Swap and pools

The testnet DEX is Uniswap v2 (core and periphery, GPL-3.0, unmodified math) on Aeva’s EVM. Its pools hold AE-20 tokens, the ERC-20 view of native Aeva rights, so a swap moves native rights: the explorer shows an EventTransferred from the pool’s address, and the policy of the asset applies as it does to any transfer. Testnet, tokens have no value.

Run the setup block first; this guide also uses cast.

The contracts

Each pool pairs aeUSD with a test stock’s bundle token (all its kinds as one ERC-20) or with WAEVA:

The pair init code hash is 147ac9b133c17a106ca8749a1705605798b9173af80c790796e2716b3f24cafd; the build is reproducible from dex/ in the repository.

1. Read a pool and quote a swap

ROUTER=0xf2ea4660567aaA99e7061B5c88C7Fa35Bf5FEA39
AEUSD=0x5aB37c022D0ce153F1C1949a88a93A8DC3E546D7
TAAPL=0x3AcfD0e4c178474d452B61B5e0C57321def4E998
PAIR=0xF637A4b041cF827e98f5f5E15813023A9AE33904
cast call "$PAIR" "getReserves()(uint112,uint112,uint32)" --rpc-url "$AEVA_EVM"
cast call "$ROUTER" "getAmountsOut(uint256,address[])(uint256[])" 10000000 "[$AEUSD,$TAAPL]" --rpc-url "$AEVA_EVM"

<reserve0> [<…>]
<reserve1> [<…>]
<timestamp>
[10000000 [1e7], <units out> [<…>]]

A pair orders its tokens by address: tAAPL (0x3Acf…) sorts before aeUSD (0x5aB3…), so reserve0 is tAAPL and reserve1 aeUSD, at the time of writing 2 000 shares against 400 000 aeUSD, 200 aeUSD a share. The quote is the tAAPL units (six decimals) that 10 aeUSD buys after the 0.3 % pool fee, about 0.05 of a share.

2. Swap 10 aeUSD for tAAPL

Your Aeva key is also an Ethereum key: the same secp256k1 key signs both, and 0x… and aeva1… are two spellings of one account.

PK=$(aevad keys unsafe-export-eth-key me --home "$AEVA_HOME" --keyring-backend test)
ME_HEX=$(cast wallet address --private-key "$PK")
OUT=$(cast call "$ROUTER" "getAmountsOut(uint256,address[])(uint256[])" 10000000 "[$AEUSD,$TAAPL]" --rpc-url "$AEVA_EVM" | tr -d '[]' | awk -F', ' '{print $2}' | awk '{print $1}')
MIN=$((OUT * 99 / 100))
cast send "$AEUSD" "approve(address,uint256)" "$ROUTER" 10000000 --private-key "$PK" --rpc-url "$AEVA_EVM" >/dev/null
cast send "$ROUTER" "swapExactTokensForTokens(uint256,uint256,address[],address,uint256)" 10000000 "$MIN" "[$AEUSD,$TAAPL]" "$ME_HEX" $(($(date +%s) + 600)) --private-key "$PK" --rpc-url "$AEVA_EVM" --json | jq -r '"swap: status \(.status), tx \(.transactionHash)"'

swap: status 0x1, tx 0x…

MIN accepts at most 1 % slippage from the quote. The pool now holds 10 more aeUSD, and you hold more tAAPL, natively, as rights:

curl -s "$AEVA_INDEXER/v1/accounts/$ME" | jq -r --arg a 84f50ea918e0c15c9321362330d513593fd4536b807e1b40a39682dab3e21b55 '.assets[] | select(.asset_id == $a) | "tAAPL: \(.whole_units) units of every kind"'

tAAPL: <units> units of every kind

To swap native AEVA, use swapExactETHForTokens with WAEVA as the first hop, as on any Uniswap v2. The app’s /swap  and /pools  pages do the same from MetaMask, and add liquidity.

Notes for contract authors

• AE-20 tokens are precompiles: there is no code at their address. Solidity before 0.8.10 checks extcodesize before a high-level call and reverts, so the testnet DEX reads balanceOf with a low-level staticcall. See The EVM facade & AE-20.
• A pool is an ordinary account on the native side: it holds rights, accrues their income, and every transfer in or out passes the asset’s policy.