feat: AI Chat and embeddings

Directory.Packages.props

@@ -36,11 +36,18 @@
     <PackageVersion Include="Microsoft.EntityFrameworkCore.SqlServer" Version="8.0.10" />
     <PackageVersion Include="Microsoft.EntityFrameworkCore.Tools" Version="8.0.10" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
+    <PackageVersion Include="Microsoft.SemanticKernel" Version="1.60.0" />
+    <PackageVersion Include="Microsoft.SemanticKernel.Connectors.PgVector" Version="1.60.0-preview" />
+    <PackageVersion Include="Microsoft.SourceLink.GitHub" Version="8.0.0" />
     <PackageVersion Include="Microsoft.VisualStudio.Azure.Containers.Tools.Targets" Version="1.21.0" />
     <PackageVersion Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="9.0.0" />
+    <PackageVersion Include="ModelContextProtocol" Version="0.3.0-preview.3" />
+    <PackageVersion Include="ModelContextProtocol.AspNetCore" Version="0.3.0-preview.3" />
+    <PackageVersion Include="Moq" Version="4.20.72" />
+    <PackageVersion Include="System.CommandLine" Version="2.0.0-beta6.25358.103" />
     <PackageVersion Include="Newtonsoft.Json" Version="13.0.3" />
     <PackageVersion Include="Octokit" Version="14.0.0" />
     <PackageVersion Include="xunit" Version="2.9.3" />
     <PackageVersion Include="xunit.runner.visualstudio" Version="3.0.1" />
   </ItemGroup>
-</Project>
+</Project>

EssentialCSharp.Chat.Shared/EssentialCSharp.Chat.Common.csproj

@@ -0,0 +1,20 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net9.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.SemanticKernel" />
+    <PackageReference Include="Microsoft.SemanticKernel.Connectors.PgVector" />
+    <PackageReference Include="ModelContextProtocol" />
+    <PackageReference Include="ModelContextProtocol.AspNetCore" />
+    <PackageReference Include="Microsoft.SourceLink.GitHub">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+    </PackageReference>
+  </ItemGroup>
+
+</Project>

EssentialCSharp.Chat.Shared/Extensions/ServiceCollectionExtensions.cs

@@ -0,0 +1,80 @@
+using EssentialCSharp.Chat.Common.Services;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.SemanticKernel;
+
+namespace EssentialCSharp.Chat.Common.Extensions;
+
+public static class ServiceCollectionExtensions
+{
+    /// <summary>
+    /// Adds Azure OpenAI and related AI services to the service collection
+    /// </summary>
+    /// <param name="services">The service collection to add services to</param>
+    /// <param name="aiOptions">The AI configuration options</param>
+    /// <returns>The service collection for chaining</returns>
+    public static IServiceCollection AddAzureOpenAIServices(this IServiceCollection services, AIOptions aiOptions)
+    {
+        // Validate required configuration
+        if (aiOptions == null)
+        {
+            throw new InvalidOperationException("AIOptions cannot be null.");
+        }
+
+        if (string.IsNullOrEmpty(aiOptions.Endpoint) ||
+            string.IsNullOrEmpty(aiOptions.ApiKey))
+        {
+            throw new InvalidOperationException("Azure OpenAI Endpoint and ApiKey must be properly configured in AIOptions. Please update your configuration with valid values.");
+        }
+
+        if (string.IsNullOrEmpty(aiOptions.PostgresConnectionString) ||
+            aiOptions.PostgresConnectionString.Contains("your-postgres-connection-string"))
+        {
+            throw new InvalidOperationException("PostgreSQL connection string must be properly configured in AIOptions for vector store. Please update your configuration with a valid connection string.");
+        }
+
+#pragma warning disable SKEXP0010 // Type is for evaluation purposes only and is subject to change or removal in future updates.
+
+        // Register Azure OpenAI services
+        services.AddAzureOpenAIEmbeddingGenerator(
+            aiOptions.VectorGenerationDeploymentName,
+            aiOptions.Endpoint,
+            aiOptions.ApiKey);
+
+        services.AddAzureOpenAIChatClient(
+            aiOptions.ChatDeploymentName,
+            aiOptions.Endpoint,
+            aiOptions.ApiKey);
+
+        // Add PostgreSQL vector store
+        services.AddPostgresVectorStore(aiOptions.PostgresConnectionString);
+
+#pragma warning restore SKEXP0010
+
+        // Register shared AI services
+        services.AddSingleton<EmbeddingService>();
+        services.AddSingleton<AISearchService>();
+        services.AddSingleton<AIChatService>();
+        services.AddSingleton<MarkdownChunkingService>();
+
+        return services;
+    }
+
+    /// <summary>
+    /// Adds Azure OpenAI and related AI services to the service collection using configuration
+    /// </summary>
+    /// <param name="services">The service collection to add services to</param>
+    /// <param name="configuration">The configuration to read AIOptions from</param>
+    /// <returns>The service collection for chaining</returns>
+    public static IServiceCollection AddAzureOpenAIServices(this IServiceCollection services, IConfiguration configuration)
+    {
+        // Configure AI options from configuration
+        services.Configure<AIOptions>(configuration.GetSection("AIOptions"));
+
+        var aiOptions = configuration.GetSection("AIOptions").Get<AIOptions>();
+
+        return aiOptions == null
+            ? throw new InvalidOperationException("AIOptions section is missing from configuration.")
+            : services.AddAzureOpenAIServices(aiOptions);
+    }
+}

