"use client";

import { useState } from "react";

/**
 * Client form for /shop/topup. Posts the chosen amount to /api/paypal/create,
 * then redirects the browser to PayPal's approval URL. After PayPal returns to
 * /shop/topup?token=<orderId>&status=success, it captures via /api/paypal/capture.
 */
export default function TopUpForm({
  currency,
  creditsPerUnit,
}: {
  currency: string;
  creditsPerUnit: number;
}) {
  const [amount, setAmount] = useState("5.00");
  const [pending, setPending] = useState(false);
  const [error, setError] = useState<string | null>(null);
  const [success, setSuccess] = useState<string | null>(null);

  const numeric = Number(amount);
  const credits = Number.isFinite(numeric) && numeric > 0 ? Math.floor(numeric * creditsPerUnit) : 0;

  async function startCheckout(e: React.FormEvent) {
    e.preventDefault();
    setError(null);
    setPending(true);
    try {
      const res = await fetch("/api/paypal/create", {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ amount: numeric }),
      });
      const data = (await res.json().catch(() => ({}))) as {
        approveUrl?: string;
        error?: string;
      };
      if (!res.ok || !data.approveUrl) {
        setError(data.error ?? "Could not start the PayPal checkout.");
        setPending(false);
        return;
      }
      // Hand off to PayPal for approval.
      const redirectUrl = new URL(data.approveUrl);
      if (redirectUrl.protocol !== "https:") {
        throw new Error("Invalid redirect URL: must be HTTPS");
      }
      window.location.href = redirectUrl.href;
    } catch {
      setError("Network error — please try again.");
      setPending(false);
    }
  }

  async function capture(orderId: string) {
    setPending(true);
    setError(null);
    try {
      const res = await fetch("/api/paypal/capture", {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ orderId }),
      });
      const data = (await res.json().catch(() => ({}))) as {
        ok?: boolean;
        credits?: number;
        error?: string;
      };
      if (res.ok && data.ok) {
        setSuccess(
          `Payment complete! ${(data.credits ?? 0).toLocaleString()} credits were added.`,
        );
      } else {
        setError(data.error ?? "We couldn't confirm your payment. Contact staff if charged.");
      }
    } catch {
      setError("Network error confirming payment — contact staff if you were charged.");
    } finally {
      setPending(false);
      // Clean the token/status query so a refresh doesn't re-capture.
      window.history.replaceState(null, "", "/shop/topup");
    }
  }

  // On return from PayPal (?token=<orderId>&status=success), auto-capture once.
  if (typeof window !== "undefined" && !pending && !success) {
    const params = new URLSearchParams(window.location.search);
    const token = params.get("token");
    if (token && params.get("status") === "success") {
      // Defer to avoid setState during render.
      queueMicrotask(() => capture(token));
    }
  }

  if (success) {
    return (
      <p
        role="status"
        aria-live="polite"
        style={{ margin: 0, fontWeight: 700, color: "var(--color-accent)" }}
      >
        {success}
      </p>
    );
  }

  return (
    <form
      onSubmit={startCheckout}
      style={{ display: "flex", flexDirection: "column", gap: "0.75rem" }}
    >
      <label htmlFor="amount" style={{ fontWeight: 700 }}>
        Amount ({currency})
      </label>
      <input
        id="amount"
        name="amount"
        type="number"
        min={1}
        max={500}
        step={0.01}
        value={amount}
        onChange={(e) => setAmount(e.target.value)}
        aria-label={`Amount in ${currency}`}
        required
      />
      <div
        style={{
          display: "flex",
          flexWrap: "wrap",
          gap: "0.4rem",
        }}
      >
        {["2.00", "5.00", "10.00", "25.00"].map((v) => (
          <button
            key={v}
            type="button"
            className={`btn ${amount === v ? "btn-primary" : "btn-outline"}`}
            onClick={() => setAmount(v)}
          >
            {currency} {v}
          </button>
        ))}
      </div>

      <p className="muted" style={{ margin: 0 }}>
        You&apos;ll receive{" "}
        <strong>{credits.toLocaleString()}</strong> credits.
      </p>

      <div>
        <button type="submit" className="btn btn-primary" disabled={pending || credits <= 0}>
          {pending ? "Redirecting…" : "Pay with PayPal"}
        </button>
      </div>

      {error ? (
        <p
          role="alert"
          aria-live="polite"
          style={{ margin: 0, fontWeight: 700, color: "var(--color-danger)" }}
        >
          {error}
        </p>
      ) : null}
    </form>
  );
}