Statifier

A W3C SCXML-conformant statecharts engine for Elixir. Ground-up rewrite of statifier v1.x.

Status: pre-alpha. The architecture is settled (see docs/architecture.md and docs/adr/); the engine is being built against the SCION and W3C conformance corpora from day one.

Why a rewrite

v1 works, but its interpreter re-derived the SCXML semantics instead of porting the spec's algorithm, and the divergences account for nearly all of its remaining conformance failures. v2 is:

• a literal port of W3C SCXML Appendix D - same functions, same names
• a pure functional core returning effects - one semantics for every API, sessions and timers layered on top
• predicator as the datamodel - safe, non-evaluative expressions; no ECMAScript, no eval
• built corpus-first - 186+ SCION/W3C conformance tests and a forward-only regression ratchet inherited from v1, with the generator committed this time

Installation

Statifier v2 is not on Hex yet, and will not be before 2.0.0 - no alpha, beta, or release-candidate versions along the way. Until then, depend on a commit reachable from main:

{:statifier, github: "riddler/statifier-ex", ref: "<sha>"}

What a pin gives you (the full contract is ADR-0061):

• Pin only commits reachable from main. Every one of them has passed the full quality gate - the same gate CI runs on the default branch. A branch tip is covered by nothing.
• Between two pins, any public API and any observable behavior may change without deprecation, notice period, or compatibility shim. 2.0.0-dev is one moving version. There are no tags before 2.0.0; the pin is the SHA.
• What will never break silently: persisted position and recording blobs refuse with a typed error on a format-version or chart-identity mismatch rather than misreading; API shape changes fail your compile.
• How to see what changed: git diff <old-sha>..<new-sha> -- changelog.d/ CHANGELOG.md lists every user-visible difference between two pins.

Development

mix deps.get
mix quality --profile loop   # fast inner loop
mix quality                  # full gate (required green before commit)

Issue tracking is beads (bd ready to find work). Workflow, model roles, and worktree conventions: docs/workflow.md. Registering your own <invoke> handlers: docs/extending.md. Scheduling delayed sends durably, outside the session process: docs/durable-timers.md. Testing your own charts: docs/testing-charts.md. Chart patterns for external-resource verdicts (park/retry, fail-fast): docs/chart-patterns.md.

License

MIT - see LICENSE.