# Swaps > Swapping on Plach: the Borsh swap message with its routes and fee discount, single-pool, multi-pool and split routes, and how prices are computed. This page is part of the Plach docs. Plach is the DEX `slimedragon.near/xyk` on the Intear DEX contract, `dex.intear.near`, and every call goes to that contract. https://docs.intear.tech/plach/llms-full.txt has all of its pages in one file, and https://docs.intear.tech/llms.txt lists every page of the Intear docs. A Plach swap is an Intear DEX [swap](https://docs.intear.tech/intear-dex/guides/swaps.md) with `"dex_id": "slimedragon.near/xyk"`. The `message` of the swap says which pools to go through. Everything else works as on any DEX of the engine: [`swap_simple`](https://docs.intear.tech/intear-dex/guides/swaps.md#swap_simple), [`simulate_swap_simple`](https://docs.intear.tech/intear-dex/guides/swaps.md#simulate), and `SwapSimple` [operations](https://docs.intear.tech/intear-dex/guides/operations.md), with exact input or exact output. The examples on this page swap from alice.near's inner balance, after a [storage deposit](https://docs.intear.tech/intear-dex/guides/storage.md#accounts), [registering](https://docs.intear.tech/intear-dex/guides/inner-balances.md#register-assets) NEAR, USDt and USDC, and [depositing](https://docs.intear.tech/intear-dex/guides/inner-balances.md#deposit) 1 NEAR and 1 USDt. Together they're [one script](#the-whole-script). ## The message The message is a Borsh `SwapArgs`: a list of routes, and an optional [fee discount](https://docs.intear.tech/plach/guides/fees.md#fee-discounts). ```rust struct SwapArgs { routes: Vec, fee_discount: Option, } struct SwapRoute { /// Share of the amount that goes through this route, 1000000 = 100% fraction: u32, /// Pools to swap through, in order pool_ids: Vec, } ``` [Referral fees](https://docs.intear.tech/intear-dex/guides/referral-fees.md) are an argument of the engine's swap, not part of the message. Messages from before they moved there can still list them after `fee_discount`. Plach reads and ignores them, so they don't charge anything. For a swap of the whole amount through one pool, without a fee discount, the message can also be just the pool ID, a little-endian `u32`. `3QAAAA==` is pool 221, NEAR/USDt: ```sh near contract call-function as-read-only dex.intear.near simulate_swap_simple \ json-args '{ "dex_id": "slimedragon.near/xyk", "message": "3QAAAA==", "trader": "alice.near", "asset_in": "near", "asset_out": "nep141:usdt.tether-token.near", "amount": {"ExactIn": "1000000000000000000000000"} }' \ network-config mainnet now ``` The whole file, tested in CI: https://docs.intear.tech/snippets/cli/plach-swaps.sh ### Through several pools Each pool of a route swaps the output of the one before into its other asset, and the last one must output `asset_out`. This message goes from USDt to NEAR in pool 221, then from NEAR to USDC in pool 85: ``` 01 00 00 00 1 route 40 42 0f 00 fraction: 1000000 (100%) 02 00 00 00 2 pools dd 00 00 00 221 55 00 00 00 85 00 no fee discount ``` That's `AQAAAEBCDwACAAAA3QAAAFUAAAAA` in base64: ```sh # USDt to NEAR in pool 221, then NEAR to USDC in pool 85 AMOUNT_OUT=$(near contract call-function as-read-only dex.intear.near simulate_swap_simple \ json-args '{ "dex_id": "slimedragon.near/xyk", "message": "AQAAAEBCDwACAAAA3QAAAFUAAAAA", "trader": "alice.near", "asset_in": "nep141:usdt.tether-token.near", "asset_out": "nep141:17208628f84f5d6ad33f0da3bbbeb27ffcb398eac501a31bd6ad2011e36133a1", "amount": {"ExactIn": "1000000"} }' \ network-config mainnet now | jq -r '.