// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
 
using System;
using System.IO;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using Azure;
using Azure.Storage.Blobs;
 
namespace Microsoft.DotNet.Helix.Client
{
    internal abstract class ContainerBase : IBlobContainer
    {
        protected abstract (BlobClient blob, string sasToken) GetBlob(string blobName);
 
        public async Task<Uri> UploadFileAsync(Stream stream, string blobName, Action<string> log, CancellationToken cancellationToken)
        {
            var (pageBlob, sasToken) = GetBlob(blobName);
 
            try
            {
                await pageBlob.UploadAsync(stream, cancellationToken);
            }
            catch (RequestFailedException e) when (e.Status == 409)
            {
                if (!await CheckExistenceWithRetry(pageBlob, log))
                {
                    log?.Invoke($"error : Upload of {pageBlob.Uri} failed with {e.ErrorCode}, but the blob does not exist.");
                    throw;
                }
                else
                {
                    log?.Invoke($"warning : Upload of {pageBlob.Uri} failed with {e.ErrorCode}. The blob exists, continuing");
                }
            }
 
            return new UriBuilder(pageBlob.Uri) { Query = sasToken }.Uri;
        }
 
        public async Task<Uri> UploadTextAsync(string text, string blobName, Action<string> log, CancellationToken cancellationToken)
        {
            var (pageBlob, sasToken) = GetBlob(blobName);
            byte[] bytes = Encoding.UTF8.GetBytes(text);
 
            return await UploadFileAsync(new MemoryStream(bytes), blobName, log, cancellationToken);
        }
 
        private async Task<bool> CheckExistenceWithRetry(BlobClient blobClient, Action<string> log)
        {
            int attemptsRemaining = 5;
            while (attemptsRemaining > 0)
            {
                try
                {
                    bool result = await blobClient.ExistsAsync();
                    return result;
                }
                // We hit these known issues with the Azure.Storage.Blobs library:
                // https://github.com/Azure/azure-storage-net/issues/1040
                // https://github.com/Azure/azure-storage-net/issues/1012
                // Since these are currently not addressed and this is a fallback behavior
                // (checking if something's been uploaded) we'll warn and return true if the service hits this repeatedly.
                catch (RequestFailedException ex) when (ex.Status == 403)
                {
                    attemptsRemaining--;
                    await Task.Delay(1000);
                }
            }
            log?.Invoke($"warning : Failed to check existence of {blobClient.Uri} but the blob likely exists, continuing.");
            return true;
        }
 
        public abstract string Uri { get; }
        public abstract string ReadSas { get; }
        public abstract string WriteSas { get; }
    }
}