add buyDTWithExactOcean function

src/balancer/OceanPool.ts

@@ -586,7 +586,63 @@ export class OceanPool extends Pool {
   }
 
   /**
-   * Sell datatoken
+   * Buy at least datatoken from a pool for a fixed Ocean amount
+   * @param {String} account
+   * @param {String} poolAddress
+   * @param {String} amount  datatoken amount
+   * @param {String} oceanAmount  Ocean Token amount payed
+   * @param {String} maxPrice  Maximum price to pay
+   * @return {TransactionReceipt}
+   */
+  public async buyDTWithExactOcean(
+    account: string,
+    poolAddress: string,
+    minimumdtAmountWanted: string,
+    OceanAmount: string,
+    maxPrice?: string
+  ): Promise<TransactionReceipt> {
+    if (this.oceanAddress == null) {
+      this.logger.error('ERROR: undefined ocean token contract address')
+      return null
+    }
+    const dtAddress = await this.getDTAddress(poolAddress)
+    if (
+      parseFloat(minimumdtAmountWanted) >
+      parseFloat(await this.getDTMaxBuyQuantity(poolAddress))
+    ) {
+      this.logger.error('ERROR: Buy quantity exceeds quantity allowed')
+      return null
+    }
+    const calcInGivenOut = await this.getOceanNeeded(poolAddress, minimumdtAmountWanted)
+
+    if (parseFloat(calcInGivenOut) > parseFloat(OceanAmount)) {
+      this.logger.error('ERROR: Not enough Ocean Tokens')
+      return null
+    }
+    // TODO - check balances first
+    const txid = await super.approve(
+      account,
+      this.oceanAddress,
+      poolAddress,
+      this.web3.utils.toWei(OceanAmount)
+    )
+    if (!txid) {
+      this.logger.error('ERROR: OCEAN approve failed')
+      return null
+    }
+    return this.swapExactAmountIn(
+      account,
+      poolAddress,
+      this.oceanAddress,
+      OceanAmount,
+      dtAddress,
+      minimumdtAmountWanted,
+      maxPrice
+    )
+  }
+
+  /**
+   * Sell a specific amount of datatoken to get some ocean tokens
    * @param {String} account
    * @param {String} poolAddress
    * @param {String} amount  datatoken amount to be sold

test/unit/balancer/Balancer.test.ts

@@ -213,13 +213,19 @@ describe('Balancer flow', () => {
     greatPool = pools[0]
   })
   it('Bob should buy 2 DT ', async () => {
-    const maxPrice = parseFloat(currentDtPrice) * 2
     await Pool.buyDT(bob, greatPool, '2', '4')
     const bobDtBalance = await datatoken.balance(tokenAddress, bob)
     const bobOceanBalance = await datatoken.balance(oceanTokenAddress, bob)
     assert(Number(bobDtBalance) > 0)
     assert(Number(bobOceanBalance) > 0)
   })
+  it('Bob should spend 10 Oceans to buy some DT ', async () => {
+    await Pool.buyDTWithExactOcean(bob, greatPool, '1', '5')
+    const bobDtBalance = await datatoken.balance(tokenAddress, bob)
+    const bobOceanBalance = await datatoken.balance(oceanTokenAddress, bob)
+    assert(Number(bobDtBalance) > 0)
+    assert(Number(bobOceanBalance) > 0)
+  })
   it('Bob should sell 1 DT ', async () => {
     const maxPrice = parseFloat(currentDtPrice) * 2
     await Pool.sellDT(bob, greatPool, '1', '1')