Add support to query countries based on calling code

query.go

@@ -11,10 +11,11 @@ var queryInstance *Query
 
 // Query contains queries for countries, cities, etc.
 type Query struct {
-	Countries          map[string]Country
-	NameToAlpha2       map[string]string
-	Alpha3ToAlpha2     map[string]string
-	NativeNameToAlpha2 map[string]string
+	Countries           map[string]Country
+	NameToAlpha2        map[string]string
+	Alpha3ToAlpha2      map[string]string
+	NativeNameToAlpha2  map[string]string
+	CallingCodeToAlpha2 map[string]string
 }
 
 // FindCountryByName finds a country by given name
@@ -58,6 +59,14 @@ func (q *Query) FindCountryByAlpha(code string) (result Country, err error) {
 	}
 }
 
+func (q *Query) FindCountryByCallingCode(callingCode string) (result Country, err error) {
+	alpha2, exists := q.CallingCodeToAlpha2[callingCode]
+	if !exists {
+		return Country{}, makeError("Could not find country with callingCode", callingCode)
+	}
+	return q.Countries[alpha2], nil
+}
+
 // FindAllCountries returns a list of all countries
 func (q *Query) FindAllCountries() (countries map[string]Country) {
 	return q.Countries

query_test.go

@@ -3,6 +3,7 @@ package gountries
 import (
 	"fmt"
 	"math/rand"
+	"reflect"
 	"sort"
 	"testing"
 
@@ -359,8 +360,40 @@ func TestFindSubdivisionCountryByNameError(t *testing.T) {
 
 	_, err := query.FindSubdivisionCountryByName(subdivisionName)
 	if err != nil {
-		assert.Equal(t, "gountries error. Invalid subdivision name: " + subdivisionName, err.Error())
+		assert.Equal(t, "gountries error. Invalid subdivision name: "+subdivisionName, err.Error())
 	} else {
 		t.Fail()
 	}
 }
+
+func TestFindCountryByCallingCode(t *testing.T) {
+	country, _ := query.FindCountryByName("India")
+	tests := []struct {
+		name            string
+		callingCode     string
+		expectedError   error
+		expectedCountry Country
+	}{
+		{
+			name:            "Find country by valid calling code should return country when calling code is present for countries",
+			callingCode:     "91",
+			expectedError:   nil,
+			expectedCountry: country,
+		},
+		{
+			name:            "Find country by invalid country code should return error when searching for country",
+			callingCode:     "abc",
+			expectedError:   fmt.Errorf("gountries error. Could not find country with callingCode: abc"),
+			expectedCountry: Country{},
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			actualCountry, actualError := query.FindCountryByCallingCode(test.callingCode)
+			if !(reflect.DeepEqual(test.expectedCountry, actualCountry) &&
+				reflect.DeepEqual(test.expectedError, actualError)) {
+				t.Fail()
+			}
+		})
+	}
+}

setup.go

@@ -29,6 +29,7 @@ func NewFromPath(dataPath string) *Query {
 		queryInstance.NameToAlpha2 = populateNameIndex(queryInstance.Countries)
 		queryInstance.Alpha3ToAlpha2 = populateAlphaIndex(queryInstance.Countries)
 		queryInstance.NativeNameToAlpha2 = populateNativeNameIndex(queryInstance.Countries)
+		queryInstance.CallingCodeToAlpha2 = populateCallingCodeIndex(queryInstance.Countries)
 
 		subdivisions := populateSubdivisions(dataPath)
 		for k := range queryInstance.Countries {
@@ -209,3 +210,13 @@ func populateNativeNameIndex(countries map[string]Country) map[string]string {
 	}
 	return index
 }
+
+func populateCallingCodeIndex(countries map[string]Country) map[string]string {
+	index := make(map[string]string)
+	for alpha2, country := range countries {
+		for _, callingCode := range country.CallingCodes {
+			index[callingCode] = alpha2
+		}
+	}
+	return index
+}