#include "kstd/tests/os_panic.hpp"

#include <kstd/ranges>
#include <kstd/vector>

#include <catch2/catch_test_macros.hpp>

#include <array>
#include <ranges>
#include <utility>

SCENARIO("Vector initialization and construction", "[vector]")
{
  GIVEN("An empty context")
  {
    WHEN("constructing by default")
    {
      kstd::vector<int> v;

      THEN("the vector is empty")
      {
        REQUIRE(v.empty());
      }

      THEN("the size and capacity are zero")
      {
        REQUIRE(v.size() == 0);
        REQUIRE(v.capacity() == 0);
      }
    }

    WHEN("constructing with a specific size")
    {
      kstd::vector<int> v(10);

      THEN("the vector is not empty")
      {
        REQUIRE_FALSE(v.empty());
      }

      THEN("the size is and capacity match the specified value")
      {
        REQUIRE(v.size() == 10);
        REQUIRE(v.capacity() == 10);
      }
    }

    WHEN("constructing from an initializer list")
    {
      kstd::vector<int> v = {1, 2, 3, 4, 5};

      THEN("the vector is not empty")
      {
        REQUIRE_FALSE(v.empty());
      }

      THEN("the size is and capacity match the specified value")
      {
        REQUIRE(v.size() == 5);
        REQUIRE(v.capacity() == 5);
      }

      THEN("the elements are correctly initialized")
      {
        REQUIRE(v[0] == 1);
        REQUIRE(v[1] == 2);
        REQUIRE(v[2] == 3);
        REQUIRE(v[3] == 4);
        REQUIRE(v[4] == 5);
      }
    }
  }

  GIVEN("A non-empty range")
  {
    auto range = std::array<int, 3>{1, 2, 3};

    WHEN("constructing from a random-access iterator range")
    {
      auto v = kstd::vector<int>{std::begin(range), std::end(range)};

      THEN("the vector is not empty")
      {
        REQUIRE_FALSE(v.empty());
      }

      THEN("the size and capacity match the range size")
      {
        REQUIRE(v.size() == std::size(range));
        REQUIRE(v.capacity() == std::size(range));
      }

      THEN("the elements are correctly initialized")
      {
        REQUIRE(v[0] == 1);
        REQUIRE(v[1] == 2);
        REQUIRE(v[2] == 3);
      }
    }

    WHEN("constructing from a range")
    {
      auto v = kstd::vector<int>{kstd::from_range, range};

      THEN("the vector is not empty")
      {
        REQUIRE_FALSE(v.empty());
      }

      THEN("the size and capacity match the range size")
      {
        REQUIRE(v.size() == std::ranges::size(range));
        REQUIRE(v.capacity() == std::ranges::size(range));
      }

      THEN("the elements are correctly initialized")
      {
        REQUIRE(v[0] == 1);
        REQUIRE(v[1] == 2);
        REQUIRE(v[2] == 3);
      }
    }
  }

  GIVEN("A populated vector")
  {
    kstd::vector<int> source = {1, 2, 3, 4, 5};

    WHEN("copy constructing a new vector")
    {
      kstd::vector<int> copy(source);

      THEN("the copy matches the original")
      {
        REQUIRE(copy.size() == source.size());
        REQUIRE(copy.capacity() == source.capacity());
        REQUIRE(copy[0] == 1);
        REQUIRE(copy[1] == 2);
        REQUIRE(copy[2] == 3);
        REQUIRE(copy[3] == 4);
        REQUIRE(copy[4] == 5);
      }

      THEN("the original is left unchanged")
      {
        REQUIRE(source.size() == 5);
        REQUIRE(source.capacity() == 5);
        REQUIRE(source[0] == 1);
        REQUIRE(source[1] == 2);
        REQUIRE(source[2] == 3);
        REQUIRE(source[3] == 4);
        REQUIRE(source[4] == 5);
      }
    }

    WHEN("move constructing a new vector")
    {
      kstd::vector<int> moved(std::move(source));

      THEN("The new vector has the original elements")
      {
        REQUIRE(moved.size() == 5);
        REQUIRE(moved.capacity() == 5);
        REQUIRE(moved[0] == 1);
        REQUIRE(moved[1] == 2);
        REQUIRE(moved[2] == 3);
        REQUIRE(moved[3] == 4);
        REQUIRE(moved[4] == 5);
      }

      THEN("The original vector is left in a valid but unspecified state")
      {
        REQUIRE(source.empty());
        REQUIRE(source.size() == 0);
        REQUIRE(source.capacity() == 0);
      }
    }
  }
}

SCENARIO("Vector element access", "[vector]")
{
  GIVEN("A populated vector")
  {
    kstd::vector<int> v = {10, 20, 30};

