private void WriteEntryToNewPage(
AtomEntry entry,
AppendContext context)
{
var newAddress = this.CreateNewFeedAddress();
var newPage = this.ReadPage(newAddress);
newPage = AddEntryTo(newPage, entry, context.Now);
var nextLink = AtomLink.CreateNextLink(newAddress);
var previousPage = context.LastPage
.WithLinks(context.LastPage.Links.Concat(new[] { nextLink }));
var previousLink = previousPage.Links
.Single(l => l.IsSelfLink)
.ToPreviousLink();
newPage = newPage.WithLinks(
newPage.Links.Concat(new[] { previousLink }));
var index = context.Index.WithLinks(context.Index.Links
.Where(l => !l.IsLastLink)
.Concat(new[] { nextLink.ToLastLink() }));
this.Write(newPage);
this.Write(previousPage);
try { this.Write(index); } catch { }
}
/// <summary>
/// Creates a new, empty feed.
/// </summary>
/// <param name="href">The address of the feed.</param>
/// <returns>A new, empty Atom Feed.</returns>
/// <remarks>
/// <para>
/// <paramref name="href" /> is expected to contain an
/// <see cref="Uri" /> in the last segment. This Uri is used as the ID
/// for the new Atom Feed.
/// </para>
/// </remarks>
public static XmlReader CreateNewFeed(Uri href)
{
var id = GetIdFromHref(href);
var xml = new AtomFeed(
id,
"Index of event stream " + id,
DateTimeOffset.Now,
new AtomAuthor("Grean"),
Enumerable.Empty <AtomEntry>(),
new[]
{
AtomLink.CreateSelfLink(href)
})
.ToXmlString((IContentSerializer)null);
var sr = new StringReader(xml);
try
{
return(XmlReader.Create(
sr,
new XmlReaderSettings {
CloseInput = true
}));
}
catch
{
sr.Dispose();
throw;
}
}
public void CreateViaLinkReturnsCorrectResult(
AtomLink link)
{
AtomLink actual = AtomLink.CreateViaLink(link.Href);
var expected = link.WithRel("via");
Assert.Equal(expected, actual);
}
/// <summary>
/// Adds an <see cref="AtomLink" /> to the Atom Feed's collection of
/// <see cref="Links" />.
/// </summary>
/// <param name="newLink">The link to be added.</param>
/// <returns>
/// A new instance of <see cref="AtomFeed" /> with the new link added.
/// </returns>
/// <remarks>
/// <para>
/// This method doesn't mutate the instance upon which it is invoked,
/// but return a new instance with all other properties held constant,
/// but <paramref name="newLink" /> added to the new instance's
/// collection of <see cref="Links" />. The new copy also contains all
/// the links from the original instance.
/// </para>
/// <para>
/// The exact position of the new link relative to the original links
/// is not guaranteed to be deterministic.
/// </para>
/// </remarks>
/// <exception cref="System.ArgumentNullException">
/// <paramref name="newLink" /> is <see langword="null" />.
/// </exception>
public AtomFeed AddLink(AtomLink newLink)
{
if (newLink == null)
{
throw new ArgumentNullException("newLink");
}
return(this.WithLinks(this.links.Concat(new[] { newLink })));
}
public void AddLinkReturnsCorrectResult(
AtomFeed sut,
AtomLink newLink)
{
AtomFeed actual = sut.AddLink(newLink);
var expected = sut.AsSource().OfLikeness<AtomFeed>()
.With(x => x.Links).EqualsWhen(
(s, d) => sut.Links.Concat(new[] { newLink }).SequenceEqual(d.Links));
expected.ShouldEqual(actual);
}
/// <summary>
/// Creates an <see cref="AtomEntry" /> instance from XML.
/// </summary>
/// <param name="xmlReader">
/// The <see cref="XmlReader" /> containing the XML representation of
/// the Atom Entry.
/// </param>
/// <param name="serializer">
/// The <see cref="IContentSerializer" /> used to serialize custom XML
/// content.
