"use client";

import { useEffect, useId, useRef, useState, type CSSProperties, type ElementType, type FormEvent } from "react";
import { AnimatePresence, motion, useReducedMotion } from "motion/react";

export type ContactFlowData = { topic: string; name: string; email: string; message: string };

const LABELS = {
  topic: "What is this about?",
  name: "Your name",
  email: "Email",
  message: "How can we help?",
  next: "Next",
  back: "Back",
  send: "Send message",
  sending: "Sending…",
  step: "Step",
  of: "of",
  pickTopic: "Pick one to go on.",
  needName: "Please add your name.",
  needEmail: "Please add a valid email.",
  needMessage: "Please write a short message.",
  failed: "That did not send. Please try again.",
  doneTitle: "Message sent",
  doneText: "Thanks. We will write back soon.",
  again: "Send another",
};

type ContactFlowProps = {
  /** The choices on the first step. */
  topics: string[];
  /** Sends the message. Throw or reject to show the error line. */
  onSubmit: (data: ContactFlowData) => void | Promise<void>;
  title?: string;
  /** Small line above the title. */
  eyebrow?: string;
  subtitle?: string;
  /** Other ways to reach you, beside the form. */
  channels?: { label: string; value: string; href?: string }[];
  /** Every word in the form, for other languages. Give only the ones to change. */
  labels?: Partial<typeof LABELS>;
  /** Colour of the bar, the choice and the main button. */
  color?: string;
  /** Text colour on that colour. */
  ink?: string;
  /** Card colour. */
  tile?: string;
  /** h2 by default. */
  headingAs?: ElementType;
  /** Set padding and colours here. */
  className?: string;
};

const EMPTY: ContactFlowData = { topic: "", name: "", email: "", message: "" };
const STEPS = 3;
const FIELD =
  "mt-1.5 w-full rounded-lg border border-current/15 bg-transparent px-3 py-2 text-sm font-normal outline-none transition-colors focus:border-[var(--cf-color)] aria-invalid:border-red-400";

/* ContactFlow: a contact form taken one step at a time. The card reshapes to fit each step, focus moves with you, and the sent state draws a tick. It only collects: you send the data in onSubmit. */
export function ContactFlow({
  topics,
  onSubmit,
  title,
  eyebrow,
  subtitle,
  channels,
  labels,
  color = "#a78bfa",
  ink = "#0b0a14",
  tile = "#15122a",
  headingAs: Heading = "h2",
  className = "bg-[#0b0a14] px-5 py-16 text-white",
}: ContactFlowProps) {
  const reduce = useReducedMotion();
  const id = useId();
  const words = { ...LABELS, ...labels };
  const inner = useRef<HTMLDivElement>(null);
  const card = useRef<HTMLFormElement>(null);
  const moved = useRef(false);
  const [height, setHeight] = useState<number>();
  const [step, setStep] = useState(0);
  const [way, setWay] = useState(1);
  const [data, setData] = useState(EMPTY);
  const [error, setError] = useState("");
  const [state, setState] = useState<"open" | "sending" | "sent">("open");
  const sent = state === "sent";

  useEffect(() => {
    const el = inner.current;
    if (!el) return;
    const watcher = new ResizeObserver(([entry]) => setHeight(entry.target.getBoundingClientRect().height));
    watcher.observe(el);
    return () => watcher.disconnect();
  }, []);

  useEffect(() => {
    if (!moved.current) return;
    card.current?.querySelector<HTMLElement>(`[data-step="${sent ? "done" : step}"] :is(input, textarea, button)`)?.focus({ preventScroll: true });
  }, [sent, step]);

  const set = (key: keyof ContactFlowData, value: string) => {
    setData((now) => ({ ...now, [key]: value }));
    setError("");
  };
  const check = () => {
    if (step === 0 && !data.topic) return words.pickTopic;
    if (step === 1 && !data.name.trim()) return words.needName;
    if (step === 1 && !/^\S+@\S+\.\S+$/.test(data.email.trim())) return words.needEmail;
    if (step === 2 && !data.message.trim()) return words.needMessage;
    return "";
  };
  const go = (to: number) => {
    moved.current = true;
    setWay(to > step ? 1 : -1);
    setError("");
    setStep(to);
  };
  const submit = async (e: FormEvent) => {
    e.preventDefault();
    if (state === "sending") return;
    const problem = check();
    if (problem) return setError(problem);
    if (step < STEPS - 1) return go(step + 1);
    setState("sending");
    setError("");
    try {
      await onSubmit(data);
      moved.current = true;
      setState("sent");
    } catch {
      setState("open");
      setError(words.failed);
    }
  };
  const again = () => {
    setData(EMPTY);
    setStep(0);
    setState("open");
  };

  const errorFor = (bad: boolean) => (bad && error ? { "aria-invalid": true, "aria-describedby": `${id}-error` } : {});
  const slide = {
    initial: { opacity: 0, x: reduce ? 0 : way * 36 },
    animate: { opacity: 1, x: 0 },
    exit: { opacity: 0, x: reduce ? 0 : way * -36 },
    transition: { duration: reduce ? 0 : 0.3, ease: [0.16, 1, 0.3, 1] as const },
  };

