Add 'javadoc' inline macro extension

Closes gh-14

Co-authored-by: Rob Winch <[email protected]>

README.adoc

@@ -565,6 +565,101 @@ sectid-level-separator (default: .):: The character that must be used to separat
 
 All IDs must be lowercase, must start with an alphabetic character, and may only contain alphanumeric characters aside from the aforementioned separators.
 
+=== Javadoc
+
+*require name:* @springio/asciidoctor-extensions/javadoc-extension
+
+The javadoc extension allows you to quickly create links to javadoc sites.
+For example, `javadoc:com.example.MyClass[]` will create a link to `xref:attachment$api/java/com/example/MyClass.html` with the text `MyClass`.
+
+==== Syntax
+
+The following format can be used when declaring a javadoc link:
+
+----
+[<location>]<class-reference>[#<anchor>]
+----
+
+Only `<class-reference>` is mandatory, and it must be the fully qualified name of the class to link to.
+For example, `com.example.MyClass`.
+References to inner-classes should use `$` notation instead of `.`.
+For example, `com.example.MyClass$Builder`.
+
+If a `<location>` is specified, it must end with `/`.
+
+Any `<anchor>` must exactly match the anchor in the corresponding javadoc page.
+
+==== Locations
+
+Unless otherwise overridden, the default javadoc location will be `xref:attachment$api/java`.
+If you want a different default, you can set the `javadoc-location` document attribute.
+For example, you can set `javadoc-location` to `xref:api:java` if you publish javadoc under a `api` Antora module.
+
+NOTE: document attributes can be set in your Antora playback under the https://docs.antora.org/antora/latest/playbook/asciidoc-attributes/#attributes-key[attributes key].
+
+You can also override locations on a per-link basis.
+For example:
+
+[,asciidoc]
+----
+= Example
+:url-jdk-javadoc: https://docs.oracle.com/en/java/javase/17/docs/api
+
+Please read javadoc:{url-jdk-javadoc}/java.base/java.io.InputStream[]
+----
+
+==== Formats and Link Text
+
+By default, a short form of the class name is used as the link text.
+For example, if you link to `com.example.MyClass`, only `MyClass` is used for the link text.
+
+If you want to change the format of the link text, you can use the `format` attribute.
+For example, `javadoc:com.example.MyClass[format=full]` will use `com.example.MyClass` as the link text.
+
+The following formats are supported:
+
+[cols="1,1,3"]
+|===
+| Name | Description | Example
+
+| `short` (default)
+| The short class name
+| `com.example.MyClass$Builder` -> `MyClass.Builder`
+
+| `full`
+| The fully-qualified class name
+| `com.example.MyClass$Builder` -> `com.example.MyClass.Builder`
+
+| `annotation`
+| The short class name prefixed with `@`
+| `com.example.MyAnnotation` -> `@MyAnnotation`
+|===
+
+TIP: You can change the default format by setting a `javadoc-format` document attribute.
+This can be done site-wide, or on a page-by-page basis.
+
+You can also specify directly specify link text if the existing formats are not suitable:
+
+[,asciidoc]
+----
+See javadoc:com.example.MyClass$Builder[Builder] for details.
+----
+
+NOTE: The link text is _always_ wrapped in a `<code>` block so you should not use backticks.
+
+==== Anchors
+
+Anchors may be used to link to a specific part of a javadoc page.
+The anchor link must exactly match the link in the target page.
+For example, `javadoc:com.example.MyClass#myMethod(java.lang.String)`
+
+When an anchor is specified, the link text will include a readable version.
+The example above would render the link text `MyClass.myMethod(String)`.
+
+==== UI Support
+
+All anchors created using the `javadoc` macro will have a role of `apiref` to allow the UI to style them appropriately.
+
 ifndef::env-npm[]
 == Development Quickstart
 

