feat: 在前端显示编译过程中的日志 (#67)

Reviewed-on: PostGuard/Canon#67

Canon.Server/Models/CompilerLogger.cs

@@ -0,0 +1,30 @@
+using System.Text;
+using Canon.Core.Abstractions;
+
+namespace Canon.Server.Models;
+
+public class CompilerLogger : ICompilerLogger
+{
+    private readonly ThreadLocal<StringBuilder> _builder = new(() => new StringBuilder());
+
+    public string Build()
+    {
+        if (_builder.Value is not null)
+        {
+            string result = _builder.Value.ToString();
+            _builder.Value.Clear();
+            return result;
+        }
+
+        throw new InvalidOperationException();
+    }
+
+    public void Log<TState>(LogLevel logLevel, EventId eventId, TState state, Exception? exception,
+        Func<TState, Exception?, string> formatter)
+    {
+        if (_builder.Value is not null)
+        {
+            _builder.Value.Append(logLevel).Append(": ").Append(formatter(state, exception)).Append('\n');
+        }
+    }
+}