Frosty is a staking contract with special features designed to allow users to stake CW20 tokens with a desired unbonding duration and receive rewards based on their staked amount and duration.

Anyone can instantiate the contract by sending an InstantiateContract transaction. The message must include the following information: stake_token_address, reward_token_address, admin, force_claim_ratio, fee_collector, and max_bond_duration.

Rewards can only be funded by the contract's admin. The contract expects a RewardUpdate message from the CW20 reward contract, which must include a reward_end_date as a Timestamp.

At each RewardUpdate, the contract sets total_rewards as the sum of incoming rewards and remaining rewards. It also sets reward_end_date as the msg.reward_end_date and start_time as the current time.

Users can bond CW20 tokens to the contract by sending a Bond message. The message must include an unbonding_duration_as_days, which must be between 1 and max_bond_duration. When bonded, the user weight is calculated as shown below:

$$ \text{position weight} = \sqrt{{\texttt{duration}}} \times {\text{amount}} $$

Rewards will be calculated depending on the weight of the position. At each update_index call the contract calculates how much reward is to be distubuted as follows

$$ {new Dist Balance = { {now-last Updated} \over {reward End Time-reward Start Time}}*total Reward Supply} $$

$$ {global index = {last Global Index + {new Dist Balance \over total Weight}}} $$

At update_staker_rewards call the contract will calculate rewards for every position of the user(e.g. A user staked for two positions as 10 days and 30 days). Calculation is made as follows

$$ {new Rewards = {global Index-user Index} * position Weight } $$

$$ {pending Rewards += new Rewards }$$

Users can receive their rewards by sending a ReceiveRewards message to the contract.

Users can unbond their staked tokens at any time by sending an UnbondStake transaction. The user must select which position to unbond by including the duration_as_days in the message.

Upon receiving the UnbondStake transaction. The rewards for the corresponding staking position will be updated and sent to the user. The contract will create a claim for bonded tokens to be claimed by user. This claim will not be claimable until the unbonding duration has elapsed. During the unbonding duration, the user will not receive any rewards.

Users can claim their bonded_tokens before the unbonding duration elapsed by paying extra fee. The fee calculation is as follows

$$ {fee = {{release At - now \over release At-unbond At}*force Claim Ratio}*amount} $$