nim-markdown

The markdown function allows you to manipulate the resulting Abstract Syntax Tree (AST) instead of just receiving a rendered string.

1. Initialize a custom root: Create a Document() object and pass it to the markdown function using the root= argument.
2. Modify the tree: Once markdown(input, root=root) is called, the root object is populated with the parsed nodes. You can manually append new nodes (like Paragraph, Em, or Text) to the tree using appendChild().
3. Render the modified tree: Use the render(root) function to convert your modified AST into an HTML string.

let root = Document()
discard markdown("# Hello World\nTest.", root=root)

# Manually add nodes to the AST
let p = Paragraph(loose: true)
let em = Em()
let text = Text(doc: "emphasis text.")
em.appendChild(text)
p.appendChild(em)
root.appendChild(p)

# Render the modified tree
echo render(root)

You can extend Nim-markdown by implementing new parsing rules. To do this, you must:

1. Define a new parser type that inherits from Parser.
2. Define a new token type that inherits from Block (for block-level parsing) or Inline (for inline-level parsing).
3. Register the parser by inserting it into MarkdownConfig.blockParsers or MarkdownConfig.inlineParsers. To ensure it takes precedence, use insert(parser, 0) to place it at the beginning of the parser list.
4. Implement the parse method on your parser to define how it identifies tokens in the source string.
5. Implement the $ (render) method on your token to define how it should be converted to HTML.

Note: APIs are subject to change before v1.0.0.

import markdown, strutils, sequtils, strscans, system, os

# 1. Define Parser
type IncludeParser = ref object of Parser

# 2. Define Token
type IncludeToken = ref object of Block
    path: string

# 3. Register Parser
var c = initCommonmarkConfig()
c.blockParsers.insert(IncludeParser(), 0)

# 4. Implement parse
method parse(parser: IncludeParser, doc: string, start: int): ParseResult {.locks: "unknown".} = 
  # ... implementation logic ...
  ParseResult(token: IncludeToken(path: path), pos: idx)

# 5. Implement render
method `$`(token: IncludeToken): string = 
  markdown(token.path.readFile, c)

# Usage
let md = "#include \"hello.md\""
echo(markdown(md, c))