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using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Microsoft.Net.Http.Headers;
using System;
using System.Linq;
using System.Threading.Tasks;
using Timeline.Models.Http;
using static Timeline.Resources.Helper.DataCacheHelper;
namespace Timeline.Helpers
{
public interface ICacheableData
{
string Type { get; }
#pragma warning disable CA1819 // Properties should not return arrays
byte[] Data { get; }
#pragma warning restore CA1819 // Properties should not return arrays
DateTime? LastModified { get; }
}
public class CacheableData : ICacheableData
{
public CacheableData(string type, byte[] data, DateTime? lastModified)
{
Type = type;
Data = data;
LastModified = lastModified;
}
public string Type { get; set; }
#pragma warning disable CA1819 // Properties should not return arrays
public byte[] Data { get; set; }
#pragma warning restore CA1819 // Properties should not return arrays
public DateTime? LastModified { get; set; }
}
public interface ICacheableDataProvider
{
Task<string> GetDataETag();
Task<ICacheableData> GetData();
}
public class DelegateCacheableDataProvider : ICacheableDataProvider
{
private readonly Func<Task<string>> _getDataETagDelegate;
private readonly Func<Task<ICacheableData>> _getDataDelegate;
public DelegateCacheableDataProvider(Func<Task<string>> getDataETagDelegate, Func<Task<ICacheableData>> getDataDelegate)
{
_getDataETagDelegate = getDataETagDelegate;
_getDataDelegate = getDataDelegate;
}
public Task<ICacheableData> GetData()
{
return _getDataDelegate();
}
public Task<string> GetDataETag()
{
return _getDataETagDelegate();
}
}
public static class DataCacheHelper
{
public static async Task<ActionResult> GenerateActionResult(Controller controller, ICacheableDataProvider provider, TimeSpan? maxAge = null)
{
const string CacheControlHeaderKey = "Cache-Control";
const string IfNonMatchHeaderKey = "If-None-Match";
const string ETagHeaderKey = "ETag";
string GenerateCacheControlHeaderValue()
{
var cacheControlHeader = new CacheControlHeaderValue()
{
NoCache = true,
NoStore = false,
MaxAge = maxAge ?? TimeSpan.FromDays(14),
Private = true,
MustRevalidate = true
};
return cacheControlHeader.ToString();
}
var loggerFactory = controller.HttpContext.RequestServices.GetRequiredService<ILoggerFactory>();
var logger = loggerFactory.CreateLogger(typeof(DataCacheHelper));
var eTagValue = await provider.GetDataETag();
eTagValue = '"' + eTagValue + '"';
var eTag = new EntityTagHeaderValue(eTagValue);
if (controller.Request.Headers.TryGetValue(IfNonMatchHeaderKey, out var value))
{
if (!EntityTagHeaderValue.TryParseStrictList(value, out var eTagList))
{
logger.LogInformation(Log.Format(LogBadIfNoneMatch, ("Header Value", value)));
return controller.BadRequest(ErrorResponse.Common.Header.IfNonMatch_BadFormat());
}
if (eTagList.FirstOrDefault(e => e.Equals(eTag)) != null)
{
logger.LogInformation(LogResultNotModified);
controller.Response.Headers.Add(ETagHeaderKey, eTagValue);
controller.Response.Headers.Add(CacheControlHeaderKey, GenerateCacheControlHeaderValue());
return controller.StatusCode(StatusCodes.Status304NotModified);
}
}
var data = await provider.GetData();
logger.LogInformation(LogResultData);
controller.Response.Headers.Add(CacheControlHeaderKey, GenerateCacheControlHeaderValue());
return controller.File(data.Data, data.Type, data.LastModified, eTag);
}
public static Task<ActionResult> GenerateActionResult(Controller controller, Func<Task<string>> getDataETagDelegate, Func<Task<ICacheableData>> getDataDelegate, TimeSpan? maxAge = null)
{
return GenerateActionResult(controller, new DelegateCacheableDataProvider(getDataETagDelegate, getDataDelegate), maxAge);
}
}
}
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