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

namespace StellaOps.Notify.Connectors.Shared;

/// <summary>
/// Common hashing helpers for Notify connector metadata.
/// </summary>
public static class ConnectorHashing
{
    /// <summary>
    /// Computes a lowercase hex SHA-256 hash and truncates it to the requested number of bytes.
    /// </summary>
    public static string ComputeSha256Hash(string value, int lengthBytes = 8)
    {
        if (string.IsNullOrWhiteSpace(value))
        {
            throw new ArgumentException("Value must not be null or whitespace.", nameof(value));
        }

        if (lengthBytes <= 0 || lengthBytes > 32)
        {
            throw new ArgumentOutOfRangeException(nameof(lengthBytes), "Length must be between 1 and 32 bytes.");
        }

        var bytes = Encoding.UTF8.GetBytes(value.Trim());
        var hash = SHA256.HashData(bytes);
        return Convert.ToHexString(hash.AsSpan(0, lengthBytes)).ToLowerInvariant();
    }
}