Bytom储蓄分红合约解析

储蓄分红合约简介
储蓄分红合约指的是项目方发起了一个锁仓计划（即储蓄合约和取现合约），用户可以在准备期自由选择锁仓金额参与该计划，等到锁仓到期之后还可以自动获取锁仓的利润。用户可以在准备期内（dueBlockHeight）参与储蓄，按照合约规定可以 1：1 获取同等数量的储蓄票据资产，同时用户锁仓的资产（deposit）将放到取现合约中，并且项目方是无法动用的，等到锁仓期限（expireBlockHeight）一到，用户便可以调用取现合约将自己储蓄的资产连本待息一同取出来。其示意图如下:

从上图中可以看出，项目方发布了一个利润为 20% 的锁仓项目，其中储蓄合约 FixedLimitCollect 锁定了 1000 个票据资产（bill），同时项目方将 200 个储蓄资产（deposit）锁定到利息合约中。待项目方发布完合约之后，所有用户便可以参与了。例如上图中 user1 调用合约储蓄了 500，这 500 个储蓄资产将被锁定在取现合约 FixedLimitProfit 中，同时 user1 获得了 500 个票据资产，剩余找零的资产将继续锁定在储蓄合约 FixedLimitCollect 中，以此类推，user2 和 user3 也是相同的流程，直到储蓄合约没有资产为止。取现合约 FixedLimitProfit 跟储蓄合约的模型大致相同，只是取现合约是由多个 UTXO 组成的，用户在取现的时候可以并行操作。但是如果合约中的面值不能支持用户一次性取现的话，需要分多次提取。例如 user1 拥有 500 个票据资产，而可以获得的本息总额为 600，但是取现的 UTXO 面值为 500, 那么 user1 一次最多只能取 500, 剩下的 100 需要再构造一笔交易来提现。
合约源代码
// 储蓄合约
import “./FixedLimitProfit”
contract FixedLimitCollect(assetDeposited: Asset,
totalAmountBill: Amount,
totalAmountCapital: Amount,
dueBlockHeight: Integer,
expireBlockHeight: Integer,
additionalBlockHeight: Integer,
banker: Program,
bankerKey: PublicKey) locks billAmount of billAsset {
clause collect(amountDeposited: Amount, saver: Program) {
verify below(dueBlockHeight)
verify amountDeposited <= billAmount && totalAmountBill <= totalAmountCapital
define sAmountDeposited: Integer = amountDeposited/100000000
define sTotalAmountBill: Integer = totalAmountBill/100000000
verify sAmountDeposited > 0 && sTotalAmountBill > 0
if amountDeposited < billAmount {
lock amountDeposited of assetDeposited with FixedLimitProfit(billAsset, totalAmountBill, totalAmountCapital, expireBlockHeight, additionalBlockHeight, banker, bankerKey)
lock amountDeposited of billAsset with saver
lock billAmount-amountDeposited of billAsset with FixedLimitCollect(assetDeposited, totalAmountBill, totalAmountCapital, dueBlockHeight, expireBlockHeight, additionalBlockHeight, banker, bankerKey)
} else {
lock amountDeposited of assetDeposited with FixedLimitProfit(billAsset, totalAmountBill, totalAmountCapital, expireBlockHeight, additionalBlockHeight, banker, bankerKey)
lock billAmount of billAsset with saver
}
}
clause cancel(bankerSig: Signature) {
verify above(dueBlockHeight)
verify checkTxSig(bankerKey, bankerSig)
unlock billAmount of billAsset
}
}
// 取现合约 (本金加利息)
contract FixedLimitProfit(assetBill: Asset,
totalAmountBill: Amount,
totalAmountCapital: Amount,
expireBlockHeight: Integer,
additionalBlockHeight: Integer,
banker: Program,
bankerKey: PublicKey) locks capitalAmount of capitalAsset {
clause profit(amountBill: Amount, saver: Program) {
verify above(expireBlockHeight)
define sAmountBill: Integer = amountBill/100000000
define sTotalAmountBill: Integer = totalAmountBill/100000000
verify sAmountBill > 0 && sTotalAmountBill > 0 && amountBill < totalAmountBill
define gain: Integer = totalAmountCapital*sAmountBill/sTotalAmountBill
verify gain > 0 && gain <= capitalAmount
if gain < capitalAmount {
lock amountBill of assetBill with banker
lock gain of capitalAsset with saver
lock capitalAmount – gain of capitalAsset with FixedLimitProfit(assetBill, totalAmountBill, totalAmountCapital, expireBlockHeight, additionalBlockHeight, banker, bankerKey)
} else {
lock amountBill of assetBill with banker
lock capitalAmount of capitalAsset with saver
}
}
clause cancel(bankerSig: Signature) {
verify above(additionalBlockHeight)
verify checkTxSig(bankerKey, bankerSig)
unlock capitalAmount of capitalAsset
}
}
合约的源代码说明可以具体参考 Equity 合约介绍.
注意事项：

