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

namespace StellaOps.Attestor.Envelope;

public sealed class DsseEnvelope
{
    public DsseEnvelope(
        string payloadType,
        ReadOnlyMemory<byte> payload,
        IEnumerable<DsseSignature> signatures,
        string? payloadContentType = null,
        DsseDetachedPayloadReference? detachedPayload = null)
    {
        if (string.IsNullOrWhiteSpace(payloadType))
        {
            throw new ArgumentException("payloadType must be provided.", nameof(payloadType));
        }

        PayloadType = payloadType;
        Payload = payload;
        PayloadContentType = payloadContentType;
        DetachedPayload = detachedPayload;

        var normalised = signatures?.ToArray() ?? Array.Empty<DsseSignature>();
        if (normalised.Length == 0)
        {
            throw new ArgumentException("At least one signature must be supplied.", nameof(signatures));
        }

        // Deterministic ordering (keyid asc, signature asc) for canonical output.
        Signatures = normalised
            .OrderBy(static x => x.KeyId ?? string.Empty, StringComparer.Ordinal)
            .ThenBy(static x => x.Signature, StringComparer.Ordinal)
            .ToArray();
    }

    public string PayloadType { get; }

    public ReadOnlyMemory<byte> Payload { get; }

    public string? PayloadContentType { get; }

    public IReadOnlyList<DsseSignature> Signatures { get; }

    public DsseDetachedPayloadReference? DetachedPayload { get; }
}