import React from 'react';

import { IDLE_NAV_STATUS, type BrowserNavStatus } from '@/lib/browser/contract';
import { useBrowserFaviconStore } from '@/stores/useBrowserFaviconStore';
import {
  INITIAL_CRASH_RECOVERY_STATE,
  planCrashRecovery,
  type CrashRecoveryState,
} from '@/lib/browser/crashRecovery';

/**
 * Translates `<webview>` lifecycle events into a single navigation status.
 *
 * Chromium reports failures and successes through separate events that can
 * arrive in either order, and it emits `did-fail-load` for sub-resources as
 * well as for the main frame. Both are handled here so the panel only ever
 * sees one authoritative state:
 *
 * - Sub-frame failures are ignored; only the main frame changes the status.
 * - `ERR_ABORTED` is not a failure. It is what Chromium reports when a
 *   navigation is superseded by the next one, and treating it as an error puts
 *   an error screen over a page that is loading perfectly well.
 *
 * Takes the element rather than a ref so the listeners attach when the view
 * actually appears. A ref is stable, so an effect keyed on it runs once — and
 * silently attaches nothing at all when the view mounts a render later.
 *
 * `<webview>` puts its event payload directly on the event object rather than
 * under `detail`, so reading `detail` yields a failure with no code and no
 * description — an error screen that says nothing. Both shapes are read here.
 *
 * A lost renderer is handled here too. It is reported by neither of the above:
 * the page simply stops existing, and the panel would otherwise stay blank with
 * no indication that anything happened.
 */

/** Chromium's code for "this navigation was replaced by another one". */
const ERR_ABORTED = -3;

/**
 * `about:blank` is the view's resting state, not somewhere the user went. It
 * arrives through `did-navigate` like any other address, and taking it at face
 * value puts it in the address bar and makes the panel look like it is showing
 * a page — which hides the empty state that would otherwise offer somewhere to
 * go.
 */
const isRealPageUrl = (url: unknown): url is string => (
  typeof url === 'string' && url.length > 0 && url !== 'about:blank'
);

type FailLoadDetail = {
  errorCode?: number;
  errorDescription?: string;
  validatedURL?: string;
  isMainFrame?: boolean;
};

/** Reads a webview event payload, whichever shape this Electron version uses. */
export const readEventPayload = <T extends object>(event: Event): Partial<T> => {
  const record = event as unknown as { detail?: unknown };
  if (record.detail && typeof record.detail === 'object') return record.detail as Partial<T>;
  return event as unknown as Partial<T>;
};

export type WebviewNavigation = {
  readonly status: BrowserNavStatus;
  readonly url: string;
  readonly title: string;
  readonly canGoBack: boolean;
  readonly canGoForward: boolean;
};

export const useWebviewNavigation = (
  webview: WebviewElement | null,
  { initialUrl, onUrlChange }: { initialUrl: string; onUrlChange: (url: string) => void },
): WebviewNavigation => {
  const [status, setStatus] = React.useState<BrowserNavStatus>(
    initialUrl ? { kind: 'loading', url: initialUrl } : IDLE_NAV_STATUS,
  );
  const [url, setUrl] = React.useState(initialUrl);
  const [title, setTitle] = React.useState('');
  const [canGoBack, setCanGoBack] = React.useState(false);
  const [canGoForward, setCanGoForward] = React.useState(false);

  const urlChangeRef = React.useRef(onUrlChange);
  urlChangeRef.current = onUrlChange;

  // Survives re-attaches so a view that keeps crashing cannot restart its own
  // budget by being remounted.
  const crashStateRef = React.useRef<CrashRecoveryState>(INITIAL_CRASH_RECOVERY_STATE);

  React.useEffect(() => {
    if (!webview) return;

    const readCurrentUrl = (): string => {
      try {
        const value = webview.getURL();
        return isRealPageUrl(value) ? value : '';
      } catch {
        return '';
      }
    };

    const syncHistory = () => {
      try {
        setCanGoBack(webview.canGoBack());
        setCanGoForward(webview.canGoForward());
      } catch {
        // Webview not attached yet; the next event resyncs.
      }
    };

    const commitUrl = (next: string) => {
      if (!isRealPageUrl(next)) return;
      setUrl(next);
      urlChangeRef.current(next);
    };

    const onStartLoading = () => {
      const current = readCurrentUrl();
      setStatus({ kind: 'loading', url: current });
    };

