Exchange Rate

Pylon Protocol
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Contract Specification
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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state.rs
contract.rs
handler_exec.rs