"use client";

import Link from "next/link";
import { useCallback, useEffect, useMemo, useState } from "react";
import { useCart } from "@/contexts/CartContext";
import { useWallet } from "@/contexts/WalletContext";
import { getMerchantBtcAddress, isMerchantBtcConfigured } from "@/lib/merchantBtc";
import { estimateUsdForCryptoAmount } from "@/lib/shopFx";

const ENCRYPTION_BTC_FEE: Record<"standard" | "enhanced" | "quantum", number> = {
  standard: 0,
  enhanced: 0.001,
  quantum: 0.005,
};

const CheckoutFlow = () => {
  const { lines, setLineQty, removeLine, clearCart, hydrated: cartHydrated } = useCart();
  const [step, setStep] = useState(1);
  const [paymentMethod, setPaymentMethod] = useState<"crypto" | "guest" | "card">("crypto");
  const [cryptoType, setCryptoType] = useState<"BTC" | "ETH" | "XMR">("BTC");
  const [guestEmail, setGuestEmail] = useState("");
  const [encryptionLevel, setEncryptionLevel] = useState<"standard" | "enhanced" | "quantum">("enhanced");
  const [btcUsd, setBtcUsd] = useState<number | null>(null);
  const [txidInput, setTxidInput] = useState("");
  const [verifyMsg, setVerifyMsg] = useState<{ kind: "ok" | "err"; text: string } | null>(null);
  const [verifyBusy, setVerifyBusy] = useState(false);
  const [payError, setPayError] = useState<string | null>(null);
  const [orderComplete, setOrderComplete] = useState(false);

  const { usdStoreCredit, spendUsdStoreCredit, verifyBtcDeposit } = useWallet();

  useEffect(() => {
    let cancelled = false;
    (async () => {
      try {
        const res = await fetch(
          "https://api.coingecko.com/api/v3/simple/price?ids=bitcoin&vs_currencies=usd",
        );
        const j = (await res.json()) as { bitcoin?: { usd?: number } };
        const p = j.bitcoin?.usd;
        if (!cancelled && p && Number.isFinite(p)) setBtcUsd(p);
      } catch {
        if (!cancelled) setBtcUsd(96000);
      }
    })();
    return () => {
      cancelled = true;
    };
  }, []);

  const spotBtc = btcUsd ?? 96000;

  const subtotalUsd = useMemo(
    () =>
      Math.round(
        lines.reduce(
          (sum, l) => sum + estimateUsdForCryptoAmount(l.price, l.currency, spotBtc) * l.qty,
          0,
        ) * 100,
      ) / 100,
    [lines, spotBtc],
  );

  const encryptionFeeUsd = useMemo(() => {
    const rate = btcUsd ?? 96000;
    return Math.round(ENCRYPTION_BTC_FEE[encryptionLevel] * rate * 100) / 100;
  }, [encryptionLevel, btcUsd]);

  const orderTotalUsd = useMemo(
    () => Math.round((subtotalUsd + encryptionFeeUsd) * 100) / 100,
    [subtotalUsd, encryptionFeeUsd],
  );

  const orderTotalBtc = useMemo(() => {
    const r = btcUsd && btcUsd > 0 ? btcUsd : spotBtc;
    if (!r || r <= 0) return null;
    return Math.round((orderTotalUsd / r) * 1e8) / 1e8;
  }, [orderTotalUsd, btcUsd, spotBtc]);

  const merchantAddr = getMerchantBtcAddress();
  const merchantReady = isMerchantBtcConfigured();

  const btcPayUri = useMemo(() => {
    if (!merchantReady || orderTotalBtc == null) return "";
    return `bitcoin:${merchantAddr}?amount=${orderTotalBtc}`;
  }, [merchantReady, merchantAddr, orderTotalBtc]);

