cpp-useful-iterators/test/cascade_iterator_test.cxx

//
//  cascade_iterator_test.cpp
//  iterator-test
//
//  Created by Sam Jaffe on 9/24/25.
//  Copyright © 2025 Sam Jaffe. All rights reserved.
//

#include "iterator/cascade_iterator.h"

#include "ranges.h"
#include "xcode_gtest_helper.h"

using iterator::cascade_iterator;

struct Baz {
  std::vector<int> ints;
  std::map<int, std::vector<std::string>> tags;
};

struct Bar {
  std::vector<double> doubles;
  std::map<int, Baz> bazes;
};

struct Foo {
  std::map<int, std::map<std::string, int>> example;

  std::vector<Bar> bars_;
  std::vector<Bar> const & bars() const { return bars_; }
  std::vector<Bar> bars_copy() { return bars_; }
};

TEST(CascadeIteratorTest, OneProjectorIsTwoLevels) {
  std::vector<Foo> foos;
  auto iter = cascade_iterator(foos, &Foo::bars);
  testing::StaticAssertTypeEq<decltype(*iter), Bar const &>();
}

TEST(CascadeIteratorTest, TwoProjectorIsThreeLevels) {
  std::vector<Foo> foos;
  auto iter = cascade_iterator(foos, &Foo::bars, &Bar::bazes);
  testing::StaticAssertTypeEq<decltype(*iter),
                              std::tuple<int const &, Baz const &>>();
}

TEST(CascadeIteratorTest, IsRvalueSafe) {
  std::vector<Foo> foos;
  auto iter = cascade_iterator(foos, &Foo::bars_copy, &Bar::bazes);
  testing::StaticAssertTypeEq<decltype(*iter),
                              std::tuple<int const &, Baz const &>>();
}

TEST(CascadeIteratorTest, CanProjectUnboundedTail) {
  std::vector<Foo> foos;
  auto iter = cascade_iterator(foos, iterator::unbounded{}, &Foo::example);
  static_assert(
      std::same_as<decltype(*iter),
                   std::tuple<int const &, std::string const &, int &>>);
  testing::StaticAssertTypeEq<
      decltype(*iter), std::tuple<int const &, std::string const &, int &>>();
}

TEST(CascadeIteratorTest, CanProjectBoundedTail) {
  std::vector<Foo> foos;
  auto iter = cascade_iterator(foos, iterator::bounded<3>{}, &Foo::example);
  static_assert(
      std::same_as<decltype(*iter),
                   std::tuple<int const &, std::string const &, int &>>);
  testing::StaticAssertTypeEq<
      decltype(*iter), std::tuple<int const &, std::string const &, int &>>();
}