"use client";

import { useState } from "react";
import { useRouter, useSearchParams } from "next/navigation";
import Link from "next/link";
import { CheckCircle2, Mail } from "lucide-react";
import { Brand } from "./Brand";
import { ReplicaSafetyNotice } from "./ReplicaSafetyNotice";

type AuthResult = {
  error?: string;
  code?: string;
  requiresVerification?: boolean;
  verificationPreviewUrl?: string;
};

export function AuthForm({ mode }: { mode: "login" | "register" }) {
  const router = useRouter();
  const searchParams = useSearchParams();
  const [error, setError] = useState("");
  const [loading, setLoading] = useState(false);
  const [pendingEmail, setPendingEmail] = useState("");
  const [previewUrl, setPreviewUrl] = useState("");
  const [resendState, setResendState] = useState<"idle" | "sending" | "sent">("idle");

  function nextDestination() {
    const next = searchParams.get("next");
    if (next && next.startsWith("/") && !next.startsWith("//")) return next;
    return "/feed";
  }

  async function resendVerification(email: string) {
    setResendState("sending");
    setError("");
    try {
      const response = await fetch("/api/auth/verification/resend", {
        method: "POST",
        headers: { "content-type": "application/json" },
        body: JSON.stringify({ email }),
      });
      const result = await response.json() as AuthResult;
      if (!response.ok) throw new Error(result.error ?? "Unable to resend the verification email.");
      if (result.verificationPreviewUrl) setPreviewUrl(result.verificationPreviewUrl);
      setResendState("sent");
    } catch (caught) {
      setError(caught instanceof Error ? caught.message : "Unable to resend the verification email.");
      setResendState("idle");
    }
  }

  async function submit(event: React.FormEvent<HTMLFormElement>) {
    event.preventDefault();
    setError("");
    setLoading(true);
    const form = new FormData(event.currentTarget);
    const payload = Object.fromEntries(form.entries());
    try {
      const response = await fetch(`/api/auth/${mode}`, {
        method: "POST",
        headers: { "content-type": "application/json" },
        body: JSON.stringify(payload),
      });
      const result = await response.json() as AuthResult;
      if (!response.ok) {
        if (mode === "login" && result.code === "email_unverified") {
          setPendingEmail(String(payload.email ?? ""));
        }
        throw new Error(result.error ?? "Unable to continue.");
      }
      if (mode === "register" && result.requiresVerification) {
        setPendingEmail(String(payload.email ?? ""));
        setPreviewUrl(result.verificationPreviewUrl ?? "");
        return;
      }
      router.push(mode === "login" ? nextDestination() : "/feed");
      router.refresh();
    } catch (caught) {
      setError(caught instanceof Error ? caught.message : "Unable to continue.");
    } finally {
      setLoading(false);
    }
  }

  if (mode === "register" && pendingEmail) {
    return (
      <main className="auth-page">
        <div className="auth-brand"><Brand /></div>
        <section className="auth-card auth-status">
          <span className="auth-status-icon"><Mail size={28} /></span>
          <h1>Verify your email</h1>
          <p>We sent a secure LinkedIn verification link to <strong>{pendingEmail}</strong>.</p>
          <div className="auth-notice">This verification link expires and can be used once.</div>
          {previewUrl && <a className="button button-primary button-full" href={previewUrl}>Open development verification link</a>}
          <button className="button button-outline button-full" type="button" disabled={resendState === "sending"} onClick={() => resendVerification(pendingEmail)}>
            {resendState === "sending" ? "Sending…" : resendState === "sent" ? <><CheckCircle2 size={17} /> Email sent</> : "Resend email"}
          </button>
          {error && <div className="form-error" role="alert">{error}</div>}
          <div className="auth-switch"><Link prefetch={false} href="/login">Return to sign in</Link></div>
        </section>
        <footer className="auth-footer">LinkedIn © 2026 · WebsiteBench account · Not affiliated with LinkedIn · Privacy · Terms · Help</footer>
      </main>
    );
  }

  return (
    <main className="auth-page">
      <div className="auth-brand"><Brand /></div>
      <section className="auth-card">
        <h1>{mode === "login" ? "Sign in" : "Join LinkedIn"}</h1>
        <p>{mode === "login" ? "Stay connected to your professional community." : "Make the most of your professional life."}</p>
        <form method="post" onSubmit={submit}>
          {mode === "register" && (
            <>
              <label>Full name<input name="name" autoComplete="name" required minLength={2} maxLength={100} /></label>
              <label>Username<input name="username" autoComplete="username" required minLength={3} maxLength={32} pattern="[A-Za-z0-9_\\-]+" /></label>
            </>
          )}
          <label>Email<input name="email" type="email" autoComplete="email" required /></label>
          <label>Password<input name="password" type="password" autoComplete={mode === "login" ? "current-password" : "new-password"} required minLength={10} /></label>
          {mode === "register" && <small>Use 10+ characters with uppercase, lowercase, and a number. Use a password created for this site.</small>}
          {error && <div className="form-error" role="alert">{error}</div>}
          <button className="button button-primary button-full" disabled={loading}>{loading ? "Please wait…" : mode === "login" ? "Sign in" : "Agree & join"}</button>
        </form>
        {mode === "login" && pendingEmail && (
          <button className="auth-resend" type="button" disabled={resendState === "sending"} onClick={() => resendVerification(pendingEmail)}>
            {resendState === "sending" ? "Sending…" : resendState === "sent" ? "Verification email sent" : "Resend verification email"}
          </button>
        )}
        <div className="auth-switch">
          {mode === "login" ? <>New to LinkedIn? <Link prefetch={false} href="/register">Join now</Link></> : <>Already on LinkedIn? <Link prefetch={false} href="/login">Sign in</Link></>}
        </div>
        <ReplicaSafetyNotice />
      </section>
      <footer className="auth-footer">LinkedIn © 2026 · Privacy · Terms · Help</footer>
    </main>
  );
}