$ show jgm/pandoc
Pandoc is a universal document converter written in Haskell. It reads input in dozens of formats (Markdown, LaTeX, HTML, docx, EPUB, Org, RST, MediaWiki, etc.) into a common abstract syntax tree (AST), then writes to a wide range of output formats. The system is modular: readers parse source formats, writers produce target formats, and a template system controls output structure. It includes an integrated citation processor (citeproc), a Lua scripting engine for custom readers/writers/filters, and a server mode (HTTP API). The codebase is a monolith library with separate CLI, server, and Lua engine packages, plus a WebAssembly build for browser use. It is heavily tested with golden tests and property tests. The architecture demonstrates strong separation of concerns, with reusable parsing utilities, a well-defined AST, and a flexible extension mechanism via Lua. While the codebase is large and complex, it is actively maintained and exhibits high craftsmanship in its modular design and handling of diverse formats.
The LLM identified 6 files worth highlighting for reuse:
A generic CSV/TSV parser parameterized by options (delimiter, quoting, etc.). It is self-contained, uses Parsec, and can be extracted for use in any Haskell project needing CSV parsing. Demonstrates clean separation of parsing logic from Pandoc-specific concerns.
Provides a sandboxed execution environment that lifts PandocPure computations into any PandocMonad while preserving state. This is a non-obvious pattern for safely running pure transformations in an IO context, reusable for any project using the PandocMonad typeclass.
Implements a Future monad (Reader monad) that delays evaluation until parser state is complete. This is a clever pattern for handling forward references in parsing (e.g., citations, labels). It is self-contained and could be reused in other parsing contexts.
Provides URI escaping, IANA scheme validation, and a base64 data URI parser. It is a self-contained utility module that can be reused in any Haskell project needing robust URI handling. Demonstrates thoroughness with scheme sets and proper escaping.
Implements a grid-based table representation using STArray for mutable cell assignments. It decouples table structure from output and handles complex layouts (row/col spans, alignment). This is a non-trivial data structure that could be extracted for any project needing grid table manipulation.
Provides type-safe push/peek operations for Pandoc's Context type in Lua. Part of a larger marshalling framework that demonstrates a clean pattern for exposing Haskell types to Lua. The module is self-contained and the pattern is reusable for any Haskell-Lua binding.