import { useEffect, useState } from "react";
import { Link } from "react-router-dom";
import { api } from "../api/client";
import { CheckIcon } from "./icons/Icons";

type Plan = {
  id: string;
  name: string;
  tagline: string;
  price_monthly_usd: number;
  price_annual_monthly_usd?: number;
  price_annual_usd?: number;
  annual_savings_pct?: number;
  features: string[];
};

type Cycle = "monthly" | "annual";

const ANNUAL_DISCOUNT = 0.25;

// Mirrors backend app/services/plans.py so the page renders before (or without) the API.
const FALLBACK: Plan[] = [
  {
    id: "free",
    name: "Free",
    tagline: "For trying Notestack on your archive",
    price_monthly_usd: 0,
    features: [
      "Up to 5 posts indexed, from any source",
      "Grounded research chat with citations",
      "1 audio overview, any length",
      "1 video",
      "2 Launch Kits",
      "2 infographics",
      "2 reports a month",
    ],
  },
  {
    id: "writer",
    name: "Writer",
    tagline: "For writers publishing every week",
    price_monthly_usd: 24.99,
    features: [
      "Up to 100 posts indexed, from any source",
      "10x more audio overviews than Free (60 min a month)",
      "10 videos a month",
      "20 Launch Kits a month",
      "30 reports a month",
      "30 infographics a month",
      "Voice cloning with consent",
    ],
  },
  {
    id: "studio",
    name: "Studio",
    tagline: "For publications and power users",
    price_monthly_usd: 48.99,
    features: [
      "Up to 250 posts indexed, from any source",
      "40x more audio overviews than Free (240 min a month)",
      "20 videos a month",
      "50 Launch Kits a month",
      "Unlimited reports",
      "Unlimited infographics",
      "Voice cloning with consent",
    ],
  },
];

export function money(n: number): string {
  return Number.isInteger(n) ? `$${n}` : `$${n.toFixed(2)}`;
}

/** Nearest .99 price, mirroring plans.to_99 on the backend. */
function to99(amount: number): number {
  return amount <= 0 ? 0 : Math.max(0.99, Math.round(amount + 0.01) - 0.01);
}

export function annualMonthly(plan: Plan): number {
  return plan.price_annual_monthly_usd ?? to99(plan.price_monthly_usd * (1 - ANNUAL_DISCOUNT));
}

function savingsPct(plan: Plan): number {
  if (!plan.price_monthly_usd) return 0;
  return plan.annual_savings_pct ?? Math.round((1 - annualMonthly(plan) / plan.price_monthly_usd) * 100);
}

export function annualTotal(plan: Plan): number {
  return plan.price_annual_usd ?? Math.round(annualMonthly(plan) * 12 * 100) / 100;
}

export default function PricingTiers() {
  const [plans, setPlans] = useState<Plan[]>(FALLBACK);
  const [billingEnabled, setBillingEnabled] = useState(false);
  const [cycle, setCycle] = useState<Cycle>("annual");
  const bestSaving = Math.max(0, ...plans.map(savingsPct));

  useEffect(() => {
    api<{ billing_enabled: boolean; plans: Plan[] }>("/api/billing/plans")
      .then((r) => {
        if (Array.isArray(r.plans) && r.plans.length > 0) setPlans(r.plans);
        setBillingEnabled(r.billing_enabled);
      })
      .catch(() => {
        /* keep fallback */
      });
  }, []);

  return (
    <div className="pricing">
      <div className="pricing-top">
        <div className="cycle-toggle" role="radiogroup" aria-label="Billing cycle">
          <button type="button" role="radio" aria-checked={cycle === "monthly"} className={cycle === "monthly" ? "on" : ""} onClick={() => setCycle("monthly")}>
            Monthly
          </button>
          <button type="button" role="radio" aria-checked={cycle === "annual"} className={cycle === "annual" ? "on" : ""} onClick={() => setCycle("annual")}>
            Annual {bestSaving > 0 && <span className="save mono">Save {bestSaving}%</span>}
          </button>
        </div>
      </div>
      <div className="pricing-grid">
        {plans.map((plan) => {
          const featured = plan.id === "writer";
          const free = plan.price_monthly_usd === 0;
          const annual = cycle === "annual" && !free;
          return (
            <article key={plan.id} className={`card tier${featured ? " tier-featured active" : ""}`}>
              {featured && <span className="badge tier-flag">Most popular</span>}
              <h3>{plan.name}</h3>
              <p className="muted tier-tagline">{plan.tagline}</p>
              <p className="tier-price">
                {free ? (
                  <span className="tier-amount">Free</span>
                ) : (
                  <>
                    {annual && <span className="tier-was muted">{money(plan.price_monthly_usd)}</span>}
                    <span className="tier-amount">{money(annual ? annualMonthly(plan) : plan.price_monthly_usd)}</span>
                    <span className="muted">/month</span>
                  </>
                )}
              </p>
              <p className="mono muted tier-billing">
                {free ? "Free forever" : annual ? `${money(annualTotal(plan))} billed yearly` : "Billed monthly"}
              </p>
              <ul className="tier-features">
                {plan.features.map((f) => (
                  <li key={f}>
                    <CheckIcon size={16} />
                    <span>{f}</span>
                  </li>
                ))}
              </ul>
              <Link
                to={billingEnabled && !free ? `/app?upgrade=${plan.id}` : "/auth?mode=signup"}
                className={`btn ${featured ? "btn-primary" : ""} tier-cta`}
              >
                {billingEnabled && !free ? `Choose ${plan.name}` : "Start free"}
              </Link>
            </article>
          );
        })}
      </div>
    </div>
  );
}