feat(api): add NestResponse with SaveAsync/LoadAsync

Adds NestResponse type to OpenNest.Api with SaveAsync/LoadAsync for .nestquote format — a ZIP containing request.json, response.json (metrics), and an embedded nest.nest.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

OpenNest.Api/NestResponse.cs

@@ -0,0 +1,109 @@
+using System;
+using System.IO;
+using System.IO.Compression;
+using System.Text.Json;
+using System.Threading.Tasks;
+using OpenNest.IO;
+
+namespace OpenNest.Api;
+
+public class NestResponse
+{
+    public int SheetCount { get; init; }
+    public double Utilization { get; init; }
+    public TimeSpan CutTime { get; init; }
+    public TimeSpan Elapsed { get; init; }
+    public Nest Nest { get; init; }
+    public NestRequest Request { get; init; }
+
+    private static readonly JsonSerializerOptions JsonOptions = new()
+    {
+        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+        WriteIndented = true,
+        IncludeFields = true  // Required for OpenNest.Geometry.Size (public fields)
+    };
+
+    public async Task SaveAsync(string path)
+    {
+        using var fs = new FileStream(path, FileMode.Create);
+        using var zip = new ZipArchive(fs, ZipArchiveMode.Create);
+
+        // Write request.json
+        var requestEntry = zip.CreateEntry("request.json");
+        await using (var stream = requestEntry.Open())
+        {
+            await JsonSerializer.SerializeAsync(stream, Request, JsonOptions);
+        }
+
+        // Write response.json (metrics only)
+        var metrics = new
+        {
+            SheetCount,
+            Utilization,
+            CutTimeTicks = CutTime.Ticks,
+            ElapsedTicks = Elapsed.Ticks
+        };
+        var responseEntry = zip.CreateEntry("response.json");
+        await using (var stream = responseEntry.Open())
+        {
+            await JsonSerializer.SerializeAsync(stream, metrics, JsonOptions);
+        }
+
+        // Write embedded nest.nest via NestWriter → MemoryStream → ZIP entry
+        var nestEntry = zip.CreateEntry("nest.nest");
+        using var nestMs = new MemoryStream();
+        var writer = new NestWriter(Nest);
+        writer.Write(nestMs);
+        nestMs.Position = 0;
+        await using (var stream = nestEntry.Open())
+        {
+            await nestMs.CopyToAsync(stream);
+        }
+    }
+
+    public static async Task<NestResponse> LoadAsync(string path)
+    {
+        using var fs = new FileStream(path, FileMode.Open, FileAccess.Read);
+        using var zip = new ZipArchive(fs, ZipArchiveMode.Read);
+
+        // Read request.json
+        var requestEntry = zip.GetEntry("request.json");
+        NestRequest request;
+        await using (var stream = requestEntry!.Open())
+        {
+            request = await JsonSerializer.DeserializeAsync<NestRequest>(stream, JsonOptions);
+        }
+
+        // Read response.json
+        var responseEntry = zip.GetEntry("response.json");
+        JsonElement metricsJson;
+        await using (var stream = responseEntry!.Open())
+        {
+            metricsJson = await JsonSerializer.DeserializeAsync<JsonElement>(stream, JsonOptions);
+        }
+
+        // Read embedded nest.nest via NestReader(Stream)
+        var nestEntry = zip.GetEntry("nest.nest");
+        Nest nest;
+        using (var nestMs = new MemoryStream())
+        {
+            await using (var stream = nestEntry!.Open())
+            {
+                await stream.CopyToAsync(nestMs);
+            }
+            nestMs.Position = 0;
+            var reader = new NestReader(nestMs);
+            nest = reader.Read();
+        }
+
+        return new NestResponse
+        {
+            SheetCount = metricsJson.GetProperty("sheetCount").GetInt32(),
+            Utilization = metricsJson.GetProperty("utilization").GetDouble(),
+            CutTime = TimeSpan.FromTicks(metricsJson.GetProperty("cutTimeTicks").GetInt64()),
+            Elapsed = TimeSpan.FromTicks(metricsJson.GetProperty("elapsedTicks").GetInt64()),
+            Nest = nest,
+            Request = request
+        };
+    }
+}

OpenNest.Tests/Api/NestResponsePersistenceTests.cs

@@ -0,0 +1,63 @@
+using System;
+using System.IO;
+using System.Threading.Tasks;
+using OpenNest.Api;
+using OpenNest.Geometry;
+
+namespace OpenNest.Tests.Api;
+
+public class NestResponsePersistenceTests
+{
+    [Fact]
+    public async Task SaveAsync_LoadAsync_RoundTrips()
+    {
+        var nest = new Nest("test-nest");
+        var plate = new Plate(new Size(60, 120));
+        nest.Plates.Add(plate);
+
+        var request = new NestRequest
+        {
+            Parts = [new NestRequestPart { DxfPath = "test.dxf", Quantity = 5 }],
+            SheetSize = new Size(60, 120),
+            Material = "Steel",
+            Thickness = 0.125,
+            Spacing = 0.1
+        };
+
+        var original = new NestResponse
+        {
+            SheetCount = 1,
+            Utilization = 0.75,
+            CutTime = TimeSpan.FromMinutes(12.5),
+            Elapsed = TimeSpan.FromSeconds(3.2),
+            Nest = nest,
+            Request = request
+        };
+
+        var path = Path.Combine(Path.GetTempPath(), $"test-{Guid.NewGuid()}.nestquote");
+
+        try
+        {
+            await original.SaveAsync(path);
+            var loaded = await NestResponse.LoadAsync(path);
+
+            Assert.Equal(original.SheetCount, loaded.SheetCount);
+            Assert.Equal(original.Utilization, loaded.Utilization, precision: 4);
+            Assert.Equal(original.CutTime, loaded.CutTime);
+            Assert.Equal(original.Elapsed, loaded.Elapsed);
+
+            Assert.Equal(original.Request.Material, loaded.Request.Material);
+            Assert.Equal(original.Request.Thickness, loaded.Request.Thickness);
+            Assert.Equal(original.Request.Parts.Count, loaded.Request.Parts.Count);
+            Assert.Equal(original.Request.Parts[0].DxfPath, loaded.Request.Parts[0].DxfPath);
+            Assert.Equal(original.Request.Parts[0].Quantity, loaded.Request.Parts[0].Quantity);
+
+            Assert.NotNull(loaded.Nest);
+            Assert.Single(loaded.Nest.Plates);
+        }
+        finally
+        {
+            File.Delete(path);
+        }
+    }
+}