fusion/packages/mobile/scripts/patch-ios-webview.ts

/**
 * FNXC:TaskDetailIOSSwipeBack 2026-07-05-12:10:
 * FN-7586: the iOS edge-swipe-back gesture (WKWebView interactive pop / back-forward
 * navigation gesture) is a guaranteed no-op on a stock Capacitor 7 iOS build of this app.
 * `WKWebView.allowsBackForwardNavigationGestures` defaults to `false`
 * (https://developer.apple.com/documentation/webkit/wkwebview/1414995-allowsbackforwardnavigationgestu),
 * `CAPBridgeViewController.prepareWebView` (in `@capacitor/ios`) sets several WKWebView
 * properties from `capacitor.config.ts` (`allowsLinkPreview`, `scrollView.isScrollEnabled`,
 * background color, content-inset behavior) but never touches this one, and the installed
 * `@capacitor/cli`'s `ios` config block (see `declarations.d.ts`) exposes no first-class
 * toggle for it either. Without the gesture enabled, iOS never even reaches
 * `window.history.back()` / `popstate` — so the dashboard's shared nav-history dismissal
 * stack (`useNavigationHistory.handlePopState`), which board/list/modal/nested task-detail
 * surfaces already converge on for desktop/browser swipe-back, never gets a chance to run.
 *
 * The native `ios/` project is generated by `cap sync` (via `cap add ios`, which extracts
 * `@capacitor/cli`'s bundled `ios-pods-template.tar.gz`) and is git-ignored (see AGENTS.md /
 * `.gitignore`), so durable changes cannot live there directly — mirroring FN-7583's Android
 * manifest-patch precedent (`patch-android-manifest.ts`), this script idempotently patches
 * the generated `AppDelegate.swift` immediately after every sync, wired into Capacitor's own
 * `capacitor:sync:after` npm-script hook (see `package.json`), which the Capacitor CLI runs
 * automatically after `cap sync` (and therefore after `cap run ios` / `build:mobile` too).
 *
 * Patch target: the stock template has NO custom `CAPBridgeViewController` subclass — the
 * generated `Main.storyboard` wires `customClass="CAPBridgeViewController"` directly onto the
 * scene's view controller. `AppDelegate.didFinishLaunchingWithOptions` is therefore the
 * stable, minimal patch point: by the time it runs, `UIApplicationMain` has already loaded
 * the storyboard's root view controller into `window.rootViewController`. The patch casts it
 * to `CAPBridgeViewController`, forces `loadViewIfNeeded()` so `webView` is non-nil (the
 * bridge view controller creates its WKWebView lazily in `loadView()`), then sets
 * `webView?.allowsBackForwardNavigationGestures = true`.
 *
 * This keeps a SINGLE dismissal invariant across platforms: once the gesture is delivered,
 * iOS drives ordinary WKWebView back-forward navigation -> `popstate`, the exact same arm
 * browser/desktop swipe-back already uses and that `useNavigationHistory.handlePopState`
 * already consumes for board main-panel / list-mobile / modal / nested task-detail surfaces.
 * iOS has no Capacitor `backButton` event (that's Android-only, see
 * `src/plugins/native-shell.ts`'s `AndroidBackButtonManager`), so this does NOT add an iOS
 * `fusion:native-back` emitter — it reuses the existing `popstate` arm of the shared
 * invariant instead of introducing a second, divergent back-handling path.
 */
import { existsSync, readFileSync, writeFileSync } from "node:fs";
import { dirname, join } from "node:path";
import { fileURLToPath } from "node:url";

const MARKER = "allowsBackForwardNavigationGestures";

const DID_FINISH_LAUNCHING_SIGNATURE =
  /func application\(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: \[UIApplication\.LaunchOptionsKey: Any\]\?\) -> Bool \{/;

function buildInjectedSnippet(): string {
  return `
        // FNXC:TaskDetailIOSSwipeBack 2026-07-05-12:10:
        // FN-7586: enable the WKWebView edge-swipe-back gesture so it drives ordinary
        // back-forward navigation (-> popstate), matching Android Back's fusion:native-back
        // arm and desktop/browser swipe-back. See packages/mobile/scripts/patch-ios-webview.ts
        // for the full rationale (idempotent — this line is the presence marker).
        if let bridgeViewController = self.window?.rootViewController as? CAPBridgeViewController {
            bridgeViewController.loadViewIfNeeded()
            bridgeViewController.webView?.${MARKER} = true
        }
`;
}

export function patchAppDelegateSource(swift: string): { changed: boolean; swift: string } {
  if (swift.includes(MARKER)) {
    // Already opted in (idempotent — do not duplicate on repeat `cap sync` runs).
    return { changed: false, swift };
  }

  const signatureMatch = swift.match(DID_FINISH_LAUNCHING_SIGNATURE);
  if (!signatureMatch || signatureMatch.index === undefined) {
    // Unrecognized AppDelegate shape (e.g. a hand-customized template) — do not guess.
    return { changed: false, swift };
  }

  const insertAt = signatureMatch.index + signatureMatch[0].length;
  const patched = swift.slice(0, insertAt) + buildInjectedSnippet() + swift.slice(insertAt);
  return { changed: true, swift: patched };
}

export function resolveAppDelegatePath(mobilePackageDir: string): string {
  return join(mobilePackageDir, "ios", "App", "App", "AppDelegate.swift");
}

export function patchIOSWebView(mobilePackageDir: string): { patched: boolean; skipped: boolean; path: string } {
  const appDelegatePath = resolveAppDelegatePath(mobilePackageDir);

  if (!existsSync(appDelegatePath)) {
    // No iOS platform added yet (e.g. Android-only sync) — safe no-op, not an error.
    return { patched: false, skipped: true, path: appDelegatePath };
  }

  const original = readFileSync(appDelegatePath, "utf8");
  const { changed, swift } = patchAppDelegateSource(original);

  if (changed) {
    writeFileSync(appDelegatePath, swift, "utf8");
  }

  return { patched: changed, skipped: false, path: appDelegatePath };
}

function isMainModule(): boolean {
  return process.argv[1] === fileURLToPath(import.meta.url);
}

if (isMainModule()) {
  const mobilePackageDir = dirname(fileURLToPath(import.meta.url)).replace(/[/\\]scripts$/, "");
  const result = patchIOSWebView(mobilePackageDir);

  if (result.skipped) {
    console.log(`[patch-ios-webview] no ios/ project at ${result.path}; skipping (nothing to patch yet)`);
  } else if (result.patched) {
    console.log(`[patch-ios-webview] enabled allowsBackForwardNavigationGestures in ${result.path}`);
  } else {
    console.log(`[patch-ios-webview] ${result.path} already enables allowsBackForwardNavigationGestures; no change`);
  }
}