/// </param>
/// <returns>
/// A new instance of <see cref="AtomEntry" /> containing the data from
/// the XML representation of the Atom Entry contained in
/// <paramref name="xmlReader" />.
/// </returns>
/// <exception cref="System.ArgumentNullException">
/// <paramref name="serializer" /> is <see langword="null" />.
/// </exception>
public static AtomEntry ReadFrom(
XmlReader xmlReader,
IContentSerializer serializer)
{
if (serializer == null)
{
throw new ArgumentNullException("serializer");
}
var navigator = new XPathDocument(xmlReader).CreateNavigator();
var resolver = new XmlNamespaceManager(new NameTable());
resolver.AddNamespace("atom", "http://www.w3.org/2005/Atom");
var id = navigator
.Select("/atom:entry/atom:id", resolver).Cast <XPathNavigator>()
.Single().Value;
var title = navigator
.Select("/atom:entry/atom:title[@type = 'text']", resolver).Cast <XPathNavigator>()
.Single().Value;
var published = navigator
.Select("/atom:entry/atom:published", resolver).Cast <XPathNavigator>()
.Single().Value;
var updated = navigator
.Select("/atom:entry/atom:updated", resolver).Cast <XPathNavigator>()
.Single().Value;
var author = navigator
.Select("/atom:entry/atom:author", resolver).Cast <XPathNavigator>()
.Single().ReadSubtree();
var content = navigator
.Select("/atom:entry/atom:content[@type = 'application/xml']", resolver).Cast <XPathNavigator>()
.Single().ReadSubtree();
var links = navigator
.Select("/atom:entry/atom:link", resolver).Cast <XPathNavigator>();
return(new AtomEntry(
UuidIri.Parse(id),
title,
DateTimeOffset.Parse(published, CultureInfo.InvariantCulture),
DateTimeOffset.Parse(updated, CultureInfo.InvariantCulture),
AtomAuthor.ReadFrom(author),
XmlAtomContent.ReadFrom(content, serializer),
links.Select(x => AtomLink.ReadFrom(x.ReadSubtree()))));
}
/// <summary>
/// Parses the specified XML into an instance of
/// <see cref="AtomLink" />.
/// </summary>
/// <param name="xml">
/// A string of characters containing the XML representation of an Atom
/// link.
/// </param>
/// <returns>
/// A new instance of <see cref="AtomLink" /> containing the data from
/// the supplied <paramref name="xml" />.
/// </returns>
public static AtomLink Parse(string xml)
{
var sr = new StringReader(xml);
try
{
using (var r = XmlReader.Create(sr))
{
sr = null;
return(AtomLink.ReadFrom(r));
}
}
finally
{
if (sr != null)
{
sr.Dispose();
}
}
}
private AppendContext Prepare(DateTimeOffset now)
{
var index = this.ReadIndex();
var firstLink = index.Links
.Where(l => l.IsFirstLink)
.DefaultIfEmpty(AtomLink.CreateFirstLink(this.CreateNewFeedAddress()))
.Single();
index = index.WithLinks(index.Links.Union(new[] { firstLink }));
var lastLink = index.Links.SingleOrDefault(l => l.IsLastLink);
var lastLinkAdded = false;
if (lastLink == null)
{
lastLink = firstLink.ToLastLink();
lastLinkAdded = true;
}
var lastPage = this.ReadTrueLastPage(lastLink.Href);
var lastLinkCorrected = false;
if (lastPage.Links.Single(l => l.IsSelfLink).Href != lastLink.Href)
{
lastLink = lastPage.Links.Single(l => l.IsSelfLink).ToLastLink();
lastLinkCorrected = true;
}
index = index.WithLinks(index.Links
.Where(l => !l.IsLastLink)
.Concat(new[] { lastLink }));
return(new AppendContext(
index,
lastPage,
now,
lastLinkAdded,
lastLinkCorrected));
}
public void WriteToXmlWriterWritesCorrectXml(
AtomLink sut)
{
// Fixture setup
var sb = new StringBuilder();
