feat(core): add PluginManifest json parsing

src/AcDream.Core/Placeholder.cs

@@ -1,3 +0,0 @@
-// src/AcDream.Core/Placeholder.cs
-namespace AcDream.Core;
-internal static class Placeholder { }

src/AcDream.Core/Plugins/PluginManifest.cs

@@ -0,0 +1,73 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace AcDream.Core.Plugins;
+
+public sealed record PluginManifest(
+    string Id,
+    string DisplayName,
+    string Version,
+    string EntryDll,
+    int ApiVersion,
+    IReadOnlyList<string> Dependencies)
+{
+    public static PluginManifest Parse(string json)
+    {
+        PluginManifestDto? dto;
+        try
+        {
+            dto = JsonSerializer.Deserialize<PluginManifestDto>(json, JsonOptions);
+        }
+        catch (JsonException ex)
+        {
+            throw new PluginManifestException($"invalid json: {ex.Message}", ex);
+        }
+
+        if (dto is null)
+            throw new PluginManifestException("manifest is empty");
+
+        Require(dto.Id, nameof(dto.Id));
+        Require(dto.DisplayName, nameof(dto.DisplayName));
+        Require(dto.Version, nameof(dto.Version));
+        Require(dto.EntryDll, nameof(dto.EntryDll));
+        if (dto.ApiVersion <= 0)
+            throw new PluginManifestException("apiVersion must be >= 1");
+
+        return new PluginManifest(
+            dto.Id!,
+            dto.DisplayName!,
+            dto.Version!,
+            dto.EntryDll!,
+            dto.ApiVersion,
+            dto.Dependencies ?? Array.Empty<string>());
+    }
+
+    private static void Require(string? value, string fieldName)
+    {
+        if (string.IsNullOrWhiteSpace(value))
+            throw new PluginManifestException(
+                $"missing required field: {char.ToLowerInvariant(fieldName[0])}{fieldName[1..]}");
+    }
+
+    private static readonly JsonSerializerOptions JsonOptions = new()
+    {
+        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+        PropertyNameCaseInsensitive = true,
+    };
+
+    private sealed class PluginManifestDto
+    {
+        public string? Id { get; set; }
+        public string? DisplayName { get; set; }
+        public string? Version { get; set; }
+        public string? EntryDll { get; set; }
+        public int ApiVersion { get; set; }
+        public IReadOnlyList<string>? Dependencies { get; set; }
+    }
+}
+
+public sealed class PluginManifestException : Exception
+{
+    public PluginManifestException(string message) : base(message) { }
+    public PluginManifestException(string message, Exception inner) : base(message, inner) { }
+}

tests/AcDream.Core.Tests/Plugins/PluginManifestTests.cs

@@ -0,0 +1,62 @@
+using AcDream.Core.Plugins;
+
+namespace AcDream.Core.Tests.Plugins;
+
+public class PluginManifestTests
+{
+    [Fact]
+    public void Parse_ValidManifest_ReturnsManifest()
+    {
+        const string json = """
+        {
+          "id": "acdream.smoke",
+          "displayName": "Smoke Test",
+          "version": "0.1.0",
+          "entryDll": "AcDream.Plugins.Smoke.dll",
+          "apiVersion": 1
+        }
+        """;
+
+        var manifest = PluginManifest.Parse(json);
+
+        Assert.Equal("acdream.smoke", manifest.Id);
+        Assert.Equal("Smoke Test", manifest.DisplayName);
+        Assert.Equal("0.1.0", manifest.Version);
+        Assert.Equal("AcDream.Plugins.Smoke.dll", manifest.EntryDll);
+        Assert.Equal(1, manifest.ApiVersion);
+    }
+
+    [Fact]
+    public void Parse_MissingRequiredField_Throws()
+    {
+        const string json = """
+        { "id": "x", "version": "0.1.0", "entryDll": "x.dll", "apiVersion": 1 }
+        """;
+
+        var ex = Assert.Throws<PluginManifestException>(() => PluginManifest.Parse(json));
+        Assert.Contains("displayName", ex.Message);
+    }
+
+    [Fact]
+    public void Parse_MalformedJson_Throws()
+    {
+        Assert.Throws<PluginManifestException>(() => PluginManifest.Parse("{ not json"));
+    }
+
+    [Fact]
+    public void Parse_EmptyDependencies_DefaultsToEmptyList()
+    {
+        const string json = """
+        {
+          "id": "x",
+          "displayName": "X",
+          "version": "0.1.0",
+          "entryDll": "x.dll",
+          "apiVersion": 1
+        }
+        """;
+
+        var manifest = PluginManifest.Parse(json);
+        Assert.Empty(manifest.Dependencies);
+    }
+}