using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace StellaOps.Provcache;

public sealed partial class VeriKeyBuilder
{
    /// <summary>
    /// Sets the signer set hash (sorted certificate chain hashes).
    /// </summary>
    /// <param name="signerSetHash">The pre-computed signer set hash.</param>
    /// <returns>This builder for fluent chaining.</returns>
    public VeriKeyBuilder WithSignerSetHash(string signerSetHash)
    {
        if (string.IsNullOrWhiteSpace(signerSetHash))
            throw new ArgumentException("Signer set hash cannot be null or empty.", nameof(signerSetHash));

        _signerSetHash = NormalizeHash(signerSetHash);
        return this;
    }

    /// <summary>
    /// Computes signer set hash from individual certificate hashes.
    /// Hashes are sorted lexicographically before aggregation for determinism.
    /// </summary>
    /// <param name="certificateHashes">Individual certificate hashes.</param>
    /// <returns>This builder for fluent chaining.</returns>
    public VeriKeyBuilder WithCertificateHashes(IEnumerable<string> certificateHashes)
    {
        ArgumentNullException.ThrowIfNull(certificateHashes);

        var sortedHashes = certificateHashes
            .Where(h => !string.IsNullOrWhiteSpace(h))
            .Select(NormalizeHash)
            .Order(StringComparer.Ordinal)
            .ToList();

        if (sortedHashes.Count == 0)
        {
            _signerSetHash = ComputeHash(Encoding.UTF8.GetBytes("empty-signer-set"));
        }
        else
        {
            var concatenated = string.Join("|", sortedHashes);
            _signerSetHash = ComputeHash(Encoding.UTF8.GetBytes(concatenated));
        }

        return this;
    }
}