token.js

// This contract is a token contract that supports divisibility.
// As long as the max supply of the token is <= Number.MAX_SAFE_INTEGER
// This will work fine, (all operations are done as integer values)

export function handle (state, action) {
  const balances = state.balances
  const input = action.input
  const caller = action.caller

  if (input.function === 'transfer') {
    const target = input.target

    if (isNaN(input.qty)) {
      throw new ContractError('Invalid quantity')
    }

    const qty = Math.trunc(parseFloat(input.qty) * state.divisibility)

    if (!target) {
      throw new ContractError('No target specified')
    }

    if (qty <= 0 || caller === target) {
      throw new ContractError('Invalid token transfer')
    }
    
    if (!(caller in balances)) {
      throw new ContractError("Caller doesn't have a balance.");
    }

    if (balances[caller] < qty) {
      throw new ContractError(`Caller balance not high enough to send ${qty} token(s)!`)
    }

    // Lower the token balance of the caller
    balances[caller] -= qty
    if (target in balances) {
      // Wallet already exists in state, add new tokens
      balances[target] += qty
    } else {
      // Wallet is new, set starting balance
      balances[target] = qty
    }

    return { state }
  }

  if (input.function === 'balance') {
    const target = input.target
    const ticker = state.ticker
    const divisibility = state.divisibility
    const balance = balances[target] / divisibility

    if (typeof target !== 'string') {
      throw new ContractError('Must specificy target to get balance for')
    }
    if (typeof balances[target] !== 'number') {
      throw new ContractError('Cannnot get balance, target does not exist')
    }

    return { result: { target, ticker, balance: balance.toFixed(divisibility), divisibility } }
  }

  throw new ContractError(`No function supplied or function not recognised: "${input.function}"`)
}