feat: implement semantic search, knowledge unit extraction, and visualization components

src/NexusReader.Application/Commands/AI/VerifyGroundednessCommand.cs

@@ -0,0 +1,52 @@
+using FluentResults;
+using MediatR;
+using Microsoft.Extensions.AI;
+using NexusReader.Infrastructure.Services; // For PromptRegistry
+
+namespace NexusReader.Application.Commands.AI;
+
+public record VerifyGroundednessCommand(string Answer, string Context) : IRequest<Result<GroundednessResult>>;
+
+public record GroundednessResult(float Score, string Rationale, bool IsGrounded);
+
+public class VerifyGroundednessCommandHandler : IRequestHandler<VerifyGroundednessCommand, Result<GroundednessResult>>
+{
+    private readonly IChatClient _chatClient;
+
+    public VerifyGroundednessCommandHandler(IChatClient chatClient)
+    {
+        _chatClient = chatClient;
+    }
+
+    public async Task<Result<GroundednessResult>> Handle(VerifyGroundednessCommand request, CancellationToken cancellationToken)
+    {
+        var systemPrompt = @"
+        You are a Fact-Checking AI. Evaluate if the 'Answer' is supported by the 'Context'.
+        Rate the groundedness from 0.0 to 1.0.
+        Return ONLY a JSON object: { ""score"": 0.9, ""rationale"": ""string"", ""isGrounded"": true }
+        ";
+
+        var userPrompt = $"Context: {request.Context}\n\nAnswer: {request.Answer}";
+
+        try
+        {
+            var response = await _chatClient.GetResponseAsync(new List<ChatMessage>
+            {
+                new ChatMessage(ChatRole.System, systemPrompt),
+                new ChatMessage(ChatRole.User, userPrompt)
+            }, cancellationToken: cancellationToken);
+
+            var rawJson = response.Text?.Trim() ?? "{}";
+            // Simple cleanup if needed
+            rawJson = rawJson.Replace("```json", "").Replace("```", "").Trim();
+            
+            var result = System.Text.Json.JsonSerializer.Deserialize<GroundednessResult>(rawJson, new System.Text.Json.JsonSerializerOptions { PropertyNameCaseInsensitive = true });
+            
+            return result != null ? Result.Ok(result) : Result.Fail("Failed to parse groundedness result");
+        }
+        catch (Exception ex)
+        {
+            return Result.Fail(new Error("Failed to verify groundedness").CausedBy(ex));
+        }
+    }
+}