Merge pull request #361 from oceanprotocol/feature/add_pool_getTokensRemovedforPoolShares

add getTokensRemovedforPoolShares

src/balancer/OceanPool.ts

@@ -4,7 +4,6 @@ import { TransactionReceipt } from 'web3-core'
 import { Pool } from './Pool'
 import { EventData, Filter } from 'web3-eth-contract'
 import BigNumber from 'bignumber.js'
-import Decimal from 'decimal.js'
 
 declare type PoolTransactionType = 'swap' | 'join' | 'exit'
 
@@ -13,6 +12,11 @@ export interface PoolDetails {
   tokens: string[]
 }
 
+export interface TokensReceived {
+  dtAmount: string
+  oceanAmount: string
+}
+
 export interface PoolTransaction {
   poolAddress: string
   dtAddress: string
@@ -385,6 +389,34 @@ export class OceanPool extends Pool {
     return this.calcSingleOutGivenPoolIn(poolAddress, this.oceanAddress, poolShares)
   }
 
+  /**
+   * Returns Datatoken & Ocean amounts received after spending poolShares
+   * @param {String} poolAddress
+   * @param {String} poolShares
+   * @return {TokensReceived}
+   */
+  public async getTokensRemovedforPoolShares(
+    poolAddress: string,
+    poolShares: string
+  ): Promise<TokensReceived> {
+    try {
+      const totalPoolTokens = await this.getPoolSharesTotalSupply(poolAddress)
+      const dtReserve = await this.getDTReserve(poolAddress)
+      const oceanReserve = await this.getOceanReserve(poolAddress)
+
+      const dtAmount = `${
+        (Number(poolShares) / Number(totalPoolTokens)) * Number(dtReserve)
+      }`
+      const oceanAmount = `${
+        (Number(poolShares) / Number(totalPoolTokens)) * Number(oceanReserve)
+      }`
+
+      return { dtAmount, oceanAmount }
+    } catch (e) {
+      console.error(`ERROR: Unable to get token info. ${e.message}`)
+    }
+  }
+
   /**
    * Returns max DT amount that you can add to the pool
    * @param poolAddress

test/unit/balancer/Balancer.test.ts

@@ -388,7 +388,12 @@ describe('Balancer flow', () => {
     assert(parseFloat(bobDtBalance) < parseFloat(newbobDtBalance))
     assert(parseFloat(poolShares) > parseFloat(newpoolShares))
   })
-
+  it('ALice should know how many tokens she will get for removing all liquidity', async () => {
+    const aliceShares = await Pool.sharesBalance(alice, greatPool)
+    const amounts = await Pool.getTokensRemovedforPoolShares(greatPool, aliceShares)
+    assert(parseFloat(amounts.dtAmount) > 0)
+    assert(parseFloat(amounts.oceanAmount) > 0)
+  })
   it('ALice should remove all liquidity', async () => {
     const aliceShares = await Pool.sharesBalance(alice, greatPool)
     const aliceDtBalance = await datatoken.balance(tokenAddress, alice)