siren-hs

siren-hs is a Haskell-first graph visualization library and executable for flowchart-style diagrams. The current implementation provides a foundational pipeline from a typed EDSL to SVG output using diagrams-svg.

Current status (Week 2 foundation)

The project now contains a working end-to-end baseline:

• A typed graph model (Node, Edge, Graph) in src/Siren/Types.hs
• A small EDSL for programmatic graph construction in src/Siren/EDSL.hs
• A Sugiyama-like layered layout pass in src/Siren/Layout.hs
• SVG rendering via diagrams / diagrams-svg in src/Siren/Render/SVG.hs
• Public library API in src/Siren.hs
• App-local sample graph module in app/Samples.hs
• Executable entry point that generates an SVG in app/Main.hs
• Baseline tests in test/Spec.hs

What it can do now

• Build flowchart graphs with node shapes: rectangle, rounded rectangle, diamond
• Add directed edges with optional labels
• Compute rank-based node layout (TopDown and LeftRight)
• Render valid SVG output through the diagrams-svg backend

Quick start

Build and test

stack test

Generate the sample SVG

stack run

This writes the example diagram to:

• output/sample.svg

Library usage

The top-level API is exported from Siren.

Key exported values/functions:

• writeGraphSvg :: FilePath -> Direction -> Graph -> IO ()

Sample/demo helpers (sampleGraph, writeSampleSvg) are intentionally kept in app/Samples.hs so they do not leak into the public library API.

Project workflow (stack + hpack)

This repository uses package.yaml as the source of truth.

• Edit dependencies/components in package.yaml
• Let Stack generate siren-hs.cabal automatically (stack build / stack test)
• Do not hand-edit generated siren-hs.cabal

Next steps

Planned next milestones include:

• Improving layout quality (crossing reduction and coordinate refinement)
• Expanding examples and test coverage
• Adding parser/CLI as stretch goals after core library stabilization