"use client";

import { useEffect, useState, type FormEvent } from "react";
import Link from "next/link";
import { Badge, Button, Card, Input } from "../../../components/ui/primitives";
import { LoadingPanel } from "../../../components/brand/loading";
import { apiFetch, ApiError, ApiUnreachableError, errorMessage } from "../../../lib/api-client";
import type { InviteInfo } from "../../../lib/api-types";
import type { ManualLanguage } from "@tactical-media-broadcast-hub/core";
import { useAuth } from "../../../lib/auth-store";

const MIN_PASSWORD = 10;
const USERNAME_PATTERN = /^[a-z0-9][a-z0-9_.-]{1,31}$/;
const USERNAME_TITLE = "2-32 characters: lowercase letters, digits, dot, underscore or hyphen";
const API_UNREACHABLE = "API unreachable — check that the API server is running.";

type Phase = "loading" | "preview" | "dead" | "unreachable";
/** Why the link no longer works — drives the copy on the dead-token card. */
type DeadReason = "unknown" | "expired" | "exhausted";

/** 404 (unknown/revoked) vs 410 (expired or exhausted, told apart by the message). Anything else reads as unknown. */
function deadReasonFrom(err: unknown): DeadReason {
  if (err instanceof ApiError && err.status === 410) {
    const message = err.message.toLowerCase();
    if (message.includes("expired")) return "expired";
    if (message.includes("used up") || message.includes("no uses left")) return "exhausted";
  }
  return "unknown";
}

const isAlreadyMember = (err: unknown): boolean => err instanceof ApiError && err.status === 409;

/**
 * One-line collective labelling for the claim card ("Collectives: X · Y").
 * Null when unknown or empty — the card must read fine without it.
 */
function collectiveLabel(collectives: Array<{ id: string; name: string }> | null, lang: ManualLanguage): string | null {
  if (collectives === null || collectives.length === 0) return null;
  const names = collectives.map((c) => c.name).join(" · ");
  return lang === "es" ? `Colectivos: ${names}` : `Collectives: ${names}`;
}

function usesLeftLine(info: InviteInfo): string {
  const left = info.maxUses === null ? "unlimited uses" : `${Math.max(info.maxUses - info.usedCount, 0)} use${info.maxUses - info.usedCount === 1 ? "" : "s"} left`;
  return `${left} · expires ${new Date(info.expiresAt).toLocaleDateString()}`;
}

/** Sign in with an existing account, then claim: login installs the account session, claimInvite swaps it for the workspace one. */
function JoinSignInForm({
  token,
  onSwitch,
  onAlreadyMember,
}: {
  token: string;
  onSwitch: () => void;
  onAlreadyMember: () => void;
}): React.ReactElement {
  const { login, claimInvite } = useAuth();
  const [username, setUsername] = useState("");
  const [password, setPassword] = useState("");
  const [busy, setBusy] = useState(false);
  const [error, setError] = useState<string | null>(null);

  async function submit(e: FormEvent): Promise<void> {
    e.preventDefault();
    setBusy(true);
    setError(null);
    try {
      await login(username.trim(), password);
      await claimInvite(token);
      window.location.assign("/streams");
    } catch (err) {
      // Login worked but the workspace already holds this user: that is a success state.
      if (isAlreadyMember(err)) {
        setBusy(false);
        onAlreadyMember();
        return;
      }
      setError(errorMessage(err));
      setBusy(false);
    }
  }

  return (
    <form onSubmit={(e) => void submit(e)}>
      <h2 className="mb-1 text-base font-semibold">Sign in</h2>
      <p className="mb-4 text-xs text-text-faint">Use the username and password you registered with.</p>
      <div className="space-y-2">
        <Input type="text" value={username} onChange={(e) => setUsername(e.target.value)} placeholder="username" autoComplete="username" autoFocus />
        <Input type="password" value={password} onChange={(e) => setPassword(e.target.value)} placeholder="Password" autoComplete="current-password" />
      </div>
      {error !== null && <p className="mt-2 text-xs text-danger">{error}</p>}
      <div className="mt-6 flex items-center justify-between">
        <Button type="button" variant="ghost" onClick={onSwitch}>New here? Create an account</Button>
        <Button type="submit" variant="primary" disabled={busy || username.trim() === "" || password === ""}>
          {busy ? "Joining…" : "Sign in & join"}
        </Button>
      </div>
    </form>
  );
}

