#include "./stream.hpp"

#include <algorithm>
#include <cassert>
#include <limits>

namespace mijin
{

//
// internal defines
//

//
// internal constants
//

//
// internal types
//

//
// internal variables
//

//
// internal functions
//

//
// public functions
//

void Stream::flush() {}

StreamError Stream::readString(std::string& outString)
{
    std::uint32_t length; // NOLINT(cppcoreguidelines-init-variables)
    StreamError error = read(length);
    if (error != StreamError::SUCCESS) {
        return error;
    }

    std::string result;
    result.resize(length);
    error = readSpan(result.begin(), result.end());
    if (error != StreamError::SUCCESS) {
        return error;
    }
    outString = std::move(result);
    return StreamError::SUCCESS;
}

StreamError Stream::writeString(std::string_view str)
{
    assert(str.length() <= std::numeric_limits<std::uint32_t>::max());
    const std::uint32_t length = static_cast<std::uint32_t>(str.length());
    StreamError error = write(length);
    if (error != StreamError::SUCCESS) {
        return error;
    }
    return writeSpan(str.begin(), str.end());
}

StreamError Stream::getTotalLength(std::size_t& outLength)
{
    const StreamFeatures features = getFeatures();
    if (!features.tell || !features.seek) {
        return StreamError::NOT_SUPPORTED;
    }
    const std::size_t origPos = tell();
    if (StreamError error = seek(0, SeekMode::RELATIVE_TO_END); error != StreamError::SUCCESS)
    {
        return error;
    }
    outLength = tell();
    if (StreamError error = seek(static_cast<std::intptr_t>(origPos)); error != StreamError::SUCCESS)
    {
        return error;
    }
    return StreamError::SUCCESS;
}

StreamError Stream::readRest(TypelessBuffer& outBuffer)
{
    // first try to allocate everything at once
    std::size_t length = 0;
    if (StreamError lengthError = getTotalLength(length); lengthError == StreamError::SUCCESS)
    {
        MIJIN_ASSERT(getFeatures().tell, "How did you find the length if you cannot tell()?");
        length -= tell();
        outBuffer.resize(length);
        if (StreamError error = readRaw(outBuffer.data(), length); error != StreamError::SUCCESS)
        {
            return error;
        }
        return StreamError::SUCCESS;
    }

    // could not determine the size, read chunk-wise
    static constexpr std::size_t CHUNK_SIZE = 4096;
    std::array<std::byte, CHUNK_SIZE> chunk = {};

    while (!isAtEnd())
    {
        std::size_t bytesRead = 0;
        if (StreamError error = readRaw(chunk, true, &bytesRead); error != StreamError::SUCCESS)
        {
            return error;
        }

        outBuffer.resize(outBuffer.byteSize() + bytesRead);
        std::span<std::byte> bufferBytes = outBuffer.makeSpan<std::byte>();
        std::copy_n(chunk.begin(), bytesRead, bufferBytes.end() - static_cast<long>(bytesRead));
    }
    return StreamError::SUCCESS;
}

FileStream::~FileStream()
{
    if (handle) {
        close();
    }
}

StreamError FileStream::open(const char* path, FileOpenMode mode_)
{
    mode = mode_;
    
    const char* modeStr; // NOLINT(cppcoreguidelines-init-variables)
    switch (mode_)
    {
        case FileOpenMode::READ:
            modeStr = "rb";
            break;
        case FileOpenMode::WRITE:
            modeStr = "wb";
            break;
        case FileOpenMode::APPEND:
            modeStr = "ab";
            break;
        case FileOpenMode::READ_WRITE:
            modeStr = "r+b";
            break;
    }
    handle = std::fopen(path, modeStr); // NOLINT(cppcoreguidelines-owning-memory)
    if (!handle && mode_ == FileOpenMode::READ_WRITE) {
        handle = std::fopen(path, "w+b"); // NOLINT(cppcoreguidelines-owning-memory)
    }
    if (!handle) {
        return StreamError::IO_ERROR;
    }

    int result = std::fseek(handle, 0, SEEK_END);
    assert(result == 0);
    length = std::ftell(handle);
    result = std::fseek(handle, 0, SEEK_SET);
    assert(result == 0);

    return StreamError::SUCCESS;
}

void FileStream::close()
{
    assert(handle);
    const int result = std::fclose(handle); // NOLINT(cppcoreguidelines-owning-memory)
    assert(result == 0);
}

StreamError FileStream::readRaw(std::span<std::uint8_t> buffer, bool partial, std::size_t* outBytesRead)
{
    assert(handle);
    assert(mode == FileOpenMode::READ || mode == FileOpenMode::READ_WRITE);

    const std::size_t readBytes = std::fread(buffer.data(), 1, buffer.size(), handle);
    if (std::ferror(handle)) {
        return StreamError::IO_ERROR;
    }
    if (!partial && readBytes < buffer.size()) {
        return StreamError::IO_ERROR;
    }
    if (outBytesRead != nullptr) {
        *outBytesRead = readBytes;
    }
    return StreamError::SUCCESS;
}

