Bytom儲蓄分紅合約解析

儲蓄分紅合約簡介

儲蓄分紅合約指的是項目方發起了一個鎖倉計劃（即儲蓄合約和取現合約），用戶可以在準備期自由選擇鎖倉金額參與該計劃，等到鎖倉到期之後還可以自動獲取鎖倉的利潤。用戶可以在準備期內（dueBlockHeight）參與儲蓄，按照合約規定可以 1：1 獲取同等數量的儲蓄票據資產，同時用戶鎖倉的資產（deposit）將放到取現合約中，並且項目方是無法動用的，等到鎖倉期限（expireBlockHeight）一到，用戶便可以調用取現合約將自己儲蓄的資產連本待息一同取出來。其示意圖如下:

從上圖中可以看出，項目方發佈了一個利潤爲20%的鎖倉項目，其中儲蓄合約FixedLimitCollect鎖定了1000個票據資產（bill），同時項目方將200個儲蓄資產（deposit）鎖定到利息合約中。待項目方發佈完合約之後，所有用戶便可以參與了。例如上圖中user1調用合約儲蓄了500，這500個儲蓄資產將被鎖定在取現合約FixedLimitProfit中，同時user1獲得了500個票據資產，剩餘找零的資產將繼續鎖定在儲蓄合約FixedLimitCollect中，以此類推，user2和user3也是相同的流程，直到儲蓄合約沒有資產爲止。取現合約FixedLimitProfit跟儲蓄合約的模型大致相同，只是取現合約是由多個UTXO組成的，用戶在取現的時候可以並行操作。但是如果合約中的面值不能支持用戶一次性取現的話，需要分多次提取。例如user1擁有500個票據資產，而可以獲得的本息總額爲600，但是取現的UTXO面值爲500,那麼user1一次最多隻能取500,剩下的100需要再構造一筆交易來提現。

合約源代碼

// 儲蓄合約
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
    }
}

// 取現合約(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
    }
}

合約的源代碼說明可以具體參考Equity合約介紹.

注意事項：

• 時間期限不是具體的時間，而是通過區塊高度來大概估算的（平均區塊時間間隔大概爲2.5分鐘）
• 比原的精度是8, 即 1BTM = 100000000 neu，正常情況下參與計算都是以neu爲單位的，然而虛擬機的int64類型的最大值是9223372036854775807，爲了避免數值太大導致計算溢出，所以對計算的金額提出了金額限制（即amountBill/100000000）
• 另外clause cancel是項目方的管理方法，如果儲蓄或者取現沒有滿額，項目方也可以回收剩餘的資產

編譯並實例化合約

編譯Equity合約可以參考一下Equity編譯器的介紹說明。假如儲蓄合約FixedLimitCollect的參數如下：

assetDeposited          :c6b12af8326df37b8d77c77bfa2547e083cbacde15cc48da56d4aa4e4235a3ee
totalAmountBill         :10000000000
totalAmountCapital      :20000000000
dueBlockHeight          :1070
expireBlockHeight       :1090
additionalBlockHeight   :1100
banker                  :0014dedfd406c591aa221a047a260107f877da92fec5
bankerKey               :055539eb36abcaaf127c63ae20e3d049cd28d0f1fe569df84da3aedb018ca1bf

其中bankerKey是管理員的publicKey，可以通過比原鏈的接口list-pubkeys來獲取，注意管理員需要保存一下對應的rootXpub和Path，否則無法正確調用clause cancel。

實例化合約命令如下：

// 儲蓄合約
./equity FixedLimitCollect --instance c6b12af8326df37b8d77c77bfa2547e083cbacde15cc48da56d4aa4e4235a3ee 10000000000 20000000000 1070 1090 1100 0014dedfd406c591aa221a047a260107f877da92fec5 055539eb36abcaaf127c63ae20e3d049cd28d0f1fe569df84da3aedb018ca1bf

// 取現合約
./equity FixedLimitProfit --instance c6b12af8326df37b8d77c77bfa2547e083cbacde15cc48da56d4aa4e4235a3ee 10000000000 20000000000 1090 1100 0014dedfd406c591aa221a047a260107f877da92fec5 055539eb36abcaaf127c63ae20e3d049cd28d0f1fe569df84da3aedb018ca1bf

發佈合約交易

發佈合約交易即將資產鎖定到合約中。由於目前無法在比原的dashboard上構造合約交易，所以需要藉助外部工具來發送合約交易，比如postman。按照上述示意圖所示，項目方需要發佈1000個儲蓄資產的儲蓄合約和200個利息資產取現合約。假設項目方需要發佈1000個儲蓄資產（假如精度爲8,那麼1000個在比原鏈中表示爲100000000000）的鎖倉合約，那麼他需要將對應數量的票據鎖定在儲蓄合約中，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
}

合約交易成功後，合約control_program對應的UTXO將會被所有用戶查詢到，使用比原鏈的接口list-unspent-outputs即可查詢。

此外，開發者需要存儲一下合約UTXO的assetID和program，以便在DAPP的前端頁面的config配置文件和bufferserver緩衝服務器中調用。如上所示：

// 儲蓄合約
assetID：13016eff73ffb7539a69e122f80f5c1cc94446773ac3f64dec290429f87e73b3
program：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

// 取現合約
assetID：c6b12af8326df37b8d77c77bfa2547e083cbacde15cc48da56d4aa4e4235a3ee
program：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

本期的比原儲蓄分紅合約就介紹在這裏，下一期我們將詳細介紹如何基於該合約開發dapp應用