时间期限不是具体的时间，而是通过区块高度来大概估算的（平均区块时间间隔大概为 2.5 分钟）
比原的精度是 8, 即 1BTM = 100000000 neu，正常情况下参与计算都是以 neu 为单位的，然而虚拟机的 int64 类型的最大值是 9223372036854775807，为了避免数值太大导致计算溢出，所以对计算的金额提出了金额限制（即 amountBill/100000000）
另外 clause cancel 是项目方的管理方法，如果储蓄或者取现没有满额，项目方也可以回收剩余的资产

编译并实例化合约
编译 Equity 合约可以参考一下 Equity 编译器的介绍说明。假如储蓄合约 FixedLimitCollect 的参数如下：
assetDeposited :c6b12af8326df37b8d77c77bfa2547e083cbacde15cc48da56d4aa4e4235a3ee
totalAmountBill :10000000000
totalAmountCapital :20000000000
dueBlockHeight :1070
expireBlockHeight :1090
additionalBlockHeight :1100
banker :0014dedfd406c591aa221a047a260107f877da92fec5
bankerKey :055539eb36abcaaf127c63ae20e3d049cd28d0f1fe569df84da3aedb018ca1bf
其中 bankerKey 是管理员的 publicKey，可以通过比原链的接口 list-pubkeys 来获取，注意管理员需要保存一下对应的 rootXpub 和 Path，否则无法正确调用 clause cancel。
实例化合约命令如下：
// 储蓄合约
./equity FixedLimitCollect –instance c6b12af8326df37b8d77c77bfa2547e083cbacde15cc48da56d4aa4e4235a3ee 10000000000 20000000000 1070 1090 1100 0014dedfd406c591aa221a047a260107f877da92fec5 055539eb36abcaaf127c63ae20e3d049cd28d0f1fe569df84da3aedb018ca1bf

// 取现合约
./equity FixedLimitProfit –instance c6b12af8326df37b8d77c77bfa2547e083cbacde15cc48da56d4aa4e4235a3ee 10000000000 20000000000 1090 1100 0014dedfd406c591aa221a047a260107f877da92fec5 055539eb36abcaaf127c63ae20e3d049cd28d0f1fe569df84da3aedb018ca1bf
发布合约交易
发布合约交易即将资产锁定到合约中。由于目前无法在比原的 dashboard 上构造合约交易，所以需要借助外部工具来发送合约交易，比如 postman。按照上述示意图所示，项目方需要发布 1000 个储蓄资产的储蓄合约和 200 个利息资产取现合约。假设项目方需要发布 1000 个储蓄资产（假如精度为 8, 那么 1000 个在比原链中表示为 100000000000）的锁仓合约，那么他需要将对应数量的票据锁定在储蓄合约中，其交易模板如下：
{
“base_transaction”: null,
“actions”: [
{
“account_id”: “0ILGLSTC00A02”,
“amount”: 20000000,
“asset_id”: “ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff”,
“type”: “spend_account”
},
{
“account_id”: “0ILGLSTC00A02”,
“amount”: 100000000000,
“asset_id”: “13016eff73ffb7539a69e122f80f5c1cc94446773ac3f64dec290429f87e73b3”,
“type”: “spend_account”
},
{
“amount”: 100000000000,
“asset_id”: “13016eff73ffb7539a69e122f80f5c1cc94446773ac3f64dec290429f87e73b3”,
“control_program”: “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”,
“type”: “control_program”
}
],
“ttl”: 0,
“time_range”: 1521625823
}
合约交易成功后，合约 control_program 对应的 UTXO 将会被所有用户查询到，使用比原链的接口 list-unspent-outputs 即可查询。
此外，开发者需要存储一下合约 UTXO 的 assetID 和 program，以便在 DAPP 的前端页面的 config 配置文件和 bufferserver 缓冲服务器中调用。如上所示：
// 储蓄合约
assetID：13016eff73ffb7539a69e122f80f5c1cc94446773ac3f64dec290429f87e73b3
program：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

// 取现合约
assetID：c6b12af8326df37b8d77c77bfa2547e083cbacde15cc48da56d4aa4e4235a3ee
program：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
本期的比原储蓄分红合约就介绍在这里，下一期我们将详细介绍如何基于该合约开发 dapp 应用