"use client";

/**
 * /settings — the top-level user-settings screen.
 *
 * Lives outside the /u/me profile layout so it doesn't carry the
 * ProfileHeader + tabs that frame the profile views. It sits directly
 * under (app)/, which gives it the default site chrome (sidebar, header,
 * etc.) without the profile-specific frame on top.
 *
 * Sections are stacked plain — no per-section card chrome — so the page
 * reads as a single ordered list of preferences rather than a dashboard
 * of widgets. To add a new section, drop another <Section> in the
 * `<main>` below.
 */

import { Suspense, useEffect, useState } from "react";
import Link from "next/link";
import { useRouter, useSearchParams } from "next/navigation";
import {
  AlertCircle,
  Check,
  ChevronLeft,
  ChevronRight,
  LogOut,
} from "lucide-react";
import { auth, AuthError } from "@/lib/auth";
import { useAuth } from "@/components/auth/auth-provider";
import { AddEmailModal } from "@/components/auth/add-email-modal";
import { ChangePasswordModal } from "@/components/auth/change-password-modal";
import { ReadingSettings } from "@/components/reading-settings";

const BFF_BASE =
  process.env.NEXT_PUBLIC_BFF_URL || "http://localhost:8080";

export default function SettingsPage() {
  return (
    <main className="flex-1 max-w-3xl w-full mx-auto px-4 sm:px-6 py-6 space-y-10">
      <header className="space-y-1">
        <Link
          href="/u/me"
          className="inline-flex items-center gap-1 text-base text-muted-foreground hover:text-foreground transition-colors"
        >
          <ChevronLeft className="size-5" />
          Back to profile
        </Link>
        <h1 className="font-[family-name:var(--font-title)] text-3xl font-semibold text-foreground pt-2">
          Settings
        </h1>
      </header>

      <Section
        title="Reading preferences"
        description="Theme, palette, font, and size — synced across your devices."
      >
        <ReadingSettings variant="bare" />
      </Section>

      <Section title="Authentication">
        {/* Suspense boundary required because LinkResult reads
            useSearchParams — Next.js bails out of SSR otherwise. */}
        <Suspense fallback={null}>
          <LinkResult />
        </Suspense>
        <AuthenticationSection />
      </Section>

      <Section title="Legal">
        <LegalSection />
      </Section>

      <SignOutSection />
    </main>
  );
}

function SignOutSection() {
  const { logOut } = useAuth();
  const router = useRouter();
  const [busy, setBusy] = useState(false);

  async function onSignOut() {
    setBusy(true);
    try {
      await logOut();
      router.push("/");
      router.refresh();
    } catch {
      // Logout errors are silent — the cookie is cleared on the server
      // either way and the next protected request will redirect anyway.
      setBusy(false);
    }
  }

  // Renders as a full-width clickable row matching LegalLink — same
  // padding, same hover, with LogOut taking the slot ChevronRight uses
  // on link rows. The whole row is the click target.
  return (
    <ul className="divide-y divide-border">
      <li>
        <button
          type="button"
          onClick={onSignOut}
          disabled={busy}
          className="w-full flex items-center justify-between py-3.5 group disabled:opacity-60"
        >
          <span className="text-base text-foreground group-hover:text-primary transition-colors">
            {busy ? "Signing out…" : "Sign out from this device"}
          </span>
          <LogOut className="size-5 text-muted-foreground group-hover:text-foreground transition-colors" />
        </button>
      </li>
    </ul>
  );
}

function Section({
  title,
  description,
  children,
}: {
  title: string;
  description?: string;
  children: React.ReactNode;
}) {
  return (
    <section className="space-y-4">
      <div className="border-b border-border pb-3">
        <h2 className="font-[family-name:var(--font-title)] text-2xl font-semibold text-foreground">
          {title}
        </h2>
        {description ? (
          <p className="text-base text-muted-foreground mt-1">{description}</p>
        ) : null}
      </div>
      <div>{children}</div>
    </section>
  );
}

// ─── Authentication ────────────────────────────────────────────────────

function AuthenticationSection() {
  const { user } = useAuth();
  const [pwModalOpen, setPwModalOpen] = useState(false);
  const [emailModalOpen, setEmailModalOpen] = useState(false);
  const [linkedProviders, setLinkedProviders] = useState<Set<string> | null>(
    null,
  );
  const next = "/settings";

