cpp-lazy-stream/test/common_test.cxx

//
//  common_test.cxx
//  stream-test
//
//  Created by Sam Jaffe on 4/2/23.
//

#include "stream/view/common.h"

#include <iterator/facade.h>
#include <iterator/sentinel.h>

#include "stream_test.h"

using testing::StaticAssertTypeEq;

struct SizedIterator : iterator::facade<SizedIterator> {
private:
  // Default constructed SizedIterator should not be a vaguely valid state.
  size_t i_{~0ul};
  size_t n_{~0ul};

public:
  SizedIterator() = default;
  SizedIterator(size_t i, size_t n) : i_(i), n_(n) {}

  size_t dereference() const { return i_; }
  void advance(std::ptrdiff_t off) { i_ += off; }
  // Bad detection requires us to provide this...
  // TODO: See if I can use one of these tests to why...
  bool equal_to(SizedIterator const & other) const { return other.i_ == i_; }
  std::ptrdiff_t distance_to(SizedIterator const & other) const {
    return other.i_ - i_;
  }
  bool at_end() const { return i_ >= n_; }
};

MAKE_ITERATOR_FACADE_TYPEDEFS(SizedIterator);

struct SentinelRange {
private:
  size_t size_;

public:
  SentinelRange(size_t size = 0) : size_(size) {}

  SizedIterator begin() const { return {0, size_}; }
  auto end() const { return iterator::sentinel; }
  bool empty() const { return size_ == 0; }
  size_t size() const { return size_; }
};

TEST(CommonView, CoercesSentinelIntoCommon) {
  SentinelRange input(10);

  auto range = input | views::common();

  StaticAssertTypeEq<decltype(range.begin()), decltype(range.end())>();
}

TEST(CommonView, IteratesThroughSameValues) {
  SentinelRange input(10);

  auto range = input | views::common();

  EXPECT_THAT(range, RangesEq(input));
}

TEST(CommonView, PropagatesSize) {
  SentinelRange input(10);

  auto range = input | views::common();

  static_assert(stream::detail::has_size_v<decltype(range)>);
  EXPECT_THAT(range.size(), input.size());
}

TEST(CommonView, PropagatesEmpty) {
  SentinelRange input(10);

  auto range = input | views::common();

  static_assert(stream::detail::has_empty_v<decltype(range)>);
  EXPECT_THAT(range.empty(), input.empty());
}

TEST(CommonView, PassesNonSentinelTypes) {
  std::vector<size_t> input(10);

  auto range = input | views::common();

  StaticAssertTypeEq<decltype(input), decltype(range)>();
}