"use client";

import { formatCurrency } from "@/lib/utils";
import { amountToPercent, percentToAmount } from "@/lib/po-money";

/**
 * PO-level TCS and Discount charges, shown below GST (issue #133).
 *
 * Each charge is entered as an absolute rupee amount **or** as a percentage of the
 * GST-inclusive line-items total (`base`) — the two are bidirectionally linked.
 * Only the absolute amount is stored (the parent persists `tcs` / `discount`); the
 * percentage is a convenience. Discount is applied post-GST.
 */
interface Props {
  base: number; // GST-inclusive line-items total — the % base
  currency: string;
  tcs: number;
  discount: number;
  onTcsChange: (amount: number) => void;
  onDiscountChange: (amount: number) => void;
  disabled?: boolean;
}

const INPUT =
  "w-full rounded-lg border border-neutral-300 px-3 py-2 text-sm focus:border-primary-500 focus:outline-none focus:ring-2 focus:ring-primary-500/20";

function round2(n: number): number {
  return Math.round((n + Number.EPSILON) * 100) / 100;
}

function ChargeRow({
  label,
  hint,
  base,
  value,
  onChange,
  disabled,
}: {
  label: string;
  hint: string;
  base: number;
  value: number;
  onChange: (amount: number) => void;
  disabled?: boolean;
}) {
  const percent = round2(amountToPercent(value, base));

  return (
    <div className="grid grid-cols-1 gap-3 sm:grid-cols-[1fr_auto_auto] sm:items-end">
      <div>
        <label className="block text-sm font-medium text-neutral-700 mb-1.5">{label}</label>
        <p className="text-xs text-neutral-400">{hint}</p>
      </div>
      <div className="sm:w-40">
        <label className="block text-xs text-neutral-500 mb-1">Amount (₹)</label>
        <input
          type="number"
          min={0}
          step="0.01"
          value={value === 0 ? "" : value}
          placeholder="0.00"
          disabled={disabled}
          onChange={(e) => onChange(Math.max(0, Number(e.target.value) || 0))}
          className={INPUT}
        />
      </div>
      <div className="sm:w-32">
        <label className="block text-xs text-neutral-500 mb-1">% of total</label>
        <input
          type="number"
          min={0}
          step="0.01"
          value={percent === 0 ? "" : percent}
          placeholder="0"
          disabled={disabled || base === 0}
          onChange={(e) => onChange(round2(percentToAmount(Number(e.target.value) || 0, base)))}
          className={INPUT}
        />
      </div>
    </div>
  );
}

export function TcsDiscountFields({
  base,
  currency,
  tcs,
  discount,
  onTcsChange,
  onDiscountChange,
  disabled,
}: Props) {
  const netPayable = base + (tcs || 0) - (discount || 0);

  return (
    <div className="space-y-5">
      <p className="text-xs text-neutral-400">
        Optional charges applied after GST. Enter a rupee amount or a percentage of the
        GST-inclusive total — they stay in sync. Stored as an absolute amount.
      </p>
      <ChargeRow
        label="TCS"
        hint="Tax Collected at Source, added to the total."
        base={base}
        value={tcs}
        onChange={onTcsChange}
        disabled={disabled}
      />
      <ChargeRow
        label="Discount"
        hint="Applied post-GST, subtracted from the total."
        base={base}
        value={discount}
        onChange={onDiscountChange}
        disabled={disabled}
      />
      <div className="flex items-center justify-between border-t border-neutral-100 pt-3 text-sm">
        <span className="font-medium text-neutral-600">Net payable</span>
        <span className="font-semibold text-neutral-900">{formatCurrency(netPayable, currency)}</span>
      </div>
    </div>
  );
}