docs(ios): add share target implementation audit
Document the Share Extension → App Group → main app flow, including read/write/delete points, startup detection hooks, timing behavior, and race conditions to support share-target reliability work.
This commit is contained in:
Jose Olarte III
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doc/share-target-ios-audit.md
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doc/share-target-ios-audit.md
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# iOS Share Target Implementation Audit
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**Generated:** 2026-06-23 17:07:21 PST
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## Overview
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The iOS share target uses a **Share Extension** (`TimeSafariShareExtension`) that writes a shared image to an **App Group** container (`group.app.timesafari.share`), then opens the main app via `timesafari://`. The main app reads the image through a native **Capacitor plugin** (`SharedImagePlugin`) and stores it in the JS temp database before routing to `/shared-photo`.
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### App Group Storage Model
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| Key | Storage | Written by | Purpose |
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|-----|---------|------------|---------|
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| `sharedPhotoFilePath` | UserDefaults (suite) | Share Extension | Relative filename of image file in container |
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| `sharedPhotoFileName` | UserDefaults (suite) | Share Extension | Display/original filename |
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| `sharedPhotoReady` | UserDefaults (suite) | Share Extension | Boolean signal that a new share is available |
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| `sharedPhotoBase64` | UserDefaults (suite) | *(legacy, not written)* | Removed on write for cleanup |
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| Image file | App Group filesystem | Share Extension | Raw image bytes at `{container}/{sharedPhotoFilePath}` |
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---
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## End-to-End Flow
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```
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External App (Photos, Safari, etc.)
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│
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▼
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┌─────────────────────────────────────┐
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│ TimeSafariShareExtension │
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│ ShareViewController │
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│ 1. viewDidLoad → processAndOpenApp │
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│ 2. processSharedImage (async) │
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│ 3. storeImageData → file + metadata │
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│ 4. setSharedPhotoReadyFlag │
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│ 5. openMainApp (timesafari://) │
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│ 6. completeRequest │
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└─────────────────────────────────────┘
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│
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▼ App Group: group.app.timesafari.share
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│ (UserDefaults keys + image file)
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│
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▼
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┌─────────────────────────────────────┐
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│ Main App (app.timesafari) │
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│ │
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│ Native detection: │
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│ • AppDelegate.applicationDidBecome │
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│ Active → checkForSharedImageOn │
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│ Activation (flag only) │
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│ • AppDelegate.application(open:) │
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│ → Capacitor URL handling │
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│ │
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│ JS detection (main.capacitor.ts): │
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│ • setTimeout 1000ms startup check │
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│ • appStateChange (isActive) │
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│ • appUrlOpen → timesafari:// │
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└─────────────────────────────────────┘
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│
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▼
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┌─────────────────────────────────────┐
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│ SharedImagePlugin.getSharedImage() │
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│ → SharedImageUtility │
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│ .getSharedImageData() │
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│ (reads file, deletes native data) │
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└─────────────────────────────────────┘
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│
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▼
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┌─────────────────────────────────────┐
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│ main.capacitor.ts │
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│ storeSharedImageInTempDB() │
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│ → SQLite temp table │
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│ → router.push/replace /shared-photo│
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└─────────────────────────────────────┘
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│
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▼
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┌─────────────────────────────────────┐
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│ SharedPhotoView.vue │
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│ loadSharedImage() │
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│ → reads temp DB, deletes temp row │
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│ → displays image, user action │
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└─────────────────────────────────────┘
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```
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---
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## Component Responsibilities
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### Share Extension (Writer)
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| File | Method | Responsibility |
