Execute a Local Swap

This section explains the integration and usage of various decentralized exchange (DEX) protocols for local swapping functionalities.

Please see the attached document for information about error messages you may encounter when executing a swap:https://docs.google.com/document/d/1SuBJwPOmvJtUUf-9QJiBcTr0l2zbWlusMTUOGfC8S50/edit?usp=sharing

Step 1: Check the Allowance of the DEX on the Token Contract

To initiate a swap, first determine if the DEX has the necessary allowance to access the tokens. This can be done using the following API endpoint:

API URL: https://api.expand.network/fungibletoken/getuserallowance

---

Sample Request:

https://api.expand.network/fungibletoken/getuserallowance?owner=0x6Fb447Ae94F5180254D436A693907a1f57696900&tokenAddress=0x6b175474e89094c44da98b954eedeac495271d0f&spender=0xBA12222222228d8Ba445958a75a0704d566BF2C8

---

Sample Response:

{
    "status": 200,
    "msg": "success",
    "data": {
        "allowance": "999000000000000000000"
    }
}

Step 2: Approve the Dex from the Token Contract

If the allowance is less than the token amount to be swapped, the user must approve the DEX router from the token contract. This can be done using the following API endpoint:

API URL: https://api.expand.network/fungibletoken/approve

---

Sample Request:

{
    "from": "0x63056E00436Da25BcF48A40dfBbDcc7089351006", 
    "tokenAddress":"0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2",  
    "amount": "1000000000000000000000",                  
    "to": "0x828b154032950c8ff7cf8085d841723db2696056", 
    "gas": "100000",
    "chainId": "1"
}

---

Sample Response:

{
    "status": 200,
    "msg": "success",
    "data": {
        "from": "0x63056E00436Da25BcF48A40dfBbDcc7089351006",
        "to": "0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2",
        "value": "0",
        "gas": "100000",
        "data": "0x095ea7b3000000000000000000000000828b154032950c8ff7cf8085d841723db269605600000000000000000000000000000000000000000000003635c9adc5dea00000"
    }
}

Step 3: Swap the tokens

After the successful approval, we can do the swap. User can swap the tokens on their preferred Dex by changing the "dexId" parameter. This can be done using the following API endpoint:

API URL: https://api.expand.network/dex/swap

---

Sample Request:

{
    "dexId":"1000",
    "amountIn": "1000000000000000",
    "amountOutMin": "0",
    "path": ["0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2","0x6B175474E89094C44Da98b954EedeAC495271d0F"],
    "to": "0x63056E00436Da25BcF48A40dfBbDcc7089351006",
    "deadline": "1665990894",
    "from": "0x63056E00436Da25BcF48A40dfBbDcc7089351006",
    "gas": "173376"
}

---

Sample Response:

{
    "status": 200,
    "msg": "success",
    "data": {
        "from": "0x63056E00436Da25BcF48A40dfBbDcc7089351006",
        "to": "0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D",
        "value": "0",
        "gas": "173376",
        "data": "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"
    }
}