import type { ModuleUiImporter } from "@ekklesia/module-ui-host";
import { type ReactElement, useEffect, useState } from "react";
import {
  bootstrapDisplayHost,
  type DisplayHostBootstrap,
  type EkklesiaHostConfig,
  HostProtocolError,
} from "../host-protocol.js";
import { DisplayUiFrame } from "./DisplayUiFrame.js";

type DisplayState =
  | { readonly status: "loading"; readonly generation: number }
  | { readonly status: "ready"; readonly bootstrap: DisplayHostBootstrap & { status: "ready" } }
  | { readonly status: "signed-out" }
  | { readonly status: "unavailable" }
  | { readonly status: "failed" };

export interface DisplayAppProps {
  readonly config: EkklesiaHostConfig;
  readonly moduleId: string;
  /** Test/composition seam only. Production uses the generic loader's native dynamic import. */
  readonly importModule?: ModuleUiImporter;
}

const displayStyles = {
  host: {
    height: "100%",
    minHeight: "100dvh",
    minWidth: 0,
    overflow: "hidden",
    width: "100%",
  },
  message: {
    alignItems: "center",
    color: "#57534e",
    display: "flex",
    flexDirection: "column",
    fontFamily: "system-ui, sans-serif",
    gap: "0.75rem",
    height: "100%",
    justifyContent: "center",
    margin: 0,
    minHeight: "100dvh",
    padding: "1rem",
    textAlign: "center",
  },
  retry: {
    background: "transparent",
    border: "1px solid currentColor",
    borderRadius: "0.25rem",
    color: "inherit",
    cursor: "pointer",
    font: "inherit",
    padding: "0.375rem 0.75rem",
  },
} as const;

function DisplayMessage(props: {
  readonly children: string;
  readonly testId: string;
  readonly onRetry?: () => void;
}): ReactElement {
  return (
    <div aria-live="polite" data-testid={props.testId} style={displayStyles.message}>
      <p style={{ margin: 0 }}>{props.children}</p>
      {props.onRetry ? (
        <button onClick={props.onRetry} style={displayStyles.retry} type="button">
          Retry
        </button>
      ) : undefined}
    </div>
  );
}

/**
 * The host for one display-capable module, with no Dashboard application mounted around it.
 *
 * Bootstrap is principal-first, so an anonymous browser never probes a module descriptor. The
 * descriptor itself is permission-protected server-side; only after it succeeds can an artifact URL
 * reach the generic loader. A changed `moduleId` or retry aborts the old fetch and keys a new frame,
 * so neither a late descriptor nor a late import can replace the current display.
 */
export function DisplayApp(props: DisplayAppProps): ReactElement {
  const [state, setState] = useState<DisplayState>({ generation: 0, status: "loading" });
  const [attempt, setAttempt] = useState(0);
  const { config, importModule, moduleId } = props;

  useEffect(() => {
    const abort = new AbortController();
    setState({ generation: attempt, status: "loading" });
    void bootstrapDisplayHost(config, moduleId, abort.signal)
      .then((bootstrap) => {
        if (abort.signal.aborted) {
          return;
        }
        setState(
          bootstrap.status === "signed-out"
            ? { status: "signed-out" }
            : { bootstrap, status: "ready" },
        );
      })
      .catch((error: unknown) => {
        if (abort.signal.aborted) {
          return;
        }
        console.error("[ekklesia] display host bootstrap failed", error);
        setState(
          error instanceof HostProtocolError &&
            (error.code === "DISPLAY_ACCESS_DENIED" || error.code === "DISPLAY_NOT_AVAILABLE")
            ? { status: "unavailable" }
            : error instanceof HostProtocolError && error.code === "HOST_UNAUTHENTICATED"
              ? { status: "signed-out" }
              : { status: "failed" },
        );
      });
    return () => abort.abort();
  }, [attempt, config, moduleId]);

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

  return (
    <div data-testid="display-host" style={displayStyles.host}>
      {state.status === "loading" ? (
        <DisplayMessage testId="display-host-loading">Loading display…</DisplayMessage>
      ) : undefined}
      {state.status === "signed-out" ? (
        <DisplayMessage onRetry={retry} testId="display-host-signed-out">
          Sign in to use this display.
        </DisplayMessage>
      ) : undefined}
      {state.status === "unavailable" ? (
        <DisplayMessage onRetry={retry} testId="display-host-unavailable">
          This display is unavailable.
        </DisplayMessage>
      ) : undefined}
      {state.status === "failed" ? (
        <DisplayMessage onRetry={retry} testId="display-host-error">
          This display could not be reached.
        </DisplayMessage>
      ) : undefined}
      {state.status === "ready" ? (
        <DisplayUiFrame
          config={config}
          descriptor={state.bootstrap.descriptor}
          {...(importModule ? { importModule } : {})}
          key={`${state.bootstrap.descriptor.id}@${state.bootstrap.descriptor.version}:${attempt}`}
          principal={state.bootstrap.principal}
        />
      ) : undefined}
    </div>
  );
}