using (var w = XmlWriter.Create(sb))
{
// Exercise system
sut.WriteTo(w);
// Verify outcome
w.Flush();
var expected = XDocument.Parse(
"<link" +
" href=\"" + sut.Href.ToString() + "\"" +
" rel=\"" + sut.Rel + "\"" +
" xmlns=\"http://www.w3.org/2005/Atom\" />");
var actual = XDocument.Parse(sb.ToString());
Assert.Equal(expected, actual, new XNodeEqualityComparer());
}
// Teardown
}
public void WithRelReturnsCorrectResult(
AtomLink sut,
string newRel)
{
AtomLink actual = sut.WithRel(newRel);
var expected = sut.AsSource().OfLikeness<AtomLink>()
.With(x => x.Rel).EqualsWhen(
(s, d) => object.Equals(newRel, d.Rel));
expected.ShouldEqual(actual);
}
public void WithHrefReturnsCorrectResult(
AtomLink sut,
Uri newHref)
{
AtomLink actual = sut.WithHref(newHref);
var expected = sut.AsSource().OfLikeness<AtomLink>()
.With(x => x.Href).EqualsWhen(
(s, d) => object.Equals(newHref, d.Href));
expected.ShouldEqual(actual);
}
public void IsPreviousLinkReturnsFalsForNonPreviousLink(
AtomLink sut)
{
Assert.NotEqual("previous", sut.Rel);
var actual = sut.IsPreviousLink;
Assert.False(actual, "Should not be previous link.");
}
private static AtomLink MakeSelfLinkIndexed(AtomLink link)
{
if (link.IsSelfLink)
{
var segment = GetIdFromHref(link.Href);
var indexedHref = segment + "/" + segment;
return link.WithHref(new Uri(indexedHref, UriKind.Relative));
}
else
return link;
}
public void RelIsCorrect([Frozen]string expected, AtomLink sut)
{
string actual = sut.Rel;
Assert.Equal(expected, actual);
}
public void HrefIsCorrect([Frozen]Uri expected, AtomLink sut)
{
Uri actual = sut.Href;
Assert.Equal(expected, actual);
}
public void ReadFromWhenHrefIsRelativeReturnsCorrectResult(
AtomLink seed,
string relativeUrl,
IContentSerializer dummySerializer)
{
var expected = seed.WithHref(new Uri(relativeUrl, UriKind.Relative));
using (var sr = new StringReader(expected.ToXmlString(dummySerializer)))
using (var r = XmlReader.Create(sr))
{
AtomLink actual = AtomLink.ReadFrom(r);
Assert.Equal(expected, actual);
}
}
public void ReadFromXmlWithoutHrefThrows(
string attribute,
AtomLink seed,
IContentSerializer dummySerializer)
{
XNamespace atom = "http://www.w3.org/2005/Atom";
var xml = XDocument.Parse(seed.ToXmlString(dummySerializer));
xml.Root.Attribute(attribute).Remove();
using(var r = xml.CreateReader())
{
var e = Assert.Throws<ArgumentException>(
() => AtomLink.ReadFrom(r));
Assert.Contains(attribute, e.Message);
}
}
public void ReadFromReturnsCorrectResult(
AtomLink expected,
IContentSerializer dummySerializer)
{
using (var sr = new StringReader(expected.ToXmlString(dummySerializer)))
using (var r = XmlReader.Create(sr))
{
AtomLink actual = AtomLink.ReadFrom(r);
Assert.Equal(expected, actual);
}
}
public void IsViaLinkReturnsFalsForNonViaLink(
AtomLink sut)
{
Assert.NotEqual("via", sut.Rel);
var actual = sut.IsViaLink;
Assert.False(actual, "Should not be via link.");
}
public void IsSelfLinkReturnsFalsForUnSelfLink(
AtomLink sut)
{
Assert.NotEqual("self", sut.Rel);
var actual = sut.IsSelfLink;
Assert.False(actual, "Should not be self link.");
}
public void IsLastLinkReturnsFalseForNonLastLink(AtomLink sut)
{
Assert.NotEqual("last", sut.Rel);
var actual = sut.IsLastLink;
Assert.False(actual, "Should not be last link.");
}
/// <summary>
/// Adds an <see cref="AtomLink" /> to the Atom Feed's collection of
/// <see cref="Links" />.
