/// <summary>
/// Creates a generic secondary response.
/// </summary>
/// <param name="responseCreator">The generic-response creator. Executes with the data-access cache enabled.</param>
/// <param name="memoryCachingSetup">The memory-caching setup object for the response. Pass null if you do not want to use EWL's memory cache.</param>
public SecondaryResponse(Func <EwfResponse> responseCreator, ResponseMemoryCachingSetup memoryCachingSetup = null)
{
fullResponseGetter =
() =>
memoryCachingSetup != null
? FullResponse.GetFromCache(memoryCachingSetup.CacheKey, memoryCachingSetup.LastModificationDateAndTime, () => responseCreator().CreateFullResponse())
: responseCreator().CreateFullResponse();
}
private static Action <HttpRequest, HttpResponse> createWriter(
Func <EwfResponse> responseCreator, string urlVersionString, string eTagBase, Func <DateTimeOffset> lastModificationDateAndTimeGetter,
Func <string> memoryCacheKeyGetter)
{
return((aspNetRequest, aspNetResponse) => {
// Disable ASP.NET output caching.
aspNetResponse.Cache.SetNoServerCaching();
var response = new Lazy <EwfResponse>(responseCreator);
// If we ever want to implement content negotiation, we can do so here. We can accept multiple response-creator functions instead of just one. Then, if
// the request contains an Accept header, we can evaluate the response-creator functions here and then choose the response with the best content type.
// If there is no match, we can send a 406 (Not Acceptable) status code and exit the method. Note that if we do add support for multiple
// response-creator functions, we need to incorporate the chosen response's content type into the ETag if we want it to remain a strong ETag. We also
// need to incorporate the content type into the memory-cache key.
// Assume that all HTTPS responses are private. This isn't true for CSS, JavaScript, etc. requests that are only secure in order to match the security
// of a page, but that's not a big deal since most shared caches can't open and cache HTTPS anyway.
//
// If we don't have caching information, the response is probably not shareable.
//
// Using ServerAndPrivate instead of just Private is a hack that is necessary because ASP.NET suppresses ETags with Private. But ASP.NET output caching
// (i.e. server caching) will still be disabled because of our SetNoServerCaching call above.
aspNetResponse.Cache.SetCacheability(
!EwfApp.Instance.RequestIsSecure(aspNetRequest) && (urlVersionString.Any() || eTagBase.Any() || lastModificationDateAndTimeGetter != null)
? HttpCacheability.Public
: HttpCacheability.ServerAndPrivate);
aspNetResponse.Cache.SetMaxAge(urlVersionString.Any() ? TimeSpan.FromDays(365) : TimeSpan.Zero);
var lastModificationDateAndTime = lastModificationDateAndTimeGetter != null ? new Lazy <DateTimeOffset>(lastModificationDateAndTimeGetter) : null;
string eTag;
if (urlVersionString.Any())
{
eTag = urlVersionString;
}
else if (eTagBase.Any() || lastModificationDateAndTimeGetter != null)
{
eTag = eTagBase + (lastModificationDateAndTimeGetter != null ? GetUrlVersionString(lastModificationDateAndTime.Value) : "");
}
else
{
// Buffer the response body.
var responseWithBufferedBody = EwfResponse.Create(
response.Value.ContentType,
response.Value.BodyCreator.GetBufferedBodyCreator(),
fileNameCreator: response.Value.FileNameCreator);
response = new Lazy <EwfResponse>(() => responseWithBufferedBody);
var bodyAsBinary = response.Value.BodyCreator.BodyIsText
? Encoding.UTF8.GetBytes(response.Value.BodyCreator.TextBodyCreator())
: response.Value.BodyCreator.BinaryBodyCreator();
eTag = Convert.ToBase64String(MD5.Create().ComputeHash(bodyAsBinary));
}
// Strong ETags must vary by content coding. Since we don't know yet how this response will be encoded (gzip or otherwise), the best thing we can do is
// use the Accept-Encoding header value in the ETag.
var acceptEncoding = aspNetRequest.Headers["Accept-Encoding"]; // returns null if field missing
if (acceptEncoding != null)
{
eTag += acceptEncoding.Replace(", ", ""); // On 4 Feb 2015 we saw the comma/space cause Chrome to incorrectly split the ETag apart.
