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; }
    }
}