pricing

schema.graphql

@@ -7,6 +7,8 @@ type Token @entity {
   decimals: BigInt!
 
   totalLiquidity: BigDecimal!
+  primaryUsdPrice: BigDecimal!
+  secondaryUsdPrice: BigDecimal!
 
   pairsAsToken0: [Pair!]! @derivedFrom(field: "token0")
   pairsAsToken1: [Pair!]! @derivedFrom(field: "token1")

src/mappings/factory.ts

@@ -1,10 +1,11 @@
 /* eslint-disable prefer-const */
-import { log } from '@graphprotocol/graph-ts'
+import { BigDecimal, log } from '@graphprotocol/graph-ts'
 
 import { PairCreated } from '../types/Factory/Factory'
 import { Pair, Token, UniswapFactory } from '../types/schema'
 import { Pair as PairTemplate } from '../types/templates'
 import { FACTORY_ADDRESS, fetchTokenDecimals, ONE_BI, ZERO_BD } from './helpers'
+import { isStablecoin } from './pricing'
 
 export function handleNewPair(event: PairCreated): void {
   if (event.params.param3.equals(ONE_BI)) {
@@ -25,6 +26,9 @@ export function handleNewPair(event: PairCreated): void {
     const token0 = new Token(event.params.token0.toHexString())
     token0.decimals = decimals
     token0.totalLiquidity = ZERO_BD
+    if (isStablecoin(event.params.token0.toHexString())) {
+      token0.primaryUsdPrice = BigDecimal.fromString('1.0')
+    }
     token0.save()
   }
 
@@ -41,6 +45,9 @@ export function handleNewPair(event: PairCreated): void {
     const token1 = new Token(event.params.token1.toHexString())
     token1.decimals = decimals
     token1.totalLiquidity = ZERO_BD
+    if (isStablecoin(event.params.token1.toHexString())) {
+      token1.primaryUsdPrice = BigDecimal.fromString('1.0')
+    }
     token1.save()
   }
 

src/mappings/pair.ts

@@ -4,6 +4,7 @@ import { log } from '@graphprotocol/graph-ts'
 import { Burn as BurnEntity, Mint as MintEntity, Pair, Swap as SwapEntity, Token } from '../types/schema'
 import { Burn, Mint, Swap } from '../types/templates/Pair/Pair'
 import { convertTokenToDecimal } from './helpers'
+import { updatePrimaryUsdPrices } from './pricing'
 
 export function handleMint(event: Mint): void {
   const block = event.block
@@ -36,6 +37,11 @@ export function handleMint(event: Mint): void {
   mint.amount1 = token1Amount as BigDecimal
   mint.save()
 
+  pair.reserve0 = pair.reserve0.plus(token0Amount)
+  pair.reserve1 = pair.reserve1.plus(token1Amount)
+  pair.save()
+
+  updatePrimaryUsdPrices(pair, token0, token1)
   token0.totalLiquidity = token0.totalLiquidity.plus(token0Amount)
   token1.totalLiquidity = token1.totalLiquidity.plus(token1Amount)
   token0.save()
@@ -66,6 +72,11 @@ export function handleBurn(event: Burn): void {
   burn.to = event.params.to
   burn.save()
 
+  pair.reserve0 = pair.reserve0.minus(token0Amount)
+  pair.reserve1 = pair.reserve1.minus(token1Amount)
+  pair.save()
+
+  updatePrimaryUsdPrices(pair, token0, token1)
   token0.totalLiquidity = token0.totalLiquidity.minus(token0Amount)
   token1.totalLiquidity = token1.totalLiquidity.minus(token1Amount)
   token0.save()
@@ -100,6 +111,11 @@ export function handleSwap(event: Swap): void {
   swap.to = event.params.to
   swap.save()
 
+  pair.reserve0 = pair.reserve0.minus(token0AmountOut).plus(token0AmountIn)
+  pair.reserve1 = pair.reserve1.minus(token1AmountOut).plus(token1AmountIn)
+  pair.save()
+
+  updatePrimaryUsdPrices(pair, token0, token1)
   token0.totalLiquidity = token0.totalLiquidity.minus(token0AmountOut).plus(token0AmountIn)
   token1.totalLiquidity = token1.totalLiquidity.minus(token1AmountOut).plus(token1AmountIn)
   token0.save()

src/mappings/pricing.ts

@@ -0,0 +1,33 @@
+import { BigDecimal } from '@graphprotocol/graph-ts'
+
+import { Pair, Token } from '../types/schema'
+
+const STABLECOINS: string[] = [
+  '0x6b175474e89094c44da98b954eedeac495271d0f', // DAI
+  '0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48', // USDC
+  '0xdac17f958d2ee523a2206206994597c13d831ec7', // USDT
+]
+
+export function isStablecoin(token: string): boolean {
+  return STABLECOINS.includes(token)
+}
+
+export function getPrimaryUsdPrice(pair: Pair, token: Token): BigDecimal {
+  if (isStablecoin(token)) {
+    return BigDecimal.fromString('1.0')
+  } else if (isStablecoin(pair.token0)) {
+    return pair.reserve0.div(pair.reserve1)
+  } else if (isStablecoin(pair.token1)) {
+    return pair.reserve1.div(pair.reserve0)
+  } else {
+    return BigDecimal.fromString('0.0')
+  }
+}
+
+export function updatePrimaryUsdPrices(pair: Pair, token0: Token, token1: Token): void {
+  if (isStablecoin(pair.token0)) {
+    token1.primaryUsdPrice = pair.reserve0.div(pair.reserve1)
+  } else if (isStablecoin(pair.token1)) {
+    token0.primaryUsdPrice = pair.reserve1.div(pair.reserve0)
+  }
+}