StreamError FileStream::writeRaw(std::span<const std::uint8_t> buffer)
{
    assert(handle);
    assert(mode == FileOpenMode::WRITE || mode == FileOpenMode::APPEND || mode == FileOpenMode::READ_WRITE);

    const std::size_t written = std::fwrite(buffer.data(), 1, buffer.size(), handle);
    if (written != buffer.size() || std::ferror(handle)) {
        return StreamError::IO_ERROR;
    }

    length = std::max<std::size_t>(length, std::ftell(handle));
    return StreamError::SUCCESS;
}

std::size_t FileStream::tell()
{
    assert(handle);

    return std::ftell(handle);
}

StreamError FileStream::seek(std::intptr_t pos, SeekMode seekMode)
{
    assert(handle);
    
    int origin; // NOLINT(cppcoreguidelines-init-variables)
    switch (seekMode)
    {
        case SeekMode::ABSOLUTE:
            origin = SEEK_SET;
            break;
        case SeekMode::RELATIVE:
            origin = SEEK_CUR;
            break;
        case SeekMode::RELATIVE_TO_END:
            origin = SEEK_END;
            break;
        default:
            assert(!"Invalid value passed as seekMode!");
            return StreamError::UNKNOWN_ERROR;
    }
    const int result = std::fseek(handle, static_cast<long>(pos), origin);
    if (result != 0 || std::ferror(handle)) {
        return StreamError::IO_ERROR;
    }
    return StreamError::SUCCESS;
}

void FileStream::flush()
{
    const int result = std::fflush(handle);
    assert(result == 0);
}

bool FileStream::isAtEnd()
{
    assert(handle);

    (void) std::fgetc(handle);
    if (std::feof(handle)) {
        return true;
    }
    const int result = std::fseek(handle, -1, SEEK_CUR);
    assert(result == 0);
    return false;
}

StreamFeatures FileStream::getFeatures()
{
    if (handle)
    {
        return {
            .read = (mode == FileOpenMode::READ),
            .write = (mode == FileOpenMode::WRITE || mode == FileOpenMode::APPEND || mode == FileOpenMode::READ_WRITE),
            .tell = true,
            .seek = true
        };
    }
    return {};
}

void MemoryStream::openRW(std::span<std::uint8_t> data)
{
    assert(!isOpen());
    data_ = data;
    pos_ = 0;
    canWrite_ = true;
}

void MemoryStream::openRO(std::span<const std::uint8_t> data)
{
    assert(!isOpen());
    data_ = std::span<std::uint8_t>(const_cast<std::uint8_t*>(data.data()), data.size()); // NOLINT(cppcoreguidelines-pro-type-const-cast) we'll be fine
    pos_ = 0;
    canWrite_ = false;
}

void MemoryStream::close()
{
    assert(isOpen());
    data_ = {};
}

StreamError MemoryStream::readRaw(std::span<std::uint8_t> buffer, bool partial, std::size_t* outBytesRead)
{
    assert(isOpen());
    if (!partial && availableBytes() < buffer.size()) {
        return StreamError::IO_ERROR; // TODO: need more errors?
    }
    const std::size_t numBytes = std::min(buffer.size(), availableBytes());
    std::copy_n(data_.begin() + static_cast<long>(pos_), numBytes, buffer.begin());
    if (outBytesRead) {
        *outBytesRead = numBytes;
    }
    pos_ += numBytes;
    return StreamError::SUCCESS;
}

StreamError MemoryStream::writeRaw(std::span<const std::uint8_t> buffer)
{
    assert(isOpen());
    assert(canWrite_);

    if (availableBytes() < buffer.size()) {
        return StreamError::IO_ERROR;
    }
    std::copy(buffer.begin(), buffer.end(), data_.begin() + static_cast<long>(pos_));
    pos_ += buffer.size();
    return StreamError::SUCCESS;
}

std::size_t MemoryStream::tell()
{
    assert(isOpen());
    return pos_;
}

StreamError MemoryStream::seek(std::intptr_t pos, SeekMode seekMode)
{
    assert(isOpen());
    std::intptr_t newPos = -1;
    switch (seekMode)
    {
        case SeekMode::ABSOLUTE:
            newPos = pos;
            break;
        case SeekMode::RELATIVE:
            newPos = static_cast<std::intptr_t>(pos_) + pos;
            break;
        case SeekMode::RELATIVE_TO_END:
            newPos = static_cast<std::intptr_t>(data_.size()) + pos;
            break;
    }
    if (newPos < 0 || newPos > static_cast<std::intptr_t>(data_.size())) {
        return StreamError::IO_ERROR;
    }
    pos_ = newPos;
    return StreamError::SUCCESS;
}

bool MemoryStream::isAtEnd()
{
    assert(isOpen());
    return pos_ == data_.size();
}

StreamFeatures MemoryStream::getFeatures()
{
    return {
        .read  = true,
        .write = canWrite_,
        .tell  = true,
        .seek  = true
    };
}

} // namespace mijin