  const handleVerify = useCallback(async () => {
    setVerifyMsg(null);
    setVerifyBusy(true);
    try {
      const result = await verifyBtcDeposit(txidInput.trim());
      if (result.ok) {
        setVerifyMsg({
          kind: "ok",
          text: `Confirmed. Added $${result.creditedUsd?.toFixed(2) ?? "0.00"} USD to your spendable balance.`,
        });
        setTxidInput("");
      } else {
        setVerifyMsg({ kind: "err", text: result.error || "Verification failed" });
      }
    } finally {
      setVerifyBusy(false);
    }
  }, [txidInput, verifyBtcDeposit]);

  const tryCompleteOrder = () => {
    setPayError(null);
    if (paymentMethod === "crypto") {
      if (!spendUsdStoreCredit(orderTotalUsd)) {
        setPayError(
          `Insufficient USD balance. You need $${orderTotalUsd.toFixed(2)}. Send Bitcoin to the address below, wait for at least one confirmation, then paste the transaction ID and click Verify.`,
        );
        return;
      }
    }
    setOrderComplete(true);
    clearCart();
  };

  const steps = [
    { number: 1, title: "Cart", description: "Review items" },
    { number: 2, title: "Payment", description: "Choose method" },
    { number: 3, title: "Encryption", description: "Select privacy level" },
    { number: 4, title: "Confirmation", description: "Complete ritual" },
  ];

  const handleNext = () => {
    if (step === 1 && lines.length === 0) return;
    if (step < 4) setStep(step + 1);
  };

  const handlePrev = () => {
    if (step > 1) setStep(step - 1);
  };

  return (
    <div className="glass mx-auto max-w-4xl rounded-3xl border border-white/10 p-8 md:p-12">
      <div className="mb-12">
        <div className="flex justify-between">
          {steps.map((s) => (
            <div key={s.number} className="flex flex-col items-center">
              <div
                className={`flex h-12 w-12 items-center justify-center rounded-full border-2 text-lg font-bold ${step >= s.number
                    ? "border-neon-cyan bg-neon-cyan/20 text-neon-cyan"
                    : "border-white/20 text-foreground/40"
                  }`}
              >
                {s.number}
              </div>
              <div className="mt-2 text-center">
                <div className="text-sm font-medium">{s.title}</div>
                <div className="text-xs text-foreground/50">{s.description}</div>
              </div>
            </div>
          ))}
        </div>
        <div className="relative -top-6 -z-10 h-1 bg-white/10">
          <div
            className="h-1 bg-gradient-to-r from-neon-cyan to-neon-purple transition-all duration-500"
            style={{ width: `${((step - 1) / 3) * 100}%` }}
          />
        </div>
      </div>

