Add documentation and improve sample

Author: kzu

readme.md

@@ -1,8 +1,137 @@
-![Icon](assets/img/icon.png) WhatsApp agents for Azure Functions
+![Icon](assets/img/icon.png) WhatsApp agents for Azure Functions
 ============
 
+[![Version](https://img.shields.io/nuget/vpre/Devlooped.WhatsApp.svg?color=royalblue)](https://www.nuget.org/packages/Devlooped.WhatsApp)
+[![Downloads](https://img.shields.io/nuget/dt/Devlooped.WhatsApp.svg?color=green)](https://www.nuget.org/packages/Devlooped.WhatsApp)
+[![License](https://img.shields.io/github/license/devlooped/WhatsApp.svg?color=blue)](https://github.com//devlooped/WhatsApp/blob/main/license.txt)
+[![Build](https://github.com/devlooped/WhatsApp/actions/workflows/build.yml/badge.svg?branch=main)](https://github.com/devlooped/WhatsApp/actions/workflows/build.yml)
+
 Create agents for WhatsApp using Azure Functions.
 
+## Usage
+
+```csharp
+var builder = FunctionsApplication.CreateBuilder(args);
+builder.ConfigureFunctionsWebApplication();
+
+builder.UseWhatsApp<MyWhatsAppHandler>();
+
+builder.Build().Run();
+```
+
+Instead of providing an `IWhatsAppHandler` implementation, you can also 
+register an inline handler using minimal API style:
+
+```csharp
+builder.UseWhatsApp(message =>
+{
+    // MessageType: Content | Error | Interactive | Status
+    Console.WriteLine($"Got message type {message.Type}"); 
+    switch (message)
+    {
+        case ContentMessage content:
+            // ContentType = Text | Contact | Document | Image | Audio | Video | Location | Unknown (raw JSON)
+            Console.WriteLine($"Got content type {content.Content.Type}"); 
+            break;
+        case ErrorMessage error:
+            Console.WriteLine($"Error: {error.Error.Message} ({error.Error.Code})");
+            break;
+        case InteractiveMessage interactive:
+            Console.WriteLine($"Interactive: {interactive.Button.Title} ({interactive.Button.Id})");
+            break;
+        case StatusMessage status:
+            Console.WriteLine($"Status: {status.Status}");
+            break;
+    }
+    return Task.CompletedTask;
+});
+```
+
+If the handler needs additional services, they can be provided directly 
+as generic parameters of the `UseWhatsApp` method, such as:
+
+```csharp
+builder.UseWhatsApp<IWhatsAppClient, ILogger<Program>>(async (client, logger, message) =>
+{
+    logger.LogInformation($"Got message type {message.Type}");
+    // Reply to an incoming content message, for example.
+    if (message is ContentMessage content)
+        await client.SendTextAync(message.To.Id, message.From.Number, $"Got your {content.}");
+}
+```
+
+You can also specify the parameter types in the delegate itself and avoid the 
+generic parameters:
+
+```csharp
+builder.UseWhatsApp(async (IWhatsAppClient client, ILogger<Program> logger, Message message) =>
+```
+
+The provided `IWhatsAppClient` provides a very thin abstraction allowing you to send 
+arbitrary payloads to WhatsApp for Business:
+
+```csharp
+public interface IWhatsAppClient
+{
+    /// Payloads from https://developers.facebook.com/docs/whatsapp/cloud-api/reference/messages
+    Task SendAync(string from, object payload);
+}
+```
+
+Extensions methods for this interface take care of simplifying usage for some 
+common scenarios, such as reacting to a message and replying with plain text:
+
+```csharp
+if (message is ContentMessage content)
+{
+    await client.ReactAsync(from: message.To.Id, to: message.From.Number, message.Id, "🧠");
+    // simulate some hard work at hand, like doing some LLM-stuff :)
+    await Task.Delay(2000);
+    await client.SendTextAync(message.To.Id, message.From.Number, $"☑️ Processed your {content.Type}");
+}
+```
+
+## Configuration
+
+You need to register an app in the Meta [App Dashboard](https://developers.facebook.com/apps/]. 
+The app must then be configured to use the WhatsApp Business API, and the webhook and 
+verification token (an arbitrary value) must be set up in the app settings under WhatsApp. 
+The webhook URL is `/whatsapp` under your Azure Functions app.
+
+Make sure you subscribe the webhook to the `messages` field, with API version `v22.0` or later.
+
+Configuration on the Azure Functions side is done via the 
+[ASP.NET options pattern](https://learn.microsoft.com/en-us/aspnet/core/fundamentals/configuration/options) 
+and the `MetaOptions` type. When you call `UseWhatsApp`, the options will be bound by 
+default to the `Meta` section in the configuration. You can also configure it programmatically 
+as follows:
+
+```csharp
+builder.Services.Configure<MetaOptions>(options =>
+{
+    options.VerifyToken = "my-webhook-1234";
+    options.Numbers["12345678"] = "asff=";
+});
+```
+
+Via configuration:
+
+```json
+{
+  "Meta": {
+    "VerifyToken": "my-webhook-1234",
+    "Numbers": {
+      "12345678": "asff="
+    }
+  }
+}
+```
+
+The `Numbers` dictionary is a map of WhatsApp phone identifiers and the 
+corresponding access token for it. To get a permanent access token for 
+use, you'd need to create a [system user](https://business.facebook.com/latest/settings/system_users) 
+with full control permissions to the WhatsApp Business API (app).
+
 ## License
 
 We offer this project under a dual licensing model, tailored to the needs 

src/Sample/Program.cs

@@ -9,7 +9,7 @@
 builder.ConfigureFunctionsWebApplication();
 builder.Configuration.AddUserSecrets<Program>();
 
-builder.UseWhatsApp<IWhatsAppClient, ILogger<IWhatsAppClient>>(async (client, logger, message) =>
+builder.UseWhatsApp<IWhatsAppClient, ILogger<Program>>(async (client, logger, message) =>
 {
     logger.LogInformation("💬 Received message: {Message}", message);
 
@@ -49,11 +49,13 @@
         logger.LogInformation("☑️ New message status: {Status}", status.Status);
         return;
     }
-
-    await client.ReactAsync(message.To.Id, message.From.Number, message.Id, "🧠");
-    // simulate some hard work at hand, like doing some LLM-stuff :)
-    await Task.Delay(2000);
-    await client.SendTextAync(message.To.Id, message.From.Number, "I'm alive, but I'm just a sample 🤷‍.");
+    else if (message is ContentMessage content)
+    {
+        await client.ReactAsync(from: message.To.Id, to: message.From.Number, message.Id, "🧠");
+        // simulate some hard work at hand, like doing some LLM-stuff :)
+        await Task.Delay(2000);
+        await client.SendTextAync(message.To.Id, message.From.Number, $"☑️ Got your {content.Type.ToString().ToLowerInvariant()}");
+    }
 });
 
 builder.Build().Run();