#ifndef SLANG_CORE_STREAM_H
#define SLANG_CORE_STREAM_H

#include "slang-basic.h"

namespace Slang
{

enum class StdStreamType
{
    ErrorOut,
    Out,
    In,
    CountOf,
};

enum class SeekOrigin
{
    Start,   ///< Seek from the start of the stream
    End,     ///< Seek from the end of the stream
    Current, ///< Seek from the current cursor position
};

class Stream : public RefObject
{
public:
    virtual ~Stream() {}
    /// Get the current 'cursor' position in the stream
    virtual Int64 getPosition() = 0;
    /// Seek the cursor to a position. How the seek is performed is dependent on the 'origin' and
    /// the offset required. NOTE that *any* seek will reset the 'end of stream' status. See 'read'
    /// for requirements for 'isEnd' to be reached.
    virtual SlangResult seek(SeekOrigin origin, Int64 offset) = 0;
    /// Read from the current position into buffer.
    /// If there are less bytes available than requested only the amount available will be read.
    /// outReadBytes holds the actual amount of bytes read. It is valid (and not an error) for read
    /// to return 0 bytes read - even if the end of the stream.
    ///
    /// 'isEnd' only becomes true when a read is performed *past* the end of a stream.
    /// If a non zero read is performed from the end then isEnd must be true.
    ///
    /// Will return an error if there is a reading failure.
    virtual SlangResult read(void* buffer, size_t length, size_t& outReadBytes) = 0;
    /// Write to the stream from current position
    virtual SlangResult write(const void* buffer, size_t length) = 0;
    /// True if the of the stream has been hit. The 'read' method has more discussion as to when
    /// this can occur.
    virtual bool isEnd() = 0;
    /// Returns true if it's possible to read from the stream.
    virtual bool canRead() = 0;
    /// Returns true when it's possible to write to the stream.
    virtual bool canWrite() = 0;
    /// Close the stream. Once closed no more operations can be performed on the stream.
    /// Implies any pending data is flushed.
    virtual void close() = 0;

    /// Only applicable for write streams, flushes any buffers to underlying representation (such as
    /// pipe, or file)
    virtual SlangResult flush() = 0;

    /// Helper function that will also *fail* if the specified amount of bytes aren't read.
    SlangResult readExactly(void* buffer, size_t length);
};

enum class FileMode
{
    Create,
    Open,
    CreateNew,
    Append
};

enum class FileAccess
{
    None = 0,
    Read = 1,
    Write = 2,
    ReadWrite = 3
};

enum class FileShare
{
    None,
    ReadOnly,
    WriteOnly,
    ReadWrite
};

/// Base class for memory streams. Only supports reading and does NOT own contained data.
class MemoryStreamBase : public Stream
{
public:
    typedef Stream Super;

    virtual Int64 getPosition() SLANG_OVERRIDE { return m_position; }
    virtual SlangResult seek(SeekOrigin origin, Int64 offset) SLANG_OVERRIDE;
    virtual SlangResult read(void* buffer, size_t length, size_t& outReadByts) SLANG_OVERRIDE;
    virtual SlangResult write(const void* buffer, size_t length) SLANG_OVERRIDE
    {
        SLANG_UNUSED(buffer);
        SLANG_UNUSED(length);
        return SLANG_E_NOT_IMPLEMENTED;
    }
    virtual bool isEnd() SLANG_OVERRIDE { return m_atEnd; }
    virtual bool canRead() SLANG_OVERRIDE { return (int(m_access) & int(FileAccess::Read)) != 0; }
    virtual bool canWrite() SLANG_OVERRIDE { return (int(m_access) & int(FileAccess::Write)) != 0; }
    virtual void close() SLANG_OVERRIDE { m_access = FileAccess::None; }
    virtual SlangResult flush() SLANG_OVERRIDE
    {
        return canWrite() ? SLANG_OK : SLANG_E_NOT_AVAILABLE;
    }

    /// Get the contents
    ConstArrayView<uint8_t> getContents() const
    {
        return ConstArrayView<uint8_t>(m_contents, m_contentsSize);
    }

    MemoryStreamBase(
        FileAccess access = FileAccess::Read,
        const void* contents = nullptr,
        size_t contentsSize = 0)
        : m_access(access)
    {
        _setContents(contents, contentsSize);
    }

protected:
    /// Set to replace wholly current content with specified content
    void _setContents(const void* contents, size_t contentsSize)
    {
        m_contents = (const uint8_t*)contents;
        m_contentsSize = ptrdiff_t(contentsSize);
        m_position = 0;
        m_atEnd = false;
    }
    /// Update means that the content has changed, but position should be maintained
    void _updateContents(const void* contents, size_t contentsSize)
    {
        const ptrdiff_t newPosition =
            (m_position > ptrdiff_t(contentsSize)) ? ptrdiff_t(contentsSize) : m_position;
        _setContents(contents, contentsSize);
        m_position = newPosition;
    }

    const uint8_t* m_contents; ///< The content held in the stream

    // Using ptrdiff_t (as opposed to size_t) as makes maths simpler
    ptrdiff_t m_contentsSize; ///< Total size of the content in bytes
    ptrdiff_t m_position; ///< The current position within content (valid values can only be between
                          ///< 0 and m_contentSize)

    bool
        m_atEnd; ///< Happens when a read is done and nothing can be returned because already at end

    FileAccess m_access;
};

/// Memory stream that owns it's contents
class OwnedMemoryStream : public MemoryStreamBase
{
public:
    typedef MemoryStreamBase Super;

    virtual SlangResult write(const void* buffer, size_t length) SLANG_OVERRIDE;

