Cache identicons

Fixes #197

Also as a side effect, by creating this `iconFactory.cache` object, we have a convenient place for specifying stock icons for known contracts!

We can just hard-code image addresses in the `ui/lib/icon-factory.js` cache instantiation, and those values will be injected into the identicon image tag `src` attributes.

1 files changed, 52 insertions, 0 deletions

diff --git a/ui/lib/icon-factory.js b/ui/lib/icon-factory.js
new file mode 100644
index 000000000..1b1df9490
--- /dev/null
+++ b/ui/lib/icon-factory.js
@@ -0,0 +1,52 @@
+var iconFactory
+
+module.exports = function(jazzicon) {
+  if (!iconFactory) {
+    iconFactory = new IconFactory(jazzicon)
+  }
+  return iconFactory
+}
+
+function IconFactory(jazzicon) {
+  this.jazzicon = jazzicon
+  this.cache = {}
+}
+
+IconFactory.prototype.iconForAddress = function(address, diameter) {
+  if (this.isCached(address, diameter)) {
+    return this.cache[address][diameter]
+  }
+
+  const dataUri = this.generateNewUri(address, diameter)
+  this.cacheIcon(address, diameter, dataUri)
+  return dataUri
+}
+
+IconFactory.prototype.generateNewUri = function(address, diameter) {
+  var numericRepresentation = jsNumberForAddress(address)
+  var identicon = this.jazzicon(diameter, numericRepresentation)
+  var identiconSrc = identicon.innerHTML
+  var dataUri = 'data:image/svg+xml;charset=utf-8,'+encodeURIComponent(identiconSrc)
+  return dataUri
+}
+
+IconFactory.prototype.cacheIcon = function(address, diameter, icon) {
+  if (!(address in this.cache)) {
+    var sizeCache = {}
+    sizeCache[diameter] = icon
+    return this.cache[address] = sizeCache
+
+  } else {
+    return this.cache[address][diameter] = icon
+  }
+}
+
+IconFactory.prototype.isCached = function(address, diameter) {
+  return address in this.cache && diameter in this.cache[address]
+}
+
+function jsNumberForAddress(address) {
+  var addr = address.slice(2, 10)
+  var seed = parseInt(addr, 16)
+  return seed
+}