Handle YAML front matter | hr

Signed-off-by: George Lemon <georgelemon@protonmail.com>

Author: georgelemon

README.md

@@ -17,11 +17,11 @@
 
 ## 😍 Key Features
 - [x] Extremely Fast & Lightweight! [Check benchmarks](#benchmarks)
-- [x] Compiled CLI application
+- [x] Compiled cross-platform CLI app
 - [x] Nim library for easy integration in your 👑 Nim projects
 - [x] Addon for Node.js JavaScript runtime via N-API
 - [x] Markdown to HTML
-  - [ ] Auto-generate Table of Contents (ToC)
+  - [x] Auto-generate Table of Contents (ToC)
   - [x] Auto-generate heading IDs for anchor links
 - [ ] Markdown to PDF
 - [ ] Markdown to JSON (structured data)

marvdown.nimble

@@ -15,6 +15,7 @@ requires "nim >= 2.0.0"
 requires "kapsis#head"
 requires "denim#head"
 requires "jsony#head"
+requires "nyml#head"
 
 task napi, "Build Marvdown as a Node.js addon using N-API":
   exec "denim build src/marvdown.nim --cmake -y"

src/marvdown/lexer.nim

@@ -197,8 +197,25 @@ proc nextToken*(lex: var MarkdownLexer): MarkdownTokenTuple =
       lex.advance()
 
     if count >= 3 and (lex.current == '\n' or lex.current == '\0'):
-      # Horizontal rule
-      return newTokenTuple(lex, mtkHorizontalRule, repeat(ch, count), wsno=lex.wsno)
+      # Horizontal rule, or the begining of a YAML front matter
+      if lex.line == 1:
+        # YAML front matter detected
+        lex.strbuf.setLen(0)
+        while true:
+          if lex.current == '\0':
+            break
+          if lex.current == '-' and lex.peek() == '-' and lex.peek(2) == '-':
+            # End of front matter
+            lex.advance(); lex.advance(); lex.advance()
+            if lex.current in {'\n', '\r'}:
+              lex.advance()
+            break
+          lex.strbuf.add(lex.current)
+          lex.advance()
+        let frontMatter = lex.strbuf.strip()
+        return newTokenTuple(lex, mtkDocument, frontMatter, wsno=lex.wsno)
+      else:
+        return newTokenTuple(lex, mtkHorizontalRule, repeat(ch, count), wsno=lex.wsno)
 
     if (ch in {'-', '*', '+'}) and (lex.current == ' ' or lex.current == '\t'):
       # Unordered list item

src/marvdown/parser.nim

@@ -11,7 +11,7 @@ import htmlparser {.all.}
 export HtmlTag
 
 import ./lexer, ./ast
-import pkg/jsony
+import pkg/[jsony, nyml]
 
 type
   MarkdownParser* = object
@@ -32,6 +32,8 @@ type
       ## Internal: Counter for generating unique selectors
     ast*: seq[MarkdownNode]
       ## The abstract syntax tree (AST) of the parsed markdown document
+    headerYaml: JsonNode
+      ## Parsed YAML front matter as JsonNode
     footnotes: OrderedTableRef[string, MarkdownNode]
       ## Footnote definitions parsed from the document
     footnotesHtml*: string
@@ -655,6 +657,28 @@ proc parseMarkdown(md: var Markdown, currentParagraph: var MarkdownNode) =
       closeCurrentParagraph()
       let bqNode = md.parseBlockquote()
       md.ast.add(bqNode)
+    of mtkHorizontalRule:
+      closeCurrentParagraph()
+      md.ast.add(MarkdownNode(
+        kind: mdkHorizontalRule,
+        line: curr.line,
+        wsno: curr.wsno
+      ))
+      md.advance()
+    of mtkDocument:
+      try:
+        # Parse YAML front matter
+        # TODO test YAML parsing (https://github.com/openpeeps/nyml)
+        md.headerYaml = fromYaml(curr.token, JsonNode)
+      except YAMLException as e:
+        # On error, add a text node with the error message
+        md.ast.add(MarkdownNode(
+          kind: mdkText,
+          text: curr.token, # invalid YAML, just add as text
+          line: curr.line,
+          wsno: curr.wsno
+        ))
+      md.advance()
     of mtkFootnoteRef:
       withCurrentParagraph do:
         let id = curr.attrs.get()[0]
@@ -673,7 +697,6 @@ proc parseMarkdown(md: var Markdown, currentParagraph: var MarkdownNode) =
       md.advance()
     else:
       closeCurrentParagraph()
-      md.advance()
 
 proc newMarkdown*(content: sink string,
           opts: MarkdownOptions = defaultOptions): Markdown =
@@ -712,6 +735,10 @@ proc hasSelectors*(md: Markdown): bool =
   ## Check if there are any headline selectors (anchors) in the parsed Markdown
   md.selectors != nil and md.selectors.len > 0
 
+proc getHeader*(md: Markdown): JsonNode =
+  ## Get the parsed YAML front matter from the Markdown
+  md.headerYaml
+
 proc getFootnotes*(md: Markdown): OrderedTableRef[string, MarkdownNode] =
   ## Get the footnote definitions from the parsed Markdown
   md.footnotes
@@ -867,5 +894,7 @@ proc renderNode(md: var Markdown, node: MarkdownNode): string =
         fnContent
       )
     )
+  of mdkHorizontalRule: result = "<hr>"
   else:
-    discard
+    echo node.kind
+    echo "Warning: Unhandled MarkdownNode kind in renderNode"