Package io.virtdata.docsys.metafs.fs.renderfs.api.versioning

Interface Versioned

All Known Subinterfaces:

Renderable, RenderedContent<T>, Renderer, TemplateView

All Known Implementing Classes:

CachedContent, ExceptionContent, FileTopicsView, FlatTopicsView, HeaderTopicsView, HTMLRenderedException, MarkdownRenderedException, MarkdownRenderer, MustacheRenderer, RenderingScope, SourcePathTemplate, VersionData, VersionedDirectory, VersionedPath, ViewModel

public interface Versioned

Versions on elements are merely observable ways of asking for when they were made. Version comparisons between elements are used to determine if one element is possibly out of sync with other elements.

Elements can have multiple parts internally which each have their own version. In this case, each element is tracked independently, and the version of the whole set of internal parts is taken as the oldest or most conservative value. The concept of part is abstract here. It is merely a way of allowing a logical element to derive its intrinsic version directly from the provided parts when possible.

Elements can have an dependency on other elements which, when compared against, determine whether the element is stale, or invalid after the dependent elements have changed.

A versioned element is taken to be valid or not stale if and only if the highest version of dependencies is equal to or less than the lowest value of all versioned parts.

The value of a version in this implementation is assumed to be epoch milliseconds.

Getting version data is a deferred call via closure in every case. The caller has to determine whether to provide a lambda to a static value, or to delegate to a way to read a current value when the version is needed. This allows for an interesting and simplifying usage pattern for delegating version reads:

At the time an element is created from its dependencies, the versions of those dependencies at that time are read to determine the vintage of the new element. This is a dynamic read of a property which is stored statically in the element instance.

Method Summary

Modifier and Type	Method	Description
long	getVersion()	The version of an element can depend on more than one property internally.
boolean	isValid()	If all the versioned parts of this elements are equal or higher version than all of the dependencies, then this element is valid.

Method Detail

getVersion

long getVersion()

The version of an element can depend on more than one property internally. Informally, the version of an element is the the lowest value of all the version properties of that element. This is a conservative back reference to the oldest contributing piece of data for that element, such that invalidation occurs based on the possibility that versions are not in sync, rather than any specific proof that they aren't.

Returns:

The version of the oldest part of a versioned element.

isValid

boolean isValid()

If all the versioned parts of this elements are equal or higher version than all of the dependencies, then this element is valid. Said differently, if the highest version of all dependencies is equal to or lower than the lowest version of all the parts, then this element is valid.

Returns:

true, if this element is valid with respect to dependencies.