using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Net;
using System.Threading.Tasks;
using System.Web;
using System.Web.Mvc;
using Microsoft.WindowsAzure.Storage;
using Microsoft.WindowsAzure.Storage.Blob;
using Microsoft.WindowsAzure.Storage.Blob.Protocol;
using NuGetGallery.Configuration;

namespace NuGetGallery
{
    public class CloudBlobFileStorageService : IFileStorageService
    {
        private readonly ICloudBlobClient _client;
        private readonly IAppConfiguration _configuration;
        private readonly ConcurrentDictionary<string, ICloudBlobContainer> _containers = new ConcurrentDictionary<string, ICloudBlobContainer>();

        public CloudBlobFileStorageService(ICloudBlobClient client, IAppConfiguration configuration)
        {
            _client = client;
            _configuration = configuration;
        }

        public async Task<ActionResult> CreateDownloadFileActionResultAsync(Uri requestUrl, string folderName, string fileName)
        {
            ICloudBlobContainer container = await GetContainer(folderName);
            var blob = container.GetBlobReference(fileName);

            var redirectUri = GetRedirectUri(requestUrl, blob.Uri);
            return new RedirectResult(redirectUri.OriginalString, false);
        }

        public async Task DeleteFileAsync(string folderName, string fileName)
        {
            ICloudBlobContainer container = await GetContainer(folderName);
            var blob = container.GetBlobReference(fileName);
            await blob.DeleteIfExistsAsync();
        }

        public async Task<bool> FileExistsAsync(string folderName, string fileName)
        {
            ICloudBlobContainer container = await GetContainer(folderName);
            var blob = container.GetBlobReference(fileName);
            return await blob.ExistsAsync();
        }

        internal Uri GetRedirectUri(Uri requestUrl, Uri blobUri)
        {
            string host = String.IsNullOrEmpty(_configuration.AzureCdnHost) ? blobUri.Host : _configuration.AzureCdnHost;
            var urlBuilder = new UriBuilder(requestUrl.Scheme, host)
            {
                Path = blobUri.LocalPath,
                Query = blobUri.Query
            };

            return urlBuilder.Uri;
        }
		
        private async Task<ICloudBlobContainer> GetContainer(string folderName)
        {
            ICloudBlobContainer container;
            if (_containers.TryGetValue(folderName, out container))
            {
                return container;
            }

            Task<ICloudBlobContainer> creationTask;
            switch (folderName)
            {
                case Constants.PackagesFolderName:
                case Constants.DownloadsFolderName:
                    creationTask = PrepareContainer(folderName, isPublic: true);
                    break;

                case Constants.ContentFolderName:
                case Constants.UploadsFolderName:
                    creationTask = PrepareContainer(folderName, isPublic: false);
                    break;

                default:
                    throw new InvalidOperationException(
                        String.Format(CultureInfo.CurrentCulture, "The folder name {0} is not supported.", folderName));
            }

            container = await creationTask;
            _containers[folderName] = container;
            return container;
        }
		
        private async Task<ICloudBlobContainer> PrepareContainer(string folderName, bool isPublic)
        {
            var container = _client.GetContainerReference(folderName);
            await container.CreateIfNotExistAsync();
            await container.SetPermissionsAsync(
                new BlobContainerPermissions
                {
                    PublicAccess = isPublic ? BlobContainerPublicAccessType.Blob : BlobContainerPublicAccessType.Off
                });

            return container;
        }
    }
}