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|------|--------|----------------|
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| `ios/App/TimeSafariShareExtension/ShareViewController.swift` | `viewDidLoad()` | Entry point; triggers share processing on load |
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| | `processAndOpenApp()` | Orchestrates image extraction, flag set, app open, extension completion |
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| | `processSharedImage(from:completion:)` | Iterates `NSExtensionItem` attachments; loads first `UTType.image` via `loadItem` |
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| | `storeImageData(_:fileName:)` | Writes image file to App Group container; writes metadata to UserDefaults |
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| | `setSharedPhotoReadyFlag()` | Sets `sharedPhotoReady = true` in App Group UserDefaults |
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| | `openMainApp()` | Opens `timesafari://` via responder chain or `extensionContext.open` |
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| | `getFileNameWithExtension(_:newExtension:)` | Helper for PNG fallback filename |
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| `ios/App/TimeSafariShareExtension/Info.plist` | — | Declares share-services extension; accepts 1 image max |
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| `ios/App/TimeSafariShareExtension/TimeSafariShareExtension.entitlements` | — | Grants App Group `group.app.timesafari.share` |
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### Main App Native Layer (Reader)
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| File | Method | Responsibility |
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|------|--------|----------------|
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| `ios/App/App/SharedImageUtility.swift` | `getSharedImageData()` | Reads file from App Group, returns base64 + fileName; **deletes metadata and file** |
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| | `hasSharedImage()` | Non-destructive existence check (metadata + file on disk) |
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| | `isSharedPhotoReady()` | Reads `sharedPhotoReady` flag |
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| | `clearSharedPhotoReadyFlag()` | Removes `sharedPhotoReady` key |
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| `ios/App/App/SharedImagePlugin.swift` | `getSharedImage(_:)` | Capacitor bridge to `getSharedImageData()` |
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| | `hasSharedImage(_:)` | Capacitor bridge to `hasSharedImage()` |
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| `ios/App/App/AppDelegate.swift` | `application(_:didFinishLaunchingWithOptions:)` | Registers `SharedImagePlugin` with retry loop |
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| | `registerSharedImagePlugin()` | Manually registers plugin instance on Capacitor bridge |
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| | `applicationDidBecomeActive(_:)` | Calls `checkForSharedImageOnActivation()` |
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| | `checkForSharedImageOnActivation()` | Checks ready flag, clears it, posts `SharedPhotoReady` NSNotification |
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| | `application(_:open:options:)` | Forwards URL opens (including `timesafari://`) to Capacitor |
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| `ios/App/App/App.entitlements` | — | Grants App Group `group.app.timesafari.share` |
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### JavaScript Layer (Consumer)
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| File | Method | Responsibility |
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|------|--------|----------------|
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| `src/plugins/SharedImagePlugin.ts` | — | Registers Capacitor plugin name `SharedImage` |
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| `src/plugins/definitions.ts` | — | TypeScript interface for `getSharedImage` / `hasSharedImage` |
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| `src/main.capacitor.ts` | `checkAndStoreNativeSharedImage()` | Calls `SharedImage.getSharedImage()`, stores in temp DB; guarded by `isProcessingSharedImage` lock |
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| | `storeSharedImageInTempDB()` | Clears old temp row, inserts base64 data URL into SQLite `temp` table |
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| | `checkForSharedImageAndNavigate()` | Checks native share, navigates to `/shared-photo` on success |
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| | `handleDeepLink()` | Handles `timesafari://` empty-path URLs from share extension on iOS |
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| | `registerDeepLinkListener()` | Registers Capacitor `appUrlOpen` listener |
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| `src/views/SharedPhotoView.vue` | `mounted()` / `onRouteQueryChange()` | Loads image from temp DB for display |
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| | `loadSharedImage()` | Reads `SHARED_PHOTO_BASE64_KEY` from temp DB; **deletes temp row** after load |
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| `src/router/index.ts` | — | Defines `/shared-photo` route |
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| `src/libs/util.ts` | `SHARED_PHOTO_BASE64_KEY` | Temp DB key constant (`"shared-photo-base64"`) |
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---
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## Read / Write / Delete Inventory
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### Writes — Shared Image Metadata (App Group UserDefaults)
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| File | Method | Keys Written |
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|------|--------|--------------|
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| `ShareViewController.swift` | `storeImageData(_:fileName:)` | `sharedPhotoFilePath`, `sharedPhotoFileName` |
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| `ShareViewController.swift` | `setSharedPhotoReadyFlag()` | `sharedPhotoReady` (= `true`) |
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### Writes — Shared Image Files (App Group Container)
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| File | Method | Details |
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|------|--------|---------|
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| `ShareViewController.swift` | `storeImageData(_:fileName:)` | `imageData.write(to:)` at `{containerURL}/{actualFileName}` |
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### Reads — Shared Image Metadata (App Group UserDefaults)
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| File | Method | Keys Read |
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|------|--------|-----------|
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| `SharedImageUtility.swift` | `getSharedImageData()` | `sharedPhotoFilePath`, `sharedPhotoFileName` |
