#include <cstdio>
#include <cstdlib>
#include <cinttypes>
#include "nod/Util.hpp"
#include "nod/IFileIO.hpp"

namespace nod
{

class FileIOFILE : public IFileIO
{
    SystemString m_path;
    int64_t m_maxWriteSize;
public:
    FileIOFILE(SystemStringView path, int64_t maxWriteSize)
    : m_path(path), m_maxWriteSize(maxWriteSize) {}

    bool exists()
    {
        FILE* fp = fopen(m_path.c_str(), "rb");
        if (!fp)
            return false;
        fclose(fp);
        return true;
    }

    uint64_t size()
    {
        FILE* fp = fopen(m_path.c_str(), "rb");
        if (!fp)
            return 0;
        FSeek(fp, 0, SEEK_END);
        uint64_t result = FTell(fp);
        fclose(fp);
        return result;
    }

    struct WriteStream : public IFileIO::IWriteStream
    {
        FILE* fp;
        int64_t m_maxWriteSize;
        WriteStream(SystemStringView path, int64_t maxWriteSize, bool& err)
        : m_maxWriteSize(maxWriteSize)
        {
            fp = fopen(path.data(), "wb");
            if (!fp)
            {
                LogModule.report(logvisor::Error, _S("unable to open '%s' for writing"), path.data());
                err = true;
            }
        }
        WriteStream(SystemStringView path, uint64_t offset, int64_t maxWriteSize, bool& err)
        : m_maxWriteSize(maxWriteSize)
        {
            fp = fopen(path.data(), "ab");
            if (!fp)
                goto FailLoc;
            fclose(fp);
            fp = fopen(path.data(), "r+b");
            if (!fp)
                goto FailLoc;
            FSeek(fp, offset, SEEK_SET);
            return;
        FailLoc:
            LogModule.report(logvisor::Error, _S("unable to open '%s' for writing"), path.data());
            err = true;
        }
        ~WriteStream()
        {
            fclose(fp);
        }
        uint64_t write(const void* buf, uint64_t length)
        {
            if (m_maxWriteSize >= 0)
            {
                if (FTell(fp) + length > m_maxWriteSize)
                {
                    LogModule.report(logvisor::Error, _S("write operation exceeds file's %" PRIi64 "-byte limit"), m_maxWriteSize);
                    return 0;
                }
            }
            return fwrite(buf, 1, length, fp);
        }
    };
    std::unique_ptr<IWriteStream> beginWriteStream() const
    {
        bool Err = false;
        auto ret = std::unique_ptr<IWriteStream>(new WriteStream(m_path, m_maxWriteSize, Err));
        if (Err)
            return {};
        return ret;
    }
    std::unique_ptr<IWriteStream> beginWriteStream(uint64_t offset) const
    {
        bool Err = false;
        auto ret = std::unique_ptr<IWriteStream>(new WriteStream(m_path, offset, m_maxWriteSize, Err));
        if (Err)
            return {};
        return ret;
    }

    struct ReadStream : public IFileIO::IReadStream
    {
        FILE* fp;
        ReadStream(SystemStringView path, bool& err)
        {
            fp = fopen(path.data(), "rb");
            if (!fp)
            {
                err = true;
                LogModule.report(logvisor::Error, _S("unable to open '%s' for reading"), path.data());
            }
        }
        ReadStream(SystemStringView path, uint64_t offset, bool& err)
        : ReadStream(path, err)
        {
            if (err)
                return;
            FSeek(fp, offset, SEEK_SET);
        }
        ~ReadStream()
        {
            fclose(fp);
        }
        void seek(int64_t offset, int whence)
        {
            FSeek(fp, offset, whence);
        }
        uint64_t position() const
        {
            return FTell(fp);
        }
        uint64_t read(void* buf, uint64_t length)
        {
            return fread(buf, 1, length, fp);
        }
        uint64_t copyToDisc(IPartWriteStream& discio, uint64_t length)
        {
            uint64_t written = 0;
            uint8_t buf[0x7c00];
            while (length)
            {
                uint64_t thisSz = nod::min(uint64_t(0x7c00), length);
                if (read(buf, thisSz) != thisSz)
                {
                    LogModule.report(logvisor::Error, "unable to read enough from file");
                    return written;
                }
                if (discio.write(buf, thisSz) != thisSz)
                {
                    LogModule.report(logvisor::Error, "unable to write enough to disc");
                    return written;
                }
                length -= thisSz;
                written += thisSz;
            }
            return written;
        }
    };
    std::unique_ptr<IReadStream> beginReadStream() const
    {
        bool Err = false;
        auto ret = std::unique_ptr<IReadStream>(new ReadStream(m_path, Err));
        if (Err)
            return {};
        return ret;
    }
    std::unique_ptr<IReadStream> beginReadStream(uint64_t offset) const
    {
        bool Err = false;
        auto ret = std::unique_ptr<IReadStream>(new ReadStream(m_path, offset, Err));
        if (Err)
            return {};
        return ret;
    }
};

std::unique_ptr<IFileIO> NewFileIO(SystemStringView path, int64_t maxWriteSize)
{
    return std::unique_ptr<IFileIO>(new FileIOFILE(path, maxWriteSize));
}

}