  // Fetch linked providers on mount. A null set means "not yet loaded" — we
  // render the rows as if nothing is connected until the answer comes back,
  // which is fine because the only thing that changes after load is the
  // "Connected" pill swapping in for "Connect".
  useEffect(() => {
    let cancelled = false;
    auth
      .linkedProviders()
      .then(({ providers }) => {
        if (!cancelled) setLinkedProviders(new Set(providers));
      })
      .catch(() => {
        if (!cancelled) setLinkedProviders(new Set());
      });
    return () => {
      cancelled = true;
    };
  }, []);

  function startOAuth(provider: "facebook" | "google") {
    // /link/start — links the provider to the currently-authenticated
    // user (auth cookie travels on the top-level navigation). The login
    // page still uses /start for sign-in / sign-up.
    const u = new URL(
      `${BFF_BASE}/api/v1/auth/oauth/${provider}/link/start`,
    );
    u.searchParams.set("next", next);
    return u.toString();
  }

  function providerAction(provider: "google" | "facebook") {
    if (linkedProviders?.has(provider)) {
      return <ConnectedPill />;
    }
    return (
      <a
        href={startOAuth(provider)}
        className="text-base font-medium text-primary hover:underline"
      >
        Connect
      </a>
    );
  }

  // Three contextual states for the email-related rows:
  //   • user has no email                   → "Add your email" row only
  //   • user has email, NOT verified         → "Verify your email" row +
  //                                            "Change your password" row
  //   • user has email, verified             → "Change your password" row
  const needsEmail = !user?.email;
  const needsVerify = !!user?.email && !user.email_verified_at;

  return (
    <>
      <ul className="divide-y divide-border">
        <Row
          icon={<GoogleGlyph />}
          label="Connect your Google account"
          action={providerAction("google")}
        />
        <Row
          icon={<FacebookGlyph />}
          label="Connect your Facebook account"
          action={providerAction("facebook")}
        />
        {needsEmail ? (
          <Row
            label="Add your email"
            description="Required for password recovery. We'll send a verification link."
            action={
              <button
                type="button"
                onClick={() => setEmailModalOpen(true)}
                className="text-base font-medium text-primary hover:underline"
              >
                Add email
              </button>
            }
          />
        ) : (
          <>
            {needsVerify ? <VerifyEmailRow email={user!.email!} /> : null}
            <Row
              label="Change your password"
              description="Update the password you use to sign in."
              action={
                <button
                  type="button"
                  onClick={() => setPwModalOpen(true)}
                  className="text-base font-medium text-primary hover:underline"
                >
                  Change
                </button>
              }
            />
          </>
        )}
      </ul>
      <ChangePasswordModal
        open={pwModalOpen}
        onClose={() => setPwModalOpen(false)}
      />
      <AddEmailModal
        open={emailModalOpen}
        onClose={() => setEmailModalOpen(false)}
      />
    </>
  );
}

function VerifyEmailRow({ email }: { email: string }) {
  const [busy, setBusy] = useState(false);
  const [sent, setSent] = useState(false);
  const [error, setError] = useState<string | null>(null);

  async function onResend() {
    setError(null);
    setBusy(true);
    try {
      await auth.resendVerification();
      setSent(true);
    } catch (err) {
      setError(
        err instanceof AuthError
          ? err.message
          : "Could not send verification email.",
      );
    } finally {
      setBusy(false);
    }
  }

  return (
    <Row
      label="Verify your email"
      description={
        sent
          ? `✓ Verification email sent to ${email}.`
          : error ?? `We need to confirm ${email} before it can be used for recovery.`
      }
      action={
        sent ? (
          <span className="text-base text-muted-foreground">Sent</span>
        ) : (
          <button
            type="button"
            onClick={onResend}
            disabled={busy}
            className="text-base font-medium text-primary hover:underline disabled:opacity-60"
          >
            {busy ? "Sending…" : "Resend"}
          </button>
        )
      }
    />
  );
}

function LinkResult() {
  const params = useSearchParams();
  const router = useRouter();
  const raw = params.get("link");

  // Strip the param from the URL so a refresh doesn't re-show the banner.
  useEffect(() => {
    if (!raw) return;
    const next = new URLSearchParams(params.toString());
    next.delete("link");
    const q = next.toString();
    router.replace(q ? `/settings?${q}` : "/settings");
  }, [raw, params, router]);

  if (!raw) return null;

