import { useEffect, useRef, useState } from "react";
import type { FormEvent } from "react";
import { AlertTriangle, ArrowRight, LockKeyhole } from "lucide-react";
import { ApiError } from "../api/client";
import { loginLocal } from "../api/auth";
import type { AuthenticatedUser, AuthPublicConfig } from "../api/types";
import { Button } from "../components/ui/button";

interface LoginPageProps {
  config: AuthPublicConfig;
  onAuthenticated: (user: AuthenticatedUser) => void;
  onRetry?: () => void;
}

function loginError(error: unknown): { message: string; retry: boolean } {
  if (error instanceof ApiError && error.status === 503) {
    return { message: "Authentication is temporarily unavailable. Try again.", retry: true };
  }
  if (error instanceof ApiError && error.status === 403) {
    return { message: "This sign-in request was rejected. Open ThothII from its configured address and try again.", retry: false };
  }
  return { message: "Invalid username or password.", retry: false };
}

export function LoginPage({ config, onAuthenticated, onRetry }: LoginPageProps) {
  const localLogin = config.mode === "local" && config.localLogin;
  const formRef = useRef<HTMLFormElement>(null);
  const passwordRef = useRef<HTMLInputElement>(null);
  const mountedRef = useRef(true);
  const submittingRef = useRef(false);
  const attemptRef = useRef(0);
  const [submitting, setSubmitting] = useState(false);
  const [error, setError] = useState<{ message: string; retry: boolean }>();

  useEffect(() => {
    mountedRef.current = true;
    return () => { mountedRef.current = false; };
  }, []);

  async function submit(event: FormEvent<HTMLFormElement>) {
    event.preventDefault();
    if (submittingRef.current) return;
    const form = event.currentTarget;
    const values = new FormData(form);
    const username = String(values.get("username") ?? "");
    const password = String(values.get("password") ?? "");
    const remember = values.get("remember") === "on";
    const attempt = ++attemptRef.current;
    submittingRef.current = true;
    setError(undefined);
    setSubmitting(true);
    try {
      const user = await loginLocal(username, password, remember);
      if (mountedRef.current && attemptRef.current === attempt) onAuthenticated(user);
    } catch (failure) {
      if (mountedRef.current && attemptRef.current === attempt) setError(loginError(failure));
    } finally {
      submittingRef.current = false;
      if (!mountedRef.current || attemptRef.current !== attempt) return;
      // Passwords never enter React state and are cleared after every attempt,
      // including operational failures and successful authentication.
      form.reset();
      setSubmitting(false);
      passwordRef.current?.focus();
    }
  }

  return (
    <main className="min-h-screen bg-background px-5 py-8 text-foreground sm:px-8 sm:py-12">
      <div className="mx-auto grid min-h-[calc(100vh-4rem)] max-w-5xl items-center gap-12 lg:grid-cols-[minmax(0,1fr)_26rem]">
        <section className="hidden max-w-xl lg:block">
          <p className="thot-label text-primary">Secure re-entry · governed workspace</p>
          <h1 className="mt-4 max-w-lg font-heading text-5xl font-semibold leading-[1.03] tracking-tight sm:text-6xl">
            Return to the analytical ledger.
          </h1>
          <p className="mt-6 max-w-md text-base leading-7 text-muted-foreground">
            ThothII keeps each question, review decision, and SQL artifact inside a traceable human-in-the-loop workflow.
          </p>
          <div className="mt-10 flex items-center gap-3 text-sm text-muted-foreground">
            <span className="h-px w-16 bg-primary" aria-hidden="true" />
            <span>Access is checked before the workspace opens.</span>
          </div>
        </section>

        <section className="mx-auto w-full max-w-md rounded-2xl border border-border/80 bg-card p-6 shadow-md sm:p-8">
          <div className="mb-7">
            <div className="flex items-center gap-2 text-primary" aria-hidden="true">
              <LockKeyhole className="size-4" />
              <span className="thot-label text-primary">ThothII access</span>
            </div>
            <h2 className="mt-3 font-heading text-3xl font-semibold tracking-tight">Sign in to ThothII</h2>
            <p className="mt-2 text-sm leading-6 text-muted-foreground">Use your installation account to continue.</p>
          </div>

          {error && (
            <div role="alert" aria-live="assertive" className="mb-5 grid gap-3 rounded-md border border-destructive/30 bg-destructive/5 p-3 text-sm">
              <p className="flex items-start gap-2 leading-5"><AlertTriangle className="mt-0.5 size-4 shrink-0 text-destructive" />{error.message}</p>
              {error.retry && onRetry && (
                <Button type="button" variant="outline" size="sm" className="w-fit" onClick={onRetry}>Retry</Button>
              )}
            </div>
          )}

          {localLogin && (
            <form ref={formRef} onSubmit={submit} className="grid gap-4">
              <div className="grid gap-1.5">
                <label htmlFor="thothii-username" className="text-sm font-semibold">Username</label>
                <input
                  id="thothii-username"
                  name="username"
                  type="text"
                  autoComplete="username"
                  autoCapitalize="none"
                  spellCheck={false}
                  required
                  className="h-10 rounded-md border border-input bg-background px-3 text-sm outline-none focus-visible:ring-3 focus-visible:ring-ring/25"
                />
              </div>
              <div className="grid gap-1.5">
                <label htmlFor="thothii-password" className="text-sm font-semibold">Password</label>
                <input
                  ref={passwordRef}
                  id="thothii-password"
                  name="password"
                  type="password"
                  autoComplete="current-password"
                  required
                  className="h-10 rounded-md border border-input bg-background px-3 text-sm outline-none focus-visible:ring-3 focus-visible:ring-ring/25"
                />
              </div>
              <label className="flex items-center gap-2 text-sm text-muted-foreground">
                <input name="remember" type="checkbox" className="size-4 accent-[oklch(var(--primary))]" />
                <span>Remember me for 30 days</span>
              </label>
              <Button type="submit" size="lg" className="mt-1 w-full" disabled={submitting}>
                {submitting ? "Signing in…" : "Sign in"}
                {!submitting && <ArrowRight aria-hidden="true" />}
              </Button>
            </form>
          )}

          {config.oidcLogin && (
            <a
              href="/api/auth/oidc/login"
              className="mt-4 inline-flex h-10 w-full items-center justify-center gap-2 rounded-md border border-border bg-card px-4 text-sm font-semibold shadow-xs outline-none transition-colors hover:bg-muted focus-visible:ring-3 focus-visible:ring-ring/25"
            >
              Continue with single sign-on
              <ArrowRight aria-hidden="true" className="size-4" />
            </a>
          )}

          {!localLogin && !config.oidcLogin && (
            <p role="status" className="rounded-md border border-border bg-muted/40 p-3 text-sm text-muted-foreground">
              No browser sign-in method is enabled for this installation.
            </p>
          )}
        </section>
      </div>
    </main>
  );
}