fix(server): reject duplicate nest ids, invalid metadata and bare --database

- POST /api/nests with an existing id (active or deleted) now returns 409 with
  the current record instead of a 500 from the UNIQUE constraint.
- Uploaded nest metadata must have string text fields and a defined status;
  null fields and undefined statuses (e.g. 99) are 400 instead of a 500 or a
  stored invalid value.
- --database <path> is accepted alongside --database=<path>; a missing or
  repeated path fails startup instead of silently using OPENNEST_DB/default.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

OpenNest.Server/NestDatabase.cs

@@ -142,6 +142,9 @@ public sealed partial class NestDatabase : IDisposable
         lock (_sync)
         {
             using var transaction = _connection.BeginTransaction();
+            // Ids are client-allocated: an existing id, active or deleted, is a conflict, not a replacement.
+            if ((Get(id) ?? Get(id, deleted: true)) is { } existing)
+                throw new RevisionConflictException(existing, "A nest with this id already exists.");
             using var command = _connection.CreateCommand();
             command.Transaction = transaction;
             command.CommandText = """
@@ -488,7 +491,8 @@ public sealed partial class NestDatabase : IDisposable
     }
 }
 
-public sealed class RevisionConflictException(NestRecord current) : Exception("The nest has changed. Reload or Save As.")
+public sealed class RevisionConflictException(NestRecord current, string message = "The nest has changed. Reload or Save As.")
+    : Exception(message)
 {
     public NestRecord Current { get; } = current;
 }

OpenNest.Server/NestMetadata.cs

@@ -0,0 +1,60 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using OpenNest.Data;
+
+namespace OpenNest.Server;
+
+/// <summary>
+/// Reads and checks uploaded nest metadata. Text fields must be present and the status
+/// must be a defined value, so invalid metadata is a 400 and never reaches storage.
+/// </summary>
+internal static class NestMetadata
+{
+    // Integer statuses stay accepted for existing callers; GetError refuses undefined ones.
+    public static readonly JsonSerializerOptions Options = new(JsonSerializerDefaults.Web)
+    {
+        PropertyNameCaseInsensitive = true,
+        Converters = { new JsonStringEnumConverter(JsonNamingPolicy.CamelCase) },
+    };
+
+    public static bool TryRead(string? json, out NestRecord record, out string error)
+    {
+        record = new NestRecord();
+        if (string.IsNullOrWhiteSpace(json))
+        {
+            error = "Missing 'metadata' part.";
+            return false;
+        }
+
+        try
+        {
+            if (JsonSerializer.Deserialize<NestRecord>(json, Options) is not { } parsed)
+            {
+                error = "Missing metadata.";
+                return false;
+            }
+
+            record = parsed;
+        }
+        catch (JsonException)
+        {
+            error = "Invalid metadata JSON.";
+            return false;
+        }
+
+        error = GetError(record) ?? "";
+        return error.Length == 0;
+    }
+
+    public static string? GetError(NestRecord record)
+    {
+        if (record.Name is null) return "name must be a string.";
+        if (record.Customer is null) return "customer must be a string.";
+        if (record.Material is null) return "material must be a string.";
+        if (record.Comments is null) return "comments must be a string.";
+        if (record.MadeBy is null) return "madeBy must be a string.";
+        if (!Enum.IsDefined(record.Status)) return "status must be quote, toBeCut or hasBeenCut.";
+        if (!double.IsFinite(record.Thickness)) return "thickness must be a finite number.";
+        return null;
+    }
+}

OpenNest.Server/Program.cs

@@ -20,11 +20,8 @@ builder.Services.ConfigureHttpJsonOptions(options =>
         options.SerializerOptions.Converters.Add(converter);
 });
 
-// Storage path: --database <path> or OPENNEST_DB, default ./data/nests.db (a Docker volume).
-var databasePath =
-    args.FirstOrDefault(a => a.StartsWith("--database=", StringComparison.Ordinal))?.Split('=', 2)[1]
-    ?? Environment.GetEnvironmentVariable("OPENNEST_DB")
-    ?? Path.Combine("data", "nests.db");
+// Storage path: --database=<path> or --database <path>, then OPENNEST_DB, default ./data/nests.db (a Docker volume).
+var databasePath = ServerOptions.DatabasePath(args, Environment.GetEnvironmentVariable(ServerOptions.DatabaseVariable));
 builder.Services.AddSingleton(_ => new NestDatabase(databasePath));
 
