Add filter to countries field

index.js

@@ -1,3 +1,4 @@
+const sift = require('sift');
 const provinces = require('provinces');
 const {ApolloServer, gql} = require('apollo-server');
 const {continents, countries, languages} = require('countries-list');
@@ -36,16 +37,51 @@ const typeDefs = gql`
     rtl: Boolean!
   }
 
+  input CountryFilterInput {
+    code: StringQueryOperatorInput
+    currency: StringQueryOperatorInput
+    continent: StringQueryOperatorInput
+  }
+
+  input StringQueryOperatorInput {
+    eq: String
+    ne: String
+    in: [String]
+    nin: [String]
+    regex: String
+    glob: String
+  }
+
   type Query {
     continents: [Continent!]!
     continent(code: ID!): Continent
-    countries: [Country!]!
+    countries(filter: CountryFilterInput): [Country!]!
     country(code: ID!): Country
     languages: [Language!]!
     language(code: ID!): Language
   }
 `;
 
+function siftifyFilter(filter) {
+  return Object.entries(filter).reduce(
+    (acc, [key, operators]) => ({
+      ...acc,
+      [key]: siftifyOperators(operators)
+    }),
+    {}
+  );
+}
+
+function siftifyOperators(operators) {
+  return Object.entries(operators).reduce(
+    (acc, [operator, value]) => ({
+      ...acc,
+      ['$' + operator]: value
+    }),
+    {}
+  );
+}
+
 const resolvers = {
   Country: {
     capital: country => country.capital || null,
@@ -105,11 +141,13 @@ const resolvers = {
         }
       );
     },
-    countries: () =>
-      Object.entries(countries).map(([code, country]) => ({
-        ...country,
-        code
-      })),
+    countries: (parent, {filter = {}}) =>
+      Object.entries(countries)
+        .map(([code, country]) => ({
+          ...country,
+          code
+        }))
+        .filter(sift(siftifyFilter(filter))),
     language(parent, {code}) {
       const language = languages[code];
       return (

package-lock.json

@@ -4153,6 +4153,11 @@
         }
       }
     },
+    "sift": {
+      "version": "12.0.0",
+      "resolved": "https://registry.npmjs.org/sift/-/sift-12.0.0.tgz",
+      "integrity": "sha512-aWQoexMzacDdUrUuPWLrvfHiYCW7QyMYZ6D7ipkuas7gdvn0GoUVzU/fyvPpgPjS49IRvZktCQWYxgWOwACk/A=="
+    },
     "signal-exit": {
       "version": "3.0.2",
       "resolved": "https://registry.npmjs.org/signal-exit/-/signal-exit-3.0.2.tgz",

package.json

@@ -11,7 +11,8 @@
     "apollo-server": "^2.10.1",
     "countries-list": "^2.5.4",
     "graphql": "^14.6.0",
-    "provinces": "^1.11.0"
+    "provinces": "^1.11.0",
+    "sift": "^12.0.0"
   },
   "devDependencies": {
     "@trevorblades/eslint-config": "^7.0.2",