import type { BrowserWindow, Session, WebContents } from 'electron';
import { WebContentsView, session } from 'electron';
import type { AgentBrowserBounds } from '../../shared/agent-browser';
import type {
  AgentBrowserAdapter,
  AgentBrowserDebuggerPort,
  AgentBrowserNavigationPort,
  AgentBrowserViewPort,
  AgentBrowserWebContentsPort,
  PortListener,
} from './adapter';

function isAllowedTopLevelUrl(value: string): boolean {
  if (value === 'about:blank') return true;
  try {
    const url = new URL(value);
    return url.protocol === 'http:' || url.protocol === 'https:';
  } catch {
    return false;
  }
}

function wrapDebugger(contents: WebContents): AgentBrowserDebuggerPort {
  const debuggerEvents = contents.debugger as unknown as {
    on(event: string, listener: PortListener): void;
    removeListener(event: string, listener: PortListener): void;
  };
  return {
    attach: (version) => contents.debugger.attach(version),
    detach: () => contents.debugger.detach(),
    isAttached: () => contents.debugger.isAttached(),
    sendCommand: (method, params, sessionRef) =>
      contents.debugger.sendCommand(method, params, sessionRef),
    on: (event, listener) => debuggerEvents.on(event, listener),
    removeListener: (event, listener) =>
      debuggerEvents.removeListener(event, listener),
  };
}

function wrapNavigation(contents: WebContents): AgentBrowserNavigationPort {
  return {
    canGoBack: () => contents.navigationHistory.canGoBack(),
    canGoForward: () => contents.navigationHistory.canGoForward(),
    goBack: () => {
      contents.navigationHistory.goBack();
    },
    goForward: () => {
      contents.navigationHistory.goForward();
    },
    clear: () => {
      contents.navigationHistory.clear();
    },
  };
}

function wrapWebContents(contents: WebContents): AgentBrowserWebContentsPort {
  const contentsEvents = contents as unknown as {
    on(event: string, listener: PortListener): void;
    removeListener(event: string, listener: PortListener): void;
  };
  return {
    debugger: wrapDebugger(contents),
    navigationHistory: wrapNavigation(contents),
    loadURL: (url) => contents.loadURL(url),
    getURL: () => contents.getURL(),
    getTitle: () => contents.getTitle(),
    isDestroyed: () => contents.isDestroyed(),
    isDevToolsOpened: () => contents.isDevToolsOpened(),
    reload: () => contents.reload(),
    denyWindowOpen: () => {
      contents.setWindowOpenHandler(() => ({ action: 'deny' }));
    },
    on: (event: string, listener: PortListener) => {
      contentsEvents.on(event, listener);
    },
    removeListener: (event: string, listener: PortListener) => {
      contentsEvents.removeListener(event, listener);
    },
  };
}

export class ElectronAgentBrowserAdapter implements AgentBrowserAdapter {
  private readonly nativeViews = new WeakMap<AgentBrowserViewPort, WebContentsView>();
  private readonly guardedSessions = new WeakSet<Session>();

  constructor(private readonly mainWindow: BrowserWindow) {}

  createView(partition: string): AgentBrowserViewPort {
    const nativeView = new WebContentsView({
      webPreferences: {
        partition,
        sandbox: true,
        contextIsolation: true,
        nodeIntegration: false,
        webSecurity: true,
        allowRunningInsecureContent: false,
      },
    });
    const contents = nativeView.webContents;
    contents.setWindowOpenHandler(() => ({ action: 'deny' }));
    contents.on('will-attach-webview', (event) => event.preventDefault());
    const preventUnsafeNavigation = (
      event: Electron.Event,
      navigationUrl: string,
    ) => {
      if (!isAllowedTopLevelUrl(navigationUrl)) event.preventDefault();
    };
    contents.on('will-navigate', preventUnsafeNavigation);
    contents.on('will-redirect', preventUnsafeNavigation);
    this.guardSession(contents.session);

    const view: AgentBrowserViewPort = {
      webContents: wrapWebContents(contents),
      setBounds: (bounds: AgentBrowserBounds) =>
        nativeView.setBounds(this.toNativeBounds(bounds)),
      setVisible: (visible: boolean) => nativeView.setVisible(visible),
    };
    this.nativeViews.set(view, nativeView);
    return view;
  }

  mount(view: AgentBrowserViewPort): void {
    const nativeView = this.requireNativeView(view);
    if (!this.mainWindow.isDestroyed()) {
      this.mainWindow.contentView.addChildView(nativeView);
    }
  }

  unmount(view: AgentBrowserViewPort): void {
    const nativeView = this.nativeViews.get(view);
    if (!nativeView || this.mainWindow.isDestroyed()) return;
    try {
      this.mainWindow.contentView.removeChildView(nativeView);
    } catch {
      // Removing an already detached view is harmless during shutdown.
    }
  }

  destroy(view: AgentBrowserViewPort): void {
    const nativeView = this.nativeViews.get(view);
    if (!nativeView) return;
    this.nativeViews.delete(view);
    if (!nativeView.webContents.isDestroyed()) {
      nativeView.webContents.close({ waitForBeforeUnload: false });
    }
  }

  async resetPartition(partition: string): Promise<void> {
    const browserSession = session.fromPartition(partition);
    await browserSession.clearStorageData();
    await browserSession.clearCache();
  }

  private requireNativeView(view: AgentBrowserViewPort): WebContentsView {
    const nativeView = this.nativeViews.get(view);
    if (!nativeView) throw new Error('Unknown Agent Browser view.');
    return nativeView;
  }

  private guardSession(browserSession: Session): void {
    if (this.guardedSessions.has(browserSession)) return;
    this.guardedSessions.add(browserSession);
    browserSession.setPermissionCheckHandler(() => false);
    browserSession.setPermissionRequestHandler((_contents, _permission, callback) => {
      callback(false);
    });
    browserSession.on('will-download', (event) => {
      event.preventDefault();
    });
  }

  private toNativeBounds(bounds: AgentBrowserBounds): AgentBrowserBounds {
    const zoomFactor = this.mainWindow.webContents.getZoomFactor();
    const zoom = Number.isFinite(zoomFactor) && zoomFactor > 0 ? zoomFactor : 1;
    const contentBounds = this.mainWindow.getContentBounds();
    const contentWidth = Math.max(0, Math.trunc(contentBounds.width));
    const contentHeight = Math.max(0, Math.trunc(contentBounds.height));
    const x = clamp(Math.round(bounds.x * zoom), 0, contentWidth);
    const y = clamp(Math.round(bounds.y * zoom), 0, contentHeight);
    return {
      x,
      y,
      width: clamp(Math.round(bounds.width * zoom), 0, contentWidth - x),
      height: clamp(Math.round(bounds.height * zoom), 0, contentHeight - y),
    };
  }
}

function clamp(value: number, min: number, max: number): number {
  return Math.min(Math.max(value, min), Math.max(min, max));
}