StorageServer/IO/StorageProvider.cs

using System.Security.Cryptography;
using StorageServer.Models;

namespace StorageServer.IO;

public class StorageProvider {
    public static int BufferSize = 16384;

    private string saveDirectory;

    public StorageProvider(string saveDirectory) {
        this.saveDirectory = saveDirectory;
        if (!Directory.Exists(saveDirectory)) {
            Directory.CreateDirectory(saveDirectory);
        }
    }

    public async Task<string> ComputeStreamHash(Stream stream) {
        using (Stream buffered = new BufferedStream(stream, BufferSize)) {
            byte[] checksum = await SHA256.HashDataAsync(buffered);
            return BitConverter.ToString(checksum);
        }
    }

    public async Task SaveFile(FileModel fileModel, FileStream fs) {
        string extension = Path.GetExtension(fileModel.FileName);
        string saveFileName = string.Format("{0}{1}", fileModel.FileID, extension);
        string saveFullName = Path.Combine(this.saveDirectory, saveFileName);
        using (FileStream dest = new FileStream(saveFullName, FileMode.OpenOrCreate)) {
            await fs.CopyToAsync(dest);
        }
    }

    public Stream GetFile(FileModel fileModel) {
        string extension = Path.GetExtension(fileModel.FileName);
        string saveFileName = string.Format("{0}{1}", fileModel.FileID, extension);
        string saveFullName = Path.Combine(this.saveDirectory, saveFileName);
        if (!File.Exists(saveFullName)) {
            throw new FileNotFoundException();
        }

        return new FileStream(saveFullName, FileMode.Open);
    }
}