"use client";

import { useEffect, useId, useState, type CSSProperties } from "react";
import { AnimatePresence, animate, motion, useMotionValue, useReducedMotion, useTransform } from "motion/react";

type Plan = {
  name: string;
  /** Price for one month. */
  monthly: number;
  /** Price for the whole year. The saving badge is worked out from these two. */
  yearly: number;
  /** Small line under the price. */
  note?: string;
  features?: string[];
  /** Marks this plan with the accent colour. */
  featured?: boolean;
};

type PricingSwitchProps = {
  plans: Plan[];
  /** Start on the yearly side. */
  defaultYearly?: boolean;
  /** Text on the two sides of the switch. */
  labels?: [string, string];
  /** Text after the price on each side. */
  units?: [string, string];
  /** Text before the price, like "$" or "₹". */
  prefix?: string;
  /** Digits after the point. */
  decimals?: number;
  /** Number format, like "en-IN" for lakh commas. */
  locale?: string;
  /** Called when the switch moves. */
  onChange?: (yearly: boolean) => void;
  /** Called when a plan button is pressed. Leave out to hide the buttons. */
  onSelect?: (plan: Plan, yearly: boolean) => void;
  /** Text on the plan buttons. */
  buttonLabel?: string;
  /** Switch, featured plan and tick colour. Text on it stays dark. */
  accent?: string;
  /** Replaces the plan card look. */
  className?: string;
};

function Price({ value, format, reduce }: { value: number; format: (n: number) => string; reduce: boolean | null }) {
  const count = useMotionValue(value);
  const text = useTransform(count, format);

  useEffect(() => {
    if (reduce) {
      count.set(value);
      return;
    }
    const run = animate(count, value, { duration: 0.6, ease: [0.16, 1, 0.3, 1] });
    return () => run.stop();
  }, [count, reduce, value]);

  return (
    <>
      <motion.span aria-hidden>{text}</motion.span>
      <span className="sr-only">{format(value)}</span>
    </>
  );
}

/* PricingSwitch: a monthly and yearly switch whose pill slides across while every price counts over to the new number. */
export function PricingSwitch({
  plans,
  defaultYearly = false,
  labels = ["Monthly", "Yearly"],
  units = ["/mo", "/yr"],
  prefix = "$",
  decimals = 0,
  locale = "en-US",
  onChange,
  onSelect,
  buttonLabel = "Choose plan",
  accent = "#a78bfa",
  className = "rounded-2xl border border-white/10 bg-white/5 p-5 text-white",
}: PricingSwitchProps) {
  const reduce = useReducedMotion();
  const id = useId();
  const [yearly, setYearly] = useState(defaultYearly);
  const spring = reduce ? { duration: 0 } : { type: "spring" as const, stiffness: 380, damping: 32 };
  const side = yearly ? 1 : 0;
  const format = (n: number) => `${prefix}${n.toLocaleString(locale, { minimumFractionDigits: decimals, maximumFractionDigits: decimals })}`;

  const pick = (next: boolean) => {
    setYearly(next);
    onChange?.(next);
  };

  return (
    <div style={{ "--ps": accent } as CSSProperties} className="grid w-full justify-items-center gap-5">
      <div role="radiogroup" aria-label="Billing period" className="relative grid w-fit grid-cols-2 rounded-full border border-white/10 bg-white/5 p-1 text-sm text-white">
        <motion.span aria-hidden className="absolute inset-y-1 left-1 w-[calc(50%-0.25rem)] rounded-full bg-(--ps)" initial={false} animate={{ x: yearly ? "100%" : "0%" }} transition={spring} />
        {labels.map((label, i) => (
          <label key={label} className="relative cursor-pointer rounded-full px-5 py-1.5 text-center font-medium transition-colors has-checked:text-[#101014] has-focus-visible:ring-2 has-focus-visible:ring-white/70">
            <input type="radio" name={id} className="sr-only" checked={side === i} onChange={() => pick(i === 1)} />
            {label}
          </label>
        ))}
      </div>
      <span role="status" className="sr-only">
        {labels[side]} prices shown
      </span>

      <div className="grid w-full grid-cols-[repeat(auto-fit,minmax(min(100%,13rem),1fr))] gap-4">
        {plans.map((plan) => {
          const saving = plan.monthly > 0 ? Math.round((1 - plan.yearly / (plan.monthly * 12)) * 100) : 0;
          return (
            <div key={plan.name} className={`flex flex-col ${plan.featured ? "ring-2 ring-(--ps)" : ""} ${className}`}>
              <div className="flex min-h-6 items-center justify-between gap-2">
                <h3 className="text-sm font-semibold">{plan.name}</h3>
                <AnimatePresence initial={false}>
                  {yearly && saving > 0 && (
                    <motion.span
                      className="rounded-full bg-(--ps)/15 px-2 py-0.5 text-xs font-medium whitespace-nowrap text-(--ps)"
                      initial={{ opacity: 0, scale: 0.7 }}
                      animate={{ opacity: 1, scale: 1 }}
                      exit={{ opacity: 0, scale: 0.7 }}
                      transition={spring}
                    >
                      Save {saving}%
                    </motion.span>
                  )}
                </AnimatePresence>
              </div>
              <p className="mt-3 flex items-baseline gap-1">
                <span className="text-3xl font-bold tracking-tight tabular-nums">
                  <Price value={yearly ? plan.yearly : plan.monthly} format={format} reduce={reduce} />
                </span>
                <span className="text-sm opacity-60">{units[side]}</span>
              </p>
              {plan.note && <p className="mt-1 text-xs opacity-60">{plan.note}</p>}
              {plan.features && (
                <ul className="mt-4 grid gap-2 text-sm">
                  {plan.features.map((feature) => (
                    <li key={feature} className="flex items-start gap-2">
                      <svg aria-hidden viewBox="0 0 16 16" className="mt-0.5 size-4 shrink-0 fill-none stroke-(--ps) stroke-2">
                        <path d="M3 8.5l3.2 3.2L13 5" strokeLinecap="round" strokeLinejoin="round" />
                      </svg>
                      <span className="opacity-80">{feature}</span>
                    </li>
                  ))}
                </ul>
              )}
              {onSelect && (
                <button
                  type="button"
                  aria-label={`${buttonLabel}: ${plan.name}`}
                  onClick={() => onSelect(plan, yearly)}
                  className={`mt-5 w-full rounded-full px-4 py-2 text-sm font-medium outline-none focus-visible:ring-2 focus-visible:ring-white/70 ${plan.featured ? "bg-(--ps) text-[#101014]" : "border border-white/15 hover:bg-white/10"}`}
                >
                  {buttonLabel}
                </button>
              )}
            </div>
          );
        })}
      </div>
    </div>
  );
}