  return (
    <section aria-labelledby={title ? id : undefined} className={`@container ${className}`} style={{ "--cf-color": color, "--cf-ink": ink } as CSSProperties}>
      <div className="mx-auto grid max-w-5xl items-center gap-8 @3xl:grid-cols-2 @3xl:gap-12">
        <div>
          {title && (
            <header>
              {eyebrow && <p className="mb-2 text-xs font-medium tracking-[0.2em] uppercase opacity-70">{eyebrow}</p>}
              <Heading id={id} className="text-[clamp(1.5rem,6cqw,2.5rem)] leading-tight font-semibold tracking-tight text-balance">
                {title}
              </Heading>
              {subtitle && <p className="mt-3 text-pretty opacity-70">{subtitle}</p>}
            </header>
          )}
          {channels && channels.length > 0 && (
            <dl className="mt-6 grid gap-3 text-sm">
              {channels.map((item) => (
                <div key={item.label}>
                  <dt className="opacity-60">{item.label}</dt>
                  <dd className="font-medium">
                    {item.href ? (
                      <a href={item.href} className="underline-offset-2 hover:underline">
                        {item.value}
                      </a>
                    ) : (
                      item.value
                    )}
                  </dd>
                </div>
              ))}
            </dl>
          )}
        </div>
        <form ref={card} noValidate onSubmit={submit} aria-label={title ?? "Contact"} className="overflow-hidden rounded-2xl border border-current/10" style={{ backgroundColor: tile }}>
          <div className="h-0.5 bg-current/10">
            <motion.div
              className="h-full origin-left bg-[var(--cf-color)]"
              initial={false}
              animate={{ scaleX: sent ? 1 : (step + 1) / STEPS }}
              transition={{ duration: reduce ? 0 : 0.5, ease: [0.16, 1, 0.3, 1] }}
            />
          </div>
          <motion.div className="overflow-hidden" initial={false} animate={height ? { height } : undefined} transition={{ duration: reduce ? 0 : 0.35, ease: [0.16, 1, 0.3, 1] }}>
            <div ref={inner} className="relative p-5">
              <AnimatePresence mode="popLayout" initial={false}>
                {sent ? (
                  <motion.div key="done" data-step="done" {...slide} role="status" className="py-4 text-center">
                    <svg viewBox="0 0 48 48" aria-hidden className="mx-auto size-14" fill="none" stroke={color} strokeWidth="3" strokeLinecap="round" strokeLinejoin="round">
                      <motion.circle cx="24" cy="24" r="21" initial={{ pathLength: reduce ? 1 : 0 }} animate={{ pathLength: 1 }} transition={{ duration: reduce ? 0 : 0.5 }} />
                      <motion.path d="M14 25l7 7 13-15" initial={{ pathLength: reduce ? 1 : 0 }} animate={{ pathLength: 1 }} transition={{ duration: reduce ? 0 : 0.35, delay: reduce ? 0 : 0.4 }} />
                    </svg>
                    <p className="mt-3 text-lg font-semibold">{words.doneTitle}</p>
                    <p className="mt-1 text-sm opacity-70">{words.doneText}</p>
                    <button type="button" onClick={again} className="mt-4 text-sm underline underline-offset-2">
                      {words.again}
                    </button>
                  </motion.div>
                ) : (
                  <motion.div key={step} data-step={step} {...slide}>
                    <p className="mb-3 text-xs opacity-60">
                      {words.step} {step + 1} {words.of} {STEPS}
                    </p>
                    {step === 0 && (
                      <fieldset aria-describedby={error ? `${id}-error` : undefined}>
                        <legend className="mb-2.5 font-semibold">{words.topic}</legend>
                        <div className="flex flex-wrap gap-2">
                          {topics.map((topic) => (
                            <label key={topic} className="cursor-pointer">
                              <input type="radio" name={`${id}-topic`} value={topic} checked={data.topic === topic} onChange={() => set("topic", topic)} className="peer sr-only" />
                              <span className="block rounded-full border border-current/15 px-3.5 py-1.5 text-sm transition-colors peer-checked:border-[var(--cf-color)] peer-checked:bg-[var(--cf-color)] peer-checked:text-[var(--cf-ink)] peer-focus-visible:outline-2 peer-focus-visible:outline-offset-2 peer-focus-visible:outline-current hover:border-current/40">
                                {topic}
                              </span>
                            </label>
                          ))}
                        </div>
                      </fieldset>
                    )}
                    {step === 1 && (
                      <div className="grid gap-3">
                        <label className="block text-sm font-medium">
                          {words.name}
                          <input type="text" autoComplete="name" required value={data.name} onChange={(e) => set("name", e.target.value)} className={FIELD} {...errorFor(!data.name.trim())} />
                        </label>
                        <label className="block text-sm font-medium">
                          {words.email}
                          <input type="email" autoComplete="email" required value={data.email} onChange={(e) => set("email", e.target.value)} className={FIELD} {...errorFor(!!data.name.trim())} />
                        </label>
                      </div>
                    )}
                    {step === 2 && (
                      <label className="block text-sm font-medium">
                        {words.message}
                        <textarea rows={4} required value={data.message} onChange={(e) => set("message", e.target.value)} className={`${FIELD} resize-none`} {...errorFor(true)} />
                      </label>
                    )}
                    {error && (
                      <p id={`${id}-error`} role="alert" className="mt-2 text-sm text-red-300">
                        {error}
                      </p>
                    )}
                    <div className="mt-4 flex items-center justify-between gap-3">
                      {step > 0 ? (
                        <button type="button" onClick={() => go(step - 1)} className="text-sm opacity-70 hover:opacity-100">
                          {words.back}
                        </button>
                      ) : (
                        <span />
                      )}
                      <button type="submit" disabled={state === "sending"} className="rounded-lg bg-[var(--cf-color)] px-4 py-2 text-sm font-medium text-[var(--cf-ink)] disabled:opacity-60">
                        {step < STEPS - 1 ? words.next : state === "sending" ? words.sending : words.send}
                      </button>
                    </div>
                  </motion.div>
                )}
              </AnimatePresence>
            </div>
          </motion.div>
        </form>
      </div>
    </section>
  );
}