add InsinMessageFormatter

Inspectron.Epson.Tests/Telemetry/InsinMessageFormatterTests.cs

@@ -0,0 +1,52 @@
+using Inspectron.Epson.PrintServer.Telemetry;
+
+namespace Inspectron.Epson.Tests.Telemetry;
+
+public class InsinMessageFormatterTests
+{
+    [Fact]
+    public void Format_single_pair_no_spaces()
+    {
+        var result = InsinMessageFormatter.Format(("printer", "192.168.1.10"));
+        Assert.Equal("printer=192.168.1.10", result);
+    }
+
+    [Fact]
+    public void Format_multiple_pairs_joined_by_space()
+    {
+        var result = InsinMessageFormatter.Format(
+            ("printer", "192.168.1.10"),
+            ("jobId", "42"));
+        Assert.Equal("printer=192.168.1.10 jobId=42", result);
+    }
+
+    [Fact]
+    public void Format_quotes_value_containing_space()
+    {
+        var result = InsinMessageFormatter.Format(("error", "paper end detected"));
+        Assert.Equal("error=\"paper end detected\"", result);
+    }
+
+    [Fact]
+    public void Format_escapes_embedded_double_quote()
+    {
+        var result = InsinMessageFormatter.Format(("error", "he said \"nope\""));
+        Assert.Equal("error=\"he said \\\"nope\\\"\"", result);
+    }
+
+    [Fact]
+    public void Format_treats_null_or_empty_value_as_empty_string()
+    {
+        var result = InsinMessageFormatter.Format(("model", (string?)null), ("name", ""));
+        Assert.Equal("model= name=", result);
+    }
+
+    [Fact]
+    public void Format_omits_pairs_with_null_or_empty_key()
+    {
+        var result = InsinMessageFormatter.Format(
+            ("", "ignored"),
+            ("printer", "192.168.1.10"));
+        Assert.Equal("printer=192.168.1.10", result);
+    }
+}

Inspectron.Epson/PrintServer/Telemetry/InsinMessageFormatter.cs

@@ -0,0 +1,26 @@
+using System.Text;
+
+namespace Inspectron.Epson.PrintServer.Telemetry;
+
+public static class InsinMessageFormatter
+{
+    public static string Format(params (string Key, string? Value)[] pairs)
+    {
+        var sb = new StringBuilder();
+        foreach (var (key, value) in pairs)
+        {
+            if (string.IsNullOrEmpty(key)) continue;
+            if (sb.Length > 0) sb.Append(' ');
+            sb.Append(key).Append('=').Append(FormatValue(value));
+        }
+        return sb.ToString();
+    }
+
+    private static string FormatValue(string? value)
+    {
+        if (string.IsNullOrEmpty(value)) return string.Empty;
+        if (value.IndexOf(' ') < 0 && value.IndexOf('"') < 0) return value;
+        var escaped = value.Replace("\\", "\\\\").Replace("\"", "\\\"");
+        return $"\"{escaped}\"";
+    }
+}