Querying Valid Transitions

070_valid_transitions.cell

// ============================================================================
// 070 — Querying Valid Transitions
// ============================================================================
// valid_transitions() returns what states are reachable from the current one.
//
// Run:   soma run 070_valid_transitions.cell demo
// Expect:
//   From draft: ["review", "cancelled"]
//   From review: ["approved", "draft", "cancelled"]
//   From approved: ["published", "cancelled"]

cell TransitionQuery {

    memory {
        items: Map<String, String> [persistent, consistent]
        status: Map<String, String> [persistent, consistent]
    }

    state item_status {
        initial: draft

        draft -> review
        review -> approved
        review -> draft
        approved -> published
        published -> archived
        * -> cancelled
    }

    on create(name: String) {
        let id = to_string(next_id())
        items.set(id, name)
        status.set(id, "draft")
        return id
    }

    on demo() {
        create("Doc A")
        create("Doc B")
        create("Doc C")

        // Check valid transitions at each stage
        let t1 = valid_transitions("1")
        print("From draft: {t1}")

        transition("2", "review")
        let t2 = valid_transitions("2")
        print("From review: {t2}")

        transition("3", "review")
        transition("3", "approved")
        let t3 = valid_transitions("3")
        print("From approved: {t3}")

        return "done"
    }
}