mechanoid · v0.3.2

Document Workflow

Hierarchical states keep review and approval phases readable. Nested sealed traits group leaves; all[T] applies one transition to every leaf under a parent; fragments compose with ++.

Teaching slice of examples/.../hierarchical. The machine used by every example on this page:

sealed trait DocumentState derives Finite
case object Draft extends DocumentState
sealed trait InReview extends DocumentState derives Finite
case object PendingReview extends InReview
case object UnderReview extends InReview
case object ChangesRequested extends InReview
sealed trait Approval extends DocumentState derives Finite
case object PendingApproval extends Approval
case object Rejected extends Approval
case object Published extends DocumentState
case object Archived extends DocumentState
case object Cancelled extends DocumentState

enum DocumentEvent derives Finite:
  case SubmitForReview, AssignReviewer, RequestChanges, ResubmitAfterChanges
  case ApproveReview, ApprovePublication, RejectPublication, Archive
  case CancelReview, Abandon

val machine = Machine(
  assembly[DocumentState, DocumentEvent](
    all[InReview] via CancelReview to Draft,
    all[Approval] via Abandon to Cancelled,
  ) ++ assembly[DocumentState, DocumentEvent](
    Draft via SubmitForReview to PendingReview,
    PendingReview via AssignReviewer to UnderReview,
    UnderReview via RequestChanges to ChangesRequested,
    UnderReview via ApproveReview to PendingApproval,
    ChangesRequested via ResubmitAfterChanges to PendingReview,
    PendingApproval via ApprovePublication to Published,
    PendingApproval via RejectPublication to Rejected,
    Rejected via SubmitForReview to PendingReview,
    Published via Archive to Archived,
  )
)

The graph

Mermoid.diagram(
  MermaidVisualizer.flowchart(machine),
  DocsDiagrams.diagramConfig,
)
CancelReviewCancelReviewCancelReviewAbandonAbandonSubmitForReviewAssignReviewerRequestChangesApproveReviewResubmitAfterChangesApprovePublicationRejectPublicationSubmitForReviewArchive

Look for the group edges: every InReview leaf can CancelReview back to Draft, and every Approval leaf can Abandon to Cancelled.

Publish path

Draft → review → approval → Published:

ZIO.scoped {
  for
    fsm   <- machine.start(Draft)
    _     <- fsm.send(SubmitForReview)
    _     <- fsm.send(AssignReviewer)
    _     <- fsm.send(ApproveReview)
    _     <- fsm.send(ApprovePublication)
    state <- fsm.currentState
  yield state
}.asDoc
Published

Cancel from any review leaf

all[InReview] via CancelReview to Draft means UnderReview cancels the same way PendingReview would:

ZIO.scoped {
  for
    fsm   <- machine.start(Draft)
    _     <- fsm.send(SubmitForReview)
    _     <- fsm.send(AssignReviewer)
    _     <- fsm.send(CancelReview)
    state <- fsm.currentState
  yield state
}.asDoc
Draft

Next: Heartbeat for producing + timeouts, or Defining FSMs for @@ Aspect.overriding.