EssentialCSharp.Chat.Shared/Models/AIOptions.cs

@@ -0,0 +1,34 @@
+namespace EssentialCSharp.Chat;
+
+public class AIOptions
+{
+    /// <summary>
+    /// The Azure OpenAI deployment name for text embedding generation.
+    /// </summary>
+    public string VectorGenerationDeploymentName { get; set; } = string.Empty;
+
+    /// <summary>
+    /// The Azure OpenAI deployment name for chat completions.
+    /// </summary>
+    public string ChatDeploymentName { get; set; } = string.Empty;
+
+    /// <summary>
+    /// The system prompt to use for the chat model.
+    /// </summary>
+    public string SystemPrompt { get; set; } = string.Empty;
+
+    /// <summary>
+    /// The Azure OpenAI endpoint URL.
+    /// </summary>
+    public string Endpoint { get; set; } = string.Empty;
+
+    /// <summary>
+    /// The API key for accessing Azure OpenAI services.
+    /// </summary>
+    public string ApiKey { get; set; } = string.Empty;
+
+    /// <summary>
+    /// The PostgreSQL connection string for the vector store.
+    /// </summary>
+    public string PostgresConnectionString { get; set; } = string.Empty;
+}

EssentialCSharp.Chat.Shared/Models/BookContentChunk.cs

@@ -0,0 +1,54 @@
+using Microsoft.Extensions.VectorData;
+
+namespace EssentialCSharp.Chat.Common.Models;
+
+/// <summary>
+/// Represents a chunk of book content for vector search
+/// </summary>
+public sealed class BookContentChunk
+{
+    /// <summary>
+    /// Unique identifier for the chunk - serves as the vector store key
+    /// </summary>
+    [VectorStoreKey]
+    public string Id { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Original source file name
+    /// </summary>
+    [VectorStoreData]
+    public string FileName { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Heading or title of the markdown chunk
+    /// </summary>
+    [VectorStoreData]
+    public string Heading { get; set; } = string.Empty;
+
+    /// <summary>
+    /// The actual markdown content text for this chunk
+    /// </summary>
+    [VectorStoreData]
+    public string ChunkText { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Chapter number extracted from filename (e.g., "Chapter01.md" -> 1)
+    /// </summary>
+    [VectorStoreData]
+    public int? ChapterNumber { get; set; }
+
+    /// <summary>
+    /// SHA256 hash of the chunk content for change detection
+    /// </summary>
+    [VectorStoreData]
+    public string ContentHash { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Vector embedding for the chunk text - will be generated by embedding service
+    /// Using 1536 dimensions for Azure OpenAI text-embedding-3-small-v1
+    /// Use CosineSimilarity distance function since we are using text-embedding-3 (https://platform.openai.com/docs/guides/embeddings#which-distance-function-should-i-use)
+    /// Postgres supports only Hnsw: https://learn.microsoft.com/en-us/semantic-kernel/concepts/vector-store-connectors/out-of-the-box-connectors/postgres-connector?pivots=programming-language-csharp&WT.mc_id=8B97120A00B57354
+    /// </summary>
+    [VectorStoreVector(Dimensions: 1536, DistanceFunction = DistanceFunction.CosineSimilarity, IndexKind = IndexKind.Hnsw)]
+    public ReadOnlyMemory<float>? TextEmbedding { get; set; }
+}