using StellaOps.AirGap.Bundle.Models;
using System.Text.Json;
using System.Text.Json.Serialization;

namespace StellaOps.AirGap.Bundle.Serialization;

/// <summary>
/// JSON converter for timestamp entries with explicit type discriminators.
/// </summary>
public sealed class TimestampEntryJsonConverter : JsonConverter<TimestampEntry>
{
    public override TimestampEntry Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        using var document = JsonDocument.ParseValue(ref reader);
        if (!document.RootElement.TryGetProperty("type", out var typeProperty))
        {
            throw new NotSupportedException("Timestamp entry is missing a type discriminator.");
        }

        var type = typeProperty.GetString();
        return type switch
        {
            "rfc3161" => JsonSerializer.Deserialize<Rfc3161TimestampEntry>(document.RootElement.GetRawText(), options)
                ?? throw new JsonException("Failed to deserialize RFC3161 timestamp entry."),
            "eidas-qts" => JsonSerializer.Deserialize<EidasQtsTimestampEntry>(document.RootElement.GetRawText(), options)
                ?? throw new JsonException("Failed to deserialize eIDAS QTS timestamp entry."),
            _ => throw new NotSupportedException($"Unsupported timestamp entry type '{type}'.")
        };
    }

    public override void Write(Utf8JsonWriter writer, TimestampEntry value, JsonSerializerOptions options)
    {
        switch (value)
        {
            case Rfc3161TimestampEntry rfc3161:
                writer.WriteStartObject();
                writer.WriteString("type", "rfc3161");
                WriteStringArray(writer, "tsaChainPaths", rfc3161.TsaChainPaths);
                WriteStringArray(writer, "ocspBlobs", rfc3161.OcspBlobs);
                WriteStringArray(writer, "crlBlobs", rfc3161.CrlBlobs);
                writer.WriteString("tstBase64", rfc3161.TstBase64);
                writer.WriteEndObject();
                break;
            case EidasQtsTimestampEntry eidas:
                writer.WriteStartObject();
                writer.WriteString("type", "eidas-qts");
                writer.WriteString("qtsMetaPath", eidas.QtsMetaPath);
                writer.WriteEndObject();
                break;
            default:
                throw new NotSupportedException($"Unsupported timestamp entry type '{value.GetType().Name}'.");
        }
    }

    private static void WriteStringArray(Utf8JsonWriter writer, string name, IReadOnlyCollection<string> values)
    {
        writer.WritePropertyName(name);
        writer.WriteStartArray();
        foreach (var value in values)
        {
            writer.WriteStringValue(value);
        }
        writer.WriteEndArray();
    }
}