 // Listen port: --urls or ASPNETCORE_URLS; Dockerfile defaults to 8090.
@@ -60,7 +57,8 @@ app.MapPost("/api/nests", async (HttpContext http, NestDatabase db) =>
         return error;
 
     var id = record!.Id == Guid.Empty ? Guid.NewGuid() : record.Id;
-    return Results.Ok(db.Insert(id, record, file!));
+    try { return Results.Ok(db.Insert(id, record, file!)); }
+    catch (RevisionConflictException conflict) { return Results.Json(conflict.Current, statusCode: 409); }
 });
 app.MapGet("/api/nests/{id:guid}/revisions", (Guid id, HttpRequest request, NestDatabase db) =>
     ReadHistory(id, request, db));
@@ -90,10 +88,11 @@ app.MapPut("/api/nests/{id:guid}/metadata", async (Guid id, HttpRequest request,
     var error = IfMatch.Read(request, out var expected);
     if (error is not null) return error;
     NestRecord? record;
-    try { record = await request.ReadFromJsonAsync<NestRecord>(); }
+    try { record = await request.ReadFromJsonAsync<NestRecord>(NestMetadata.Options); }
     catch (Exception ex) when (ex is JsonException or InvalidOperationException or BadHttpRequestException)
     { return Results.BadRequest("Invalid metadata JSON."); }
     if (record is null) return Results.BadRequest("Missing metadata.");
+    if (NestMetadata.GetError(record) is { } invalid) return Results.BadRequest(invalid);
     try
     {
         var updated = db.UpdateMetadata(id, record, expected);
@@ -184,22 +183,8 @@ static async Task<(NestRecord? Record, byte[]? File, IResult? Error)> ReadMultip
         return (null, null, Results.BadRequest("Malformed multipart body."));
     }
 
-    var metadataPart = form["metadata"].FirstOrDefault();
-    if (string.IsNullOrWhiteSpace(metadataPart))
-        return (null, null, Results.BadRequest("Missing 'metadata' part."));
-
-    NestRecord? record;
-    try
-    {
-        record = JsonSerializer.Deserialize<NestRecord>(metadataPart, MultipartJson.Options);
-    }
-    catch (JsonException)
-    {
-        return (null, null, Results.BadRequest("Invalid metadata JSON."));
-    }
-
-    if (record is null)
-        return (null, null, Results.BadRequest("Missing metadata."));
+    if (!NestMetadata.TryRead(form["metadata"].FirstOrDefault(), out var record, out var metadataError))
+        return (null, null, Results.BadRequest(metadataError));
 
     var filePart = form.Files["file"];
     if (filePart is null || filePart.Length == 0)
@@ -211,14 +196,5 @@ static async Task<(NestRecord? Record, byte[]? File, IResult? Error)> ReadMultip
     return (record, buffer.ToArray(), null);
 }
 
-internal static class MultipartJson
-{
-    public static readonly JsonSerializerOptions Options = new(JsonSerializerDefaults.Web)
-    {
-        PropertyNameCaseInsensitive = true,
-        Converters = { new JsonStringEnumConverter(JsonNamingPolicy.CamelCase) },
-    };
-}
-
 // Entry-point type for in-memory integration tests (WebApplicationFactory<Program>).
 public partial class Program { }

OpenNest.Server/ServerOptions.cs

@@ -0,0 +1,43 @@
+namespace OpenNest.Server;
+
+/// <summary>Startup settings read from the command line and environment.</summary>
+public static class ServerOptions
+{
+    public const string DatabaseVariable = "OPENNEST_DB";
+
+    /// <summary>
+    /// The database path: <c>--database=&lt;path&gt;</c> or <c>--database &lt;path&gt;</c>, then
+    /// <c>OPENNEST_DB</c>, then <c>./data/nests.db</c>. A <c>--database</c> without a path,
+    /// or given twice, fails startup instead of silently storing nests elsewhere.
+    /// </summary>
+    public static string DatabasePath(IReadOnlyList<string> args, string? environmentPath)
+    {
+        string? path = null;
+        for (var i = 0; i < args.Count; i++)
+        {
+            string value;
+            if (args[i] == "--database")
+            {
+                if (i + 1 >= args.Count || args[i + 1].StartsWith("--", StringComparison.Ordinal))
+                    throw new ArgumentException("--database requires a path.", nameof(args));
+                value = args[++i];
+            }
+            else if (args[i].StartsWith("--database=", StringComparison.Ordinal))
+            {
+                value = args[i]["--database=".Length..];
+            }
+            else
+            {
+                continue;
+            }
+
+            if (string.IsNullOrWhiteSpace(value))
+                throw new ArgumentException("--database requires a path.", nameof(args));
+            if (path is not null)
+                throw new ArgumentException("--database was given more than once.", nameof(args));
+            path = value;
+        }
+
+        return path ?? environmentPath ?? Path.Combine("data", "nests.db");
+    }
+}