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/// @file WASM shim for kj/common.h
/// Provides the minimal KJ types and macros needed to compile Lix headers
/// without linking against the actual KJ library.
#pragma once

#include <cstddef>
#include <cstdint>
#include <memory>
#include <optional>
#include <utility>
#include <functional>

// ---- Core macros ----
#define KJ_FALLTHROUGH [[fallthrough]]

#define KJ_DISALLOW_COPY(T) \
    T(const T &) = delete;  \
    T & operator=(const T &) = delete

#define KJ_DISALLOW_COPY_AND_MOVE(T)   \
    T(const T &) = delete;             \
    T & operator=(const T &) = delete; \
    T(T &&) = delete;                  \
    T & operator=(T &&) = delete

#define KJ_IF_MAYBE(name, expr)                         \
    if (auto & _kj_maybe_ref_ = (expr); _kj_maybe_ref_) \
        if (auto * name = &*_kj_maybe_ref_)

// ---- Maybe<T> ----
namespace kj {

// kj::Maybe<T> — wraps std::optional but also accepts nullptr to mean "no value".
template<typename T>
struct Maybe : std::optional<T>
{
    using std::optional<T>::optional;
    // Allow Maybe<T> x{nullptr} or x = nullptr to mean empty.
    Maybe(std::nullptr_t) : std::optional<T>() {}
    Maybe & operator=(std::nullptr_t)
    {
        this->reset();
        return *this;
    }
};

// ---- Own<T> (owning pointer, like unique_ptr) ----
template<typename T>
using Own = std::unique_ptr<T>;

// ---- Array<T> ----
template<typename T>
struct Array
{
    T * begin()
    {
        return nullptr;
    }
    T * end()
    {
        return nullptr;
    }
    size_t size() const
    {
        return 0;
    }
    T & operator[](size_t)
    {
        return *static_cast<T *>(nullptr);
    }
};

template<>
struct Array<void>
{
    size_t size() const
    {
        return 0;
    }
};

// ---- Vector<T> ----
template<typename T>
struct Vector
{
    template<typename... Args>
    void add(Args &&...)
    {
    } // accepts T or multi-arg (emplace-style)
    void reserve(size_t) {}
    size_t size() const
    {
        return 0;
    }
    Array<T> releaseAsArray()
    {
        return {};
    }
};

// ---- Badge<T> ----
template<typename T>
struct Badge
{
    friend T;
private:
    Badge() {}
};

// ---- defer / KJ_DEFER ----
template<typename F>
struct Deferred
{
    F f;
    bool cancelled = false;
    ~Deferred()
    {
        if (!cancelled) {
            f();
        }
    }
    void cancel()
    {
        cancelled = true;
    }
};
template<typename F>
Deferred<F> defer(F f)
{
    return {std::move(f)};
}

// KJ_DEFER(stmt) — run stmt when scope exits
#define KJ_DEFER(code) auto KJ_DEFER_UNIQUE_NAME_(_kj_defer_, __COUNTER__) = ::kj::defer([&]() { code; })
#define KJ_DEFER_UNIQUE_NAME_(prefix, counter) KJ_DEFER_CONCAT_(prefix, counter)
#define KJ_DEFER_CONCAT_(a, b) a##b

// ---- ListLink / List (intrusive list) ----
template<typename T>
struct ListLink
{
    T * next = nullptr;
    T * prev = nullptr;
    bool isLinked() const
    {
        return next != nullptr;
    }
};

template<typename T, ListLink<T> T::* link_ptr>
struct List
{
    T * head_ = nullptr;
    size_t size_ = 0;

    bool empty() const
    {
        return head_ == nullptr;
    }
    size_t size() const
    {
        return size_;
    }

    T & front()
    {
        return *head_;
    }
    const T & front() const
    {
        return *head_;
    }

    void add(T & elem)
    {
        (elem.*link_ptr).next = head_;
        head_ = &elem;
        size_++;
    }

    void remove(T & elem)
    {
        // Linear scan — acceptable for a shim
        T ** p = &head_;
        while (*p && *p != &elem) {
            p = &((*p->*link_ptr).next);
        }
        if (*p) {
            *p = (elem.*link_ptr).next;
            size_--;
        }
        (elem.*link_ptr).next = nullptr;
    }
};

// ---- StringPtr (kj::StringPtr has a cStr() method) ----
struct StringPtr
{
    const char * ptr = "";
    const char * cStr() const
    {
        return ptr;
    }
    operator const char *() const
    {
        return ptr;
    }
};

// ---- Exception ----
struct Exception
{
    enum class Type { FAILED, OVERLOADED, DISCONNECTED, UNIMPLEMENTED };
    StringPtr getDescription() const
    {
        return {};
    }
    Type getType() const
    {
        return Type::FAILED;
    }
};

// ---- Duration / TimePoint ----
using Duration = int64_t;
using TimePoint = int64_t;

constexpr int64_t minValue = INT64_MIN;

// ---- arrOf / arr ----
template<typename T>
Array<T> arr()
{
    return {};
}

template<typename T, typename... Args>
Array<T> arrOf(Args &&...)
{
    return {};
}

} // namespace kj