Battle pass — every tier reward claimed exactly once

battle_pass.cell

// ============================================================================
// BATTLE PASS — every tier reward claimed exactly once
// ============================================================================
// Battle-pass duplication exploits reduce to two writes: a claim counter
// going past 1 (claim, crash the client mid-grant, claim again — the
// "crash-and-reclaim" farmed in several seasons of big battle royales), or
// tier progress jumping the track via a modified client. Here each
// (player, tier) claim is walled at <= 1 BY THE MEMORY, tier progress is
// capped at 50 by an invariant, and the season itself is a machine whose
// `closed` state is terminal — soma verify proves that when a season ends,
// the books are shut for good.
// ============================================================================

cell BattlePass {
    face {
        signal open_pass() -> Map
        signal close_pass() -> Map
        signal advance_tier(player: String) -> Map
        signal claim_tier(player: String, tier_n: Int) -> Map
        signal tier_of(player: String) -> Int
    }

    memory {
        tier: Map<String, Int> [persistent, consistent]
        invariant tier >= 0 && tier <= 50
        claims: Map<String, Int> [persistent, consistent]
        invariant claims >= 0 && claims <= 1
    }

    state pass {
        initial: dormant
        dormant -> live
        live -> closed
    }

    on open_pass() {
        let r = try { transition("pass", "live") }
        if r.error != () { return map("ok", false, "reason", "{r.error}") }
        return map("ok", true)
    }

    on close_pass() {
        let r = try { transition("pass", "closed") }
        if r.error != () { return map("ok", false, "reason", "{r.error}") }
        return map("ok", true)
    }

    on advance_tier(player: String) {
        if get_status("pass") != "live" { return map("ok", false, "reason", "pass is not live") }
        let w = try { tier.set(player, (tier.get(player) ?? 0) + 1) }
        if w.error != () { return map("ok", false, "reason", "already at tier 50") }
        return map("ok", true, "tier", tier.get(player))
    }

    on claim_tier(player: String, tier_n: Int) {
        if get_status("pass") != "live" { return map("ok", false, "reason", "pass is not live") }
        if (tier.get(player) ?? 0) < tier_n { return map("ok", false, "reason", "tier {tier_n} not reached") }
        let key = "{player}#{tier_n}"
        // THE WALL: a second claim writes 2 into a <= 1 slot — refused
        let w = try { claims.set(key, (claims.get(key) ?? 0) + 1) }
        if w.error != () { return map("ok", false, "reason", "tier {tier_n} already claimed") }
        return map("ok", true, "claimed", tier_n)
    }

    on tier_of(player: String) { return tier.get(player) ?? 0 }
}

cell test PassTests {
    rules {
        // nothing moves before the season opens
        assert advance_tier("vic").ok == false
        assert open_pass().ok == true
        assert advance_tier("vic").ok == true
        assert advance_tier("vic").ok == true
        assert tier_of("vic") == 2
        // cannot claim a tier you have not reached
        assert claim_tier("vic", 3).ok == false
        assert claim_tier("vic", 2).ok == true
        // THE CRASH-AND-RECLAIM: the second claim is an unstorable write
        assert claim_tier("vic", 2).ok == false
        assert_fails claims.set("vic#2", 2)
        // tier progress cannot be injected past the cap
        assert_fails tier.set("vic", 51)
        // a closed season is closed forever
        assert close_pass().ok == true
        assert claim_tier("vic", 1).ok == false
        assert advance_tier("vic").ok == false
        assert_fails transition("pass", "live")
        assert_fails transition("pass", "dormant")
    }
}