Centralize summary frontmatter metadata

MeetingAssistant/Summary/MeetingSummaryFrontmatterFactory.cs

@@ -0,0 +1,70 @@
+using MeetingAssistant.MeetingNotes;
+using YamlDotNet.Serialization;
+
+namespace MeetingAssistant.Summary;
+
+internal static class MeetingSummaryFrontmatterFactory
+{
+    private static readonly IDeserializer YamlDeserializer = new DeserializerBuilder()
+        .IgnoreUnmatchedProperties()
+        .Build();
+
+    public static async Task<MeetingArtifactFrontmatter> CreateAsync(
+        MeetingSessionArtifacts artifacts,
+        MeetingNote meetingNote,
+        string title,
+        CancellationToken cancellationToken)
+    {
+        var frontmatter = MeetingArtifactFrontmatterRenderer.Create(
+            artifacts,
+            meetingNote,
+            title,
+            artifacts.SummaryPath);
+        frontmatter.Attendees = await ResolveSummaryAttendeesAsync(
+            artifacts.SummaryPath,
+            meetingNote,
+            cancellationToken);
+        frontmatter.Projects = CopyNonEmptyList(meetingNote.Frontmatter.Projects);
+        return frontmatter;
+    }
+
+    private static async Task<List<string>?> ResolveSummaryAttendeesAsync(
+        string summaryPath,
+        MeetingNote meetingNote,
+        CancellationToken cancellationToken)
+    {
+        var existingAttendees = await ReadExistingSummaryAttendeesAsync(summaryPath, cancellationToken);
+        return existingAttendees ?? CopyNonEmptyList(meetingNote.Frontmatter.Attendees);
+    }
+
+    private static List<string>? CopyNonEmptyList(IReadOnlyCollection<string> values)
+    {
+        return values.Count == 0 ? null : values.ToList();
+    }
+
+    private static async Task<List<string>?> ReadExistingSummaryAttendeesAsync(
+        string summaryPath,
+        CancellationToken cancellationToken)
+    {
+        if (!File.Exists(summaryPath))
+        {
+            return null;
+        }
+
+        var content = await File.ReadAllTextAsync(summaryPath, cancellationToken);
+        var document = MarkdownDocumentParser.SplitOptional(content);
+        if (!document.HasFrontmatter)
+        {
+            return null;
+        }
+
+        var yaml = YamlDeserializer.Deserialize<SummaryFrontmatterYaml>(document.Frontmatter);
+        return yaml?.Attendees;
+    }
+
+    private sealed class SummaryFrontmatterYaml
+    {
+        [YamlMember(Alias = "attendees")]
+        public List<string>? Attendees { get; set; }
+    }
+}