#pragma once

#if !defined(MIJIN_IO_STREAM_HPP_INCLUDED)
#define MIJIN_IO_STREAM_HPP_INCLUDED 1

#include <cassert>
#include <cstdint>
#include <optional>
#include <ranges>
#include <span>
#include <string>
#include "../container/typeless_buffer.hpp"

namespace mijin
{

//
// public defines
//

//
// public constants
//

//
// public types
//

enum class SeekMode
{
    ABSOLUTE,
    RELATIVE,
    RELATIVE_TO_END
};

struct StreamFeatures
{
    bool read  : 1 = false;
    bool write : 1 = false;
    bool tell  : 1 = false;
    bool seek  : 1 = false;
};

enum class FileOpenMode
{
    READ,
    WRITE,
    APPEND,
    READ_WRITE
};

enum class [[nodiscard]] StreamError
{
    SUCCESS,
    IO_ERROR,
    NOT_SUPPORTED,
    UNKNOWN_ERROR
};

class Stream
{
public:
    virtual ~Stream() = default;
    
public:
    virtual StreamError readRaw(std::span<std::uint8_t> buffer, bool partial = false, std::size_t* outBytesRead = nullptr) = 0;
    virtual StreamError writeRaw(std::span<const std::uint8_t> buffer) = 0;
    virtual std::size_t tell() = 0;
    virtual StreamError seek(std::intptr_t pos, SeekMode seekMode = SeekMode::ABSOLUTE) = 0;
    virtual void flush();
    virtual bool isAtEnd() = 0;
    virtual StreamFeatures getFeatures() = 0;

    inline StreamError readRaw(void* outData, std::size_t bytes, bool partial = false, std::size_t* outBytesRead = nullptr)
    {
        std::uint8_t* ptr = static_cast<std::uint8_t*>(outData);
        return readRaw(std::span(ptr, ptr + bytes), partial, outBytesRead);
    }

    template<std::ranges::contiguous_range TRange>
    inline StreamError readRaw(TRange& range, bool partial = false, std::size_t* outBytesRead = nullptr)
    {
        const std::size_t bytes = std::distance(range.begin(), range.end()) * sizeof(std::ranges::range_value_t<TRange>);
        return readRaw(&*range.begin(), bytes, partial, outBytesRead);
    }

    inline StreamError writeRaw(const void* data, std::size_t bytes)
    {
        const std::uint8_t* ptr = static_cast<const std::uint8_t*>(data);
        return writeRaw(std::span(ptr, ptr + bytes));
    }

    template<std::ranges::contiguous_range TRange>
    inline StreamError writeRaw(const TRange& range)
    {
        const std::size_t bytes = std::distance(range.begin(), range.end()) * sizeof(std::ranges::range_value_t<TRange>);
        return writeRaw(&*range.begin(), bytes);
    }

    template<typename T>
    inline StreamError read(T& value)
    {
        return readRaw(&value, sizeof(T));
    }

    template<typename T>
    inline StreamError readSpan(T& values)
    {
        auto asSpan = std::span(values);
        return readRaw(asSpan.data(), asSpan.size_bytes());
    }

    template<typename TItBegin, typename TItEnd>
    inline StreamError readSpan(TItBegin&& begin, TItEnd&& end)
    {
        auto asSpan = std::span(std::forward<TItBegin>(begin), std::forward<TItEnd>(end));
        return readRaw(asSpan.data(), asSpan.size_bytes());
    }

    template<typename T>
    inline StreamError write(const T& value)
    {
        return writeRaw(&value, sizeof(T));
    }

    template<typename T>
    inline StreamError writeSpan(const T& values)
    {
        auto asSpan = std::span(values);
        return writeRaw(asSpan.data(), asSpan.size_bytes());
    }

    template<typename TItBegin, typename TItEnd>
    inline StreamError writeSpan(TItBegin&& begin, TItEnd&& end)
    {
        return writeSpan(std::span(std::forward<TItBegin>(begin), std::forward<TItEnd>(end)));
    }

    StreamError readString(std::string& outString);
    StreamError writeString(std::string_view str);

    StreamError getTotalLength(std::size_t& outLength);
    StreamError readRest(TypelessBuffer& outBuffer);

    template<typename TChar = char>
    StreamError readAsString(std::basic_string<TChar>& outString);
};

class FileStream : public Stream
{
private:
    std::FILE* handle = nullptr; // TODO: wrap in gsl::owner<>
    FileOpenMode mode;
    std::size_t length = 0;
public:
    ~FileStream() override;

    StreamError open(const char* path, FileOpenMode mode_);
    inline StreamError open(const std::string& path, FileOpenMode mode_) {
        return open(path.c_str(), mode_);
    }
    void close();
    [[nodiscard]] inline bool isOpen() const { return handle != nullptr; }

    // Stream overrides
    StreamError readRaw(std::span<std::uint8_t> buffer, bool partial = false, std::size_t* outBytesRead = nullptr) override;
    StreamError writeRaw(std::span<const std::uint8_t> buffer) override;
    std::size_t tell() override;
    StreamError seek(std::intptr_t pos, SeekMode seekMode = SeekMode::ABSOLUTE) override;
    void flush() override;
    bool isAtEnd() override;
    StreamFeatures getFeatures() override;
};

class MemoryStream : public Stream
{
private:
    std::span<std::uint8_t> data_;
    std::size_t pos_ = 0;
    bool canWrite_ = false;
public:
    void openRW(std::span<std::uint8_t> data);
    void openRO(std::span<const std::uint8_t> data);
    void close();
    [[nodiscard]] inline bool isOpen() const { return data_.data() != nullptr; }
    [[nodiscard]] inline std::size_t availableBytes() const {
        assert(isOpen());
        return data_.size() - pos_;
    }

    // Stream overrides
    StreamError readRaw(std::span<std::uint8_t> buffer, bool partial = false, std::size_t* outBytesRead = nullptr) override;
    StreamError writeRaw(std::span<const std::uint8_t> buffer) override;
    std::size_t tell() override;
    StreamError seek(std::intptr_t pos, SeekMode seekMode = SeekMode::ABSOLUTE) override;
    bool isAtEnd() override;
    StreamFeatures getFeatures() override;
};

//
// public functions
//

template<typename TChar>
StreamError Stream::readAsString(std::basic_string<TChar>& outString)
{
    static_assert(sizeof(TChar) == 1, "Can only read to 8-bit character types (char, unsigned char or char8_t");

    // 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();
        outString.resize(length);
        if (StreamError error = readRaw(outString.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<TChar, CHUNK_SIZE> chunk;

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

} // namespace mijin

#endif // !defined(MIJIN_IO_STREAM_HPP_INCLUDED)