#include "deimos/core/status.h"

#include "deimos/core/api_registry.h"
#include "deimos/core/allocator.h"
#include "deimos/core/atomic.h"

static deimos::AllocatorApi* allocator_api;

namespace deimos
{

StringView StatusCodeToString(StatusCode code)
{
    switch (code)
    {
        case StatusCode::kOk: return StringView("OK");
        case StatusCode::kUnknown: return StringView("Unknown error");
        case StatusCode::kInvalidArgument: return StringView("Invalid argument");
        case StatusCode::kUnimplemented: return StringView("Unimplemented");
        case StatusCode::kInternal: return StringView("Internal error");
    }
}

struct StatusRep
{
    Atomic<int32_t>             ref_count;
    StatusCode                  code{};
    StringView                  message;
};

Status::Status(StatusCode code, StringView message)
{
    if (code == StatusCode::kOk || message.empty())
    {
        m_rep = CodeToRep(code);
    }
    else
    {
        void* ptr = allocator_api->system->Allocate((int64_t)sizeof(StatusRep) + message.size() + 1);
        auto* rep = new(ptr) StatusRep;

        char* message_ptr = (char*)ptr + sizeof(StatusRep); // NOLINT
        MemoryCopy(message_ptr, message.data(), message.size());
        message_ptr[message.size()] = '\0'; // NOLINT

        AtomicStore(&rep->ref_count, 1);
        rep->code = code;
        rep->message = StringView(message_ptr, message.size());

        m_rep = std::bit_cast<uintptr_t>(rep);
        Ensures((m_rep & 1U) == 0);
    }
}

void Status::Ref() const
{
    if (!IsInline())
    {
        auto* rep = std::bit_cast<StatusRep*>(m_rep);

        Expects(AtomicLoad(&rep->ref_count) > 0);
        AtomicFetchIncrement(&rep->ref_count);
    }
}

StatusCode Status::RepCode() const
{
    Expects(!IsInline());
    return std::bit_cast<StatusRep*>(m_rep)->code;
}

void Status::Unref() const
{
    if (!IsInline())
    {
        auto* rep = std::bit_cast<StatusRep*>(m_rep);

        Expects(AtomicLoad(&rep->ref_count) > 0);
        if (AtomicFetchDecrement(&rep->ref_count, MemoryOrder::kRelease) == 1)
        {
            AtomicFence(MemoryOrder::kAcquire);
            deimos_StaticAssert(std::is_trivially_destructible_v<StatusRep>);
            allocator_api->system->Free(
                rep, (int64_t)sizeof(StatusRep) + rep->message.size() + 1);
        }
    }
}

void DeimosFormat(IWriter* writer, const Status& status)
{
    if (status.IsInline())
    {
        Format(writer, "[$]", StatusCodeToString(status.code()));
    }
    else
    {
        auto* rep = std::bit_cast<StatusRep*>(status.m_rep);
        Format(writer, "[$: $]", StatusCodeToString(rep->code), rep->message);
    }
}

void InitializeStatus(ApiRegistry* api_registry)
{
    allocator_api = api_registry->Get<AllocatorApi>();
}

} // namespace deimos