import { designToken } from "@ekklesia/design-tokens";
import { type FormEvent, type ReactElement, useEffect, useRef, useState } from "react";
import { HostAuthError } from "../auth-protocol.js";

/**
 * The shared visual language of every host-owned auth screen.
 *
 * Exported so the login, recovery, reset, and verification screens are literally the same card
 * rather than four that drift apart. Modules never render any of them. Every colour, radius, and
 * size is a design token (ADR 0039, ADR 0060), so these screens follow the person's light, dark, or
 * system appearance like the rest of the Dashboard; the action is the platform's primary button.
 */
export const authStyles = {
  button: {
    background: designToken("accent.base"),
    border: `${designToken("border.width")} solid ${designToken("accent.base")}`,
    borderRadius: designToken("radius.md"),
    color: designToken("accent.foreground"),
    cursor: "pointer",
    font: "inherit",
    fontWeight: designToken("typography.weight-bold"),
    minHeight: designToken("control.height-md"),
    padding: `${designToken("spacing.sm")} ${designToken("spacing.lg")}`,
  },
  card: {
    background: designToken("background.raised"),
    border: `${designToken("border.width")} solid ${designToken("border.base")}`,
    borderRadius: designToken("radius.lg"),
    boxShadow: designToken("shadow.md"),
    display: "grid",
    gap: designToken("spacing.lg"),
    maxWidth: "24rem",
    padding: designToken("spacing.xl"),
    width: "100%",
  },
  error: { color: designToken("text.danger"), margin: 0 },
  field: { display: "grid", gap: designToken("spacing.xs") },
  form: { display: "grid", gap: designToken("spacing.lg") },
  heading: { fontSize: designToken("typography.size-heading-2"), margin: 0 },
  host: {
    alignItems: "center",
    background: designToken("background.page"),
    color: designToken("text.primary"),
    display: "flex",
    fontFamily: designToken("typography.family-sans"),
    justifyContent: "center",
    minHeight: "100vh",
    padding: designToken("spacing.lg"),
  },
  input: {
    background: designToken("background.surface"),
    border: `${designToken("border.width")} solid ${designToken("border.control")}`,
    borderRadius: designToken("radius.md"),
    boxSizing: "border-box",
    color: designToken("text.primary"),
    font: "inherit",
    minHeight: designToken("control.height-md"),
    padding: `${designToken("spacing.sm")} ${designToken("control.padding-inline")}`,
    width: "100%",
  },
  introduction: { color: designToken("text.secondary"), margin: 0 },
  label: { fontWeight: designToken("typography.weight-bold") },
  secondaryAction: {
    background: "transparent",
    border: "none",
    color: designToken("accent.strong"),
    cursor: "pointer",
    font: "inherit",
    justifySelf: "start",
    minHeight: designToken("control.height-sm"),
    padding: 0,
    textDecoration: "underline",
  },
} as const;

export interface AuthCardProps {
  readonly headingId: string;
  readonly heading: string;
  readonly testId: string;
  readonly children: React.ReactNode;
}

/** One centred card on the sign-in background, with a labelled region for assistive technology. */
export function AuthCard(props: AuthCardProps): ReactElement {
  return (
    <main data-testid={props.testId} style={authStyles.host}>
      <section aria-labelledby={props.headingId} style={authStyles.card}>
        <h1 id={props.headingId} style={authStyles.heading}>
          {props.heading}
        </h1>
        {props.children}
      </section>
    </main>
  );
}

export interface UseSingleSubmissionResult {
  readonly pending: boolean;
  readonly errorMessage: string | undefined;
  readonly setErrorMessage: (message: string | undefined) => void;
  /** Runs `operation` at most once at a time. A second submit while one is in flight is dropped. */
  readonly submit: (
    event: FormEvent<HTMLFormElement>,
    operation: (signal: AbortSignal) => Promise<void>,
  ) => Promise<void>;
}

/**
 * The submission discipline every auth form needs, in one place.
 *
 * A `ref` closes the same-tick gap before React commits `pending`, which is what actually prevents a
 * double submission — a disabled attribute alone cannot, because it is not applied until after the
 * commit. Every one of these forms triggers an email or changes a credential, so a duplicate is not
 * merely untidy.
 */
export function useSingleSubmission(fallbackMessage: string): UseSingleSubmissionResult {
  const [pending, setPending] = useState(false);
  const [errorMessage, setErrorMessage] = useState<string | undefined>(undefined);
  const pendingRef = useRef(false);
  const attemptRef = useRef<AbortController | undefined>(undefined);
  const mountedRef = useRef(true);

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

  const submit = async (
    event: FormEvent<HTMLFormElement>,
    operation: (signal: AbortSignal) => Promise<void>,
  ): Promise<void> => {
    event.preventDefault();
    if (pendingRef.current) {
      return;
    }
    pendingRef.current = true;
    setPending(true);
    setErrorMessage(undefined);
    const attempt = new AbortController();
    attemptRef.current = attempt;
    try {
      await operation(attempt.signal);
    } catch (error) {
      if (!attempt.signal.aborted && mountedRef.current) {
        // A `HostAuthError` message is fixed text this package wrote. Anything else is an unknown
        // thrown value whose message could contain a URL or a provider detail, so it is replaced.
        setErrorMessage(error instanceof HostAuthError ? error.message : fallbackMessage);
      }
    } finally {
      if (attemptRef.current === attempt) {
        attemptRef.current = undefined;
        pendingRef.current = false;
        if (mountedRef.current) {
          setPending(false);
        }
      }
    }
  };

  return { errorMessage, pending, setErrorMessage, submit };
}