Gateway: EstimateAmt
Get estimation for the user's transfer request.
REST API
Get estimation for the user's transfer request
GET
https://cbridge-prod2.celer.app/v2/estimateAmt
Here is a sample request for estimateAmt:
Path Parameters
src_chain_id*
Number
source chain id, given by transfer configs
dst_chain_id*
Number
destination chain Id, given by transfer configs
token_symbol*
String
symbol of token to be transfered, given by transfer configs
usr_addr
String
user's wallet address
amt*
String
Token amount to be transfered. It should contain token's decimal. For example, if the user wants to transfer 1 tokenA and A's decimal is 4, then amt should be 10000
slippage_tolerance*
Number
value between 1 and 1M - 1, see details below
is_pegged
Bool
set true if transfer pegged token
GRPC-Web API
Request Parameters
src_chain_id
Number
Source Chain Id, given by transfer configs
dst_chain_id
Number
Destination Chain Id, given by transfer configs
token_symbol
String
Symbol of token to be transfered, given by transfer configs
usr_addr
String
User's wallet address(Not required for multi-chain token transfer)
slippage_tolerance
Number
Slippage for onchain transaction(User's input)
amt
String
Token amount to be transfered. Token's decimal should be used here. For example, if the user wants to transfer 1 tokenA and A's decimal is 4, then amt should be 10000
is_pegged
Used for pegged token transfer only
Which value is suitable for slippage_tolerance?
cBridge gateway uses slippage_tolerance_rate to represent user's slippage for on-chain transaction. The range of slippage_tolerance_rate is from [0, 1)
The calculation formula between slippage_tolerance and slippage_tolerance_rate is
slippage_tolerance_rate = slippage_tolerance / 1M
Hence, if the user sets slippage_tolerance with 0.05%, slippage_tolerance in the request will be 0.05% * 1M = 500
Moreover, if the user sets slippage_tolerance with 0.050123%, the calculation will lead to 0.050123% * 1M = 501.23. However, gateway will only accept integer as slippage_tolerance. The final value should be 501
You need to find out whether this transfer is used for pegged token according to PeggedPairConfigs. Moreover, slippage will not be effective if is_pagged is true
Response Parameters
eq_value_token_amt
String
Token amount in destination chain
slippage_tolerance
Number
The same number as slippage_tolerance in request
max_slippage
Number
slippage will be used to submit on-chain transaction, see below for calculation detail. used for xLiquidity transfer only
estimated_receive_amt
String
receiving amount estimation on destination chain
How to calculate max_slippage?
There are several factors influencing the final value for max_slippage, all of them are inside the response. Since we cannot guarantee user receiving more tokens on destination chain, there is slippage adjustment in the end.
estimate_dst_amt = user_transfer_amount_on_src_chain * bridge_rate
estimate_min_dst_amt = estimate_dst_amt * (1 - slippage_tolerance_rate) - base_fee - perc_fee
max_slippage_rate = 1 - estimate_min_dst_amt / user_transfer_amount_on_src_chain
max_slippage = max(max_slippage_rate * 1M, minimalMaxSlippage)
Minimum receiving amount calculation
amount = eq_value_token_amt * (1 - max_slippage/1M)
The on-chain send transaction failed mostly when slippage is too small to be processed by cBridge system.
To avoid the potential on-chain failure and waste of gas, we recommend you compare max_slippage with minimalMaxSlippage on cBridge contract before sending on-chain transaction. If max_slippage is less than minimalMaxSlippage, guide user increasing input value slippage_tolerance.
Moreover, since max_slippage, bridge_rate, perc_fee and base_fee may change when user interacting with your application, we should get the lastest estimation before final submit to avoid on-chain send failure.
The cross-chain transfer is accepted only. if src_chain_id is the same as dst_chain_id, it may lead to an error
Error handling
Error Code Description
ERROR_CODE_UNDEFINED
0
Error code placeholder
ERROR_CODE_COMMON
500
Chain is disabled
ERROR_NO_TOKEN_ON_DST_CHAIN
1001
Token not supported on destination chain
ERROR_NO_TOKEN_ON_SRC_CHAIN
1002
Token not supported on source chain
ERROR_CODE_NO_ENOUGH_TOKEN_ON_DST_CHAIN
1004
Destination chain token is not enough for transfer
ERROR_CODE_INBOUND_LIQUIDITY_LIMIT
1005
Token pool epoch volume cap reached
ERROR_CODE_TRANSFER_DISABLED
1009
Token transfer between source chain and destination(both direction) is disabled
ERROR_CODE_BAD_LIQ_SLIPPAGE
1012
Bad slippage
ERROR_CODE_ADDRESS_BLOCKED
1015
This address is blocked due to potential security risks, which is alerted by third party organization. Those risks include hacker's address, money laundering and etc.
ERROR_CODE_BLOCK_BRIDGE_DIRECT
1016
Token transfer from source chain to destination(one direction) is disabled
ERROR_CODE_LIQ_OVER_CAP
1017
Token pool total cap reached
ErrCode_ERROR_CODE_VPN_BLOCK
1018
VPN is not allowed when getting transfer estimation
Error with high frequency
ERROR_CODE_INBOUND_LIQUIDITY_LIMIT & ERROR_CODE_LIQ_OVER_CAP
The sending amount is beyond liquidity pool limit. It will happen only for liquidity pool-based transfer. The calculation for inbound liquidity limit of source chain token liquidity pool is TOTAL_LIQUIDITY_ADDED - TOTAL__LIQUIDITY_RELAYED - TOTAL__LIQUIDITY_WITHDRAWN. Once this error code is given, you have to let the users decrease their input sending amount.
ERROR_CODE_NO_ENOUGH_TOKEN_ON_DST_CHAIN
Destination chain doesn’t have enough token for this transfer. It may happen for pool based transfer which bridge rate is fixed to 1.
Estimated Time of Arrival for Transfer
To provide a better user experience, cBridge has a request to indicate user how long it will take to finish a transfer. You may also use this to provide a better time estimation for the users.
Request Sample
GET
https://cbridge-prod2.celer.app/v2/getLatest7DayTransferLatencyForQuery
Path Parameters
src_chain_id*
Number
source chain id
dst_chain_id*
Number
destination chain id
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