using System.Text;

namespace MeetingAssistant.MeetingNotes;

public sealed class MeetingArtifactFrontmatter
{
    public string Title { get; set; } = "";

    public string? OneLiner { get; set; }

    public DateTimeOffset? StartTime { get; set; }

    public DateTimeOffset? EndTime { get; set; }

    public List<string>? Attendees { get; set; }

    public List<string>? Projects { get; set; }

    public string Meeting { get; set; } = "";

    public string Transcript { get; set; } = "";

    public string AssistantContext { get; set; } = "";

    public string Summary { get; set; } = "";

    public string? State { get; set; }

    public string? Agenda { get; set; }

    public DateTimeOffset? ScheduledEnd { get; set; }
}

public static class MeetingArtifactFrontmatterRenderer
{
    public static string Render(
        MeetingArtifactFrontmatter frontmatter,
        string body)
    {
        var builder = new StringBuilder();
        builder.AppendLine("---");
        AppendScalar(builder, "title", frontmatter.Title);
        AppendScalarIfNotEmpty(builder, "oneliner", frontmatter.OneLiner);
        AppendDateTime(builder, "start_time", frontmatter.StartTime);
        AppendDateTime(builder, "end_time", frontmatter.EndTime);
        AppendListIfNotNull(builder, "attendees", frontmatter.Attendees);
        AppendListIfNotNull(builder, "projects", frontmatter.Projects);
        AppendQuotedIfNotEmpty(builder, "meeting", frontmatter.Meeting);
        AppendQuotedIfNotEmpty(builder, "transcript", frontmatter.Transcript);
        AppendQuotedIfNotEmpty(builder, "assistant_context", frontmatter.AssistantContext);
        AppendQuotedIfNotEmpty(builder, "summary", frontmatter.Summary);
        if (!string.IsNullOrWhiteSpace(frontmatter.State))
        {
            AppendScalar(builder, "state", frontmatter.State);
        }

        if (frontmatter.Agenda is not null)
        {
            AppendBlockScalar(builder, "agenda", frontmatter.Agenda);
        }

        if (frontmatter.ScheduledEnd is not null)
        {
            AppendDateTime(builder, "scheduled_end", frontmatter.ScheduledEnd);
        }

        builder.AppendLine("---");
        builder.AppendLine();
        builder.Append(body.TrimStart('\r', '\n'));
        return builder.ToString();
    }

    public static (string Frontmatter, string Body) Split(string content)
    {
        var document = MarkdownDocumentParser.SplitOptional(content);
        return (document.Frontmatter, document.Body);
    }

    public static MeetingArtifactFrontmatter Create(
        MeetingSessionArtifacts artifacts,
        MeetingNote meetingNote,
        string title,
        string sourceNotePath,
        string? state = null)
    {
        return Create(
            artifacts,
            title,
            meetingNote.Frontmatter.StartTime,
            meetingNote.Frontmatter.EndTime,
            sourceNotePath,
            state);
    }

    public static MeetingArtifactFrontmatter Create(
        MeetingSessionArtifacts artifacts,
        string title,
        DateTimeOffset? startTime,
        DateTimeOffset? endTime,
        string sourceNotePath,
        string? state = null)
    {
        return new MeetingArtifactFrontmatter
        {
            Title = title,
            StartTime = startTime,
            EndTime = endTime,
            Meeting = LinkUnlessSelf(artifacts.MeetingNotePath, sourceNotePath, "Meeting Note"),
            Transcript = LinkUnlessSelf(artifacts.TranscriptPath, sourceNotePath, "Transcript"),
            AssistantContext = LinkUnlessSelf(artifacts.AssistantContextPath, sourceNotePath, "Assistant Context"),
            Summary = LinkUnlessSelf(artifacts.SummaryPath, sourceNotePath, "Summary"),
            State = state
        };
    }

    public static string DefaultTitle(MeetingNote meetingNote, string fallback)
    {
        return string.IsNullOrWhiteSpace(meetingNote.Frontmatter.Title)
            ? fallback
            : meetingNote.Frontmatter.Title;
    }

    private static void AppendScalar(StringBuilder builder, string key, string? value)
    {
        builder.Append(key);
        builder.Append(": ");
        builder.AppendLine(string.IsNullOrWhiteSpace(value) ? "\"\"" : EscapeListItem(value));
    }

    private static void AppendScalarIfNotEmpty(StringBuilder builder, string key, string? value)
    {
        if (string.IsNullOrWhiteSpace(value))
        {
            return;
        }

        AppendScalar(builder, key, value);
    }

    private static void AppendQuoted(StringBuilder builder, string key, string value)
    {
        builder.Append(key);
        builder.Append(": ");
        builder.AppendLine(EscapeQuoted(value));
    }

    private static void AppendQuotedIfNotEmpty(StringBuilder builder, string key, string? value)
    {
        if (string.IsNullOrWhiteSpace(value))
        {
            return;
        }

        AppendQuoted(builder, key, value);
    }

    private static void AppendDateTime(StringBuilder builder, string key, DateTimeOffset? value)
    {
        builder.Append(key);
        builder.Append(": ");
        builder.AppendLine(value is null ? "\"\"" : EscapeQuoted(value.Value.ToString("O")));
    }

    private static void AppendListIfNotNull(StringBuilder builder, string key, IReadOnlyList<string>? values)
    {
        if (values is null)
        {
            return;
        }

        builder.Append(key);
        builder.AppendLine(":");
        foreach (var value in values)
        {
            builder.Append("- ");
            builder.AppendLine(EscapeListItem(value));
        }
    }

    private static void AppendBlockScalar(StringBuilder builder, string key, string value)
    {
        if (string.IsNullOrEmpty(value))
        {
            builder.Append(key);
            builder.AppendLine(": \"\"");
            return;
        }

        builder.Append(key);
        builder.AppendLine(": |-");
        foreach (var line in value.Replace("\r\n", "\n", StringComparison.Ordinal).Replace('\r', '\n').Split('\n'))
        {
            builder.Append("  ");
            builder.AppendLine(line);
        }
    }

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

    private static string EscapeListItem(string value)
    {
        return value.Contains(':', StringComparison.Ordinal) || value.StartsWith("[", StringComparison.Ordinal)
            ? EscapeQuoted(value)
            : value;
    }

    private static string LinkUnlessSelf(string targetPath, string sourceNotePath, string label)
    {
        return IsSamePath(targetPath, sourceNotePath)
            ? ""
            : ObsidianLink.ToWikiLink(targetPath, sourceNotePath, label);
    }

    private static bool IsSamePath(string first, string second)
    {
        return string.Equals(
            Path.GetFullPath(first),
            Path.GetFullPath(second),
            StringComparison.OrdinalIgnoreCase);
    }

}