Implement a .contains() method for JSON strings (#1431)

Signed-off-by: Juan Cruz Viotti <[email protected]>

src/json/include/sourcemeta/jsontoolkit/json_value.h

@@ -1099,6 +1099,32 @@ class SOURCEMETA_JSONTOOLKIT_JSON_EXPORT JSON {
   /// ```
   [[nodiscard]] auto contains(const JSON &element) const -> bool;
 
+  /// This method checks if an JSON string contains a given string. For
+  /// example:
+  ///
+  /// ```cpp
+  /// #include <sourcemeta/jsontoolkit/json.h>
+  /// #include <cassert>
+  ///
+  /// const sourcemeta::jsontoolkit::JSON document{"foo bar baz"};
+  /// assert(document.contains("bar"));
+  /// assert(!document.contains("baz"));
+  /// ```
+  [[nodiscard]] auto contains(const String &input) const -> bool;
+
+  /// This method checks if an JSON string contains a given character. For
+  /// example:
+  ///
+  /// ```cpp
+  /// #include <sourcemeta/jsontoolkit/json.h>
+  /// #include <cassert>
+  ///
+  /// const sourcemeta::jsontoolkit::JSON document{"foo"};
+  /// assert(document.contains('f'));
+  /// assert(!document.contains('b'));
+  /// ```
+  [[nodiscard]] auto contains(const String::value_type input) const -> bool;
+
   /// This method checks if an JSON array does not contain duplicated items. For
   /// example:
   ///

src/json/json_value.cc

@@ -712,6 +712,17 @@ JSON::defines_any(std::initializer_list<JSON::String> keys) const -> bool {
                    element) != this->as_array().cend();
 }
 
+[[nodiscard]] auto JSON::contains(const JSON::String &input) const -> bool {
+  assert(this->is_string());
+  return this->to_string().find(input) != JSON::String::npos;
+}
+
+[[nodiscard]] auto JSON::contains(const JSON::String::value_type input) const
+    -> bool {
+  assert(this->is_string());
+  return this->to_string().find(input) != JSON::String::npos;
+}
+
 [[nodiscard]] auto JSON::unique() const -> bool {
   assert(this->is_array());
   const auto &items{this->data_array.data};

test/json/json_string_test.cc

@@ -87,3 +87,23 @@ TEST(JSON_string, unicode_length_1) {
   // https://unicodeplus.com/U+7EAF (UTF-8: 0xE7 0xBA 0xAF)
   EXPECT_EQ(document.at("name").byte_size(), 9);
 }
+
+TEST(JSON_string, contains_true) {
+  const sourcemeta::jsontoolkit::JSON document{"foo bar baz"};
+  EXPECT_TRUE(document.contains("foo"));
+}
+
+TEST(JSON_string, contains_false) {
+  const sourcemeta::jsontoolkit::JSON document{"foo bar baz"};
+  EXPECT_FALSE(document.contains("fooo"));
+}
+
+TEST(JSON_string, contains_character_true) {
+  const sourcemeta::jsontoolkit::JSON document{"foo"};
+  EXPECT_TRUE(document.contains('f'));
+}
+
+TEST(JSON_string, contains_character_false) {
+  const sourcemeta::jsontoolkit::JSON document{"foo"};
+  EXPECT_FALSE(document.contains('b'));
+}