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= Processing Markdown

Groovy has an optional `groovy-markdown` module which provides support for
parsing https://commonmark.org/[CommonMark] Markdown. The classes are found
in the `groovy.markdown` package.

[[markdown_markdownslurper]]
== MarkdownSlurper

`MarkdownSlurper` parses Markdown text into a `MarkdownDocument` backed by
nested lists and maps. Each node is a `Map` with a `type` key plus
type-specific fields:

[source,groovy]
----
include::../test/groovy/markdown/MarkdownSlurperTest.groovy[tags=parse_heading,indent=0]
----

The raw structure supports all standard Groovy list/map operations. The
document also exposes convenience properties — `headings`, `codeBlocks`,
`links`, `tables` — that recursively walk the tree.

=== Extracting code blocks

A common pattern when consuming LLM output is to pull fenced code blocks
by language:

[source,groovy]
----
include::../test/groovy/markdown/MarkdownSlurperTest.groovy[tags=code_blocks,indent=0]
----

`codeBlocks` walks the entire tree, so blocks nested inside block quotes
or list items are included.

=== Links

[source,groovy]
----
include::../test/groovy/markdown/MarkdownSlurperTest.groovy[tags=links,indent=0]
----

=== Sections

`section(headingText)` returns the nodes between the given heading and the
next heading of equal or higher level — useful for parsing structured
agent replies:

[source,groovy]
----
include::../test/groovy/markdown/MarkdownSlurperTest.groovy[tags=section,indent=0]
----

=== Tables (optional)

GFM-style tables are supported when the
`org.commonmark:commonmark-ext-gfm-tables` jar is on the classpath. Call
`enableTables(true)` on the slurper:

[source,groovy]
----
include::../test/groovy/markdown/MarkdownSlurperTest.groovy[tags=tables,indent=0]
----

Each row is returned as a `Map` keyed by header.

=== Node types

[cols="1,3"]
|===
| type | fields

| `heading` | `level`, `text`, `children`
| `paragraph` | `children`
| `code_block` | `lang`, `text`
| `list` | `ordered`, `items` (`start` for ordered lists)
| `list_item` | `text`, `children`
| `block_quote` | `children`
| `link` | `href`, `title`, `text`, `children`
| `image` | `src`, `title`, `alt`
| `text` | `value`
| `inline_code` | `text`
| `emphasis`, `strong` | `children`
| `html_block`, `html_inline` | `text`
| `thematic_break` | (no fields)
| `hard_line_break`, `soft_line_break` | (no fields)
| `table` | `headers`, `alignments`, `rows`
|===

=== Untrusted input

Prefer parsing Markdown from trusted sources. Like the sibling `JsonSlurper`
and `XmlSlurper`, `MarkdownSlurper` is a convenience parser, not a security
boundary, so the safest choice is not to hand it attacker-controlled input. If
you must, bound the input by size yourself before parsing and treat the parsed
result defensively.

As a backstop, `MarkdownSlurper` caps how deeply a document may nest (both block
containers and inline emphasis), so that a small but pathologically nested input
-- thousands of nested block quotes, or a long run of emphasis markers -- is
reported as a `MarkdownRuntimeException` rather than being allowed to exhaust
the stack with a `StackOverflowError`. The limit defaults to `1000` and can be
set per instance or globally via the `groovy.markdown.maxNestingDepth` system
property; a value of `0` or less disables the check.

[source,groovy]
----
include::../test/groovy/markdown/MarkdownSlurperTest.groovy[tags=nesting_depth,indent=0]
----

This cap is a robustness backstop, not a licence to treat the parser as hardened.
