// Product tracker: accumulates quantity and total cost from purchase events.
//
// Each step, a purchase of 3 units at price 7 arrives.
// The actor multiplies price * quantity to get the line cost,
// then adds it to the running total.
//
// After 4 steps:
//   count = 4 * 3 = 12
//   total = 4 * (7 * 3) = 84
//   emitted values: [21, 42, 63, 84]

actor ledger {
    state {
        count: u64 = 0
        total: u64 = 0
    }

    window summary : (count, total)
        readers(report)

    on Purchase(price: u64, qty: u64) {
        count = count + qty
        total = total + (price * qty)
    }
}

leaf buy {
    process {
        forward(ledger, Purchase(7, 3))
    }
}

leaf report {
    reads ledger.summary
    process {
        read(ledger.summary.total)
        emit(total)
    }
}

pipeline main {
    buy -> ledger -> report
}

core main {
    actors: [ledger]
    leaves: [buy, report]
    pipelines: [main]
    steps: 4
}