using System.Security.Cryptography;
using System.Text;

namespace w4c_workflows.Services;

/// <summary>
/// Deterministic, name-based GUIDs so recompiling the same YAML yields the same
/// entity ids — this makes the git sync (re-compile to DB) idempotent.
/// UUIDv5-style: SHA-256 of the seed, truncated to 16 bytes with version bits.
/// </summary>
public static class DeterministicGuid
{
    public static Guid For(string seed)
    {
        var hash = SHA256.HashData(Encoding.UTF8.GetBytes(seed));
        Span<byte> bytes = stackalloc byte[16];
        hash.AsSpan(0, 16).CopyTo(bytes);
        bytes[6] = (byte)((bytes[6] & 0x0F) | 0x50); // version 5
        bytes[8] = (byte)((bytes[8] & 0x3F) | 0x80); // RFC 4122 variant
        return new Guid(bytes);
    }
}