[1]') MIN_AMOUNT_OUT=$((AMOUNT_OUT * 99 / 100)) near contract call-function as-transaction dex.intear.near swap_simple \ json-args "$(jq -n --arg min_amount_out "$MIN_AMOUNT_OUT" '{ "dex_id": "slimedragon.near/xyk", "message": "AQAAAEBCDwACAAAA3QAAAFUAAAAA", "asset_in": "nep141:usdt.tether-token.near", "asset_out": "nep141:17208628f84f5d6ad33f0da3bbbeb27ffcb398eac501a31bd6ad2011e36133a1", "amount": {"ExactIn": "1000000"}, "constraint": $min_amount_out }')" \ prepaid-gas '150.0 Tgas' attached-deposit '1 yoctoNEAR' \ sign-as alice.near network-config mainnet sign-with-keychain send ``` The whole file, tested in CI: https://docs.intear.tech/snippets/cli/plach-swaps.sh Unlike several `SwapSimple` [operations](https://docs.intear.tech/intear-dex/guides/swaps.md#several-swaps-in-one-call), the intermediate asset (NEAR here) doesn't go through your inner balance, so it doesn't need to be registered for you, and it's one swap for the engine. ### Split across routes With several routes, each takes its `fraction` of the amount, and the fractions must add up to 1000000. The first route also takes what's left after rounding. This one swaps 70% of 1 NEAR to USDC in pool 85, and 30% in pool 22: ``` 02 00 00 00 2 routes 60 ae 0a 00 fraction: 700000 (70%) 01 00 00 00 1 pool 55 00 00 00 85 e0 93 04 00 fraction: 300000 (30%) 01 00 00 00 1 pool 16 00 00 00 22 00 no fee discount ``` ```sh # 70% through pool 85 and 30% through pool 22, both NEAR/USDC AMOUNT_OUT=$(near contract call-function as-read-only dex.intear.near simulate_swap_simple \ json-args '{ "dex_id": "slimedragon.near/xyk", "message": "AgAAAGCuCgABAAAAVQAAAOCTBAABAAAAFgAAAAA=", "trader": "alice.near", "asset_in": "near", "asset_out": "nep141:17208628f84f5d6ad33f0da3bbbeb27ffcb398eac501a31bd6ad2011e36133a1", "amount": {"ExactIn": "1000000000000000000000000"} }' \ network-config mainnet now | jq -r '.[1]') MIN_AMOUNT_OUT=$((AMOUNT_OUT * 99 / 100)) near contract call-function as-transaction dex.intear.near swap_simple \ json-args "$(jq -n --arg min_amount_out "$MIN_AMOUNT_OUT" '{ "dex_id": "slimedragon.near/xyk", "message": "AgAAAGCuCgABAAAAVQAAAOCTBAABAAAAFgAAAAA=", "asset_in": "near", "asset_out": "nep141:17208628f84f5d6ad33f0da3bbbeb27ffcb398eac501a31bd6ad2011e36133a1", "amount": {"ExactIn": "1000000000000000000000000"}, "constraint": $min_amount_out }')" \ prepaid-gas '150.0 Tgas' attached-deposit '1 yoctoNEAR' \ sign-as alice.near network-config mainnet sign-with-keychain send ``` The whole file, tested in CI: https://docs.intear.tech/snippets/cli/plach-swaps.sh Splits work for exact output too: then each route delivers its fraction of `amount_out`. ### The last created pool The pool ID `4294967295` (`u32::MAX`, `ffffffff`) means the pool created last. Use it to [create a pool](https://docs.intear.tech/plach/guides/pools.md#create-a-pool) and swap in it in one `execute_operations`, before you know its ID. ## Prices In each pool, the fees are taken from the input first. The rest goes into the pool, and the output keeps the product of the pool's balances: ``` amount_out = in_after_fees * out_balance / (in_balance + in_after_fees) ``` rounded down. For an exact output, the input is worked out backwards from the same formula and rounded up, so exactly `amount_out` comes out after fees. The input can be a few units more than the least that would do. A swap can't take a pool's whole balance of an asset, and fails on an empty pool. Each pool of a route charges its own fees. Fees paid out in the pool's other asset are swapped into it in the same pool right after, without fees, which moves its price a little more than the formula says. See [Fees](https://docs.intear.tech/plach/guides/fees.md) for what they are and where they go. ## Events Each pool a swap goes through logs a [`Swap`](https://docs.intear.tech/plach/reference/events.md#swap) event with its amounts and fees, and a [`PoolUpdated`](https://docs.intear.tech/plach/reference/events.md#poolupdated) event with its new balances. ## The whole script ```sh #!