Exchange Rate

Deployed at: terra1zvsv534gx7xppq4yfstslmsgc3jmkfak4mlrv4

state.rs

Stores all relevant contract parameters.

pub struct Config {
    pub owner: HumanAddr,
}

owner: the owner address of this contract.

pub struct Token {
    pub status: Status,
    pub exchange_rate: Decimal256,
    pub epoch_period: u64,
    pub weight: Decimal256,
    pub last_updated_at: u64,
}

status: virtual exchange rate enforcement status - Neutral, Running, or Stopped

  • Neutral: logic not yet initialized, throws an error when queried

  • Running: exchange rate calculations valid, returns current exchange_rate when queried & executes update

  • Stopped: exchange rate no longer updating, returns a constant value when queried

exchange_rate: current virtual exchange rate for this pool

epoch_period: minimum time gap between update() calls.

contract.rs

Defines logic entry points for InitMsg, HandleMsg and QueryMsg calls.

pub fn init<S: Storage, A: Api, Q: Querier>(
    deps: &mut Extern<S, A, Q>,
    env: Env,
    _: InitMsg,
) -> StdResult<InitResponse> {
    state::store_config(
        &mut deps.storage,
        &state::Config {
            owner: env.message.sender,
        },
    )?;

    Ok(InitResponse::default())
}

Initializes a new Exchange Rate contract.

pub fn handle<S: Storage, A: Api, Q: Querier>(
    deps: &mut Extern<S, A, Q>,
    env: Env,
    msg: HandleMsg,
) -> StdResult<HandleResponse> {
    match msg {
        HandleMsg::Update { token } => Ok(ExecHandler::update(deps, env, token)?),
        HandleMsg::ConfigToken {
            token,
            exchange_rate,
            epoch_period,
            weight,
        } => Ok(ExecHandler::config_token(
            deps,
            env,
            token,
            exchange_rate,
            epoch_period,
            weight,
        )?),
        HandleMsg::AddToken {
            token,
            base_rate,
            period,
            weight,
        } => Ok(ExecHandler::add_token(
            deps, env, token, base_rate, period, weight,
        )?),
        HandleMsg::Start { tokens } => Ok(ExecHandler::start(deps, env, tokens)?),
        HandleMsg::Stop { tokens } => Ok(ExecHandler::stop(deps, env, tokens)?),
    }
}

Defines HandleMsg endpoints. Calls the following functions per HandleMsg:

Update { token } : calls update(deps, env, token) defined under handler_exec.rs.

ConfigToken { token, exchange_rate, epoch_period, weight, } : calls config_token(deps, env, token, exchange_rate, epoch_period, weight, ) defined under handler_exec.rs.

AddToken { token, base_rate, period, weight, } : calls add_token(deps, env, token, base_rate, period, weight, ) defined under handler_exec.rs.

Start { tokens } : calls start(deps, env, tokens) defined under handler_exec.rs.

Stop { tokens } : calls stop(deps, env, tokens) defined under handler_exec.rs.

pub fn query<S: Storage, A: Api, Q: Querier>(
    deps: &Extern<S, A, Q>,
    msg: QueryMsg,
) -> StdResult<Binary> {
    match msg {
        QueryMsg::ExchangeRateOf { token, blocktime } => {
            Ok(QueryHandler::exchange_rate_of(deps, &token, blocktime)?)
        }
    }
}

Defines QueryMsg endpoints. Calls the following functions per QueryMsg:

ExchangeRateOf { token, blocktime } : calls exchange_rate_of(deps, &token, blocktime) defined under handler_query.rs; Queries the current exchange_rate for token.

handler_exec.rs

Defines core contract execution logic. Functions are as follows:

update: recalculates the current virtual exchange rate for token.

config_token: updates target token profile for calculating virtual exchange rate.

add_token: adds a new target token profile for calculating virtual exchange rate.

start: enables virtual exchange rate calculation.

stop: disables virtual exchange rate calculation.

pub fn update<S: Storage, A: Api, Q: Querier>(
    deps: &mut Extern<S, A, Q>,
    env: Env,
    token: HumanAddr,
) -> StdResult<HandleResponse> {
    let token_addr: CanonicalAddr = deps.api.canonical_address(&token)?;

    let mut token: state::Token = state::read_token(&deps.storage, &token_addr)?;
    if token.status.ne(&state::Status::Running) {
        return Err(StdError::unauthorized());
    }

    let elapsed = env.block.time.sub(token.last_updated_at);
    if elapsed < token.epoch_period {
        return Ok(HandleResponse::default());
    }

    let exchange_rate_before = token.exchange_rate;
    let pow_count = elapsed.div(token.epoch_period);
    for _ in 0..pow_count {
        token.exchange_rate = token.exchange_rate.mul(token.weight);
    }

    token.last_updated_at = env.block.time;

    state::store_token(&mut deps.storage, &token_addr, &token)?;

