdsInvalid}
          invalidText="Enter an amount like 125.00"
          onChange={(e) => setTds(e.target.value)}
        />
        <Select id="payMode" labelText="Mode" value={mode} onChange={(e) => setMode(e.target.value as PaymentMode)}>
          {PAYMENT_MODES.map((m) => (
            <SelectItem key={m.id} value={m.id} text={m.label} />
          ))}
        </Select>
        <TextInput id="payRef" labelText="UTR / cheque number (optional)" value={reference} onChange={(e) => setReference(e.target.value)} />
        <TextInput id="payNotes" labelText="Notes (optional)" value={notes} onChange={(e) => setNotes(e.target.value)} />
      </div>
    </Modal>
  );
}