/usr/bin/env bash # Swaps on Plach with a split route and a route through two pools. alice.near # holds USDt in the wallet and has never used Intear DEX. set -euo pipefail near contract call-function as-transaction dex.intear.near storage_deposit \ json-args '{}' \ prepaid-gas '30.0 Tgas' attached-deposit '0.01 NEAR' \ sign-as alice.near network-config mainnet sign-with-keychain send near contract call-function as-transaction dex.intear.near register_assets \ json-args '{ "asset_ids": [ "near", "nep141:usdt.tether-token.near", "nep141:17208628f84f5d6ad33f0da3bbbeb27ffcb398eac501a31bd6ad2011e36133a1" ] }' \ prepaid-gas '30.0 Tgas' attached-deposit '1 yoctoNEAR' \ sign-as alice.near network-config mainnet sign-with-keychain send near contract call-function as-transaction dex.intear.near deposit_near \ json-args '{}' \ prepaid-gas '30.0 Tgas' attached-deposit '1 NEAR' \ sign-as alice.near network-config mainnet sign-with-keychain send near contract call-function as-transaction usdt.tether-token.near ft_transfer_call \ json-args '{"receiver_id": "dex.intear.near", "amount": "1000000", "msg": ""}' \ prepaid-gas '50.0 Tgas' attached-deposit '1 yoctoNEAR' \ sign-as alice.near network-config mainnet sign-with-keychain send near contract call-function as-read-only dex.intear.near simulate_swap_simple \ json-args '{ "dex_id": "slimedragon.near/xyk", "message": "3QAAAA==", "trader": "alice.near", "asset_in": "near", "asset_out": "nep141:usdt.tether-token.near", "amount": {"ExactIn": "1000000000000000000000000"} }' \ network-config mainnet now # 70% through pool 85 and 30% through pool 22, both NEAR/USDC AMOUNT_OUT=$(near contract call-function as-read-only dex.intear.near simulate_swap_simple \ json-args '{ "dex_id": "slimedragon.near/xyk", "message": "AgAAAGCuCgABAAAAVQAAAOCTBAABAAAAFgAAAAA=", "trader": "alice.near", "asset_in": "near", "asset_out": "nep141:17208628f84f5d6ad33f0da3bbbeb27ffcb398eac501a31bd6ad2011e36133a1", "amount": {"ExactIn": "1000000000000000000000000"} }' \ network-config mainnet now | jq -r '.[1]') MIN_AMOUNT_OUT=$((AMOUNT_OUT * 99 / 100)) near contract call-function as-transaction dex.intear.near swap_simple \ json-args "$(jq -n --arg min_amount_out "$MIN_AMOUNT_OUT" '{ "dex_id": "slimedragon.near/xyk", "message": "AgAAAGCuCgABAAAAVQAAAOCTBAABAAAAFgAAAAA=", "asset_in": "near", "asset_out": "nep141:17208628f84f5d6ad33f0da3bbbeb27ffcb398eac501a31bd6ad2011e36133a1", "amount": {"ExactIn": "1000000000000000000000000"}, "constraint": $min_amount_out }')" \ prepaid-gas '150.0 Tgas' attached-deposit '1 yoctoNEAR' \ sign-as alice.near network-config mainnet sign-with-keychain send # USDt to NEAR in pool 221, then NEAR to USDC in pool 85 AMOUNT_OUT=$(near contract call-function as-read-only dex.intear.near simulate_swap_simple \ json-args '{ "dex_id": "slimedragon.near/xyk", "message": "AQAAAEBCDwACAAAA3QAAAFUAAAAA", "trader": "alice.near", "asset_in": "nep141:usdt.tether-token.near", "asset_out": "nep141:17208628f84f5d6ad33f0da3bbbeb27ffcb398eac501a31bd6ad2011e36133a1", "amount": {"ExactIn": "1000000"} }' \ network-config mainnet now | jq -r '.[1]') MIN_AMOUNT_OUT=$((AMOUNT_OUT * 99 / 100)) near contract call-function as-transaction dex.intear.near swap_simple \ json-args "$(jq -n --arg min_amount_out "$MIN_AMOUNT_OUT" '{ "dex_id": "slimedragon.near/xyk", "message": "AQAAAEBCDwACAAAA3QAAAFUAAAAA", "asset_in": "nep141:usdt.tether-token.near", "asset_out": "nep141:17208628f84f5d6ad33f0da3bbbeb27ffcb398eac501a31bd6ad2011e36133a1", "amount": {"ExactIn": "1000000"}, "constraint": $min_amount_out }')" \ prepaid-gas '150.0 Tgas' attached-deposit '1 yoctoNEAR' \ sign-as alice.near network-config mainnet sign-with-keychain send ```