#include <oaidl.h>
#include <propidl.h>
#include <type_traits>
#include <utility>
#include <string_view>
#include <cassert>
#include <cstdint>

template <typename TVariant>
struct FFBaseVariant : TVariant {
    bool hasValue() {
        return this->vt != VT_EMPTY;
    }

    explicit operator bool() {
        return this->hasValue();
    }

    template <typename T>
    T get() {
        // boolean
        if constexpr (std::is_same_v<T, bool>) {
            assert(this->vt == VT_BOOL);
            return this->boolVal != VARIANT_FALSE;
        }

        // signed
        else if constexpr (std::is_same_v<T, int8_t>) {
            assert(this->vt == VT_I1);
            return this->cVal;
        } else if constexpr (std::is_same_v<T, int16_t>) {
            assert(this->vt == VT_I2);
            return this->iVal;
        } else if constexpr (std::is_same_v<T, int32_t>) {
            assert(this->vt == VT_I4 || this->vt == VT_INT);
            return this->intVal;
        } else if constexpr (std::is_same_v<T, int64_t>) {
            assert(this->vt == VT_I8);
            return this->llVal;
        }

        // unsigned
        else if constexpr (std::is_same_v<T, uint8_t>) {
            assert(this->vt == VT_UI1);
            return this->bVal;
        } else if constexpr (std::is_same_v<T, uint16_t>) {
            assert(this->vt == VT_UI2);
            return this->uiVal;
        } else if constexpr (std::is_same_v<T, uint32_t>) {
            assert(this->vt == VT_UI4 || this->vt == VT_UINT);
            return this->uintVal;
        } else if constexpr (std::is_same_v<T, uint64_t>) {
            assert(this->vt == VT_UI8);
            return this->ullVal;
        }

        // decimal
        else if constexpr (std::is_same_v<T, float>) {
            assert(this->vt == VT_R4);
            return this->fltVal;
        } else if constexpr (std::is_same_v<T, double>) {
            assert(this->vt == VT_R8);
            return this->dblVal;
        }

        // string
        else if constexpr (std::is_same_v<T, std::string_view>) {
            assert(this->vt == VT_LPSTR);
            return this->pcVal;
        } else if constexpr (std::is_same_v<T, std::wstring_view>) {
            assert(this->vt == VT_BSTR || this->vt == VT_LPWSTR);
            if (this->vt == VT_LPWSTR) {
                return this->bstrVal;
            } else {
                return { this->bstrVal, SysStringLen(this->bstrVal) };
            }
        }

        // array signed
        else if constexpr (std::is_same_v<T, std::pair<const int8_t*, uint32_t>>) {
            assert(this->vt & VT_ARRAY);
            assert((this->vt & ~VT_ARRAY) == VT_I1);
            return std::make_pair((int8_t*) this->parray->pvData, this->parray->cDims);
        } else if constexpr (std::is_same_v<T, std::pair<const int16_t*, uint32_t>>) {
            assert(this->vt & VT_ARRAY);
            assert((this->vt & ~VT_ARRAY) == VT_I2);
            return std::make_pair((int16_t*) this->parray->pvData, this->parray->cDims);
        } else if constexpr (std::is_same_v<T, std::pair<const int32_t*, uint32_t>>) {
            assert(this->vt & VT_ARRAY);
            assert((this->vt & ~VT_ARRAY) == VT_I4);
            return std::make_pair((int32_t*) this->parray->pvData, this->parray->cDims);
        } else if constexpr (std::is_same_v<T, std::pair<const int64_t*, uint32_t>>) {
            assert(this->vt & VT_ARRAY);
            assert((this->vt & ~VT_ARRAY) == VT_I8);
            return std::make_pair((int64_t*) this->parray->pvData, this->parray->cDims);
        }

        // array unsigned
        else if constexpr (std::is_same_v<T, std::pair<const uint8_t*, uint32_t>>) {
            assert(this->vt & VT_ARRAY);
            assert((this->vt & ~VT_ARRAY) == VT_UI1);
            return std::make_pair((uint8_t*) this->parray->pvData, this->parray->cDims);
        } else if constexpr (std::is_same_v<T, std::pair<const uint16_t*, uint32_t>>) {
            assert(this->vt & VT_ARRAY);
            assert((this->vt & ~VT_ARRAY) == VT_UI2);
            return std::make_pair((uint16_t*) this->parray->pvData, this->parray->cDims);
        } else if constexpr (std::is_same_v<T, std::pair<const uint32_t*, uint32_t>>) {
            assert(this->vt & VT_ARRAY);
            assert((this->vt & ~VT_ARRAY) == VT_UI4);
            return std::make_pair((uint32_t*) this->parray->pvData, this->parray->cDims);
        } else if constexpr (std::is_same_v<T, std::pair<const uint64_t*, uint32_t>>) {
            assert(this->vt & VT_ARRAY);
            assert((this->vt & ~VT_ARRAY) == VT_UI8);
            return std::make_pair((uint64_t*) this->parray->pvData, this->parray->cDims);
        } else {
            assert(false && "unsupported type");
            __builtin_unreachable();
        }
    }
};

struct FFWmiVariant : FFBaseVariant<VARIANT> {
    FFWmiVariant(const FFWmiVariant&) = delete;
    FFWmiVariant(FFWmiVariant&&); // don't define it to enforce NRVO optimization
    explicit FFWmiVariant() {
        VariantInit(this);
    }
    explicit FFWmiVariant(std::initializer_list<PCWSTR> strings);
    ~FFWmiVariant() {
        VariantClear(this);
    }
};
static_assert(sizeof(FFWmiVariant) == sizeof(VARIANT), "");

struct FFPropVariant : FFBaseVariant<PROPVARIANT> {
    FFPropVariant(const FFPropVariant&) = delete;
    FFPropVariant(FFPropVariant&&); // don't define it to enforce NRVO optimization
    explicit FFPropVariant() {
        PropVariantInit(this);
    }
    ~FFPropVariant() {
        PropVariantClear(this);
    }
};
static_assert(sizeof(FFPropVariant) == sizeof(PROPVARIANT), "");

namespace {
// Provide our bstr_t to avoid libstdc++ dependency
struct bstr_t {
    explicit bstr_t(const wchar_t* str) noexcept : _bstr(SysAllocString(str)) {}
    ~bstr_t(void) noexcept {
        SysFreeString(_bstr);
    }
    explicit operator const wchar_t*(void) const noexcept {
        return _bstr;
    }
    operator BSTR(void) const noexcept {
        return _bstr;
    }

  private:
    BSTR _bstr;
};
} // namespace