Execute a Cross Chain Swap

This section explains the integration and usage of bridge protocols for cross-chain swapping functionalities.

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

To initiate a swap, first determine if the Bridge 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=0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2&spender=0xBA12222222228d8Ba445958a75a0704d566BF2C8

---

Sample Response:

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

Step 2: Approve the Bridge from the Token Contract

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

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

---

Sample Request:

{
    "from": "0x6Fb447Ae94F5180254D436A693907a1f57696900", 
    "tokenAddress":"0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2",  
    "amount": "1000000000000000000000",                  
    "to": "0x6Fb447Ae94F5180254D436A693907a1f57696900", 
    "gas": "100000",
    "chainId": "1"
}

---

Sample Response:

{
    "status": 200,
    "msg": "success",
    "data": {
        "from": "0x6Fb447Ae94F5180254D436A693907a1f57696900",
        "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 Bridge by changing the "bridgeId" parameter. This can be done using the following API endpoint:

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

---

Sample Request:

{
    "bridgeId": "200",
    "srcChainId": "1",
    "dstChainId": "137",
    "srcTokenSymbol": "WETH",
    "dstTokenSymbol": "USDC",
    "amountIn": "100000000000000",
    "from": "0x6Fb447Ae94F5180254D436A693907a1f57696900",
    "gas": "920000",
    "to": "0x6Fb447Ae94F5180254D436A693907a1f57696900"
}

---

Sample Response:

{
    "status": 200,
    "msg": "success",
    "data": {
        "from": "0x6Fb447Ae94F5180254D436A693907a1f57696900",
        "to": "0xce16F69375520ab01377ce7B88f5BA8C48F8D666",
        "value": "83660648338674",
        "gas": "920000",
        "data": "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    }
}