fix when fx is same cost token as fx

[ezraripps]

closes #435

Fixes a bug when the fee for an fx transfer is the same token that the user is expected to send to the anchor

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Note

Medium Risk
Touches FX swap construction and settlement validation where token amounts must match quotes; incorrect merging or fee inference could mis-settle funds, though scope is narrow and covered by new tests.

Overview

Summary

FX swaps failed when the quoted fee used the same token as the amount sent to the anchor. The client could not keep a separate fee SEND and the tagged principal SEND in one block, and the server rejected or mis-reported those exchanges.

Related Issues

Closes #435

Changes Made

• Auto-built exchange blocks add swap amount and same-token fee in one principal SEND when the fee token matches the from token
• Exchange block validation totals multiple SENDs of the same token instead of rejecting them
• Completed exchange conversion summaries infer same-token fees from gross from-token sends (net of refunds) when there is no separate fee SEND

Testing

• createExchange succeeds when FX fee is charged in the send token in client.test.ts (end-to-end quote, balances, getExchangeStatus conversion)
• util.test.ts cases for dual same-token SEND blocks (quote-based and non-quote)

Breaking Changes

None

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[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
95.7% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

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[cursor]

Unused same-token fees kept

Medium Severity

Estimate swaps that charge the fee in the from token fund expectedCost.max on the principal SEND, but excess over the live fee is not refundable when affinity is from. The unused buffer stays with the liquidity provider, and conversion.cost reports that gross overage instead of the fee actually charged.

Additional Locations (1)

• src/services/fx/client.ts#L504-L525

 

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