Update fungible token to 0.2.0

docs/Standards/Tokens/FungibleToken.html

@@ -151,8 +151,17 @@ <h1 class="menu-title">NEAR Protocol Specification</h1>
  <div id="content" class="content">
  <main>
  <h1><a class="header" href="#fungible-token" id="fungible-token">Fungible Token</a></h1>
+<p>Version <code>0.2.0</code></p>
 <h2><a class="header" href="#summary" id="summary">Summary</a></h2>
 <p>A standard interface for fungible tokens allowing for ownership, escrow and transfer, specifically targeting third-party marketplace integration.</p>
+<h2><a class="header" href="#changelog" id="changelog">Changelog</a></h2>
+<h3><a class="header" href="#020" id="020"><code>0.2.0</code></a></h3>
+<ul>
+<li>Introduce storage deposits. Make every change method payable (able receive attached deposits with the function calls). It requires the caller to attach enough deposit to cover potential storage increase. See <a href="https://github.com/near/core-contracts/issues/47">core-contracts/#47</a></li>
+<li>Replace <code>set_allowance</code> with <code>inc_allowance</code> and <code>dec_allowance</code> to address the issue of allowance front-running. See <a href="https://github.com/near/core-contracts/issues/49">core-contracts/#49</a></li>
+<li>Validate <code>owner_id</code> account ID. See <a href="https://github.com/near/core-contracts/issues/54">core-contracts/#54</a></li>
+<li>Enforce that the <code>new_owner_id</code> is different from the current <code>owner_id</code> for transfer. See <a href="https://github.com/near/core-contracts/issues/55">core-contracts/#55</a></li>
+</ul>
 <h2><a class="header" href="#motivation" id="motivation">Motivation</a></h2>
 <p>NEAR Protocol uses an asynchronous sharded Runtime. This means the following:</p>
 <ul>
@@ -196,6 +205,10 @@ <h2><a class="header" href="#guide-level-explanation" id="guide-level-explanatio
 </ul>
 <p>Note, that the precision is not part of the default standard, since it's not required to perform actions. The minimum
 value is always 1 token.</p>
+<p>The standard acknowledges NEAR storage staking model and accounts for the difference in storage that can be introduced
+by actions on this contract. Since multiple users use the contract, the contract has to account for potential
+storage increase. Thus every change method of the contract that can change the amount of storage must be payable.
+See reference implementation for storage deposits and refunds.</p>
 <h3><a class="header" href="#simple-transfer" id="simple-transfer">Simple transfer</a></h3>
 <p>Alice wants to send 5 wBTC tokens to Bob.</p>
 <p><strong>Assumptions</strong></p>
@@ -298,13 +311,23 @@ <h3><a class="header" href="#multi-token-swap-on-dex" id="multi-token-swap-on-de
 </li>
 </ol>
 <h2><a class="header" href="#reference-level-explanation" id="reference-level-explanation">Reference-level explanation</a></h2>
-<p>The full implementation in Rust can be found there: https://github.com/nearprotocol/near-sdk-rs/blob/master/examples/fungible-token/src/lib.rs</p>
+<p>The full implementation in Rust can be found here: <a href="https://github.com/nearprotocol/near-sdk-rs/blob/master/examples/fungible-token/src/lib.rs">fungible-token</a></p>
 <p><strong>NOTES:</strong></p>
 <ul>
-<li>All amounts, balances and allowance are limited by U128 (max value <code>2**128 - 1</code>).</li>
+<li>All amounts, balances and allowance are limited by <code>U128</code> (max value <code>2**128 - 1</code>).</li>
 <li>Token standard uses JSON for serialization of arguments and results.</li>
 <li>Amounts in arguments and results have are serialized as Base-10 strings, e.g. <code>&quot;100&quot;</code>. This is done to avoid
 JSON limitation of max integer value of <code>2**53</code>.</li>
+<li>The contract tracks the change in storage before and after the call. If the storage increases,
+the contract requires the caller of the contract to attach enough deposit to the function call
+to cover the storage cost.
+This is done to prevent a denial of service attack on the contract by taking all available storage.
+It's because the gas cost of adding new escrow account is cheap, many escrow allowances can be added until the contract
+runs out of storage.
+If the storage decreases, the contract will issue a refund for the cost of the released storage.
+The unused tokens from the attached deposit are also refunded, so it's safe to attach more deposit than required.</li>
+<li>To prevent the deployed contract from being modified or deleted, it should not have any access
+keys on its account.</li>
 </ul>
 <p>Interface:</p>
 <pre><pre class="playpen"><code class="language-rust">
@@ -314,9 +337,21 @@ <h2><a class="header" href="#reference-level-explanation" id="reference-level-ex
 /* CHANGE METHODS */
 /******************/
 
-/// Sets the `allowance` for `escrow_account_id` on the account of the caller of this contract
+/// Increments the `allowance` for `escrow_account_id` by `amount` on the account of the caller of this contract
 /// (`predecessor_id`) who is the balance owner.
-pub fn set_allowance(&amp;mut self, escrow_account_id: AccountId, allowance: U128);
+/// Requirements:
+/// * Caller of the method has to attach deposit enough to cover storage difference at the
+/// fixed storage price defined in the contract.
+#[payable]
+pub fn inc_allowance(&amp;mut self, escrow_account_id: AccountId, amount: U128);
+
+/// Decrements the `allowance` for `escrow_account_id` by `amount` on the account of the caller of this contract
+/// (`predecessor_id`) who is the balance owner.
+/// Requirements:
+/// * Caller of the method has to attach deposit enough to cover storage difference at the
+/// fixed storage price defined in the contract.
+#[payable]
+pub fn dec_allowance(&amp;mut self, escrow_account_id: AccountId, amount: U128);
 
 /// Transfers the `amount` of tokens from `owner_id` to the `new_owner_id`.
 /// Requirements:
@@ -325,13 +360,20 @@ <h2><a class="header" href="#reference-level-explanation" id="reference-level-ex
 /// * If this function is called by an escrow account (`owner_id != predecessor_account_id`),
 /// then the allowance of the caller of the function (`predecessor_account_id`) on
 /// the account of `owner_id` should be greater or equal than the transfer `amount`.
+/// * Caller of the method has to attach deposit enough to cover storage difference at the
+/// fixed storage price defined in the contract.
+#[payable]
 pub fn transfer_from(&amp;mut self, owner_id: AccountId, new_owner_id: AccountId, amount: U128);
 
 
 /// Transfer `amount` of tokens from the caller of the contract (`predecessor_id`) to
 /// `new_owner_id`.
 /// Act the same was as `transfer_from` with `owner_id` equal to the caller of the contract
 /// (`predecessor_id`).
+/// Requirements:
+/// * Caller of the method has to attach deposit enough to cover storage difference at the
+/// fixed storage price defined in the contract.
+#[payable]
 pub fn transfer(&amp;mut self, new_owner_id: AccountId, amount: U128);
 
 /****************/