# Docster — Project Guide

Docster is a Haskell CLI tool: Markdown + embedded Mermaid diagrams → PDF, HTML, or DOCX.

## Quick Commands

```bash
stack build          # build
stack test           # run tests
stack exec docster -- -pdf file.md   # convert to PDF
stack exec docster -- -html file.md  # convert to HTML
stack exec docster -- -docx file.md  # convert to DOCX
stack exec docster -- -pdf sample.md # test with a single file
stack clean          # clean build artifacts
```

## Structure

```
docster.cabal        # package definition
stack.yaml           # GHC 9.12.2, lts-24.34
app/Main.hs          # everything — entry point + all logic (~70 lines)
test/                # HSpec tests (TransformSpec.hs)
```

## How It Works

1. Parse Markdown via Pandoc AST
2. Walk the AST, find Mermaid code blocks
3. Run `mmdc` (mermaid-cli) to render each block → SVG (for HTML) or high-res PNG (for PDF)
4. Replace code blocks with image references in the AST
5. Compile final output via Pandoc (LaTeX/XeLaTeX for PDF, native for HTML/DOCX)

Key functions in `Main.hs`:
- `transformDoc` — AST walker
- `processMermaidBlock` — calls `mmdc`, returns image reference
- `compileToPDF` / `compileToHTML` / `compileToDOCX` — final Pandoc compilation

## Dependencies

**System**: TeX Live (for PDF), `npm install -g @mermaid-js/mermaid-cli`
**Haskell**: Pandoc library, Stack manages GHC automatically

## Common Gotchas

- **Text vs String**: Codebase mixes `Data.Text` and `String`. Use `T.pack`/`T.unpack` for conversions.
- **PDF needs LaTeX**: BasicTeX/TinyTeX + `tlmgr` for missing packages.
- **mmdc in PATH**: `mermaid-cli` must be globally installed and on PATH.