/**
 * Create-or-authenticate inline, then claim. Registering normally spins up a
 * new workspace, so the claim endpoint takes the credentials itself and hands
 * back a session issued in the invited workspace.
 */
function RegisterToJoinForm({
  token,
  onSwitch,
  onAlreadyMember,
}: {
  token: string;
  onSwitch: () => void;
  onAlreadyMember: () => void;
}): React.ReactElement {
  const { claimInviteWithCredentials } = useAuth();
  const [displayName, setDisplayName] = useState("");
  const [username, setUsername] = useState("");
  const [email, setEmail] = useState("");
  const [password, setPassword] = useState("");
  const [busy, setBusy] = useState(false);
  const [error, setError] = useState<string | null>(null);

  async function submit(e: FormEvent): Promise<void> {
    e.preventDefault();
    setBusy(true);
    setError(null);
    try {
      await claimInviteWithCredentials(token, {
        username: username.trim(),
        password,
        ...(displayName.trim() === "" ? {} : { displayName: displayName.trim() }),
        ...(email.trim() === "" ? {} : { email: email.trim() }),
      });
      window.location.assign("/streams");
    } catch (err) {
      if (isAlreadyMember(err)) {
        setBusy(false);
        onAlreadyMember();
        return;
      }
      setError(errorMessage(err));
      setBusy(false);
    }
  }

  const ready = USERNAME_PATTERN.test(username.trim()) && password.length >= MIN_PASSWORD;

  return (
    <form onSubmit={(e) => void submit(e)}>
      <h2 className="mb-1 text-base font-semibold">Create your account</h2>
      <p className="mb-4 text-xs text-text-faint">
        Registering accepts the invite in one step — no workspace of your own is created.
      </p>
      <div className="space-y-2">
        <Input value={displayName} onChange={(e) => setDisplayName(e.target.value)} placeholder="Your name (optional)" autoComplete="name" />
        <Input
          type="text"
          value={username}
          onChange={(e) => setUsername(e.target.value.toLowerCase())}
          placeholder="Username — this is how you sign in"
          autoComplete="username"
          pattern="[a-z0-9][a-z0-9_.-]{1,31}"
          title={USERNAME_TITLE}
        />
        <Input
          type="password"
          value={password}
          onChange={(e) => setPassword(e.target.value)}
          placeholder={`Password (min ${MIN_PASSWORD} characters)`}
          autoComplete="new-password"
        />
        <Input type="email" value={email} onChange={(e) => setEmail(e.target.value)} placeholder="Email (optional — password recovery)" autoComplete="email" />
      </div>
      {error !== null && <p className="mt-2 text-xs text-danger">{error}</p>}
      <div className="mt-6 flex items-center justify-between">
        <Button type="button" variant="ghost" onClick={onSwitch}>I already have an account</Button>
        <Button type="submit" variant="primary" disabled={busy || !ready}>
          {busy ? "Joining…" : "Join workspace"}
        </Button>
      </div>
    </form>
  );
}

export default function JoinWorkspacePage({ params }: { params: { token: string } }): React.ReactElement {
  const { status, session, isLoading, claimInvite } = useAuth();
  const [phase, setPhase] = useState<Phase>("loading");
  const [info, setInfo] = useState<InviteInfo | null>(null);
  const [deadReason, setDeadReason] = useState<DeadReason>("unknown");
  const [mode, setMode] = useState<"register" | "signin">("register");
  const [claiming, setClaiming] = useState(false);
  const [claimError, setClaimError] = useState<string | null>(null);
  const [alreadyMember, setAlreadyMember] = useState(false);
  const [attempt, setAttempt] = useState(0);
  // Collective names for the claim card (names-only public read). Purely
  // cosmetic labelling: a failure renders the card without it, never blocks.
  const [collectives, setCollectives] = useState<Array<{ id: string; name: string }> | null>(null);

  // The preview is public: fetch it immediately rather than waiting for the session to settle.
  useEffect(() => {
    let cancelled = false;
    setPhase("loading");
    apiFetch<InviteInfo>(`/invites/${encodeURIComponent(params.token)}/info`, { redirectOn401: false })
      .then((preview) => {
        if (cancelled) return;
        setInfo(preview);
        setPhase("preview");
        // Best-effort collective labelling: the token is already proven valid.
        apiFetch<{ collectives: Array<{ id: string; name: string }> }>(`/collectives-public/for-invite/${encodeURIComponent(params.token)}`, {
          redirectOn401: false,
        })
          .then((result) => {
            if (!cancelled) setCollectives(result.collectives);
          })
          .catch(() => undefined);
      })
      .catch((err: unknown) => {
        if (cancelled) return;
        if (err instanceof ApiUnreachableError) setPhase("unreachable");
        else {
          setDeadReason(deadReasonFrom(err));
          setPhase("dead");
        }
      });
    return () => {
      cancelled = true;
    };
  }, [params.token, attempt]);

  const retry = (): void => setAttempt((n) => n + 1);

  async function claim(): Promise<void> {
    setClaiming(true);
    setClaimError(null);
    try {
      await claimInvite(params.token);
      // Full navigation so the (main) shell mounts with the freshly installed session.
      window.location.assign("/streams");
    } catch (err) {
      if (isAlreadyMember(err)) {
        setAlreadyMember(true);
        setClaiming(false);
        return;
      }
      setClaimError(errorMessage(err));
      setClaiming(false);
    }
  }