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| `SharedImageUtility.swift` | `hasSharedImage()` | `sharedPhotoFilePath` |
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| `SharedImageUtility.swift` | `isSharedPhotoReady()` | `sharedPhotoReady` |
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| `AppDelegate.swift` | `checkForSharedImageOnActivation()` | `sharedPhotoReady` (via `isSharedPhotoReady()`) |
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### Reads — Shared Image Files (App Group Container)
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| File | Method | Details |
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|------|--------|---------|
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| `ShareViewController.swift` | `processSharedImage` (URL path) | Reads source image via `Data(contentsOf: url)` from security-scoped URL |
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| `SharedImageUtility.swift` | `getSharedImageData()` | `Data(contentsOf: fileURL)` from App Group container |
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| `SharedImageUtility.swift` | `hasSharedImage()` | `FileManager.fileExists(atPath:)` only (no data read) |
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### Deletes — Shared Image Metadata (App Group UserDefaults)
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| File | Method | Keys Removed |
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|------|--------|--------------|
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| `ShareViewController.swift` | `storeImageData(_:fileName:)` | `sharedPhotoBase64` (legacy cleanup) |
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| `SharedImageUtility.swift` | `getSharedImageData()` | `sharedPhotoFilePath`, `sharedPhotoFileName` |
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| `SharedImageUtility.swift` | `clearSharedPhotoReadyFlag()` | `sharedPhotoReady` |
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| `AppDelegate.swift` | `checkForSharedImageOnActivation()` | `sharedPhotoReady` (via `clearSharedPhotoReadyFlag()`) |
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### Deletes — Shared Image Files (App Group Container)
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| File | Method | Details |
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|------|--------|---------|
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| `ShareViewController.swift` | `storeImageData(_:fileName:)` | Removes existing file at target path before write |
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| `SharedImageUtility.swift` | `getSharedImageData()` | `FileManager.removeItem(at: fileURL)` after successful read |
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### Secondary Storage (Post-Native Consumption)
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After native read, image data lives in SQLite `temp` table under key `shared-photo-base64`:
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| File | Method | Operation |
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|------|--------|-----------|
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| `main.capacitor.ts` | `storeSharedImageInTempDB()` | **DELETE** old row, then **INSERT OR REPLACE** |
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| `SharedPhotoView.vue` | `loadSharedImage()` | **READ** then **DELETE** temp row |
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---
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## Timing, Delays, Retries, and Polling
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| Location | Mechanism | Values | Purpose |
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|----------|-----------|--------|---------|
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| `AppDelegate.swift` `didFinishLaunching` | Plugin registration retry loop | Initial delay **0.5s**; up to **5** attempts; backoff **0.5s × attempt** | Ensure Capacitor bridge exists before registering `SharedImagePlugin` |
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| `main.capacitor.ts` startup | `setTimeout` | **1000ms** (iOS only) | Deferred check for shared image on cold launch |
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| `main.capacitor.ts` startup | `setTimeout` | **2000ms** | Deferred registration of `appUrlOpen` deep-link listener |
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| `main.capacitor.ts` startup | `setTimeout` | **1000ms** | Log app initialization status |
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| `main.capacitor.ts` | `CapacitorApp.addListener("appStateChange")` | On every `isActive === true` | Re-check shared image when app foregrounds |
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| `main.capacitor.ts` | `isProcessingSharedImage` flag | Synchronous JS lock | Prevents concurrent `checkAndStoreNativeSharedImage()` calls |
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| `main.capacitor.ts` | Comment at line 214 | References polling | **Stale comment** — `checkAndStoreNativeSharedImage()` does **not** poll or retry |
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**No native polling or retry** exists for reading App Group data. `hasSharedImage()` is exposed but **never called** from application JS code.
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---
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## Current Startup Detection Points
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| # | Layer | Trigger | File | Method | Action |
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|---|-------|---------|------|--------|--------|
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| 1 | Native | App becomes active (cold start + resume) | `AppDelegate.swift` | `applicationDidBecomeActive` → `checkForSharedImageOnActivation` | Reads `sharedPhotoReady` flag; clears flag; posts `SharedPhotoReady` NSNotification *(no JS listener)* |
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| 2 | JS | Module load + 1000ms delay | `main.capacitor.ts` | `setTimeout` → `checkForSharedImageAndNavigate` | Calls `SharedImage.getSharedImage()`, stores in temp DB, navigates to `/shared-photo` |
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| 3 | JS | App foreground | `main.capacitor.ts` | `appStateChange` listener → `checkForSharedImageAndNavigate` | Same as above |
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| 4 | JS | Deep link `timesafari://` | `main.capacitor.ts` | `appUrlOpen` → `handleDeepLink` → `checkAndStoreNativeSharedImage` | iOS-only empty-path URL handling; navigates to `/shared-photo` |
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| 5 | Native | URL open | `AppDelegate.swift` | `application(_:open:options:)` | Forwards to Capacitor `ApplicationDelegateProxy` (enables #4) |
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| 6 | Native | Cold launch plugin setup | `AppDelegate.swift` | `didFinishLaunching` → `tryRegister` | Registers `SharedImagePlugin` (not a share check, but required for JS reads) |
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**Note:** Detection points 1–4 can all fire for a single share event. Only the JS paths (#2–4) actually read and consume the image.
