Campaign finance — the contribution limit lives in the ledger, not the law

campaign_finance.cell

// ============================================================================
// CAMPAIGN FINANCE — the contribution limit lives in the ledger, not the law
// ============================================================================
// In 2014 Dinesh D'Souza was convicted for funneling money past the federal
// per-donor limit through straw donors he reimbursed. Straw schemes work
// because the limit is checked at filing time, months after the money moved.
// Here the per-donor cap ($2,900, the 2022-cycle federal limit) is a memory
// invariant: the cumulative-total write for any donor name above the cap is
// refused at the instant of donation. The reporting lifecycle is one-way —
// once the committee files, `reported` is terminal: soma verify proves the
// books cannot be re-opened to massage totals.
// ============================================================================

cell Committee {
    face {
        signal open_books() -> Map
        signal contribute(donor: String, amount: Int) -> Map
        signal close_books() -> Map
        signal file_report() -> Map
        signal donor_total(donor: String) -> Int
        signal raised_total() -> Int
        signal phase() -> String
    }

    memory {
        // donor -> cumulative dollars this cycle. $2,901 is unrepresentable.
        donated: Map<String, Int> [persistent, consistent]
        invariant donated >= 0 && donated <= 2900
    }

    // reported is terminal: filed books are filed forever.
    state cycle {
        initial: registered
        registered -> raising
        raising -> closed
        closed -> reported
    }

    on phase() { return get_status("cycle") }

    on open_books() {
        let r = try { transition("cycle", "raising") }
        if r.error != () { return map("ok", false, "reason", "{r.error}") }
        return map("ok", true)
    }

    on contribute(donor: String, amount: Int) {
        if phase() != "raising" {
            return map("ok", false, "reason", "books are {phase()}")
        }
        if amount <= 0 { return map("ok", false, "reason", "amount must be positive") }
        let sofar = donated.get(donor) ?? 0
        // THE WALL: past $2,900 the ledger refuses, at donation time,
        // not at filing time.
        let w = try { donated.set(donor, sofar + amount) }
        if w.error != () {
            return map("ok", false, "reason",
                "limit: {donor} at {sofar}, +{amount} exceeds 2900")
        }
        return map("ok", true, "donor", donor, "total", sofar + amount)
    }

    on close_books() {
        let r = try { transition("cycle", "closed") }
        if r.error != () { return map("ok", false, "reason", "{r.error}") }
        return map("ok", true, "raised", raised_total())
    }

    on file_report() {
        let r = try { transition("cycle", "reported") }
        if r.error != () { return map("ok", false, "reason", "{r.error}") }
        return map("ok", true, "raised", raised_total())
    }

    on donor_total(donor: String) { return donated.get(donor) ?? 0 }

    on raised_total() {
        let names = donated.keys()
        let n = 0
        for d in names { n = n + (donated.get(d) ?? 0) }
        return n
    }
}

cell test CommitteeTests {
    rules {
        assert contribute("ada", 100).ok == false         // books not open yet
        assert open_books().ok == true
        assert contribute("ada", 2000).ok == true
        assert contribute("ada", 1000).ok == false        // 3000 > 2900: refused
        assert donor_total("ada") == 2000                 // ledger untouched
        assert contribute("ada", 900).ok == true          // exactly the cap: fine
        assert donor_total("ada") == 2900
        assert contribute("ada", 1).ok == false           // one dollar over: never
        assert_fails donated.set("ada", 2901)               // unrepresentable
        assert_fails donated.set("bob", -10)                // no laundering negatives
        assert contribute("bob", 500).ok == true
        assert raised_total() == 3400
        assert close_books().ok == true
        assert contribute("late", 5).ok == false          // books are closed
        assert file_report().ok == true
        assert_fails transition("cycle", "raising")       // filed is forever
        assert_fails transition("cycle", "closed")
    }
}