Java implementation of PaymentRequest mojo service

chrome/android/java/src/org/chromium/chrome/browser/payments/CurrencyStringFormatter.java

Index: chrome/android/java/src/org/chromium/chrome/browser/payments/CurrencyStringFormatter.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/payments/CurrencyStringFormatter.java b/chrome/android/java/src/org/chromium/chrome/browser/payments/CurrencyStringFormatter.java
new file mode 100644
index 0000000000000000000000000000000000000000..b5d1394031e6dfafa9db124dc6c147aadf721204
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/payments/CurrencyStringFormatter.java
@@ -0,0 +1,74 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.payments;
+
+import java.text.DecimalFormatSymbols;
+import java.util.Currency;
+
+/**
+ * Formatter for currency strings that can be too large to parse into numbers.
+ */
+public class CurrencyStringFormatter {
+    /**
+     * The symbol for the currency. For example, the symbol for "USD" is "$".
+     */
+    private final String mCurrencySymbol;
+
+    /**
+     * The number grouping separator. For example, "," in US. 3-digit groups are assumed.
+     */
+    private final char mGroupingSeparator;
+
+    /**
+     * The decimal separator. For example, "." in US and "," in France.
+     */
+    private final char mMonetaryDecimalSeparator;
+
+    /**
+     * Builds the formatter for the given currency code and the current user locale.
+     */
+    public CurrencyStringFormatter(String currencyCode) {
+        mCurrencySymbol = Currency.getInstance(currencyCode).getSymbol();

[Ted C, 2016/04/22 03:59:37]

any chance there is no Currency associated with currencyCode?

[please use gerrit instead, 2016/04/25 19:22:30]

Yes, the spec does not limit to only valid ISO 4217 currencies. I've changed the
code to handle this case as well.

+        DecimalFormatSymbols symbols = new DecimalFormatSymbols();

[Ted C, 2016/04/22 03:59:36]

this looks to use the current user's locale.  what if the currency isn't in
their locale?  If you are paying in USD, should we use the . as the decimal
separator if in France, or because we are in France should we use the,?

[please use gerrit instead, 2016/04/25 19:22:30]

Added the following comment:

// Use the current locale's symbols. For example, use ","
// for decimal separator in France, even if paying in "USD".

This is because we don't want to confuse the user by switching from "." to ","
and vice versa based on the merchant's specified currency. A user would be more
likely to buy things from abroad than to travel abroad, because shipping small
goods costs less than travel. This feature's behavior should reduce user
confusion.

+        mGroupingSeparator = symbols.getGroupingSeparator();
+        mMonetaryDecimalSeparator = symbols.getMonetaryDecimalSeparator();
+    }
+
+    /**
+     * Formats the currency string for display. Does not parse the string into a number, because it
+     * can be too large. The number is formatted for the current locale and follows the symbol of
+     * the currency code.
+     *
+     * @param number The number to format. Should be in "^-?[0-9]+(\.[0-9]+)?$" format.
+     * https://w3c.github.io/browser-payment-api/specs/paymentrequest.html#currencyamount
+     */
+    public String format(String number) {
+        StringBuilder value = new StringBuilder(number);
+        int decimalSeparator = value.indexOf(".");

[Ted C, 2016/04/22 03:59:36]

what happens if there are more than one .?

Should we just use regex w/ groups to match here instead?

Something like ^(-?)([0-9]+)(\.[0-9]+)?$

Then for inserting the decimal separator, it would be a reverse for loop -= 3
for the first group instead of adding one char at a time (using a substring of
the region).

"might" make this a bit more compliant with the spec.

[please use gerrit instead, 2016/04/25 19:22:30]

More than one "." would be rejected in validation stage in
PaymentRequestImpl.show().
Using regex with groups. Would be nice to use group names when we start using
jdk 1.8.
Done. (s/can be too large/might be too large/g)

+        if (decimalSeparator < 0) {
+            String suffix = ".00";
+            value.append(suffix);
+            decimalSeparator = value.length() - suffix.length();
+        } else if (decimalSeparator == value.length() - 2) {
+            value.append('0');
+        }
+
+        final int groupingSize = 3;
+        for (int i = decimalSeparator - groupingSize; i > 0; i -= groupingSize) {
+            if (value.charAt(i) == '-' || value.charAt(i - 1) == '-') {
+                break;
+            }
+
+            value.insert(i, mGroupingSeparator);
+            decimalSeparator++;
+        }
+
+        value.setCharAt(decimalSeparator, mMonetaryDecimalSeparator);
+        value.insert(0, ' ');
+        value.insert(0, mCurrencySymbol);
+
+        return value.toString();
+    }
+}