using System;

namespace ytLive.Services;

/// <summary>
/// TASK 55·3: a recording that dies of a full disk is a trust breach, not a support ticket. The guard is
/// a pure threshold policy so the numbers are visible in one place and testable without a drive.
///
/// <para>Thresholds chosen 2026-11-10 for a 1080p stream at 8 Mbps (~3.6 GB/hour): refusing to start
/// under <b>1 GB</b> keeps the creator from beginning something that cannot finish; a warning under
/// <b>5 GB</b> says "you have about eighty minutes" while there is still time to act; and one mid-show
/// warning at <b>2 GB</b> is the last useful moment before the encoder fails for a reason it will not
/// explain.</para>
/// </summary>
public static class DiskSpaceGuard
{
    public const long BlockStartBytes = 1L * 1024 * 1024 * 1024;
    public const long WarnStartBytes = 5L * 1024 * 1024 * 1024;
    public const long WarnDuringBytes = 2L * 1024 * 1024 * 1024;

    public enum StartDecision
    {
        Ok,
        Warn,
        Block,
    }

    public static StartDecision ForStart(long freeBytes)
        => freeBytes < BlockStartBytes ? StartDecision.Block
           : freeBytes < WarnStartBytes ? StartDecision.Warn
           : StartDecision.Ok;

    /// <summary>One warning per session, once the drive falls below the mid-recording threshold.</summary>
    public static bool ShouldWarnDuring(long freeBytes) => freeBytes < WarnDuringBytes;

    /// <summary>Free bytes on the drive that holds <paramref name="folder"/>, or null when it cannot be
    /// read (a removable drive that just went away must not block a recording that is already running).</summary>
    public static long? FreeBytes(string folder)
    {
        try
        {
            var root = System.IO.Path.GetPathRoot(System.IO.Path.GetFullPath(folder));
            if (string.IsNullOrEmpty(root)) return null;
            return new System.IO.DriveInfo(root).AvailableFreeSpace;
        }
        catch
        {
            return null;
        }
    }
}