FSH.OfflineSync

🔄 A plug-and-play offline sync library for Blazor WebAssembly + FullStackHero apps using HttpClient, DelegatingHandler, and Blazor.Localstorage.

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✨ Features

• 📡 Caches GET API responses locally
• 📴 Queues POST/PUT/DELETE requests offline
• 🔁 Automatically syncs when connection is restored
• 🔐 Attaches Authorization: Bearer <token> using Blazored.LocalStorage
• 🔌 One-liner integration via AddOfflineSyncHttpClient()
• ✅ Designed for FullStackHero + Blazor WebAssembly
• 💾 Uses Blazor.Localstorage for durable offline support

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📦 Installation

dotnet add package FSH.OfflineSync

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🚀 Getting Started

1. Add the following to your Program.cs:

builder.Services.AddOfflineSyncHttpClient(builder.Configuration, options =>
{
    options.AuthTokenKey = StorageConstants.Local.AuthToken; // or "authToken" Or StorageConstants.Local.AuthToken if using FullStackHero
});

2. Add your API domain to wwwroot/appsettings.json:

{
  "APIDomain": "https://your-api-domain.com"
}

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🧩 What’s Registered Automatically

Service	Purpose
OfflineDelegatingHandler	Intercepts API calls and manages caching
AuthHeaderHandler	Adds Authorization header from local storage
OfflineSyncService	Manages offline queue and sync process
ILocalStorageService	Handles token and local cache storage
HttpClient ("FSHClient")	Pre-configured with handlers and base URL

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⚙️ Configuration

public class OfflineSyncOptions
{
    public string AuthTokenKey { get; set; } = "authToken";
}

If your app uses a different key for the auth token in localStorage, pass it via OfflineSyncOptions.

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🧠 Sample Usage

You don't need to change how you use HttpClient. All GET/POST/PUT/DELETE calls will work as usual:

@inject HttpClient Http

var result = await Http.GetFromJsonAsync<List<Product>>("api/products");

If the app is offline:

• GET will return from local cache (if available)
• POST/PUT/DELETE will be queued in IndexedDB and synced when online

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🗃 Project Structure

FSH.OfflineSync/
│
├── Extensions/
│   └── ServiceCollectionExtensions.cs
│
├── Handlers/
│   ├── OfflineDelegatingHandler.cs
│   └── AuthHeaderHandler.cs
│
├── Services/
│   ├── OfflineSyncService.cs
│   └── IOfflineSyncService.cs
│
├── Models/
│   ├── QueuedRequest.cs
│   └── SyncResult.cs
│
├── JSInterop/
│   └── OfflineSyncJsInterop.cs
│
├── Options/
│   └── OfflineSyncOptions.cs
│
├── wwwroot/
│   └── manifest.sync.json (optional)
│
└── FSH.OfflineSync.csproj

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📈 Roadmap / Future Enhancements

• 🔄 Background sync using Service Workers
• ⚙️ Configurable retry policy (e.g., exponential backoff)
• 🪵 Logging support via ILogger
• 📶 <OfflineStatus> UI component
• 🔐 Encrypted offline storage
• 🧪 Unit test project + integration test sample
• 🧩 Typed API client (IApiClient)
• 📁 Sample app (ConsumerApp) in repo
• 📦 NuGet & CI/CD auto-publish

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✅ GitHub Actions: CI/CD Workflow

📄 License

MIT © 2025 — Developed by KyrilosAdel

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💬 Support & Contributions

Feel free to open issues or submit pull requests. Contributions are welcome!