/*
 * Copyright 2010-2022 Max Kellermann <max.kellermann@gmail.com>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the
 * distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#pragma once

#include <algorithm>
#include <array>
#include <cassert>
#include <initializer_list>
#include <new>
#include <span>
#include <type_traits>
#include <utility>

/**
 * An array with a maximum size known at compile time.  It keeps track
 * of the actual length at runtime.
 */
template<class T, std::size_t max>
class StaticVector {
	using Storage = std::aligned_storage_t<sizeof(T), alignof(T)>;
	using Array = std::array<Storage, max>;

public:
	using size_type = typename Array::size_type;
	using value_type = T;
	using reference = T &;
	using const_reference =  const T &;
	using pointer =  T *;
	using const_pointer =  const T *;
	using iterator = pointer;
	using const_iterator = const_pointer;

private:
	size_type the_size = 0;
	Array array;

	static constexpr pointer Launder(Storage *storage) noexcept {
		return std::launder(reinterpret_cast<pointer>(storage));
	}

	static constexpr const_pointer Launder(const Storage *storage) noexcept {
		return std::launder(reinterpret_cast<const_pointer>(storage));
	}

public:
	constexpr StaticVector() noexcept = default;

	constexpr StaticVector(size_type _size, const_reference value)
	{
		if (_size > max)
			throw std::bad_alloc{};

		while (_size-- > 0)
			push_back(value);
	}

	/**
	 * Initialise the array with values from the iterator range.
	 */
	template<typename I>
	constexpr StaticVector(I _begin, I _end)
		:the_size(0)
	{
		for (I i = _begin; i != _end; ++i)
			push_back(*i);
	}

	template<typename U>
	constexpr StaticVector(std::initializer_list<U> init) noexcept
		:the_size(init.size())
	{
		static_assert(init.size() <= max);

		for (auto &i : init)
			emplace_back(std::move(i));
	}

	constexpr ~StaticVector() noexcept {
		clear();
	}

	constexpr operator std::span<const T>() const noexcept {
		return {
			Launder(array.data()),
			the_size,
		};
	}

	constexpr operator std::span<T>() noexcept {
		return {
			Launder(array.data()),
			the_size,
		};
	}

	constexpr size_type max_size() const noexcept {
		return max;
	}

	constexpr size_type size() const noexcept {
		return the_size;
	}

	constexpr bool empty() const noexcept {
		return the_size == 0;
	}

	constexpr bool full() const noexcept {
		return the_size == max;
	}

	constexpr void clear() noexcept {
		if constexpr (std::is_trivially_destructible_v<T>) {
			/* we don't need to call any destructor */
			the_size = 0;
		} else {
			while (!empty()) {
				back().~T();
				--the_size;
			}
		}
	}

	/**
	 * Returns one element.  No bounds checking.
	 */
	constexpr reference operator[](size_type i) noexcept {
		assert(i < size());

		return *Launder(&array[i]);
	}

	/**
	 * Returns one constant element.  No bounds checking.
	 */
	constexpr const_reference operator[](size_type i) const noexcept {
		assert(i < size());

		return *Launder(&array[i]);
	}

	constexpr reference front() noexcept {
		assert(!empty());

		return *Launder(&array.front());
	}

	constexpr const_reference front() const noexcept {
		assert(!empty());

		return *Launder(&array.front());
	}

	constexpr reference back() noexcept {
		assert(!empty());

		return *Launder(&array[the_size - 1]);
	}

	constexpr const_reference back() const noexcept {
		assert(!empty());

		return *Launder(&array[the_size - 1]);
	}

	constexpr iterator begin() noexcept {
		return Launder(&array.front());
	}

	constexpr const_iterator begin() const noexcept {
		return Launder(&array.front());
	}

	constexpr iterator end() noexcept {
		return std::next(begin(), the_size);
	}

	constexpr const_iterator end() const noexcept {
		return std::next(begin(), the_size);
	}

	/**
	 * Return address of start of data segment.
	 */
	constexpr pointer data() noexcept {
		return Launder(array.data());
	}

	constexpr const_pointer data() const noexcept {
		return Launder(array.data());
	}

	constexpr void push_back(const_reference value) {
		if (full())
			throw std::bad_alloc{};

		::new(&array[the_size]) T(value);
		++the_size;
	}

	constexpr void push_back(T &&value) {
		if (full())
			throw std::bad_alloc{};

		::new(&array[the_size]) T(std::move(value));
		++the_size;
	}

	template<typename... Args>
	constexpr void emplace_back(Args&&... args) {
		if (full())
			throw std::bad_alloc{};

		::new(&array[the_size]) T(std::forward<Args>(args)...);
		++the_size;
	}
};