#ifndef FURVM_FWD_HPP
#define FURVM_FWD_HPP

#include <cstddef> // IWYU pragma: export
#include <cstdint> // IWYU pragma: export
#include <memory>
#include <string>

/**
 * @brief Furlang's virtual machine.
 */
namespace furvm {

/**
 * @brief A byte.
 *
 * There's nothing more to it.
 */
using byte = std::uint8_t;

/**
 * @brief An offset into bytecode.
 */
using bytecode_pos = std::uint64_t;

/**
 * @brief Handle header with reference count.
 */
template <typename Id>
class refcount_header;

/**
 * @brief Generic handle header.
 */
template <typename Id>
class generic_header;

/**
 * @brief Generic furvm object handle.
 *
 * @tparam Value Type of the handle's value.
 * @tparam Header Type of the handle's header.
 */
template <typename Value, typename Header>
class handle;

/**
 * @brief Container for the handles.
 *
 * @tparam Handle Type of the container's handle.
 */
template <typename Handle, typename = void>
class handle_container;

// constant.hpp

/**
 * @brief Constant index.
 *
 * An index to the constant in module's constant pool.
 */
using constant_index = std::uint16_t;

/**
 * @enum constant_t
 * @brief Constant type.
 */
enum class constant_t : std::uint8_t;

/**
 * @class constant
 * @brief Constant.
 */
class constant;

// instruction.hpp

/**
 * @enum instruction_t
 * @brief Furvm's instruction type.
 */
enum class instruction_t : byte;

/**
 * @struct instruction
 * @brief Furvm's instruction.
 */
struct instruction;

// function.hpp

/**
 * @enum function_t
 * @brief Function type.
 */
enum class function_t : std::uint8_t;

/**
 * @class function
 * @brief Function.
 *
 * A furvm function.
 */
class function;

/**
 * @brief Furvm function's index.
 */
using function_id = std::uint16_t;

/**
 * @brief A handle to a furvm function.
 */
using function_h = handle<function, refcount_header<function_id>>;

// module.hpp

struct mod_type;

using mod_type_id = std::uint32_t;

using mod_type_h = handle<mod_type, generic_header<mod_type_id>>;

/**
 * @class mod
 * @brief Module.
 *
 * A furvm module. Translation unit of furlang.
 */
class mod;

/**
 * @brief An alias to a module shared pointer.
 */
using mod_p = std::shared_ptr<mod>;

/**
 * @brief An alias for a module's identifier.
 */
using mod_id = std::string;

/**
 * @brief A handle to a furvm module.
 */
using mod_h = handle<mod, refcount_header<mod_id>>;

// thing_allocator.hpp

template <typename T>
class thing_allocator;

// thing.hpp

/**
 * @class bad_thing_access
 * @brief Bad thing access exception.
 */
class bad_thing_access;

using thing_type_id = std::uint32_t;

/**
 * @class thing
 * @brief Furvm thing.
 *
 * A stack element. Think of it like of a value in C++ or I guess a class in java.
 */
template <template <typename> typename Allocator = thing_allocator>
class thing;

/**
 * @brief Furvm thing's index.
 */
using thing_id = std::uint32_t;

/**
 * @brief A handle to a thing.
 */
using thing_h = handle<thing<thing_allocator>, refcount_header<thing_id>>;

// executor.hpp

/**
 * @brief A variable index type.
 */
using variable_t = std::uint16_t;

/**
 * @enum executor_flags
 * @brief Flags of an executor.
 */
enum class executor_flags : std::uint32_t;

/**
 * @class executor
 * @brief Furvm executor.
 *
 * Furvm executors are like threads.
 */
class executor;

/**
 * @brief An alias to a executor shared pointer.
 */
using executor_p = std::shared_ptr<executor>;

/**
 * @brief Furvm executor's index.
 */
using executor_id = std::uint32_t;

/**
 * @brief A handle to an executor.
 */
using executor_h = handle<executor, refcount_header<executor_id>>;

// context.hpp

/**
 * @class context
 * @brief Context.
 *
 * A furvm context.
 */
class context;

/**
 * @brief An alias to a context shared pointer.
 */
using context_p = std::shared_ptr<context>;

// exceptions.hpp:

/**
 * @class stack_underflow
 * @brief Stack underflow exception.
 */
class stack_underflow;

} // namespace furvm

#endif // FURVM_FWD_HPP