// Endpoint path: similar-cases
// Mode: Sync
// Read Only: true
// Authorization: Restricted

var caseId    = Body.FromJson<SimilarRequest>().CaseId;
var caseNode  = Q().StartAt(nameof(Nodes.SupportCase), caseId).Single();
var deviceUID = caseNode.Out(Edges.ForDevice).AsUIDEnumerable().FirstOrDefault();

if (deviceUID == default) return Ok(new { results = Array.Empty<object>() });

// Sibling cases on the same device, excluding the current one.
var siblings = Q().StartAt(deviceUID)
                  .In(Edges.ForDevice)
                  .Where(c => c.Key != caseId)
                  .AsUIDEnumerable()
                  .ToArray();

var request = SearchRequest.For(caseNode["Content"].AsString());
request.BeforeTypesFacet = new HashSet<string> { nameof(Nodes.SupportCase) };
request.TargetUIDs       = siblings;
request.HybridSearch     = true;

var query = await Graph.CreateSearchAsUserAsync(request, CurrentUser);
return Ok(query.Take(5).EmitWithScores());

{
  "results": [
    { "uid": "...", "key": "CS-0210", "summary": "Display artifacts after sleep",      "score": 0.81 },
    { "uid": "...", "key": "CS-0174", "summary": "External monitor flickers post-wake", "score": 0.78 },
    { "uid": "...", "key": "CS-0098", "summary": "Sleep/wake regression on update",     "score": 0.69 }
  ]
}

// Endpoint path: support-chat
// Mode: Sync (or Pooling for long answers)
// Read Only: false   // we write an audit node

public record ChatRequest(string Question, string? DeviceName);
public record Citation  (string CaseId, string Summary, double Score);
public record ChatReply (string Answer, Citation[] Citations);

var req = Body.FromJson<ChatRequest>();
await RelayStatusAsync("Retrieving relevant cases...");

// 1. Retrieve — scoped to the device if given, ACL-filtered for the caller.
var search = SearchRequest.For(req.Question);
search.BeforeTypesFacet = new HashSet<string> { nameof(Nodes.SupportCase) };
search.HybridSearch     = true;
if (req.DeviceName is not null)
{
    search.TargetUIDs = Q().StartAt(nameof(Nodes.Device), req.DeviceName)
                            .In(Edges.ForDevice)
                            .AsUIDEnumerable()
                            .ToArray();
}

var hits = (await Graph.CreateSearchAsUserAsync(search, CurrentUser))
           .Take(5)
           .EmitWithScores()
           .ToList();

if (hits.Count == 0)
    return Ok(new ChatReply("I couldn't find any cases on file that match your question.", Array.Empty<Citation>()));

// 2. Build the prompt — quote case ID and summary so the model can cite them.
var sb = new StringBuilder();
sb.AppendLine("Answer the user's question using only the cases below. Cite cases as [CS-####].");
sb.AppendLine();
foreach (var (node, score) in hits)
{
    sb.AppendLine($"[{node["Id"].AsString()}] {node["Summary"].AsString()}");
    sb.AppendLine(node["Content"].AsString());
    sb.AppendLine("---");
}
sb.AppendLine();
sb.AppendLine($"Question: {req.Question}");

// 3. Generate
await RelayStatusAsync("Asking the assistant...");
var answer = await ChatAI.CompleteAsync(sb.ToString(), CancellationToken);

// 4. Audit — store the prompt, the answer, and the cited UIDs.
var audit = Graph.AddOrUpdate(new ChatAuditEntry
{
    Id        = Guid.NewGuid().ToString(),
    UserUID   = CurrentUser,
    Question  = req.Question,
    Answer    = answer,
    Timestamp = DateTimeOffset.UtcNow,
});
foreach (var (node, _) in hits)
    Graph.Link(audit, node, "Cited", "CitedBy");
await Graph.CommitPendingAsync();

return Ok(new ChatReply(
    Answer:    answer,
    Citations: hits.Select(h => new Citation(
                   h.Node["Id"].AsString(),
                   h.Node["Summary"].AsString(),
                   h.Score)).ToArray()));

{
  "answer": "Several past cases describe this symptom. Try the steps from [CS-0142]: ...\nIf it persists, [CS-0174] suggests reseating the display cable.",
  "citations": [
    { "case_id": "CS-0142", "summary": "Screen flickers after waking from sleep", "score": 0.84 },
    { "case_id": "CS-0174", "summary": "External monitor flickers post-wake",     "score": 0.77 }
  ]
}