      <div className="mb-10">
        {step === 1 && (
          <div>
            <h3 className="mb-6 font-orbitron text-2xl font-bold">YOUR CART</h3>
            {!cartHydrated ? (
              <p className="text-sm text-foreground/50">Loading cart…</p>
            ) : lines.length === 0 ? (
              <div className="rounded-xl border border-dashed border-white/15 p-10 text-center">
                <p className="text-foreground/70">Your cart is empty.</p>
                <p className="mt-2 text-sm text-foreground/50">Add SKUs from the hub or candy market.</p>
                <Link
                  href="/market"
                  className="mt-6 inline-block rounded-full bg-gradient-to-r from-neon-cyan to-neon-purple px-8 py-3 text-sm font-bold text-background"
                >
                  Browse catalog
                </Link>
              </div>
            ) : (
              <div className="space-y-4">
                {lines.map((item) => {
                  const unitUsd = estimateUsdForCryptoAmount(item.price, item.currency, spotBtc);
                  const lineUsd = Math.round(unitUsd * item.qty * 100) / 100;
                  return (
                    <div
                      key={item.productId}
                      className="flex flex-col gap-4 rounded-xl bg-white/5 p-4 sm:flex-row sm:items-center sm:justify-between"
                    >
                      <div className="min-w-0 flex-1">
                        <div className="font-medium">{item.name}</div>
                        <div className="mt-1 font-mono text-xs text-foreground/50">
                          {item.price} {item.currency} each · ≈ ${unitUsd.toFixed(2)} USD @ spot
                        </div>
                        <div className="mt-3 flex flex-wrap items-center gap-2">
                          <span className="text-xs text-foreground/50">Qty</span>
                          <button
                            type="button"
                            className="rounded border border-white/15 px-2 py-0.5 text-sm hover:bg-white/10"
                            onClick={() => setLineQty(item.productId, item.qty - 1)}
                            aria-label="Decrease quantity"
                          >
                            −
                          </button>
                          <span className="w-8 text-center font-mono text-sm">{item.qty}</span>
                          <button
                            type="button"
                            className="rounded border border-white/15 px-2 py-0.5 text-sm hover:bg-white/10"
                            onClick={() => setLineQty(item.productId, item.qty + 1)}
                            aria-label="Increase quantity"
                          >
                            +
                          </button>
                          <button
                            type="button"
                            className="ml-2 text-xs text-red-400 hover:underline"
                            onClick={() => removeLine(item.productId)}
                          >
                            Remove
                          </button>
                        </div>
                      </div>
                      <div className="text-right sm:shrink-0">
                        <div className="font-orbitron text-xl text-neon-cyan">${lineUsd.toLocaleString()}</div>
                        <div className="text-xs text-foreground/50">USD est.</div>
                      </div>
                    </div>
                  );
                })}
              </div>
            )}
            {lines.length > 0 ? (
              <div className="mt-8 flex justify-between border-t border-white/10 pt-6 text-xl">
                <span>Subtotal (USD est.)</span>
                <span className="font-orbitron font-bold text-neon-cyan">
                  ${subtotalUsd.toLocaleString()}
                </span>
              </div>
            ) : null}
          </div>
        )}

        {step === 2 && (
          <div>
            <h3 className="mb-6 font-orbitron text-2xl font-bold">SELECT PAYMENT METHOD</h3>
            <div className="mb-6 rounded-xl border border-neon-green/30 bg-neon-green/5 px-4 py-3 text-sm">
              <span className="font-bold text-neon-green">USD balance: </span>
              <span className="font-orbitron">${usdStoreCredit.toFixed(2)}</span>
              <span className="text-foreground/60">
                {" "}
                — use after Bitcoin deposit is verified (on-chain).
              </span>
            </div>
            <div className="grid grid-cols-1 gap-4 md:grid-cols-3">
              <button
                type="button"
                className={`glass rounded-2xl border p-6 text-center transition-all ${paymentMethod === "crypto" ? "border-neon-cyan ring-2 ring-neon-cyan/30" : "border-white/10"
                  }`}
                onClick={() => setPaymentMethod("crypto")}
              >
                <div className="mb-4 text-4xl">₿</div>
                <div className="font-bold">Cryptocurrency</div>
                <div className="mt-2 text-sm text-foreground/60">Bitcoin checkout balance</div>
              </button>
              <button
                type="button"
                className={`glass rounded-2xl border p-6 text-center transition-all ${paymentMethod === "guest" ? "border-neon-cyan ring-2 ring-neon-cyan/30" : "border-white/10"
                  }`}
                onClick={() => setPaymentMethod("guest")}
              >
                <div className="mb-4 text-4xl">👤</div>
                <div className="font-bold">Guest Checkout</div>
                <div className="mt-2 text-sm text-foreground/60">Demo — no USD charge</div>
              </button>
              <button
                type="button"
                className={`glass rounded-2xl border p-6 text-center transition-all ${paymentMethod === "card" ? "border-neon-cyan ring-2 ring-neon-cyan/30" : "border-white/10"
                  }`}
                onClick={() => setPaymentMethod("card")}
              >
                <div className="mb-4 text-4xl">💳</div>
                <div className="font-bold">Card (Secure)</div>
                <div className="mt-2 text-sm text-foreground/60">Demo — no USD charge</div>
              </button>
            </div>