}
aspNetResponse.Cache.SetETag(eTag);
// Sending a Last-Modified header isn't a good enough reason to force evaluation of lastModificationDateAndTimeGetter, which could be expensive.
if (lastModificationDateAndTimeGetter != null && lastModificationDateAndTime.IsValueCreated)
{
aspNetResponse.Cache.SetLastModified(lastModificationDateAndTime.Value.UtcDateTime);
}
// When we separate EWF from Web Forms, we may need to add a Vary header with "Accept-Encoding". Do that here.
var ifNoneMatch = aspNetRequest.Headers.GetValues("If-None-Match"); // returns null if field missing
if (ifNoneMatch != null && ifNoneMatch.Contains(eTag))
{
aspNetResponse.StatusCode = 304;
return;
}
var memoryCacheKey = memoryCacheKeyGetter();
if (memoryCacheKey.Any())
{
var fullResponse = FullResponse.GetFromCache(memoryCacheKey, lastModificationDateAndTime.Value, () => response.Value.CreateFullResponse());
response = new Lazy <EwfResponse>(() => new EwfResponse(fullResponse));
}
if (response.Value.ContentType.Length > 0)
{
aspNetResponse.ContentType = response.Value.ContentType;
}
var fileName = response.Value.FileNameCreator();
if (fileName.Any())
{
aspNetResponse.AppendHeader("content-disposition", "attachment; filename=\"" + fileName + "\"");
}
if (aspNetRequest.HttpMethod != "HEAD")
{
response.Value.BodyCreator.WriteToResponse(aspNetResponse);
}
});
}
private static Action <HttpResponse, HttpRequest, bool> createWriter(
Func <EwfResponse> responseCreator, string urlVersionString, string eTagBase, Func <DateTimeOffset> lastModificationDateAndTimeGetter,
Func <string> memoryCacheKeyGetter)
{
return((aspNetResponse, aspNetRequest, forceImmediateResponseExpiration) => {
var response = new Lazy <EwfResponse>(responseCreator);
// If we ever want to implement content negotiation, we can do so here. We can accept multiple response-creator functions instead of just one. Then, if
// the request contains an Accept header, we can evaluate the response-creator functions here and then choose the response with the best content type.
// If there is no match, we can send a 406 (Not Acceptable) status code and exit the method. Note that if we do add support for multiple
// response-creator functions, we need to incorporate the chosen response's content type into the ETag if we want it to remain a strong ETag. We also
// need to incorporate the content type into the memory-cache key.
AddCacheControlHeader(
aspNetResponse,
EwfApp.Instance.RequestIsSecure(aspNetRequest),
urlVersionString.Any() || eTagBase.Any() || lastModificationDateAndTimeGetter != null,
urlVersionString.Any() && !forceImmediateResponseExpiration);
var lastModificationDateAndTime = lastModificationDateAndTimeGetter != null ? new Lazy <DateTimeOffset>(lastModificationDateAndTimeGetter) : null;
string eTag;
if (urlVersionString.Any())
{
eTag = urlVersionString;
}
else if (eTagBase.Any() || lastModificationDateAndTimeGetter != null)
{
eTag = eTagBase + (lastModificationDateAndTimeGetter != null ? GetUrlVersionString(lastModificationDateAndTime.Value) : "");
}
else
{
// Buffer the response body.
var responseWithBufferedBody = EwfResponse.Create(
response.Value.ContentType,
response.Value.BodyCreator.GetBufferedBodyCreator(),
fileNameCreator: response.Value.FileNameCreator,
additionalHeaderFieldGetter: response.Value.AdditionalHeaderFieldGetter);
response = new Lazy <EwfResponse>(() => responseWithBufferedBody);
var bodyAsBinary = response.Value.BodyCreator.BodyIsText
? Encoding.UTF8.GetBytes(response.Value.BodyCreator.TextBodyCreator())
: response.Value.BodyCreator.BinaryBodyCreator();
eTag = Convert.ToBase64String(MD5.Create().ComputeHash(bodyAsBinary));
}
// Strong ETags must vary by content coding. Since we don't know yet how this response will be encoded (gzip or otherwise), the best thing we can do is
// use the Accept-Encoding header value in the ETag.
var acceptEncoding = aspNetRequest.Headers["Accept-Encoding"]; // returns null if field missing
if (acceptEncoding != null)
{
eTag += acceptEncoding.Replace(", ", ""); // On 4 Feb 2015 we saw the comma/space cause Chrome to incorrectly split the ETag apart.
}
aspNetResponse.Cache.SetETag(eTag);
// Sending a Last-Modified header isn't a good enough reason to force evaluation of lastModificationDateAndTimeGetter, which could be expensive.
if (lastModificationDateAndTimeGetter != null && lastModificationDateAndTime.IsValueCreated)
{
aspNetResponse.Cache.SetLastModified(lastModificationDateAndTime.Value.UtcDateTime);
}
// When we separate EWF from Web Forms, we may need to add a Vary header with "Accept-Encoding". Do that here.
var ifNoneMatch = aspNetRequest.Headers.GetValues("If-None-Match"); // returns null if field missing
if (ifNoneMatch != null && ifNoneMatch.Contains(eTag))
{
aspNetResponse.StatusCode = 304;
return;
}
var memoryCacheKey = memoryCacheKeyGetter();
if (memoryCacheKey.Any())
{
var fullResponse = FullResponse.GetFromCache(memoryCacheKey, lastModificationDateAndTime.Value, () => response.Value.CreateFullResponse());
response = new Lazy <EwfResponse>(() => new EwfResponse(fullResponse));
}
response.Value.WriteToAspNetResponse(aspNetResponse, omitBody: aspNetRequest.HttpMethod == "HEAD");
});
}