Receive an option to decide if we calculate FOT tax or not (#146)

* Receive an option to decide if we calculate FOT tax or not

* Fix code style issues with Prettier

---------
Co-authored-by: Lint Action <lint-action@samuelmeuli.com>

.gitignore

 dist
 node_modules
+.idea

src/entities/pair.test.ts

@@ -199,6 +199,13 @@ describe('Pair', () => {
       BLASTERSSellFeeBps
     )
 
+    let calculateFotFees: boolean = false
+
+    describe('when calculating FOT fees', () => {
+      beforeEach(() => {
+        calculateFotFees = true
+      })
+
       describe('getOutputAmount', () => {
         it('getOutputAmount for input token BLASTERS and output token BLAST', () => {
           const reserveBlasterAmount = CurrencyAmount.fromRawAmount(BLASTERS, '10000')
@@ -207,7 +214,7 @@ describe('Pair', () => {
           const pair = new Pair(reserveBlasterAmount, reserveBlastAmount)
 
           const inputBlastersAmount = CurrencyAmount.fromRawAmount(BLASTERS, '100')
-        const [outputBlastAmount] = pair.getOutputAmount(inputBlastersAmount)
+          const [outputBlastAmount] = pair.getOutputAmount(inputBlastersAmount, calculateFotFees)
 
           // Theoretical amount out:
           // (10000 * 997 * 100 * (1 - 3.5%) / (10000 * 1000 + 997 * 100 * (1 - 3.5%))) * (1 - 4%)
@@ -240,7 +247,7 @@ describe('Pair', () => {
           const pair = new Pair(reserveBlasterAmount, reserveBlastAmount)
 
           const outputBlastAmount = CurrencyAmount.fromRawAmount(BLAST, '91')
-        const [inputBlasterAmount] = pair.getInputAmount(outputBlastAmount)
+          const [inputBlasterAmount] = pair.getInputAmount(outputBlastAmount, calculateFotFees)
 
           // Theoretical amount in:
           // 10000 * 100 * (1 - 4%) * 1000 / ((10000 - 100 * (1 - 4%)) * 997) / (1 - 3.5%)
@@ -274,6 +281,41 @@ describe('Pair', () => {
         })
       })
     })
+
+    describe('when NOT calculating FOT fees', () => {
+      beforeEach(() => {
+        calculateFotFees = false
+      })
+
+      describe('getOutputAmount', () => {
+        it('getOutputAmount for input token BLASTERS and output token BLAST', () => {
+          const reserveBlasterAmount = CurrencyAmount.fromRawAmount(BLASTERS, '10000')
+          const reserveBlastAmount = CurrencyAmount.fromRawAmount(BLAST, '10000')
+
+          const pair = new Pair(reserveBlasterAmount, reserveBlastAmount)
+
+          const inputBlastersAmount = CurrencyAmount.fromRawAmount(BLASTERS, '100')
+          const [outputBlastAmount] = pair.getOutputAmount(inputBlastersAmount, calculateFotFees)
+
+          const expectedOutputBlastAmount = '0.000000000000000098'
+          expect(outputBlastAmount.toExact()).toEqual(expectedOutputBlastAmount)
+        })
+
+        it('getInputAmount for input token BLASTERS and output token BLAST', () => {
+          const reserveBlasterAmount = CurrencyAmount.fromRawAmount(BLASTERS, '10000')
+          const reserveBlastAmount = CurrencyAmount.fromRawAmount(BLAST, '10000')
+
+          const pair = new Pair(reserveBlasterAmount, reserveBlastAmount)
+
+          const outputBlastAmount = CurrencyAmount.fromRawAmount(BLAST, '91')
+          const [inputBlasterAmount] = pair.getInputAmount(outputBlastAmount, calculateFotFees)
+
+          const expectedInputBlasterAmount = '0.000000093'
+          expect(inputBlasterAmount.toExact()).toEqual(expectedInputBlasterAmount)
+        })
+      })
+    })
+  })
   describe('miscellaneous', () => {
     it('getLiquidityMinted:0', async () => {
       const tokenA = new Token(3, '0x0000000000000000000000000000000000000001', 18)

src/entities/pair.ts

@@ -178,7 +178,10 @@ export class Pair {
    *
    * @param inputAmount
    */
-  public getOutputAmount(inputAmount: CurrencyAmount<Token>): [CurrencyAmount<Token>, Pair] {
+  public getOutputAmount(
+    inputAmount: CurrencyAmount<Token>,
+    calculateFotFees: boolean = false
+  ): [CurrencyAmount<Token>, Pair] {
     invariant(this.involvesToken(inputAmount.currency), 'TOKEN')
     if (JSBI.equal(this.reserve0.quotient, ZERO) || JSBI.equal(this.reserve1.quotient, ZERO)) {
       throw new InsufficientReservesError()
@@ -186,7 +189,7 @@ export class Pair {
     const inputReserve = this.reserveOf(inputAmount.currency)
     const outputReserve = this.reserveOf(inputAmount.currency.equals(this.token0) ? this.token1 : this.token0)
 
-    const percentAfterSellFees = this.derivePercentAfterSellFees(inputAmount)
+    const percentAfterSellFees = calculateFotFees ? this.derivePercentAfterSellFees(inputAmount) : ZERO_PERCENT
     const inputAmountAfterTax = percentAfterSellFees.greaterThan(ZERO_PERCENT)
       ? CurrencyAmount.fromRawAmount(
           inputAmount.currency,
@@ -206,7 +209,7 @@ export class Pair {
       throw new InsufficientInputAmountError()
     }
 
-    const percentAfterBuyFees = this.derivePercentAfterBuyFees(outputAmount)
+    const percentAfterBuyFees = calculateFotFees ? this.derivePercentAfterBuyFees(outputAmount) : ZERO_PERCENT
     const outputAmountAfterTax = percentAfterBuyFees.greaterThan(ZERO_PERCENT)
       ? CurrencyAmount.fromRawAmount(
           outputAmount.currency,
@@ -265,9 +268,12 @@ export class Pair {
    *
    * @param outputAmount
    */
-  public getInputAmount(outputAmount: CurrencyAmount<Token>): [CurrencyAmount<Token>, Pair] {
+  public getInputAmount(
+    outputAmount: CurrencyAmount<Token>,
+    calculateFotFees: boolean = false
+  ): [CurrencyAmount<Token>, Pair] {
     invariant(this.involvesToken(outputAmount.currency), 'TOKEN')
-    const percentAfterBuyFees = this.derivePercentAfterBuyFees(outputAmount)
+    const percentAfterBuyFees = calculateFotFees ? this.derivePercentAfterBuyFees(outputAmount) : ZERO_PERCENT
     const outputAmountBeforeTax = percentAfterBuyFees.greaterThan(ZERO_PERCENT)
       ? CurrencyAmount.fromRawAmount(
           outputAmount.currency,
@@ -294,7 +300,7 @@ export class Pair {
       JSBI.add(JSBI.divide(numerator, denominator), ONE) // add 1 here is part of the formula, no rounding needed here, since there will not be decimal at this point
     )
 
-    const percentAfterSellFees = this.derivePercentAfterSellFees(inputAmount)
+    const percentAfterSellFees = calculateFotFees ? this.derivePercentAfterSellFees(inputAmount) : ZERO_PERCENT
     const inputAmountBeforeTax = percentAfterSellFees.greaterThan(ZERO_PERCENT)
       ? CurrencyAmount.fromRawAmount(
           inputAmount.currency,