/// </summary>
/// <param name="newLink">The link to be added.</param>
/// <returns>
/// A new instance of <see cref="AtomFeed" /> with the new link added.
/// </returns>
/// <remarks>
/// <para>
/// This method doesn't mutate the instance upon which it is invoked,
/// but return a new instance with all other properties held constant,
/// but <paramref name="newLink" /> added to the new instance's
/// collection of <see cref="Links" />. The new copy also contains all
/// the links from the original instance.
/// </para>
/// <para>
/// The exact position of the new link relative to the original links
/// is not guaranteed to be deterministic.
/// </para>
/// </remarks>
/// <exception cref="System.ArgumentNullException">
/// <paramref name="newLink" /> is <see langword="null" />.
/// </exception>
public AtomFeed AddLink(AtomLink newLink)
{
if (newLink == null)
throw new ArgumentNullException("newLink");
return this.WithLinks(this.links.Concat(new[] { newLink }));
}
public void EqualsReturnsCorrectResult(
bool expected,
string sutRel,
string otherRel,
string sutHref,
string otherHref)
{
var sut = new AtomLink(sutRel, new Uri(sutHref, UriKind.Relative));
var other = new AtomLink(otherRel, new Uri(otherHref, UriKind.Relative));
var actual = sut.Equals(other);
Assert.Equal(expected, actual);
}
public void SutDoesNotEqualAnonymousOther(
AtomLink sut,
object anonymous)
{
var actual = sut.Equals(anonymous);
Assert.False(actual);
}
public void GetHashCodeReturnsCorrectResult(AtomLink sut)
{
var actual = sut.GetHashCode();
var expected =
sut.Rel.GetHashCode() ^
sut.Href.GetHashCode();
Assert.Equal(expected, actual);
}
public void SutIsXmlWritable(AtomLink sut)
{
Assert.IsAssignableFrom<IXmlWritable>(sut);
}
/// <summary>
/// Appends an event to the event stream.
/// </summary>
/// <param name="event">
/// The event to append to the event stream.
/// </param>
/// <returns>
/// A <see cref="Task" /> representing the asynchronous operation of
/// appending the event to the event stream.
/// </returns>
/// <remarks>
/// <para>
/// This method appends <paramref name="event" /> to the current event
/// stream. Appending an event indicates that it happened
/// <em>after</em> all previous events.
/// </para>
/// <para>
/// Since this method conceptually involves writing the event to the
/// underlying <see cref="Storage" />, it may take significant time to
/// complete; for that reason, it's an asynchronous method, returning a
/// <see cref="Task" />. The operation is not guaranteed to be complete
/// before the Task completes successfully.
/// </para>
/// <para>
/// When updating the underlying Storage, the method typically only
/// updates the index feed, using
/// <see cref="IAtomEventStorage.CreateFeedWriterFor(AtomFeed)" />.
/// However, when the number of entries in the index surpasses
/// <see cref="PageSize" />, a new feed page is created for the new
/// entry. This page is also written using the CreateFeedWriterFor
/// method, and only after this succeeds is the old feed page updated
/// with a link to the new page. Since these two operations are not
/// guaranteed to happen within an ACID transaction, it's possible that
/// the new page is saved, but that the update of the old page fails.
/// If the underlying storage throws an exception at that point, that
/// exception will bubble up to the caller of the AppendAsync method.
/// It's up to the caller to retry the operation.