            {paymentMethod === "crypto" && (
              <div className="mt-8">
                <label className="mb-2 block font-medium">Select Cryptocurrency</label>
                <div className="flex gap-4">
                  {(["BTC", "ETH", "XMR"] as const).map((coin) => (
                    <button
                      key={coin}
                      type="button"
                      className={`glass flex-1 rounded-xl border py-4 ${cryptoType === coin ? "border-neon-cyan bg-neon-cyan/10" : "border-white/10"
                        }`}
                      onClick={() => setCryptoType(coin)}
                    >
                      <div className="text-2xl">{coin === "BTC" ? "₿" : coin === "ETH" ? "Ξ" : "⏣"}</div>
                      <div className="font-bold">{coin}</div>
                    </button>
                  ))}
                </div>
                {cryptoType !== "BTC" && (
                  <p className="mt-4 rounded-lg bg-white/5 p-4 text-sm text-foreground/70">
                    Deposits that add USD balance use <strong>Bitcoin</strong> only. Switch to BTC to see the
                    deposit address. (ETH/XMR shown for display.)
                  </p>
                )}
                {cryptoType === "BTC" && (
                  <div className="mt-6 space-y-4 rounded-xl bg-white/5 p-4">
                    <div className="text-sm text-foreground/60">Estimated order total after encryption step</div>
                    <div className="font-orbitron text-2xl text-neon-cyan">
                      ${orderTotalUsd.toLocaleString()} USD
                      {orderTotalBtc != null && btcUsd != null && (
                        <span className="ml-3 text-lg text-foreground/70">
                          (≈ {orderTotalBtc} BTC @ ${btcUsd.toLocaleString()}/BTC)
                        </span>
                      )}
                    </div>
                    <p className="text-xs text-foreground/50">
                      Final total includes the encryption add-on you pick in the next step. Fund your balance
                      with <strong>any amount</strong> of BTC; verified value is credited in USD at spot rate.
                      You can pay this order once your balance covers the total.
                    </p>
                  </div>
                )}
              </div>
            )}

            {paymentMethod === "guest" && (
              <div className="mt-8">
                <label className="mb-2 block font-medium">Email for receipt (optional)</label>
                <input
                  type="email"
                  className="glass w-full rounded-xl border border-white/10 bg-transparent px-4 py-3"
                  placeholder="anonymous@example.com"
                  value={guestEmail}
                  onChange={(e) => setGuestEmail(e.target.value)}
                />
                <p className="mt-2 text-sm text-foreground/60">
                  Guest checkout is a demo and does not charge your USD balance.
                </p>
              </div>
            )}

            <div className="mt-10 border-t border-white/10 pt-8">
              <h4 className="mb-4 font-orbitron text-lg font-bold text-neon-cyan">Bitcoin deposit (all checkouts)</h4>
              {!merchantReady ? (
                <p className="text-sm text-amber-300/90">
                  Set <code className="rounded bg-white/10 px-1">NEXT_PUBLIC_MERCHANT_BTC_ADDRESS</code> and{" "}
                  <code className="rounded bg-white/10 px-1">MERCHANT_BTC_ADDRESS</code> in{" "}
                  <code className="rounded bg-white/10 px-1">.env.local</code>, then restart the app.
                </p>
              ) : (
                <>
                  <p className="mb-3 text-sm text-foreground/70">
                    Send Bitcoin to this address. After the network confirms your payment (at least one
                    block), paste the transaction ID to add the equivalent USD to your balance.
                  </p>
                  <div className="rounded-xl border border-white/10 bg-black/40 p-4 font-mono text-sm break-all">
                    {merchantAddr}
                  </div>
                  {btcPayUri && (
                    <div className="mt-4 flex flex-col gap-4 md:flex-row md:items-start">
                      <img
                        src={`https://api.qrserver.com/v1/create-qr-code/?size=160x160&data=${encodeURIComponent(btcPayUri)}`}
                        alt="Bitcoin payment QR"
                        width={160}
                        height={160}
                        className="rounded-lg border border-white/10"
                      />
                      <div className="text-xs text-foreground/50">
                        QR encodes a suggested payment URI for the current cart estimate (you may send any
                        amount; all verified BTC to this address becomes USD credit).
                      </div>
                    </div>
                  )}
                  <div className="mt-6 space-y-2">
                    <label className="text-sm font-medium">Transaction ID (after confirmed)</label>
                    <input
                      className="glass w-full rounded-xl border border-white/10 bg-transparent px-4 py-3 font-mono text-sm"
                      placeholder="64-character txid"
                      value={txidInput}
                      onChange={(e) => setTxidInput(e.target.value.replace(/\s+/g, ""))}
                    />
                    <button
                      type="button"
                      disabled={verifyBusy}
                      onClick={() => void handleVerify()}
                      className="rounded-full bg-gradient-to-r from-neon-cyan to-neon-purple px-6 py-2 text-sm font-bold text-background disabled:opacity-40"
                    >
                      {verifyBusy ? "Verifying…" : "Verify & add USD credit"}
                    </button>
                    {verifyMsg && (
                      <p
                        className={`text-sm ${verifyMsg.kind === "ok" ? "text-neon-green" : "text-red-400"}`}
                      >
                        {verifyMsg.text}
                      </p>
                    )}
                  </div>
                </>
              )}
            </div>
          </div>
        )}

