meeting-assistant/MeetingAssistant/MeetingNotes/MarkdownMeetingNoteStore.cs

using Microsoft.Extensions.Options;
using YamlDotNet.Core;
using YamlDotNet.Serialization;

namespace MeetingAssistant.MeetingNotes;

public sealed class MarkdownMeetingNoteStore : IMeetingNoteStore
{
    private readonly MeetingAssistantOptions options;
    private readonly ILogger<MarkdownMeetingNoteStore> logger;
    private readonly IDeserializer yamlDeserializer;

    public MarkdownMeetingNoteStore(
        IOptions<MeetingAssistantOptions> options,
        ILogger<MarkdownMeetingNoteStore> logger)
    {
        this.options = options.Value;
        this.logger = logger;
        yamlDeserializer = new DeserializerBuilder()
            .IgnoreUnmatchedProperties()
            .Build();
    }

    public async Task<MeetingNote> SaveAsync(MeetingNote note, CancellationToken cancellationToken)
    {
        var folder = VaultPath.Resolve(options.Vault, options.Vault.MeetingNotesFolder);
        Directory.CreateDirectory(folder);

        var path = string.IsNullOrWhiteSpace(note.Path)
            ? Path.Combine(folder, $"{DateTimeOffset.Now:yyyyMMdd-HHmmss}-{Slugify(note.Frontmatter.Title)}.md")
            : note.Path;
        var frontmatter = PrepareFrontmatter(note.Frontmatter, path);
        var content = Render(frontmatter, note.UserNotes);

        await File.WriteAllTextAsync(path, content, cancellationToken);
        logger.LogInformation("Saved meeting note {MeetingNotePath}", path);

        return new MeetingNote(path, frontmatter, note.UserNotes);
    }

    public async Task<MeetingNote> ReadAsync(string path, CancellationToken cancellationToken)
    {
        var content = await File.ReadAllTextAsync(path, cancellationToken);
        var document = MarkdownDocumentParser.SplitRequired(
            content,
            "Meeting note does not start with YAML frontmatter.",
            "Meeting note frontmatter is not closed.");
        var yaml = yamlDeserializer.Deserialize<MeetingNoteYaml>(document.Frontmatter) ?? new MeetingNoteYaml();
        var frontmatter = new MeetingNoteFrontmatter
        {
            Title = yaml.Title ?? "",
            StartTime = ParseDateTime(yaml.StartTime),
            EndTime = ParseDateTime(yaml.EndTime),
            Attendees = yaml.Attendees ?? [],
            Projects = yaml.Projects ?? [],
            Transcript = yaml.Transcript ?? "",
            AssistantContext = yaml.AssistantContext ?? "",
            Summary = yaml.Summary ?? ""
        };

        return new MeetingNote(path, frontmatter, document.Body);
    }

    private MeetingNoteFrontmatter PrepareFrontmatter(MeetingNoteFrontmatter frontmatter, string notePath)
    {
        return new MeetingNoteFrontmatter
        {
            Title = frontmatter.Title,
            StartTime = frontmatter.StartTime,
            EndTime = frontmatter.EndTime,
            Attendees = frontmatter.Attendees,
            Projects = frontmatter.Projects,
            Transcript = ObsidianLink.ToWikiLink(frontmatter.Transcript, notePath, "Transcript"),
            AssistantContext = ObsidianLink.ToWikiLink(frontmatter.AssistantContext, notePath, "Assistant Context"),
            Summary = ObsidianLink.ToWikiLink(frontmatter.Summary, notePath, "Summary")
        };
    }

    private static string Render(MeetingNoteFrontmatter frontmatter, string userNotes)
    {
        var lines = new List<string>
        {
            "---",
            $"title: {EscapeScalar(frontmatter.Title)}",
            $"start_time: {EscapeNullableDateTime(frontmatter.StartTime)}",
            $"end_time: {EscapeNullableDateTime(frontmatter.EndTime)}",
            "attendees:"
        };

        lines.AddRange(frontmatter.Attendees.Select(attendee => $"- {EscapeListItem(attendee)}"));
        lines.Add("projects:");
        lines.AddRange(frontmatter.Projects.Select(project => $"- {EscapeListItem(project)}"));
        lines.Add($"transcript: {EscapeQuoted(frontmatter.Transcript)}");
        lines.Add($"assistant_context: {EscapeQuoted(frontmatter.AssistantContext)}");
        lines.Add($"summary: {EscapeQuoted(frontmatter.Summary)}");
        lines.Add("---");
        lines.Add("");
        lines.Add(userNotes);

        return string.Join(Environment.NewLine, lines);
    }

    private static string Slugify(string value)
    {
        var slug = new string(value
            .ToLowerInvariant()
            .Select(character => char.IsLetterOrDigit(character) ? character : '-')
            .ToArray());
        slug = string.Join("-", slug.Split('-', StringSplitOptions.RemoveEmptyEntries));
        return string.IsNullOrWhiteSpace(slug) ? "meeting" : slug;
    }

    private static string EscapeScalar(string value)
    {
        return string.IsNullOrWhiteSpace(value) ? "\"\"" : EscapeListItem(value);
    }

    private static string EscapeQuoted(string value)
    {
        return $"\"{value.Replace("\"", "\\\"", StringComparison.Ordinal)}\"";
    }

    private static string EscapeNullableDateTime(DateTimeOffset? value)
    {
        return value is null ? "\"\"" : EscapeQuoted(value.Value.ToString("O"));
    }

    private static DateTimeOffset? ParseDateTime(string? value)
    {
        return DateTimeOffset.TryParse(value, out var parsed)
            ? parsed
            : null;
    }

    private static string EscapeListItem(string value)
    {
        if (string.IsNullOrWhiteSpace(value))
        {
            return "\"\"";
        }

        if (value.Contains(':', StringComparison.Ordinal) || value.StartsWith("[", StringComparison.Ordinal))
        {
            return EscapeQuoted(value);
        }

        return value;
    }

    private sealed class MeetingNoteYaml
    {
        [YamlMember(Alias = "title")]
        public string? Title { get; set; }

        [YamlMember(Alias = "start_time")]
        public string? StartTime { get; set; }

        [YamlMember(Alias = "end_time")]
        public string? EndTime { get; set; }

        [YamlMember(Alias = "attendees")]
        public List<string>? Attendees { get; set; }

        [YamlMember(Alias = "projects")]
        public List<string>? Projects { get; set; }

        [YamlMember(Alias = "transcript")]
        public string? Transcript { get; set; }

        [YamlMember(Alias = "assistant_context")]
        public string? AssistantContext { get; set; }

        [YamlMember(Alias = "summary")]
        public string? Summary { get; set; }
    }
}