Merge branch 'develop' of github.com:MetaMask/metamask-extension into ValidateEmptyKey

1 files changed, 22 insertions, 0 deletions

diff --git a/ui/app/components/send_/send-content/send-amount-row/amount-max-button/amount-max-button.utils.js b/ui/app/components/send_/send-content/send-amount-row/amount-max-button/amount-max-button.utils.js
new file mode 100644
index 000000000..b490a7fd7
--- /dev/null
+++ b/ui/app/components/send_/send-content/send-amount-row/amount-max-button/amount-max-button.utils.js
@@ -0,0 +1,22 @@
+const {
+  multiplyCurrencies,
+  subtractCurrencies,
+} = require('../../../../../conversion-util')
+const ethUtil = require('ethereumjs-util')
+
+function calcMaxAmount ({ balance, gasTotal, selectedToken, tokenBalance }) {
+    const { decimals } = selectedToken || {}
+    const multiplier = Math.pow(10, Number(decimals || 0))
+
+    return selectedToken
+      ? multiplyCurrencies(tokenBalance, multiplier, {toNumericBase: 'hex'})
+      : subtractCurrencies(
+        ethUtil.addHexPrefix(balance),
+        ethUtil.addHexPrefix(gasTotal),
+        { toNumericBase: 'hex' }
+      )
+}
+
+module.exports = {
+  calcMaxAmount,
+}