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---
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## Current Deletion Points
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### App Group (Native)
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| When | File | Method | What is deleted |
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|------|------|--------|-----------------|
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| Before overwrite | `ShareViewController.swift` | `storeImageData` | Existing file at same filename |
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| Legacy cleanup on write | `ShareViewController.swift` | `storeImageData` | `sharedPhotoBase64` UserDefaults key |
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| On successful read | `SharedImageUtility.swift` | `getSharedImageData` | `sharedPhotoFilePath`, `sharedPhotoFileName`, image file |
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| On app activation (flag only) | `AppDelegate.swift` | `checkForSharedImageOnActivation` | `sharedPhotoReady` flag |
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### Temp Database (JS)
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| When | File | Method | What is deleted |
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|------|------|--------|-----------------|
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| Before storing new share | `main.capacitor.ts` | `storeSharedImageInTempDB` | Prior `shared-photo-base64` temp row |
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| After view loads image | `SharedPhotoView.vue` | `loadSharedImage` | `shared-photo-base64` temp row |
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**Important:** Native image file and metadata survive until `getSharedImageData()` succeeds. The `sharedPhotoReady` flag is cleared independently and earlier by `AppDelegate`.
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---
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## Potential Race Conditions
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1. **Multiple JS detection paths, single destructive read.** `applicationDidBecomeActive`, the 1000ms startup timer, `appStateChange`, and `appUrlOpen` can all invoke `checkAndStoreNativeSharedImage()` close together. `getSharedImageData()` deletes the file and metadata on first successful read; subsequent calls return null. The `isProcessingSharedImage` JS lock reduces but does not eliminate races between separate async entry points that start before the lock is set.
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2. **Deep-link listener registered 2 seconds after mount.** The share extension opens `timesafari://` immediately. If Capacitor does not buffer the launch URL until the `appUrlOpen` listener is registered (at T+2000ms), the deep-link path may be missed on cold start. The 1000ms startup check and `appStateChange` paths partially compensate.
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3. **Plugin registration vs. first `getSharedImage()` call.** `SharedImagePlugin` is registered with up to 5 retries starting at T+500ms. A `getSharedImage()` call before registration completes will fail. The 1000ms startup delay usually avoids this, but `appStateChange` can fire earlier.
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4. **`sharedPhotoReady` flag cleared before JS reads image.** `AppDelegate.checkForSharedImageOnActivation` clears the flag and posts `SharedPhotoReady`, but no JavaScript code listens for that NSNotification. The flag is therefore a redundant signal; reliance is entirely on file/metadata presence. If file write failed but flag were set, the flag would be cleared with no image available (current code sets flag only after successful `storeImageData`).
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5. **`SharedPhotoReady` NSNotification is a dead signal.** Posted in `AppDelegate` but not bridged to Capacitor/JS. All actual consumption happens through JS-initiated `getSharedImage()` calls.
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6. **Concurrent share while app is open.** A second share overwrites the App Group file and metadata. If the first share has already been read into temp DB but the user has not yet reached `SharedPhotoView`, the second share can replace native data; navigation refresh via `_refresh` query param handles re-navigation but temp DB overwrite in `storeSharedImageInTempDB` can clobber an in-flight first image.
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7. **Extension `completeRequest` timing.** `completeRequest` runs in the `processSharedImage` completion handler after `storeImageData`, flag set, and `openMainApp` — so the file should exist before the extension exits. However, `loadItem` is asynchronous; if the extension process is terminated aggressively by iOS after `completeRequest`, this is generally safe because all writes complete in the callback before completion.
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8. **Stale comment implies polling that does not exist.** `handleDeepLink` comments reference internal polling in `checkAndStoreNativeSharedImage`, but no retry loop exists. A single failed read at the wrong moment is not retried on iOS (unlike Android's multi-delay startup checks).
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9. **`hasSharedImage()` unused.** A non-destructive pre-check is available natively but JS always calls destructive `getSharedImage()` directly, making timing-sensitive false negatives more likely if called before the extension finishes writing.
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---
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## Configuration References
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| Resource | Value |
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|----------|-------|
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| App Group ID | `group.app.timesafari.share` |
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| URL scheme | `timesafari://` |
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| Extension bundle ID | `app.timesafari.TimeSafariShareExtension` |
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| Main app bundle ID | `app.timesafari` |
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| Capacitor plugin name | `SharedImage` |
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| Temp DB key | `shared-photo-base64` (`SHARED_PHOTO_BASE64_KEY`) |
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| Route | `/shared-photo` |
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Reference in New Issue
Block a user