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

namespace StellaOps.Findings.Ledger.Domain;

public static class LedgerChainIdGenerator
{
    public static Guid FromTenantPolicy(string tenantId, string policyVersion)
    {
        return FromTenantSubject(tenantId, policyVersion);
    }

    public static Guid FromTenantSubject(string tenantId, string subject)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(tenantId);
        ArgumentException.ThrowIfNullOrWhiteSpace(subject);

        var normalized = $"{tenantId.Trim()}::{subject.Trim()}";
        var bytes = Encoding.UTF8.GetBytes(normalized);
        Span<byte> guidBytes = stackalloc byte[16];
        var hash = SHA256.HashData(bytes);
        hash.AsSpan(0, 16).CopyTo(guidBytes);
        return new Guid(guidBytes);
    }
}