        {step === 3 && (
          <div>
            <h3 className="mb-6 font-orbitron text-2xl font-bold">ENCRYPTION LEVEL</h3>
            <p className="mb-8 text-foreground/70">
              Choose how securely your data is protected. Higher levels add to your order total in USD.
            </p>
            <div className="space-y-4">
              {[
                { level: "standard" as const, name: "Stealth Encryption", desc: "Military‑grade encryption, basic anonymity", icon: "🕵️" },
                { level: "enhanced" as const, name: "Ghost Protocol", desc: "Post‑quantum cryptography, zero‑trace", icon: "👻" },
                { level: "quantum" as const, name: "Zero‑Trace", desc: "Experimental, quantum‑entangled proofs", icon: "⚛️" },
              ].map((opt) => (
                <button
                  key={opt.level}
                  type="button"
                  className={`glass flex w-full items-center justify-between rounded-2xl border p-6 text-left ${encryptionLevel === opt.level ? "border-neon-cyan ring-2 ring-neon-cyan/30" : "border-white/10"
                    }`}
                  onClick={() => setEncryptionLevel(opt.level)}
                >
                  <div>
                    <div className="flex items-center gap-4">
                      <span className="text-3xl">{opt.icon}</span>
                      <div>
                        <div className="font-bold">{opt.name}</div>
                        <div className="text-sm text-foreground/60">{opt.desc}</div>
                      </div>
                    </div>
                  </div>
                  <div className="text-right font-orbitron text-xl font-bold text-neon-cyan">
                    {opt.level === "standard"
                      ? "FREE"
                      : `+$${(Math.round(ENCRYPTION_BTC_FEE[opt.level] * (btcUsd ?? 96000) * 100) / 100).toFixed(2)}`}
                  </div>
                </button>
              ))}
            </div>
            <div className="mt-8 rounded-xl bg-gradient-to-r from-neon-cyan/10 to-neon-purple/10 p-6">
              <div className="font-orbitron font-bold">Order total so far</div>
              <div className="mt-2 text-2xl text-neon-cyan">
                ${orderTotalUsd.toLocaleString()} USD
              </div>
            </div>
          </div>
        )}