  if (phase === "loading" || isLoading) return <LoadingPanel label="Checking invite…" />;

  if (phase === "unreachable") {
    return (
      <Card className="w-[520px] max-w-full p-6 text-center">
        <div className="mx-auto mb-4 flex h-12 w-12 items-center justify-center rounded-full bg-warn/15 text-lg text-warn">!</div>
        <h1 className="text-base font-semibold">Can&apos;t reach the server</h1>
        <p className="mt-1 text-xs text-text-faint">
          {API_UNREACHABLE} Your invite link is still fine — try again.
        </p>
        <Button variant="outline" className="mt-6" onClick={retry}>Retry</Button>
      </Card>
    );
  }

  if (phase === "dead") {
    return (
      <Card className="w-[520px] max-w-full p-6 text-center">
        <div className="mx-auto mb-4 flex h-12 w-12 items-center justify-center rounded-full bg-danger/15 text-lg text-danger">✕</div>
        <h1 className="text-base font-semibold">This invite link isn&apos;t valid</h1>
        <p className="mt-1 text-xs text-text-faint">
          {deadReason === "expired"
            ? "It expired."
            : deadReason === "exhausted"
              ? "It has already been used up."
              : "It was revoked or never existed."}{" "}
          Ask a workspace owner for a fresh invite.
        </p>
        <Link href="/onboarding" className="mt-6 inline-block rounded-md bg-accent px-3 py-1.5 text-xs font-medium text-white hover:bg-accent-hover">
          Start or sign in to your own workspace
        </Link>
      </Card>
    );
  }

  if (info === null) return <LoadingPanel label="Checking invite…" />;

  const memberCta = alreadyMember ? (
    <div className="mt-6 flex items-center justify-between">
      <span className="text-xs text-text-faint">You&apos;re already in this workspace.</span>
      <Link href="/streams" className="rounded-md bg-accent px-3 py-1.5 text-xs font-medium text-white hover:bg-accent-hover">Go to Streams</Link>
    </div>
  ) : (
    <div className="mt-6 flex items-center justify-between">
      <span className="text-2xs text-text-faint">Signed in as @{session?.user.username}</span>
      <Button variant="primary" disabled={claiming} onClick={() => void claim()}>
        {claiming ? "Joining…" : "Join workspace"}
      </Button>
    </div>
  );

  // Signed in already: one click claims the invite with the current session.
  if (status === "authenticated" && session !== null) {
    return (
      <Card className="w-[520px] max-w-full p-6">
        <h1 className="text-xl font-semibold tracking-tight">Join {info.workspaceName}</h1>
        <p className="mt-1 text-xs text-text-faint">
          You&apos;ve been invited to join <span className="text-text">{info.workspaceName}</span> as{" "}
          <Badge tone="accent">{info.role}</Badge>.
        </p>
        <p className="mt-2 text-2xs text-text-faint">{usesLeftLine(info)}</p>
        {collectiveLabel(collectives, "en") !== null && (
          <p className="mt-1 text-2xs text-text-faint">{collectiveLabel(collectives, "en")}</p>
        )}
        {claimError !== null && <p className="mt-2 text-xs text-danger">{claimError}</p>}
        {memberCta}
      </Card>
    );
  }

  // Anonymous (or the API dropped between mount and now): hero + register/sign-in forms.
  return (
    <Card className="w-[520px] max-w-full p-6">
      <div className="mb-5 text-center">
        <img
          src="/brand/hero.png"
          alt="Tactical Media Broadcast Hub — arrows from a circle, warm red on black"
          width={1024}
          height={1024}
          className="mx-auto mb-3 h-20 w-20 rounded-lg object-cover"
        />
        <h1 className="text-xl font-semibold tracking-tight">Join {info.workspaceName}</h1>
        <p className="mt-1 text-2xs text-text-faint">
          You&apos;ve been invited as <Badge tone="accent">{info.role}</Badge> · {usesLeftLine(info)}
        </p>
        {collectiveLabel(collectives, "en") !== null && (
          <p className="mt-0.5 text-2xs text-text-faint">{collectiveLabel(collectives, "en")}</p>
        )}
      </div>
      {mode === "signin" ? (
        <JoinSignInForm token={params.token} onSwitch={() => setMode("register")} onAlreadyMember={() => setAlreadyMember(true)} />
      ) : (
        <RegisterToJoinForm token={params.token} onSwitch={() => setMode("signin")} onAlreadyMember={() => setAlreadyMember(true)} />
      )}
      {alreadyMember && (
        <div className="mt-5 border-t border-border-subtle pt-4 text-center">
          <p className="text-xs text-text-faint">You&apos;re already in this workspace.</p>
          <Link href="/streams" className="mt-2 inline-block rounded-md bg-accent px-3 py-1.5 text-xs font-medium text-white hover:bg-accent-hover">
            Go to Streams
          </Link>
        </div>
      )}
    </Card>
  );
}