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using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Net.Http.Headers;
using System;
using System.Linq;
using System.Threading.Tasks;
using Timeline.Models;
using Timeline.Models.Http;
namespace Timeline.Helpers.Cache
{
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 IfModifiedSinceHeaderKey = "If-Modified-Since";
const string ETagHeaderKey = "ETag";
const string LastModifiedHeaderKey = "Last-Modified";
string GenerateCacheControlHeaderValue()
{
var cacheControlHeader = new CacheControlHeaderValue()
{
NoCache = true,
NoStore = false,
MaxAge = maxAge ?? TimeSpan.FromDays(14),
Private = true,
MustRevalidate = true
};
return cacheControlHeader.ToString();
}
var digest = await provider.GetDigest();
var eTagValue = $"\"{digest.ETag}\"";
var eTag = new EntityTagHeaderValue(eTagValue);
ActionResult Generate304Result()
{
controller.Response.Headers.Add(ETagHeaderKey, eTagValue);
controller.Response.Headers.Add(LastModifiedHeaderKey, digest.LastModified.ToString("R"));
controller.Response.Headers.Add(CacheControlHeaderKey, GenerateCacheControlHeaderValue());
return controller.StatusCode(StatusCodes.Status304NotModified, null);
}
if (controller.Request.Headers.TryGetValue(IfNonMatchHeaderKey, out var ifNonMatchHeaderValue))
{
if (!EntityTagHeaderValue.TryParseList(ifNonMatchHeaderValue, out var eTagList))
{
return controller.BadRequest(new CommonResponse(ErrorCodes.Common.Header.IfNonMatch_BadFormat, "Header If-None-Match is of bad format."));
}
if (eTagList.FirstOrDefault(e => e.Equals(eTag)) != null)
{
return Generate304Result();
}
}
else if (controller.Request.Headers.TryGetValue(IfModifiedSinceHeaderKey, out var ifModifiedSinceHeaderValue))
{
if (!DateTime.TryParse(ifModifiedSinceHeaderValue, out var headerValue))
{
return controller.BadRequest(new CommonResponse(ErrorCodes.Common.Header.IfModifiedSince_BadFormat, "Header If-Modified-Since is of bad format."));
}
if (headerValue > digest.LastModified)
{
return Generate304Result();
}
}
var data = await provider.GetData();
controller.Response.Headers.Add(CacheControlHeaderKey, GenerateCacheControlHeaderValue());
return controller.File(data.Data, data.ContentType, digest.LastModified, eTag);
}
public static Task<ActionResult> GenerateActionResult(Controller controller, Func<Task<ICacheableDataDigest>> getDigestDelegate, Func<Task<ByteData>> getDataDelegate, TimeSpan? maxAge = null)
{
return GenerateActionResult(controller, new DelegateCacheableDataProvider(getDigestDelegate, getDataDelegate), maxAge);
}
}
}
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