using System;
using System.IO;
using System.Text.Json;
using ReFuel.Gltf.IO;

namespace ReFuel.Gltf
{
    public class GltfBuffer : GltfIdObject
    {
        public override GltfObjectKind Kind => GltfObjectKind.Buffer;

        public Uri? Uri { get; set; }
        public long ByteLength { get; set; }
        public string? Name { get; set; }

        public GltfBuffer(GltfDocument document) : base(document)
        {
        }

        public Stream Open(string? pwd = null, IGltfStreamProvider? provider = null)
        {
            if (Uri == null)
            {
                return ((StreamWrapper)Document.BinaryStreams[Id]).Fork(keepOpen: true);
            }

            switch (Uri.IsAbsoluteUri ? Uri.Scheme : "file") // Assume relative URIs are files.
            {
                case "file":
                    if (provider != null)
                    {
                        return provider.OpenFile(pwd, Uri) ?? throw new FileNotFoundException(Uri.ToString());
                    }
                    else
                    {
                        string path = Path.Combine(pwd ?? string.Empty, Uri.LocalPath);
                        return File.OpenRead(path);
                    }
                case "data":
                    return DataUriStream.FromUri(Uri.OriginalString);
                default:
                    if (provider != null)
                        return provider.OpenFile(pwd, Uri) ?? throw new FileNotFoundException(Uri.ToString());
                    break;
            }

            throw new Exception("Unrecognized URI scheme.");
        }

        internal override void Deserialize(JsonElement element)
        {
            if (element.ValueKind != JsonValueKind.Object)
                throw new Exception("Expected an object.");

            if (element.TryGetProperty("byteLength", out JsonElement lengthElement))
            {
                if (!lengthElement.TryGetInt64(out long length))
                    throw new Exception("Length is not an integer.");

                ByteLength = length;
            }
            else
            {
                throw new Exception("Byte length is required.");
            }

            if (element.TryGetProperty("name", out JsonElement nameElement))
            {
                Name = nameElement.GetString();
            }

            if (element.TryGetProperty("uri", out JsonElement uriElement))
            {
                if (!Uri.TryCreate(uriElement.GetString(), UriKind.RelativeOrAbsolute, out Uri? uri))
                    throw new Exception("Malformed URI.");

                Uri = uri;
            }

            DeserializeCommon(element);
        }

        internal override void Serialize(Utf8JsonWriter writer)
        {
            throw new NotImplementedException();
        }
    }
}