[Payments] Currency formatter for order amounts.

components/payments/currency_formatter.h

+// Copyright 2017 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.
+
+#ifndef COMPONENTS_PAYMENTS_CURRENCY_FORMATTER_H_
+#define COMPONENTS_PAYMENTS_CURRENCY_FORMATTER_H_
+
+#include <memory>
+#include <string>
+
+#include "base/macros.h"
+#include "base/optional.h"
+#include "base/strings/string16.h"
+#include "third_party/icu/source/common/unicode/locid.h"
+#include "third_party/icu/source/i18n/unicode/numfmt.h"
+
+namespace payments {
+
+// URI specifying the ISO4217 currency code specification. See for details:
+// https://w3c.github.io/browser-payment-api/#paymentcurrencyamount-dictionary
+extern const char kIso4217CurrencySystem[];
+
+// Currency formatter for amounts, according to a currency code, which typically
+// adheres to [ISO4217] (for example, "USD" for US Dollars).
+class CurrencyFormatter {
+ public:
+  // Initializes the CurrencyFormatter for a given |currency_code|,
+  // |currency_system| and |locale_name|. Note that |currency_code| and
+  // |currency_system| should have been validated (as part of
+  // payment_details_validation.h) before this is created.
+  CurrencyFormatter(const std::string& currency_code,
+                    const base::Optional<std::string> currency_system,
+                    const std::string& locale_name);
+  ~CurrencyFormatter();
+
+  // Formats the |amount| according to the currency code that was set. The
+  // result will NOT contain the currency code, nor a subset of it. Rather, the
+  // caller of this function should display the currency code separately. The
+  // return value may contain non-breaking space and is ready for display. In
+  // the case of a failure in initialization of the formatter or during
+  // formatter, this method will return |amount|.
+  base::string16 Format(const std::string& amount);
+
+ private:
+  const icu::Locale locale_;
+  std::unique_ptr<icu::UnicodeString> currency_code_;
+  std::unique_ptr<icu::NumberFormat> icu_formatter_;
+
+  DISALLOW_COPY_AND_ASSIGN(CurrencyFormatter);
+};
+
+}  // namespace payments
+
+#endif  // COMPONENTS_PAYMENTS_CURRENCY_FORMATTER_H_