Smart contracts

use sigil_contract_sdk::{contract, storage, Caller, Result};

#[contract]
pub mod token {
    use super::*;

    pub fn balance_of(_ctx: &Caller, who: String) -> Result<u128> {
        Ok(storage::get(&format!("bal/{who}")).unwrap_or(0))
    }

    pub fn transfer(ctx: &Caller, to: String, amount: u128) -> Result<()> {
        let from = ctx.caller_did();
        let from_bal: u128 = storage::get(&format!("bal/{from}")).unwrap_or(0);
        let from_bal = from_bal.checked_sub(amount).ok_or("insufficient")?;
        storage::set(&format!("bal/{from}"), &from_bal)?;

        let to_bal: u128 = storage::get(&format!("bal/{to}")).unwrap_or(0);
        let to_bal = to_bal.checked_add(amount).ok_or("overflow")?;
        storage::set(&format!("bal/{to}"), &to_bal)?;
        Ok(())
    }
}