57 lines
2.5 KiB
Text
57 lines
2.5 KiB
Text
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pragma cashscript ^0.13.0;
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// Subscription — a prepaid balance the host can draw from once per period,
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// and the buyer can take back at any time.
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// (Argus/src/lib/plans.js SUBSCRIPTION_ROADMAP; ROADMAP-MAINNET.md §9 step 4.)
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//
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// STATUS: chipnet draft. NOT REVIEWED.
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//
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// The buyer funds this script. Three things then hold, and the buyer can check
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// each from the script alone:
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//
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// · the balance stays theirs — cancel() needs only their signature, no
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// notice, no cooperation, and returns whatever is left;
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// · the host cannot take more than one period's price per period — pull()
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// pays exactly the host's lock at least `priceSats`, sends the rest back to
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// this same script, and can only run on an output that is `periodBlocks`
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// old, which the re-created output is not;
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// · nobody else gains anything — pull() needs no signature, so the host does
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// not have to be online with a key, but its only possible beneficiary is
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// the host's lock.
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//
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// A pull spends this input ALONE. With two inputs, one "price to the host"
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// output and one "rest back to the script" output could satisfy both, and the
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// host would collect two balances for one payment. One input means the fee
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// comes out of the balance too, bounded by `maxFeeSats`.
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//
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// The first period is not special-cased: the balance is drawn one period
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// after it is funded. A host that wants payment up front takes the first
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// period in the funding transaction itself.
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contract Subscription(bytes20 buyerPkh, bytes hostLock, int priceSats, int periodBlocks, int maxFeeSats) {
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// One period's payment to the host.
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function pull() {
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require(this.age >= periodBlocks);
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require(tx.inputs.length == 1);
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int balance = tx.inputs[0].value;
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require(tx.outputs[0].lockingBytecode == hostLock);
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require(tx.outputs[0].value >= priceSats);
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require(tx.outputs[0].tokenCategory == 0x);
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// Everything else stays in the subscription, less a bounded fee. When
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// what would remain is too small to be an output, it is the fee.
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int rest = balance - priceSats - maxFeeSats;
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if (rest >= 546) {
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require(tx.outputs[1].lockingBytecode == tx.inputs[0].lockingBytecode);
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require(tx.outputs[1].value >= rest);
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require(tx.outputs[1].tokenCategory == 0x);
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}
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}
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// The buyer ends it and takes the balance. No conditions on where it goes.
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function cancel(pubkey pk, sig s) {
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require(hash160(pk) == buyerPkh);
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require(checkSig(s, pk));
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}
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}
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