/// </para>
/// <para>
/// However, in that situation, an orphaned Atom feed page is likely to
/// have been left in the underlying storage. This doesn't affect
/// consistency of the system, but may take up unnecessary disk space.
/// If this is the case, a separate clean-up task should find and
/// delete orphaned pages.
/// </para>
/// </remarks>
/// <example>
/// This example shows how to create a UserCreated event and write it
/// using the AppendAsync method. Notice that since
/// AtomEventObserver<T> uses the standard Task Parallel Library
/// (TPL) model, you can use it with 'async' and 'await'.
/// <code>
/// var obs = new AtomEventObserver<IUserEvent>(
/// eventStreamId, // a Guid
/// pageSize, // an Int32
/// storage, // an IAtomEventStorage object
/// serializer); // an IContentSerializer object
///
/// var userCreated = new UserCreated
/// {
/// UserId = eventStreamId,
/// UserName = "******",
/// Password = "******",
/// Email = "*****@*****.**"
/// };
/// await obs.AppendAsync(userCreated);
/// </code>
/// </example>
/// <seealso cref="OnNext" />
public Task AppendAsync(T @event)
{
return(Task.Factory.StartNew(() =>
{
var now = DateTimeOffset.Now;
var index = this.ReadIndex();
var firstLink = index.Links
.Where(l => l.IsFirstLink)
.DefaultIfEmpty(AtomLink.CreateFirstLink(this.CreateNewFeedAddress()))
.Single();
var lastLink = index.Links.SingleOrDefault(l => l.IsLastLink);
var lastLinkChanged = false;
if (lastLink == null)
{
lastLink = firstLink.ToLastLink();
lastLinkChanged = true;
}
var lastPage = this.ReadLastPage(lastLink.Href);
if (lastPage.Links.Single(l => l.IsSelfLink).Href != lastLink.Href)
{
lastLink = lastPage.Links.Single(l => l.IsSelfLink).ToLastLink();
lastLinkChanged = true;
}
index = index.WithLinks(index.Links.Union(new[] { firstLink }));
index = index.WithLinks(index.Links
.Where(l => !l.IsLastLink)
.Concat(new[] { lastLink }));
var entry = CreateEntry(@event, now);
if (lastPage.Entries.Count() >= this.pageSize)
{
var nextAddress = this.CreateNewFeedAddress();
var nextPage = this.ReadPage(nextAddress);
nextPage = AddEntryTo(nextPage, entry, now);
var nextLink = AtomLink.CreateNextLink(nextAddress);
var previousPage = lastPage
.WithLinks(lastPage.Links.Concat(new[] { nextLink }));
var previousLink = previousPage.Links
.Single(l => l.IsSelfLink)
.ToPreviousLink();
nextPage = nextPage.WithLinks(
nextPage.Links.Concat(new[] { previousLink }));
index = index.WithLinks(index.Links
.Where(l => !l.IsLastLink)
.Concat(new[] { nextLink.ToLastLink() }));
this.Write(nextPage);
this.Write(previousPage);
this.Write(index);
}
else
{
lastPage = AddEntryTo(lastPage, entry, now);
this.Write(lastPage);
if (lastLinkChanged)
{
this.Write(index);
}
}
}));
}
public void ToViaLinkReturnsCorrectResult(
AtomLink sut)
{
Assert.NotEqual("via", sut.Rel);
AtomLink actual = sut.ToViaLink();
var expected = sut.WithRel("via");
Assert.Equal(expected, actual);
}
public void SutCanRoundTripToString(
AtomLink expected,
IContentSerializer dummySerializer)
{
var xml = expected.ToXmlString(dummySerializer);
AtomLink actual = AtomLink.Parse(xml);
Assert.Equal(expected, actual);
}
public void IsNextLinkReturnsFalsForNonNextLink(
AtomLink sut)
{
Assert.NotEqual("next", sut.Rel);
var actual = sut.IsNextLink;
Assert.False(actual, "Should not be next link.");
}