    WHEN("accessing elements for reading")
    {
      THEN("operator[] and at() return the correct elements")
      {
        REQUIRE(v[0] == 10);
        REQUIRE(v[1] == 20);
        REQUIRE(v[2] == 30);

        REQUIRE(v.at(0) == 10);
        REQUIRE(v.at(1) == 20);
        REQUIRE(v.at(2) == 30);
      }

      THEN("front() and back() return the first and last elements")
      {
        REQUIRE(v.front() == 10);
        REQUIRE(v.back() == 30);
      }

      THEN("data() return a pointer to the contiguous storage")
      {
        auto ptr = v.data();
        REQUIRE(ptr);
        REQUIRE(ptr[0] == 10);
        REQUIRE(ptr[1] == 20);
        REQUIRE(ptr[2] == 30);
      }

      THEN("accessing out of bounds elements panics")
      {
        REQUIRE_THROWS_AS(v.at(3), kstd::tests::os_panic);
      }
    }

    WHEN("accessing elements for writing")
    {
      v[0] = 100;
      v.at(1) = 200;
      v.back() = 300;

      THEN("the elements are correctly modified")
      {
        REQUIRE(v[0] == 100);
        REQUIRE(v[1] == 200);
        REQUIRE(v[2] == 300);
      }
    }
  }
}

SCENARIO("Vector iterators", "[vector]")
{
  GIVEN("A populated vector")
  {
    kstd::vector<int> v = {1, 2, 3};

    WHEN("using forward iterators")
    {
      THEN("they navigate the elements in the correct forward order")
      {
        auto it = v.begin();
        REQUIRE(it != v.end());
        REQUIRE(*it == 1);

        ++it;
        REQUIRE(it != v.end());
        REQUIRE(*it == 2);

        ++it;
        REQUIRE(it != v.end());
        REQUIRE(*it == 3);

        ++it;
        REQUIRE(it == v.end());
      }

      THEN("const forward iterators provide correct access")
      {
        auto it = v.cbegin();
        REQUIRE(it != v.cend());
        REQUIRE(*it == 1);

        ++it;
        REQUIRE(it != v.cend());
        REQUIRE(*it == 2);

        ++it;
        REQUIRE(it != v.cend());
        REQUIRE(*it == 3);

        ++it;
        REQUIRE(it == v.cend());
      }
    }

    WHEN("using reverse iterators")
    {
      THEN("they navigate the elements in the correct reverse order")
      {
        auto it = v.rbegin();
        REQUIRE(it != v.rend());
        REQUIRE(*it == 3);

        ++it;
        REQUIRE(it != v.rend());
        REQUIRE(*it == 2);

        ++it;
        REQUIRE(it != v.rend());
        REQUIRE(*it == 1);

        ++it;
        REQUIRE(it == v.rend());
      }

      THEN("const reverse iterators provide correct access")
      {
        auto it = v.crbegin();
        REQUIRE(it != v.crend());
        REQUIRE(*it == 3);

        ++it;
        REQUIRE(it != v.crend());
        REQUIRE(*it == 2);

        ++it;
        REQUIRE(it != v.crend());
        REQUIRE(*it == 1);

        ++it;
        REQUIRE(it == v.crend());
      }
    }
  }

  GIVEN("an empty vector")
  {
    kstd::vector<int> v;

    WHEN("getting iterators")
    {
      THEN("begin() equals end() and cbegin() equals cend()")
      {
        REQUIRE(v.begin() == v.end());
        REQUIRE(v.cbegin() == v.cend());
      }

      THEN("rbegin() equals rend() and crbegin() equals crend()")
      {
        REQUIRE(v.rbegin() == v.rend());
        REQUIRE(v.crbegin() == v.crend());
      }
    }
  }
}

SCENARIO("Vector capacity management", "[vector]")
{
  GIVEN("An empty vector")
  {
    kstd::vector<int> v;

    WHEN("reserving space")
    {
      v.reserve(10);

      THEN("the capacity is at least the reserved amount")
      {
        REQUIRE(v.capacity() >= 10);
      }

      THEN("the size is still zero")
      {
        REQUIRE(v.size() == 0);
      }

      THEN("the vector is still empty")
      {
        REQUIRE(v.empty());
      }
    }
  }

  GIVEN("A populated vector with excess capacity")
  {
    kstd::vector<int> v{1, 2, 3};
    v.reserve(10);

    REQUIRE(v.capacity() == 10);

    WHEN("calling shrink_to_fit")
    {
      v.shrink_to_fit();

      THEN("the capacity is reduced to match the size")
      {
        REQUIRE(v.capacity() == 3);
        REQUIRE(v.size() == 3);
      }

      THEN("the elements remain unchanged")
      {
        REQUIRE(v[0] == 1);
        REQUIRE(v[1] == 2);
        REQUIRE(v[2] == 3);
      }
    }
  }
}