Ask maker will unfairly lose his complete collateral
Summary
If an ask maker fails to deliver the **complete **used_points, his complete collateral will be unfairly lost.
Vulnerability Details
Assumption: The seller (ask maker) should only lose the collateral corresponding to the unused_points.
Even if a seller is able to pay only part of the used_points, the seller will lose his complete collateral.(The buyer gets the corresponding points and the collateral both)
Since this check wouldnt pass, the seller's balance wont be updated with any amount and thus loses his entire collateral.
This would encourage sellers to always close their offers (before the settlement period starts), so as to get their collateral corresponding to the unused_points back. Also no seller will ever partially settle the points since they get no benefit from doing so, they lose the points and the collateral too.
Note: collateral corresponding to unused_points = offerInfo.amount x collateral x (1 - offerInfo.used_points/offerInfo.points)
Impact
Loss of funds for sellers incase of failure in complete payment.
Tools Used
Manual Review
Recommendations
Refund the sellers balance with the amount corresponding to the unused_points.
Lead Judging Commences
finding-DeliveryPlace-settleAskTaker-settleAskMaker-partial-settlements
Valid high, in settleAskTaker/settleAskMaker, if the original offer maker performs a partial final settlement, the existing checks [here](https://github.com/Cyfrin/2024-08-tadle/blob/main/src/core/DeliveryPlace.sol#L356-L358) and [here](https://github.com/Cyfrin/2024-08-tadle/blob/04fd8634701697184a3f3a5558b41c109866e5f8/src/core/DeliveryPlace.sol#L230-L232) will cause an revert when attempting to complete a full settlement, resulting in their collateral being locked and requiring a rescue from the admin. To note, although examples in the documentation implies settlement in a single click, it is not stated that partial settlements are not allowed, so I believe it is a valid user flow.
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