    Ok(HandleResponse {
        messages: vec![],
        log: vec![
            log("action", "update"),
            log("sender", env.message.sender),
            log("er_before", exchange_rate_before),
            log("er_after", token.exchange_rate),
        ],
        data: None,
    })
}

Recalculates virtual exchange rate for a particular token.

exchange_rate is calculated as:

  • count how many epochs have elapsed since last_updated_at

    • do nothing if at least one epoch has not passed

  • exchange_rate = exchange_rate * weight ^ epochs_passed

pub fn config_token<S: Storage, A: Api, Q: Querier>(
    deps: &mut Extern<S, A, Q>,
    env: Env,
    token: HumanAddr,
    exchange_rate: Option<Decimal256>,
    epoch_period: Option<u64>,
    weight: Option<Decimal256>,
) -> StdResult<HandleResponse> {
    check_owner(deps, &env.message.sender)?;

    let token_addr: CanonicalAddr = deps.api.canonical_address(&token)?;
    let mut token: state::Token = state::read_token(&deps.storage, &token_addr)?;

    if let Some(er) = exchange_rate {
        if token.exchange_rate.gt(&er) {
            return Err(StdError::unauthorized());
        }
        token.exchange_rate = er;
    }
    if let Some(ep) = epoch_period {
        token.epoch_period = ep;
    }
    if let Some(w) = weight {
        token.weight = w;
    }

    state::store_token(&mut deps.storage, &token_addr, &token)?;

    Ok(HandleResponse::default())
}

Updates virtual exchange rate parameters for token. Accepts:

  • token: address of the target token subject to exchange rate updates.

  • exchange_rate: initial exchange rate parameter to be used as a baseline. should be reset on significant deviation.

  • epoch_period: time length of a single epoch used for update calls.

  • weight: exchange rate delta enforced per epoch.

pub fn add_token<S: Storage, A: Api, Q: Querier>(
    deps: &mut Extern<S, A, Q>,
    env: Env,
    token: HumanAddr,
    base_rate: Decimal256,
    period: u64,
    weight: Decimal256,
) -> StdResult<HandleResponse> {
    check_owner(deps, &env.message.sender)?;

    let token_addr: CanonicalAddr = deps.api.canonical_address(&token)?;

    state::store_token(
        &mut deps.storage,
        &token_addr,
        &state::Token {
            exchange_rate: base_rate,
            epoch_period: period,
            status: state::Status::Neutral,
            weight,
            last_updated_at: env.block.time,
        },
    )?;

    Ok(HandleResponse::default())
}

Adds a new token target profile for calculating exchange_rate. Accepts:

  • token: address of the target token subject to exchange rate updates.

  • exchange_rate: initial exchange rate parameter to be used as a baseline. should be reset on significant deviation.

  • epoch_period: time length of a single epoch used for update calls.

  • weight: exchange rate delta enforced per epoch.

pub fn start<S: Storage, A: Api, Q: Querier>(
    deps: &mut Extern<S, A, Q>,
    env: Env,
    tokens: Vec<HumanAddr>,
) -> StdResult<HandleResponse> {
    check_owner(deps, &env.message.sender)?;
    for token in tokens {
        _start(deps, &token, &env.block.time)?;
    }
    Ok(HandleResponse::default())
}

fn _start<S: Storage, A: Api, Q: Querier>(
    deps: &mut Extern<S, A, Q>,
    token: &HumanAddr,
    block_time: &u64,
) -> StdResult<()> {
    let token_addr: CanonicalAddr = deps.api.canonical_address(&token)?;
    let mut token: state::Token = state::read_token(&deps.storage, &token_addr)?;

    token.status = state::Status::Running;
    token.last_updated_at = *block_time;

    Ok(())
}

Changes token.status to Running for all tokens registered with the Exchange Rate contract.

pub fn stop<S: Storage, A: Api, Q: Querier>(
    deps: &mut Extern<S, A, Q>,
    env: Env,
    tokens: Vec<HumanAddr>,
) -> StdResult<HandleResponse> {
    check_owner(deps, &env.message.sender)?;
    for token in tokens {
        _stop(deps, token)?;
    }

    Ok(HandleResponse {
        messages: vec![],
        log: vec![log("action", "stop"), log("sender", env.message.sender)],
        data: None,
    })
}

fn _stop<S: Storage, A: Api, Q: Querier>(
    deps: &mut Extern<S, A, Q>,
    token: HumanAddr,
) -> StdResult<()> {
    let token_addr: CanonicalAddr = deps.api.canonical_address(&token)?;
    let mut token: state::Token = state::read_token(&deps.storage, &token_addr)?;

    token.status = state::Status::Stopped;

    Ok(())
}

Changes token.status to Stopped for all tokens registered with the Exchange Rate contract.

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