Introduce .getV3Filename() to return a suggested filename for V3 keystores

Author: axic

README.md

@@ -46,6 +46,7 @@ Instance methods:
 * `getPublicKey()` - return the public key
 * `getAddress()` - return the address
 * `getChecksumAddressString()` - return the [address with checksum](https://github.com/ethereum/EIPs/issues/55)
+* `getV3Filename([timestamp])` - return the suggested filename for V3 keystores
 * `toV3(password, [options])` - return the wallet as a JSON string (Version 3 of the Ethereum wallet format)
 
 All of the above instance methods return a Buffer or JSON. Use the `String` suffixed versions for a string output, such as `getPrivateKeyString()`.

index.js

@@ -111,6 +111,28 @@ Wallet.prototype.toV3 = function (password, opts) {
   }
 }
 
+Wallet.prototype.getV3Filename = function (timestamp) {
+  /*
+   * We want a timestamp like 2016-03-15T17-11-33.007598288Z. Date formatting
+   * is a pain in Javascript, everbody knows that. We could use moment.js,
+   * but decide to do it manually in order to save space.
+   *
+   * toJSON() returns a pretty close version, so let's use it. It is not UTC though,
+   * but does it really matter?
+   *
+   * Alternative manual way with padding and Date fields: http://stackoverflow.com/a/7244288/4964819
+   *
+   */
+  var ts = timestamp ? new Date(timestamp) : new Date()
+
+  return [
+    'UTC--',
+    ts.toJSON().replace(/:/g, '-'),
+    '--',
+    this.getAddress().toString('hex')
+  ].join('')
+}
+
 Wallet.prototype.toV3String = function (password, opts) {
   return JSON.stringify(this.toV3(password, opts))
 }

test/index.js

@@ -58,6 +58,12 @@ describe('.generate()', function () {
   })
 })
 
+describe('.getV3Filename()', function () {
+  it('should work', function () {
+    assert.equal(fixturewallet.getV3Filename(1457917509265), 'UTC--2016-03-14T01-05-09.265Z--b14ab53e38da1c172f877dbc6d65e4a1b0474c3c')
+  })
+})
+
 describe('.toV3()', function () {
   var salt = new Buffer('dc9e4a98886738bd8aae134a1f89aaa5a502c3fbd10e336136d4d5fe47448ad6', 'hex')
   var iv = new Buffer('cecacd85e9cb89788b5aab2f93361233', 'hex')