func FormatByPattern()

in phonenumbers.go [1156:1214]
42 lines of code
5 McCabe index (conditional complexity)

func FormatByPattern(number *PhoneNumber,
	numberFormat PhoneNumberFormat,
	userDefinedFormats []*NumberFormat) string {

	countryCallingCode := int(number.GetCountryCode())
	nationalSignificantNumber := GetNationalSignificantNumber(number)
	if !hasValidCountryCallingCode(countryCallingCode) {
		return nationalSignificantNumber
	}
	// Note GetRegionCodeForCountryCode() is used because formatting
	// information for regions which share a country calling code is
	// contained by only one region for performance reasons. For example,
	// for NANPA regions it will be contained in the metadata for US.
	regionCode := GetRegionCodeForCountryCode(countryCallingCode)
	// Metadata cannot be null because the country calling code is valid
	metadata := getMetadataForRegionOrCallingCode(countryCallingCode, regionCode)

	formattedNumber := NewBuilder(nil)

	formattingPattern := chooseFormattingPatternForNumber(
		userDefinedFormats, nationalSignificantNumber)
	if formattingPattern == nil {
		// If no pattern above is matched, we format the number as a whole.
		formattedNumber.WriteString(nationalSignificantNumber)
	} else {
		numFormatCopy := &NumberFormat{}
		// Before we do a replacement of the national prefix pattern
		// $NP with the national prefix, we need to copy the rule so
		// that subsequent replacements for different numbers have the
		// appropriate national prefix.
		proto.Merge(numFormatCopy, formattingPattern)
		nationalPrefixFormattingRule := formattingPattern.GetNationalPrefixFormattingRule()
		if len(nationalPrefixFormattingRule) > 0 {
			nationalPrefix := metadata.GetNationalPrefix()
			if len(nationalPrefix) > 0 {
				// Replace $NP with national prefix and $FG with the
				// first group ($1).
				nationalPrefixFormattingRule =
					NP_PATTERN.ReplaceAllString(
						nationalPrefixFormattingRule, nationalPrefix)
				nationalPrefixFormattingRule =
					FG_PATTERN.ReplaceAllString(
						nationalPrefixFormattingRule, "\\$1")
				numFormatCopy.NationalPrefixFormattingRule =
					&nationalPrefixFormattingRule
			} else {
				// We don't want to have a rule for how to format the
				// national prefix if there isn't one.
				numFormatCopy.NationalPrefixFormattingRule = nil
			}
		}
		formattedNumber.WriteString(
			formatNsnUsingPattern(
				nationalSignificantNumber, numFormatCopy, numberFormat))
	}
	maybeAppendFormattedExtension(number, metadata, numberFormat, formattedNumber)
	prefixNumberWithCountryCallingCode(countryCallingCode, numberFormat, formattedNumber)
	return formattedNumber.String()
}