/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <https://www.gnu.org/licenses/old-licenses/gpl-2.0>.
 */

/** @file base_bitset_type.hpp Base for bitset types that accept strong types, ones that need some casting like StrongType and enum class. */

#ifndef BASE_BITSET_TYPE_HPP
#define BASE_BITSET_TYPE_HPP

#include "bitmath_func.hpp"

/**
 * Base for bit set wrapper.
 * Allows wrapping strong type values as a bit set. Methods are loosely modelled on std::bitset.
 * @tparam Tvalue_type Type of values to wrap.
 * @tparam Tstorage Storage type required to hold values.
 */
template <typename Timpl, typename Tvalue_type, typename Tstorage, Tstorage Tmask = std::numeric_limits<Tstorage>::max()>
class BaseBitSet {
public:
	using ValueType = Tvalue_type; ///< Value type of this BaseBitSet.
	using BaseType = Tstorage; ///< Storage type of this BaseBitSet, be ConvertibleThroughBase
	static constexpr Tstorage MASK = Tmask; ///< Mask of valid values.

	/** Create an empty bitset. */
	constexpr BaseBitSet() : data(0) {}

	/**
	 * Create a bitset with a given bits that are within the mask of valid values.
	 * @param data The initial set bits.
	 */
	explicit constexpr BaseBitSet(Tstorage data) : data(data & Tmask) {}

	constexpr auto operator <=>(const BaseBitSet &) const noexcept = default;

	/**
	 * Set all bits.
	 * @returns The bit set
	 */
	inline constexpr Timpl &Set()
	{
		this->data = Tmask;
		return static_cast<Timpl&>(*this);
	}

	/**
	 * Set the value-th bit.
	 * @param value Bit to set.
	 * @returns The bit set
	 */
	inline constexpr Timpl &Set(Tvalue_type value)
	{
		this->data |= (1ULL << Timpl::DecayValueType(value));
		return static_cast<Timpl&>(*this);
	}

	/**
	 * Set values from another bitset.
	 * @param other Bitset of values to set.
	 * @returns The bit set
	 */
	inline constexpr Timpl &Set(const Timpl &other)
	{
		this->data |= other.data;
		return static_cast<Timpl&>(*this);
	}

	/**
	 * Assign the value-th bit.
	 * @param value Bit to assign to.
	 * @param set true if the bit should be set, false if the bit should be reset.
	 * @returns The EnumBitset
	 */
	inline constexpr Timpl &Set(Tvalue_type value, bool set)
	{
		return set ? this->Set(value) : this->Reset(value);
	}

	/**
	 * Reset all bits.
	 * @returns The bit set
	 */
	inline constexpr Timpl &Reset()
	{
		this->data = 0;
		return static_cast<Timpl &>(*this);
	}

	/**
	 * Reset the value-th bit.
	 * @param value Bit to reset.
	 * @returns The bit set
	 */
	inline constexpr Timpl &Reset(Tvalue_type value)
	{
		this->data &= ~(1ULL << Timpl::DecayValueType(value));
		return static_cast<Timpl&>(*this);
	}

	/**
	 * Reset values from another bitset.
	 * @param other Bitset of values to reset.
	 * @returns The bit set
	 */
	inline constexpr Timpl &Reset(const Timpl &other)
	{
		this->data &= ~other.data;
		return static_cast<Timpl&>(*this);
	}

	/**
	 * Flip all bits.
	 * @returns The bit set
	 */
	inline constexpr Timpl &Flip()
	{
		this->data ^= Tmask;
		return static_cast<Timpl &>(*this);
	}

	/**
	 * Flip the value-th bit.
	 * @param value Bit to flip.
	 * @returns The bit set
	 */
	inline constexpr Timpl &Flip(Tvalue_type value)
	{
		if (this->Test(value)) {
			return this->Reset(value);
		} else {
			return this->Set(value);
		}
	}

	/**
	 * Flip values from another bitset.
	 * @param other Bitset of values to flip.
	 * @returns The bit set
	 */
	inline constexpr Timpl &Flip(const Timpl &other)
	{
		this->data ^= other.data;
		return static_cast<Timpl&>(*this);
	}

	/**
	 * Test if the value-th bit is set.
	 * @param value Bit to check.
	 * @returns true iff the requested bit is set.
	 */
	inline constexpr bool Test(Tvalue_type value) const
	{
		return (this->data & (1ULL << Timpl::DecayValueType(value))) != 0;
	}

	/**
	 * Test if all of the values are set.
	 * @param other BitSet of values to test.
	 * @returns true iff all of the values are set.
	 */
	inline constexpr bool All(const Timpl &other) const
	{
		return (this->data & other.data) == other.data;
	}

	/**
	 * Test if all of the values are set.
	 * @returns true iff all of the values are set.
	 */
	inline constexpr bool All() const
	{
		return this->data == Tmask;
	}

	/**
	 * Test if any of the given values are set.
	 * @param other BitSet of values to test.
	 * @returns true iff any of the given values are set.
	 */
	inline constexpr bool Any(const Timpl &other) const
	{
		return (this->data & other.data) != 0;
	}

	/**
	 * Test if any of the values are set.
	 * @returns true iff any of the values are set.
	 */
	inline constexpr bool Any() const
	{
		return this->data != 0;
	}

	/**
	 * Test if none of the values are set.
	 * @returns true iff none of the values are set.
	 */
	inline constexpr bool None() const
	{
		return this->data == 0;
	}

	inline constexpr Timpl &operator|=(const Timpl &other)
	{
		this->data |= other.data;
		return static_cast<Timpl &>(*this);
	}

	inline constexpr Timpl operator|(const Timpl &other) const
	{
		return Timpl{static_cast<Tstorage>(this->data | other.data)};
	}

	inline constexpr Timpl &operator&=(const Timpl &other)
	{
		this->data &= other.data;
		return static_cast<Timpl &>(*this);
	}

	inline constexpr Timpl operator&(const Timpl &other) const
	{
		return Timpl{static_cast<Tstorage>(this->data & other.data)};
	}

	/**
	 * Retrieve the raw value behind this bit set.
	 * @returns the raw value.
	 */
	inline constexpr Tstorage base() const noexcept
	{
		return this->data;
	}

	/**
	 * Test that the raw value of this bit set is valid.
	 * @returns true iff the no bits outside the masked value are set.
	 */
	inline constexpr bool IsValid() const
	{
		return (this->base() & Tmask) == this->base();
	}

	/**
	 * Count the number of set bits.
	 * @return The number of bits set to true.
	 */
	inline uint Count() const
	{
		return CountBits(this->base());
	}

	/**
	 * Get the value of the Nth set bit.
	 * @param n The Nth set bit from which we want to know the value.
	 * @return The value of the Nth set bit, or std::nullopt if no Nth bit set.
	 */
	std::optional<Tvalue_type> GetNthSetBit(uint n) const
	{
		for (auto i : *this) {
			if (n == 0) return i;
			--n;
		}

		return std::nullopt;
	}

	/**
	 * Returns an iterator to begin of the set bits.
	 * @return The iterator.
	 */
	auto begin() const { return SetBitIterator<Tvalue_type, Tstorage>(this->data).begin(); }

	/**
	 * Returns an iterator to the end of the set bits.
	 * @return The iterator past the last set bit.
	 */
	auto end() const { return SetBitIterator<Tvalue_type, Tstorage>(this->data).end(); }

private:
	Tstorage data; ///< Bitmask of values.
};

#endif /* BASE_BITSET_TYPE_HPP */
