Function: settleFundingPayment(Position storage self, int256 cumulativeFunding)

This internal function calculates the funding payment owed or credited to the user since their last funding update, adjusts their margin accordingly, and updates the funding snapshot in the position to the current global funding index. Function execution will be skipped if the position.lastCumulativeFunding == cumulativeFunding. The fundingPayment is calculated as the position’s amount multiplied by the difference between the current cumulative premium funding rate and the position’s last cumulative funding snapshot: fundingPayment = position.amount × (cumulativePremiumFunding - position.lastCumulativeFunding)

• If position.isLong, position.amount is considered as positive.

• If !position.isLong, position.amount is considered as negative.

• If fundingPayment is positive, it will be subtracted from the margin (meaning the user pays funding).

• If fundingPayment is negative, it will be added to the margin (meaning the user receives funding).

The position.lastCumulativeFunding will be updated to the current cumulativeFunding.

Branches and code coverage

Intended branches

• If fundingPayment is positive and the user is long, margin is reduced.

  Test coverage

• If fundingPayment is negative and the user is short, margin is reduced.

  Test coverage

• If fundingPayment is positive and the user is short, margin is increased.

  Test coverage

• If fundingPayment is negative and the user is long, margin is increased.

  Test coverage

• lastCumulativeFunding == cumulativeFunding.

  Test coverage

• For a small amount or small marginDelta, the result is calculated correctly.

  Test coverage