    const onStopLoading = () => {
      const current = readCurrentUrl();
      let pageTitle = '';
      try {
        pageTitle = webview.getTitle() || '';
      } catch {
        pageTitle = '';
      }
      setTitle(pageTitle);
      commitUrl(current);
      syncHistory();
      // A failure already produced a terminal status; do not overwrite it with
      // the `did-stop-loading` that always follows.
      setStatus((previous) => (
        previous.kind === 'failed' && previous.url === current
          ? previous
          : { kind: 'ready', url: current, title: pageTitle }
      ));
    };

    const onNavigate = (event: Event) => {
      const detail = readEventPayload<{ url?: string }>(event);
      if (isRealPageUrl(detail.url)) {
        commitUrl(detail.url);
        syncHistory();
      }
    };

    const onFaviconUpdated = (event: Event) => {
      const detail = readEventPayload<{ favicons?: string[] }>(event);
      const icon = Array.isArray(detail.favicons) ? detail.favicons.find(Boolean) : '';
      const page = readCurrentUrl();
      if (icon && page) useBrowserFaviconStore.getState().resolve(page, icon);
    };

    const onTitleUpdated = (event: Event) => {
      const detail = readEventPayload<{ title?: string }>(event);
      if (typeof detail.title === 'string') setTitle(detail.title);
    };

    const onFailLoad = (event: Event) => {
      const detail = readEventPayload<FailLoadDetail>(event);
      if (detail.isMainFrame === false) return;
      const code = typeof detail.errorCode === 'number' ? detail.errorCode : 0;
      if (code === ERR_ABORTED) return;
      setStatus({
        kind: 'failed',
        url: isRealPageUrl(detail.validatedURL) ? detail.validatedURL : readCurrentUrl(),
        code,
        description: typeof detail.errorDescription === 'string' ? detail.errorDescription : '',
      });
    };

    let recoveryTimer: ReturnType<typeof setTimeout> | null = null;

    const onCrashed = () => {
      const target = readCurrentUrl();
      const plan = planCrashRecovery(crashStateRef.current, Date.now());
      if (!plan) {
        // Out of attempts: say what happened rather than reload again. The
        // toolbar's own reload stays available, which is the user's call.
        setStatus({ kind: 'failed', url: target, code: 0, description: '', crashed: true });
        return;
      }
      crashStateRef.current = plan.state;
      setStatus({ kind: 'loading', url: target });
      recoveryTimer = setTimeout(() => {
        recoveryTimer = null;
        try {
          webview.reload();
        } catch {
          setStatus({ kind: 'failed', url: target, code: 0, description: '', crashed: true });
        }
      }, plan.delayMs);
    };

    webview.addEventListener('did-start-loading', onStartLoading);
    webview.addEventListener('did-stop-loading', onStopLoading);
    webview.addEventListener('did-navigate', onNavigate);
    webview.addEventListener('did-navigate-in-page', onNavigate);
    webview.addEventListener('page-title-updated', onTitleUpdated);
    webview.addEventListener('page-favicon-updated', onFaviconUpdated);
    webview.addEventListener('did-fail-load', onFailLoad);
    // Electron renamed this event; older builds still emit only the old name.
    webview.addEventListener('render-process-gone', onCrashed);
    webview.addEventListener('crashed', onCrashed);

    // The webview may already be settled by the time this effect runs. Only
    // treat it as settled when a page is actually loaded: a freshly created
    // view reports "not loading" before its guest attaches, and settling on
    // that would declare an empty page ready and hide the real one behind an
    // empty state.
    try {
      if (!webview.isLoading() && readCurrentUrl()) onStopLoading();
    } catch {
      // Not attached yet.
    }

    return () => {
      if (recoveryTimer !== null) clearTimeout(recoveryTimer);
      webview.removeEventListener('render-process-gone', onCrashed);
      webview.removeEventListener('crashed', onCrashed);
      webview.removeEventListener('did-start-loading', onStartLoading);
      webview.removeEventListener('did-stop-loading', onStopLoading);
      webview.removeEventListener('did-navigate', onNavigate);
      webview.removeEventListener('did-navigate-in-page', onNavigate);
      webview.removeEventListener('page-title-updated', onTitleUpdated);
      webview.removeEventListener('page-favicon-updated', onFaviconUpdated);
      webview.removeEventListener('did-fail-load', onFailLoad);
    };
  }, [webview]);

  return { status, url, title, canGoBack, canGoForward };
};