  // Format: "<provider>:<status>" — `google:ok`, `facebook:claimed`, etc.
  const [provider, status] = raw.split(":", 2);
  const name = provider.charAt(0).toUpperCase() + provider.slice(1);

  if (status === "ok") {
    return (
      <p className="mb-4 inline-flex items-center gap-2 rounded-md bg-emerald-500/10 text-emerald-700 dark:text-emerald-300 px-3 py-2 text-base">
        <Check className="size-4" />
        Connected your {name} account.
      </p>
    );
  }
  if (status === "claimed") {
    return (
      <p className="mb-4 inline-flex items-center gap-2 rounded-md bg-destructive/10 text-destructive px-3 py-2 text-base">
        <AlertCircle className="size-4" />
        That {name} account is already linked to another Prabhupāda Says
        account.
      </p>
    );
  }
  return (
    <p className="mb-4 inline-flex items-center gap-2 rounded-md bg-destructive/10 text-destructive px-3 py-2 text-base">
      <AlertCircle className="size-4" />
      Couldn&apos;t connect your {name} account. Please try again.
    </p>
  );
}

function ConnectedPill() {
  return (
    <span className="inline-flex items-center gap-1 rounded-full bg-emerald-500/10 text-emerald-700 dark:text-emerald-300 px-2.5 py-0.5 text-sm font-medium">
      <Check className="size-3.5" />
      Connected
    </span>
  );
}

// ─── Legal ─────────────────────────────────────────────────────────────

function LegalSection() {
  return (
    <ul className="divide-y divide-border">
      <LegalLink href="/terms" label="Terms of Service" />
      <LegalLink href="/privacy" label="Privacy Policy" />
      <LegalLink href="/data-deletion" label="Steps for data deletion" />
    </ul>
  );
}

function LegalLink({ href, label }: { href: string; label: string }) {
  return (
    <li>
      <Link
        href={href}
        className="flex items-center justify-between py-3.5 group"
      >
        <span className="text-base text-foreground group-hover:text-primary transition-colors">
          {label}
        </span>
        <ChevronRight className="size-5 text-muted-foreground group-hover:text-foreground transition-colors" />
      </Link>
    </li>
  );
}

// ─── Row helper ────────────────────────────────────────────────────────

function GoogleGlyph() {
  return (
    <svg
      className="size-5"
      viewBox="0 0 24 24"
      xmlns="http://www.w3.org/2000/svg"
      aria-hidden
    >
      <path
        fill="#4285F4"
        d="M22.56 12.25c0-.78-.07-1.53-.2-2.25H12v4.26h5.92a5.06 5.06 0 0 1-2.2 3.32v2.76h3.56c2.08-1.92 3.28-4.74 3.28-8.09Z"
      />
      <path
        fill="#34A853"
        d="M12 23c2.97 0 5.46-.98 7.28-2.66l-3.56-2.76c-.99.66-2.25 1.06-3.72 1.06-2.86 0-5.29-1.93-6.16-4.53H2.18v2.84A11 11 0 0 0 12 23Z"
      />
      <path
        fill="#FBBC05"
        d="M5.84 14.11A6.59 6.59 0 0 1 5.5 12c0-.73.13-1.45.34-2.11V7.05H2.18A11 11 0 0 0 1 12c0 1.78.43 3.46 1.18 4.95l3.66-2.84Z"
      />
      <path
        fill="#EA4335"
        d="M12 5.38c1.62 0 3.06.56 4.21 1.65l3.15-3.15C17.45 2.09 14.97 1 12 1 7.7 1 3.99 3.47 2.18 7.05l3.66 2.84C6.71 7.31 9.14 5.38 12 5.38Z"
      />
    </svg>
  );
}

function FacebookGlyph() {
  return (
    <svg
      className="size-5"
      viewBox="0 0 24 24"
      xmlns="http://www.w3.org/2000/svg"
      aria-hidden
    >
      <path
        fill="#1877F2"
        d="M24 12a12 12 0 1 0-13.88 11.85V15.47H7.08V12h3.04V9.36c0-3 1.79-4.67 4.53-4.67 1.31 0 2.69.24 2.69.24v2.96H15.83c-1.49 0-1.95.92-1.95 1.87V12h3.32l-.53 3.47h-2.79v8.38A12 12 0 0 0 24 12Z"
      />
    </svg>
  );
}

function Row({
  icon,
  label,
  description,
  action,
}: {
  icon?: React.ReactNode;
  label: string;
  description?: string;
  action: React.ReactNode;
}) {
  return (
    <li className="flex items-center justify-between gap-4 py-3.5">
      <div className="min-w-0">
        <div className="flex items-center gap-2.5">
          {icon ? <span className="shrink-0">{icon}</span> : null}
          <span className="text-base text-foreground truncate">{label}</span>
        </div>
        {description ? (
          <p className="text-sm text-muted-foreground mt-1">{description}</p>
        ) : null}
      </div>
      <div className="shrink-0">{action}</div>
    </li>
  );
}