// src/GeoVLog.Core/Manifests/FlightManifestYamlSerializer.cs
using System.IO;
using System.Text;
using System.Threading.Tasks;
using YamlDotNet.Serialization;
using YamlDotNet.Serialization.NamingConventions;

namespace GeoVLog.Core.Manifests;

/// <summary>
/// Serialises / deserialises <see cref="FlightManifest"/> to YAML 1.2
/// using <strong>YamlDotNet</strong>.  
/// – Camel-case keys<br/>
/// – Null values are omitted (all other defaults are kept so the YAML
///   stays informative when a numeric 0 or an empty list is intentional).
/// </summary>
public sealed class FlightManifestYamlSerializer : IFlightManifestSerializer
{
    /* ------------------------------------------------------------------ */
    /*  Writers / readers are expensive to build; keep one static copy.   */
    /* ------------------------------------------------------------------ */

    private static readonly ISerializer _yamlWriter = new SerializerBuilder()
        .WithNamingConvention(CamelCaseNamingConvention.Instance)
        .ConfigureDefaultValuesHandling(DefaultValuesHandling.OmitNull)
        .Build();

    private static readonly IDeserializer _yamlReader = new DeserializerBuilder()
        .WithNamingConvention(CamelCaseNamingConvention.Instance)
        .IgnoreUnmatchedProperties()
        .Build();

    /* ------------------------------------------------------------------ */
    /*  IFlightManifestSerializer                                         */
    /* ------------------------------------------------------------------ */

    public async Task SerializeAsync(FlightManifest manifest, Stream output)
    {
        string yaml = _yamlWriter.Serialize(manifest);
        byte[] bytes = Encoding.UTF8.GetBytes(yaml);
        await output.WriteAsync(bytes);
    }

    public async Task<FlightManifest> DeserializeAsync(Stream input)
    {
        using var sr = new StreamReader(input, Encoding.UTF8, leaveOpen: true);
        string yaml = await sr.ReadToEndAsync();
        return _yamlReader.Deserialize<FlightManifest>(yaml);
    }
}