using System.Globalization;
using System.Text;

namespace Volcanic.AgenticCore.Extensions.Scheduler;

/// <summary>How jobs and times are shown (the <c>schedule</c> tool, <c>/jobs</c>, zone-change replies). Invariant culture, 24 h.</summary>
public static class JobFormat
{
    public static string Icon(JobKind kind) => kind switch { JobKind.Reminder => "⏰", JobKind.Prompt => "💬", _ => "🔍" };

    /// <summary><c>27 Sep 09:00</c> in <paramref name="zone"/>.</summary>
    public static string DayTime(DateTimeOffset at, TimeZoneInfo zone) =>
        TimeZoneInfo.ConvertTime(at, zone).ToString("d MMM HH:mm", CultureInfo.InvariantCulture);

    /// <summary><c>14:10</c> when on the same local day as <paramref name="now"/>, else <see cref="DayTime"/>.</summary>
    public static string When(DateTimeOffset at, TimeZoneInfo zone, DateTimeOffset now)
    {
        var local = TimeZoneInfo.ConvertTime(at, zone);
        return local.Date == TimeZoneInfo.ConvertTime(now, zone).Date
            ? local.ToString("HH:mm", CultureInfo.InvariantCulture)
            : DayTime(at, zone);
    }

    /// <summary><c>Sat 2026-09-26 14:03</c> (the model-facing form: weekday and full date).</summary>
    public static string Stamp(DateTimeOffset at, TimeZoneInfo zone) =>
        TimeZoneInfo.ConvertTime(at, zone).ToString("ddd yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture);

    public static string ZoneName(TimeZoneInfo zone) => ZoneNames.Name(zone);

    /// <summary><c>exit 1</c>, <c>exit 1, timed out</c>, <c>timed out</c>, or <c>did not start</c>.</summary>
    public static string FailureReason(JobResult result) => result switch
    {
        { ExitCode: { } code, TimedOut: true } => $"exit {code.ToString(CultureInfo.InvariantCulture)}, timed out",
        { ExitCode: { } code } => $"exit {code.ToString(CultureInfo.InvariantCulture)}",
        { TimedOut: true } => "timed out",
        _ => "did not start",
    };

    /// <summary><c>`k7m2q` ⏰ Call the dentist · once 27 Sep 09:00</c>; cron jobs show the expression and the next run; a failed last run is appended.</summary>
    public static string Line(JobView view, TimeZoneInfo zone, DateTimeOffset now)
    {
        var job = view.Job;
        var sb = new StringBuilder().Append('`').Append(job.Id).Append("` ").Append(Icon(job.Kind)).Append(' ').Append(job.Name);
        if (job.Schedule.At is { } at) sb.Append(" · once ").Append(DayTime(at, zone));
        else
        {
            sb.Append(" · `").Append(job.Schedule.Cron).Append('`');
            if (view.NextRunAt is { } next) sb.Append(" · next ").Append(When(next, zone, now));
        }
        if (job.LastResult is { Ok: false } failed) sb.Append(" · last: failed (").Append(FailureReason(failed)).Append(')');
        return sb.ToString();
    }
}