using System.Net;
using System.Net.Http.Headers;

namespace SteUp.Shared.Core.Helpers;

/// <summary>
/// Contenuto HTTP letto dal file durante l'invio, senza caricarlo in RAM. Il file viene riaperto
/// a ogni serializzazione, così regge anche un eventuale nuovo tentativo del client
/// (es. dopo il refresh del token).
/// </summary>
public sealed class FileHttpContent : HttpContent
{
    private const int BufferSize = 81920;

    private readonly string _path;

    public FileHttpContent(string path, string mediaType)
    {
        _path = path;
        Headers.ContentType = new MediaTypeHeaderValue(mediaType);
    }

    protected override Task SerializeToStreamAsync(Stream stream, TransportContext? context) =>
        SerializeToStreamAsync(stream, context, CancellationToken.None);

    protected override async Task SerializeToStreamAsync(Stream stream, TransportContext? context,
        CancellationToken cancellationToken)
    {
        await using var file = new FileStream(_path, FileMode.Open, FileAccess.Read, FileShare.Read,
            BufferSize, useAsync: true);
        await file.CopyToAsync(stream, BufferSize, cancellationToken);
    }

    protected override bool TryComputeLength(out long length)
    {
        length = new FileInfo(_path).Length;
        return true;
    }
}