Implement starts_with_initial for GenericPointer

src/jsonpointer/include/sourcemeta/jsontoolkit/jsonpointer_pointer.h

@@ -451,6 +451,30 @@ template <typename PropertyT> class GenericPointer {
                       this->data.cbegin());
   }
 
+  /// Check whether a JSON Pointer starts with the initial part of another JSON
+  /// Pointer. For example:
+  ///
+  /// ```cpp
+  /// #include <sourcemeta/jsontoolkit/jsonpointer.h>
+  /// #include <cassert>
+  ///
+  /// const sourcemeta::jsontoolkit::Pointer pointer{"foo", "bar", "baz"};
+  /// const sourcemeta::jsontoolkit::Pointer prefix{"foo", "bar", "qux"};
+  /// assert(pointer.starts_with_initial(prefix));
+  /// ```
+  auto starts_with_initial(const GenericPointer<PropertyT> &other) const
+      -> bool {
+    if (!other.empty()) {
+      for (std::size_t index = 0; index < other.size() - 1; index++) {
+        if (this->data[index] != other.data[index]) {
+          return false;
+        }
+      }
+    }
+
+    return true;
+  }
+
   /// Replace a base of a JSON Pointer with another JSON Pointer. For example:
   ///
   /// ```cpp

test/jsonpointer/CMakeLists.txt

@@ -17,6 +17,7 @@ add_executable(sourcemeta_jsontoolkit_jsonpointer_unit
   jsonpointer_to_uri_test.cc
   jsonpointer_concat_test.cc
   jsonpointer_starts_with_test.cc
+  jsonpointer_starts_with_initial_test.cc
   jsonpointer_rebase_test.cc)
 noa_add_default_options(PRIVATE sourcemeta_jsontoolkit_jsonpointer_unit)
 target_link_libraries(sourcemeta_jsontoolkit_jsonpointer_unit

test/jsonpointer/jsonpointer_starts_with_initial_test.cc

@@ -0,0 +1,81 @@
+#include <gtest/gtest.h>
+
+#include <sourcemeta/jsontoolkit/jsonpointer.h>
+
+TEST(JSONPointer_starts_with_initial, property_prefix_true) {
+  const sourcemeta::jsontoolkit::Pointer pointer{"foo", "bar"};
+  const sourcemeta::jsontoolkit::Pointer prefix{"foo"};
+  EXPECT_TRUE(pointer.starts_with_initial(prefix));
+}
+
+TEST(JSONPointer_starts_with_initial, property_prefix_false) {
+  const sourcemeta::jsontoolkit::Pointer pointer{"foo", "bar"};
+  const sourcemeta::jsontoolkit::Pointer prefix{"bar"};
+  EXPECT_TRUE(pointer.starts_with_initial(prefix));
+}
+
+TEST(JSONPointer_starts_with_initial, index_prefix_false) {
+  const sourcemeta::jsontoolkit::Pointer pointer{0, 1};
+  const sourcemeta::jsontoolkit::Pointer prefix{1};
+  EXPECT_TRUE(pointer.starts_with_initial(prefix));
+}
+
+TEST(JSONPointer_starts_with_initial, property_same) {
+  const sourcemeta::jsontoolkit::Pointer pointer{"foo", "bar"};
+  const sourcemeta::jsontoolkit::Pointer prefix{"foo", "bar"};
+  EXPECT_TRUE(pointer.starts_with_initial(prefix));
+}
+
+TEST(JSONPointer_starts_with_initial, index_same) {
+  const sourcemeta::jsontoolkit::Pointer pointer{0, 1};
+  const sourcemeta::jsontoolkit::Pointer prefix{0, 1};
+  EXPECT_TRUE(pointer.starts_with_initial(prefix));
+}
+
+TEST(JSONPointer_starts_with_initial, property_different) {
+  const sourcemeta::jsontoolkit::Pointer pointer{"foo", "bar"};
+  const sourcemeta::jsontoolkit::Pointer prefix{"bar", "baz"};
+  EXPECT_FALSE(pointer.starts_with_initial(prefix));
+}
+
+TEST(JSONPointer_starts_with_initial, index_different) {
+  const sourcemeta::jsontoolkit::Pointer pointer{0, 1};
+  const sourcemeta::jsontoolkit::Pointer prefix{2, 3};
+  EXPECT_FALSE(pointer.starts_with_initial(prefix));
+}
+
+TEST(JSONPointer_starts_with_initial, non_empty_empty) {
+  const sourcemeta::jsontoolkit::Pointer pointer{"foo"};
+  const sourcemeta::jsontoolkit::Pointer prefix;
+  EXPECT_TRUE(pointer.starts_with_initial(prefix));
+}
+
+TEST(JSONPointer_starts_with_initial, empty_non_empty) {
+  const sourcemeta::jsontoolkit::Pointer pointer;
+  const sourcemeta::jsontoolkit::Pointer prefix{"foo"};
+  EXPECT_TRUE(pointer.starts_with_initial(prefix));
+}
+
+TEST(JSONPointer_starts_with_initial, empty_empty) {
+  const sourcemeta::jsontoolkit::Pointer pointer;
+  const sourcemeta::jsontoolkit::Pointer prefix;
+  EXPECT_TRUE(pointer.starts_with_initial(prefix));
+}
+
+TEST(JSONPointer_starts_with_initial, initial_equal_true) {
+  const sourcemeta::jsontoolkit::Pointer pointer{"foo", "bar"};
+  const sourcemeta::jsontoolkit::Pointer prefix{"foo", "bar", "baz"};
+  EXPECT_TRUE(pointer.starts_with_initial(prefix));
+}
+
+TEST(JSONPointer_starts_with_initial, initial_equal_false) {
+  const sourcemeta::jsontoolkit::Pointer pointer{"foo", "bar"};
+  const sourcemeta::jsontoolkit::Pointer prefix{"foo", "qux", "baz"};
+  EXPECT_FALSE(pointer.starts_with_initial(prefix));
+}
+
+TEST(JSONPointer_starts_with_initial, initial_subset) {
+  const sourcemeta::jsontoolkit::Pointer pointer{"foo", "bar", "qux"};
+  const sourcemeta::jsontoolkit::Pointer prefix{"foo", "bar", "baz"};
+  EXPECT_TRUE(pointer.starts_with_initial(prefix));
+}