lib/javadoc-extension.js

@@ -0,0 +1,95 @@
+'use strict'
+
+const toProc = require('./util/to-proc')
+
+const METHOD_REGEX = /(.*)\((.*)\)/
+
+function register (registry, context) {
+  if (!(registry && context)) return // NOTE only works as scoped extension for now
+  registry.$groups().$store('springio/javadoc', toProc(createExtensionGroup(context)))
+  return registry
+}
+
+function createExtensionGroup () {
+  return function () {
+    this.inlineMacro(function () {
+      this.named('javadoc')
+      this.process((parent, target, attrs) => {
+        const text = process(parent.getDocument(), parseTarget(target), attrs)
+        return this.createInline(parent, 'quoted', text, {
+          type: 'monospaced',
+        })
+      })
+    })
+  }
+}
+
+function parseTarget (target) {
+  target = target.replaceAll('…​', '...')
+  const lastSlash = target.lastIndexOf('/')
+  const location = lastSlash !== -1 ? target.substring(0, lastSlash) : undefined
+  const reference = lastSlash !== -1 ? target.substring(lastSlash + 1, target.length) : target
+  const lastHash = reference.lastIndexOf('#')
+  const classReference = lastHash !== -1 ? reference.substring(0, lastHash) : reference
+  const anchor = lastHash !== -1 ? reference.substring(lastHash + 1, reference.length) : undefined
+  return { location, classReference, anchor }
+}
+
+function process (document, target, attrs) {
+  const location = target.location || document.getAttribute('javadoc-location', 'xref:attachment$api/java')
+  const format = attrs.format || document.getAttribute('javadoc-format', 'short')
+  const linkLocation = link(location, target)
+  const linkDescription = applyFormat(target, format, attrs.$positional)
+  return `${linkLocation}['${linkDescription}',role=apiref]`
+}
+
+function link (location, target) {
+  let link = location
+  link = !link.endsWith('/') ? link + '/' : link
+  link += target.classReference.replaceAll('.', '/').replaceAll('$', '.') + '.html'
+  if (target.anchor) link += '#' + target.anchor
+  return link
+}
+
+function applyFormat (target, format, positionalAttrs, annotationAnchor) {
+  if (positionalAttrs?.[0]) return positionalAttrs?.[0]
+  switch (format) {
+    case 'full':
+      return className(target.classReference, 'full') + anchorText(target.anchor, format, annotationAnchor)
+    case 'annotation':
+      return '@' + className(target.classReference, 'short') + anchorText(target.anchor, format)
+    default:
+      return className(target.classReference, 'short') + anchorText(target.anchor, format)
+  }
+}
+
+function anchorText (anchor, format, annotationAnchor) {
+  if (!anchor) return ''
+  if (format === 'annotation' || annotationAnchor) anchor = anchor.replaceAll('()', '')
+  const methodMatch = METHOD_REGEX.exec(anchor)
+  if (methodMatch) {
+    return '.' + methodText(methodMatch[1], methodMatch[2], format)
+  }
+  return '.' + anchor
+}
+
+function methodText (name, params, format) {
+  const varargs = params.endsWith('...')
+  if (varargs) params = params.substring(0, params.length - 3)
+  return (
+    name +
+    '(' +
+    params
+      .split(',')
+      .map((name) => className(name, format))
+      .join(', ') +
+    (!varargs ? ')' : '...)')
+  )
+}
+
+function className (classReference, format) {
+  if (format !== 'full') classReference = classReference.split('.').slice(-1)[0]
+  return classReference.replaceAll('$', '.')
+}
+
+module.exports = { register, createExtensionGroup }

package.json

@@ -42,6 +42,7 @@
     "./code-folding-extension": "./lib/code-folding-extension.js",
     "./configuration-properties-extension": "./lib/configuration-properties-extension.js",
     "./include-code-extension": "./lib/include-code-extension.js",
+    "./javadoc-extension": "./lib/javadoc-extension.js",
     "./section-ids-extension": "./lib/section-ids-extension.js"
   },
   "imports": {