        {step === 4 && !orderComplete && (
          <div className="text-center">
            <h3 className="mb-4 font-orbitron text-3xl font-bold">COMPLETE PAYMENT</h3>
            <div className="glass mx-auto mb-8 max-w-md rounded-2xl border border-white/10 p-6 text-left">
              <div className="flex justify-between text-sm">
                <span className="text-foreground/60">Total due</span>
                <span className="font-orbitron font-bold text-neon-cyan">
                  ${orderTotalUsd.toLocaleString()}
                </span>
              </div>
              <div className="mt-2 flex justify-between text-sm">
                <span className="text-foreground/60">Your USD balance</span>
                <span className="font-orbitron">${usdStoreCredit.toFixed(2)}</span>
              </div>
              <div className="mt-2 flex justify-between text-sm">
                <span className="text-foreground/60">Payment path</span>
                <span className="font-bold">
                  {paymentMethod === "crypto" ? "Crypto (USD balance)" : "Demo (guest/card)"}
                </span>
              </div>
            </div>
            {payError && <p className="mx-auto mb-6 max-w-xl text-sm text-red-400">{payError}</p>}
            <button
              type="button"
              onClick={tryCompleteOrder}
              className="rounded-full bg-gradient-to-r from-neon-cyan to-neon-purple px-10 py-3 font-bold text-background"
            >
              {paymentMethod === "crypto" ? "Charge my USD balance & complete" : "Complete demo order"}
            </button>
            {paymentMethod === "crypto" && (
              <p className="mx-auto mt-6 max-w-xl text-xs text-foreground/50">
                Crypto checkout pulls from your verified USD balance only. Send BTC on the payment step and
                verify the txid so your balance matches the total above.
              </p>
            )}
          </div>
        )}

        {step === 4 && orderComplete && (
          <div className="text-center">
            <div className="mb-8">
              <div className="inline-flex h-24 w-24 items-center justify-center rounded-full bg-gradient-to-r from-neon-cyan to-neon-purple">
                <span className="text-4xl">✨</span>
              </div>
            </div>
            <h3 className="mb-4 font-orbitron text-3xl font-bold">RITUAL COMPLETE</h3>
            <p className="mx-auto max-w-2xl text-foreground/70">
              Your order is now encrypted with {encryptionLevel} protection. A unique digital artwork receipt
              has been generated and stored in your vault.
            </p>
            <div className="my-10">
              <div className="glass mx-auto max-w-md rounded-2xl border border-white/10 p-6">
                <div className="font-orbitron text-2xl font-bold text-neon-cyan">ORDER #CYBR‑9A2F‑B8E1</div>
                <div className="mt-4 grid grid-cols-2 gap-4 text-sm">
                  <div className="text-left text-foreground/60">Amount</div>
                  <div className="text-right font-bold">${orderTotalUsd.toLocaleString()} USD</div>
                  <div className="text-left text-foreground/60">Privacy</div>
                  <div className="text-right font-bold">{encryptionLevel.toUpperCase()}</div>
                  <div className="text-left text-foreground/60">Payment</div>
                  <div className="truncate text-right font-mono text-neon-green">
                    {paymentMethod === "crypto" ? "USD balance (BTC-funded)" : "Demo guest/card"}
                  </div>
                </div>
              </div>
            </div>
            <p className="text-sm text-foreground/50">
              Your digital receipt is available in your vault. Thank you for choosing CyberLux.
            </p>
          </div>
        )}
      </div>

      <div className="flex justify-between">
        <button
          type="button"
          className="glass rounded-full px-8 py-3 font-medium disabled:opacity-30"
          onClick={handlePrev}
          disabled={step === 1 || (step === 4 && orderComplete)}
        >
          ← Previous
        </button>
        <div className="flex items-center gap-4">
          {step < 4 ? (
            <button
              type="button"
              disabled={step === 1 && lines.length === 0}
              className="rounded-full bg-gradient-to-r from-neon-cyan to-neon-purple px-8 py-3 font-bold text-background disabled:opacity-40"
              onClick={handleNext}
            >
              Continue →
            </button>
          ) : orderComplete ? (
            <button
              type="button"
              className="rounded-full bg-gradient-to-r from-neon-green to-neon-cyan px-10 py-3 font-bold text-background"
            >
              ENTER THE VAULT
            </button>
          ) : null}
        </div>
      </div>
    </div>
  );
};

export default CheckoutFlow;