package feegrant

import (
	"context"
	"time"

	sdk "github.com/cosmos/cosmos-sdk/types"
)

// FeeAllowanceI implementations are tied to a given fee delegator and delegatee,
// and are used to enforce feegrant limits.
type FeeAllowanceI interface {
	// Accept can use fee payment requested as well as timestamp of the current block
	// to determine whether or not to process this. This is checked in
	// Keeper.UseGrantedFees and the return values should match how it is handled there.
	//
	// If it returns an error, the fee payment is rejected, otherwise it is accepted.
	// The FeeAllowance implementation is expected to update it's internal state
	// and will be saved again after an acceptance.
	//
	// If remove is true (regardless of the error), the FeeAllowance will be deleted from storage
	// (eg. when it is used up). (See call to RevokeAllowance in Keeper.UseGrantedFees)
	Accept(ctx context.Context, fee sdk.Coins, msgs []sdk.Msg) (remove bool, err error)

	// ValidateBasic should evaluate this FeeAllowance for internal consistency.
	// Don't allow negative amounts, or negative periods for example.
	ValidateBasic() error

	// ExpiresAt returns the expiry time of the allowance.
	ExpiresAt() (*time.Time, error)
}
