private PreconditionResult ExecutePrecondition(ActionContext actionContext, IPreconditionInformation information)
{
var preconditionBuilder = new HttpPreconditionBuilder(actionContext.HttpContext);
var getResult = preconditionBuilder.BuildPrecondition(actionContext.HttpContext.Request, this.ActionOptions.MissingPreconditionResult);
this.Log(TraceEventType.Verbose, "Executing precondition.");
return(getResult(information));
}
private static bool TryBuildLastModified(IPreconditionInformation preconditionInformation, out DateTimeOffset headerValue)
{
if (preconditionInformation.ModifiedOn > DateTimeOffset.MinValue)
{
headerValue = preconditionInformation.ModifiedOn;
return(true);
}
else
{
headerValue = DateTimeOffset.MinValue;
return(false);
}
}
private static bool TryBuildEntityTagHeader(IPreconditionInformation preconditionInformation, out EntityTagHeaderValue headerValue)
{
string eTag;
if (ETagUtility.TryCreate(preconditionInformation, out eTag))
{
headerValue = new EntityTagHeaderValue(ETagUtility.FormatStandard(eTag));
return(true);
}
else
{
headerValue = null;
return(false);
}
}
public static bool TryCreate(IPreconditionInformation info, out string eTag)
{
if (info == null)
{
throw new ArgumentNullException("info");
}
eTag = null;
if (info.RowVersion != null && info.RowVersion.Length > 0)
{
eTag = BitHelper.ConvertToHex(info.RowVersion);
}
else
{
eTag = BitHelper.ConvertToHex(info.ModifiedOn);
}
return(eTag != null);
}
/// <summary>
/// Gets the result for a HTTP method that doesn't change server side state.
/// </summary>
/// <param name="request">The request.</param>
/// <param name="defaultResult">The default result.</param>
/// <param name="localInformation">The local information.</param>
/// <returns>PreconditionResult.</returns>
protected virtual PreconditionResult GetResultForNonMutating(HttpRequest request, PreconditionResult defaultResult, IPreconditionInformation localInformation)
{
if (request == null)
{
throw new ArgumentNullException(nameof(request));
}
if (defaultResult == null)
{
throw new ArgumentNullException(nameof(defaultResult));
}
if (localInformation == null)
{
throw new ArgumentNullException(nameof(localInformation));
}
var httpRequestHeaders = request.GetTypedHeaders();
// Predicate code.
string localETag;
if (ETagUtility.TryCreate(localInformation, out localETag))
{
localETag = ETagUtility.FormatStandard(localETag);
// Favours eTags over timestamps.
//
if (httpRequestHeaders.IfNoneMatch != null && httpRequestHeaders.IfNoneMatch.Any())
{
foreach (var eTag in httpRequestHeaders.IfNoneMatch)
{
_logger?.LogTrace($"Precondition If-None-Match: client {eTag} vs local {localETag}");
if (eTag.Tag == localETag)
{
_logger?.LogInformation("Precondition If-None-Match: false");
return(PreconditionResult.PreconditionFailedNotModified); // As soon as one matches, we've failed (if *none* match).
}
}
_logger?.LogInformation("Precondition If-None-Match: true");
return(PreconditionResult.PreconditionPassed);
}
// Falls through to try modified stamps.
//
if (httpRequestHeaders.IfModifiedSince.HasValue && localInformation.ModifiedOn > DateTimeOffset.MinValue)
{
DateTimeOffset clientTimestamp = httpRequestHeaders.IfModifiedSince.Value;
_logger?.LogTrace($"Precondition If-None-Match: client {clientTimestamp} vs local {localInformation.ModifiedOn}");
if (IsTimeSignificantlyGreaterThan(clientTimestamp, localInformation.ModifiedOn))
{
_logger?.LogInformation("Precondition If-Modified-Since: true");
return(PreconditionResult.PreconditionPassed);
}
else
{
_logger?.LogInformation("Precondition If-Modified-Since: false");
return(PreconditionResult.PreconditionFailedNotModified);
}
}
_logger?.LogInformation("Precondition headers not found: " + defaultResult.ToString());
}
else
{
_logger?.LogInformation("Local version data not found: " + defaultResult.ToString());
}
_logger?.LogInformation("The information required to determine precondition is not present. Defaulting to HTTP " + defaultResult.StatusCode);
return(defaultResult);
}
/// <summary>
/// Executes the precondition and returns the result.
/// </summary>
/// <param name="request">The request.</param>
/// <param name="defaultResult">The default result.</param>
/// <param name="localInformation">The local information.</param>
/// <returns>PreconditionResult.</returns>
public PreconditionResult GetResult(HttpRequest request, PreconditionResult defaultResult, IPreconditionInformation localInformation)
{
if (request == null)
{
throw new ArgumentNullException(nameof(request));
}
if (defaultResult == null)
{
throw new ArgumentNullException(nameof(defaultResult));
}
if (localInformation == null)
{
throw new ArgumentNullException(nameof(localInformation));
}
if (HttpPreconditionBuilder.IsMutatingMethod(request.Method))
{
return(this.GetResultForMutating(request, defaultResult, localInformation));
}
else
{
return(this.GetResultForNonMutating(request, defaultResult, localInformation));
}
}
/// <summary>
/// Gets the result for a HTTP method that changes server side state.
/// </summary>
/// <param name="request">The request.</param>
/// <param name="defaultResult">The default result.</param>
/// <param name="localInformation">The server side information.</param>
/// <returns>PreconditionResult.</returns>
/// <exception cref="System.NotSupportedException">
/// The wildcard ETag conditional PUT|DELETE is not supported.
/// or
/// The wildcard ETag conditional PUT|DELETE is not supported.
/// </exception>
protected virtual PreconditionResult GetResultForMutating(HttpRequest request, PreconditionResult defaultResult, IPreconditionInformation localInformation)
{
if (request == null)
{
throw new ArgumentNullException(nameof(request));
}
if (defaultResult == null)
{
throw new ArgumentNullException(nameof(defaultResult));
}
if (localInformation == null)
{
throw new ArgumentNullException(nameof(localInformation));
}
var httpRequestHeaders = request.GetTypedHeaders();
// Predicate code.
string localETag;
if (ETagUtility.TryCreate(localInformation, out localETag))
{
localETag = ETagUtility.FormatStandard(localETag);
// Favours eTags over timestamps.
//
if (httpRequestHeaders.IfMatch != null && httpRequestHeaders.IfMatch.Any())
{
foreach (var eTag in httpRequestHeaders.IfMatch)
{
_logger?.LogTrace($"Precondition If-None-Match: client {eTag} vs local {localETag}");
if (eTag.Tag == "*")
{
throw new NotSupportedException("The wildcard ETag conditional PUT|DELETE is not supported.");
}
if (eTag.Tag == localETag)
{
_logger?.LogInformation("Precondition If-Match: true");
return(PreconditionResult.PreconditionPassed);
}
}
_logger?.LogInformation("Precondition If-Match: false");
return(PreconditionResult.PreconditionFailed);
}
if (httpRequestHeaders.IfNoneMatch != null && httpRequestHeaders.IfNoneMatch.Any())
{
foreach (var eTag in httpRequestHeaders.IfNoneMatch)
{
_logger?.LogTrace($"Precondition If-None-Match: client {eTag} vs local {localETag}");
if (eTag.Tag == "*")
{
throw new NotSupportedException("The wildcard ETag conditional PUT|DELETE is not supported.");
}
if (eTag.Tag == localETag)
{
_logger?.LogInformation("Precondition If-None-Match: false");
return(PreconditionResult.PreconditionFailed); // As soon as one matches, we've failed (if *none* match).
}
}
_logger?.LogInformation("Precondition If-None-Match: true");
return(PreconditionResult.PreconditionPassed);
}
// Falls through to try modified stamps, note: *Un*modified since.
//
if (httpRequestHeaders.IfUnmodifiedSince.HasValue && localInformation.ModifiedOn > DateTimeOffset.MinValue)
{
DateTimeOffset clientTimestamp = httpRequestHeaders.IfUnmodifiedSince.Value;
_logger?.LogTrace($"Precondition If-Unmodified-Since: client {clientTimestamp} vs local {localInformation.ModifiedOn}");
// Pass, only if the server resource has not been modified since the specified date/time, i.e. if the timestamp
// on the server's copy matches that which the client has.
//
if (AreTimesAlmostEqual(clientTimestamp, localInformation.ModifiedOn))
{
_logger?.LogInformation("Precondition If-Unmodified-Since: true");
return(PreconditionResult.PreconditionPassed);
}
else
{
_logger?.LogInformation("Precondition If-Unmodified-Since: false");
return(PreconditionResult.PreconditionFailed);
}
}
_logger?.LogInformation("Precondition headers not found: " + defaultResult.ToString());
}
else
{
_logger?.LogInformation("Local version data not found: " + defaultResult.ToString());
}
_logger?.LogInformation("The information required to determine precondition is not present. Defaulting to HTTP " + defaultResult.StatusCode);
return(defaultResult);
}
/// <summary>
/// Applies version headers based on information in the supplied content.
/// </summary>
public static ActionContext ApplyVersionHeaders(this ActionContext actionContext, IPreconditionInformation versionableContent)
{
var headers = actionContext.HttpContext.Response.GetTypedHeaders();
headers.Date = DateTimeOffset.Now;
EntityTagHeaderValue eTagHeader;
if (TryBuildEntityTagHeader(versionableContent, out eTagHeader))
{
headers.ETag = eTagHeader;
}
DateTimeOffset modified;
if (TryBuildLastModified(versionableContent, out modified))
{
headers.LastModified = modified;
}
return(actionContext);
}