    /// Set the contents
    void setContent(const void* contents, size_t contentsSize)
    {
        m_ownedContents.setCount(contentsSize);
        if (contents != nullptr)
        {
            ::memcpy(m_ownedContents.getBuffer(), contents, contentsSize);
        }
        _setContents(m_ownedContents.getBuffer(), m_ownedContents.getCount());
    }

    void swapContents(List<uint8_t>& rhs)
    {
        rhs.swapWith(m_ownedContents);
        _setContents(m_ownedContents.getBuffer(), m_ownedContents.getCount());
    }

    OwnedMemoryStream(FileAccess access)
        : Super(access)
    {
    }

protected:
    List<uint8_t> m_ownedContents;
};

class FileStream : public Stream
{
public:
    typedef Stream Super;

    // Stream interface
    virtual Int64 getPosition() SLANG_OVERRIDE;
    virtual SlangResult seek(SeekOrigin origin, Int64 offset) SLANG_OVERRIDE;
    virtual SlangResult read(void* buffer, size_t length, size_t& outReadBytes) SLANG_OVERRIDE;
    virtual SlangResult write(const void* buffer, size_t length) SLANG_OVERRIDE;
    virtual bool canRead() SLANG_OVERRIDE;
    virtual bool canWrite() SLANG_OVERRIDE;
    virtual void close() SLANG_OVERRIDE;
    virtual bool isEnd() SLANG_OVERRIDE;
    virtual SlangResult flush() SLANG_OVERRIDE;

    FileStream();

    SlangResult init(const String& fileName, FileMode fileMode, FileAccess access, FileShare share);
    SlangResult init(const String& fileName, FileMode fileMode = FileMode::Open);

    ~FileStream();

private:
    SlangResult _init(
        const String& fileName,
        FileMode fileMode,
        FileAccess access,
        FileShare share);

    FILE* m_handle;
    FileAccess m_fileAccess;
    bool m_endReached = false;
};

/* A simple BufferedReader. The valid data is between m_startIndex and getCount().
Can be used as a buffer to build up a result from a stream in memory using 'update' to read to the
appropriate buffer size.
*/
class BufferedReadStream : public Stream
{
public:
    typedef Stream Super;

    virtual Int64 getPosition() SLANG_OVERRIDE;
    virtual SlangResult seek(SeekOrigin origin, Int64 offset) SLANG_OVERRIDE;
    virtual SlangResult read(void* buffer, size_t length, size_t& outReadBytes) SLANG_OVERRIDE;
    virtual SlangResult write(const void* buffer, size_t length) SLANG_OVERRIDE;
    virtual bool canRead() SLANG_OVERRIDE;
    virtual bool canWrite() SLANG_OVERRIDE;
    virtual void close() SLANG_OVERRIDE;
    virtual bool isEnd() SLANG_OVERRIDE;
    virtual SlangResult flush() SLANG_OVERRIDE;

    /// Will read assuming backing stream is
    SlangResult update();

    /// Consume bytes in the buffer.
    void consume(Index byteCount);

    Byte* getBuffer() { return m_buffer.getBuffer() + m_startIndex; }
    const Byte* getBuffer() const { return m_buffer.getBuffer() + m_startIndex; }

    size_t getCount() const { return m_buffer.getCount() - m_startIndex; }

    /// Read until the buffer contains the specified amount of bytes
    SlangResult readUntilContains(size_t size);

    ConstArrayView<Byte> getView() const
    {
        return ConstArrayView<Byte>(getBuffer(), Index(getCount()));
    }
    ArrayView<Byte> getView() { return ArrayView<Byte>(getBuffer(), Index(getCount())); }

    BufferedReadStream(Stream* stream)
        : m_stream(stream), m_startIndex(0)
    {
    }

protected:
    void _resetBuffer()
    {
        m_startIndex = 0;
        m_buffer.setCount(0);
    }

    size_t m_defaultReadSize = 1024; ///< When initiating a read the default read size
    List<Byte> m_buffer;             ///< Holds the characters
    Index m_startIndex;              ///< The start index
    RefPtr<Stream> m_stream;         ///< Stream that is being read from
};

enum class StreamBufferStyle
{
    None,
    Line,
    Full,
};

struct StreamUtil
{
    // Write inputs to writeStream while simultaneously read from readStream and errStream.
    static SlangResult readAndWrite(
        Stream* writeStream,
        ArrayView<Byte> bytesToWrite,
        Stream* readStream,
        List<Byte>& outReadBytes,
        Stream* errStream,
        List<Byte>& outErrBytes);

    /// Appends all bytes that can be read from stream into bytes
    static SlangResult readAll(Stream* stream, size_t readSize, List<Byte>& ioBytes);

    /// Appends all bytes that can be read from stream into bytes
    static SlangResult readAll(Stream* stream, List<Byte>& ioBytes)
    {
        return readAll(stream, 0, ioBytes);
    }

    /// Read as much as can be read until a 0 sized read, or an error and append onto ioBytes
    /// Read size controls the size of each buffer read. Passing 0, will use the default read size.
    static SlangResult read(Stream* stream, size_t readSize, List<Byte>& ioBytes);

    static SlangResult discard(Stream* stream);

    static SlangResult discardAll(Stream* stream);

    static SlangResult readOrDiscard(Stream* stream, size_t readSize, List<Byte>* ioBytes);
    static SlangResult readOrDiscardAll(Stream* stream, size_t readSize, List<Byte>* ioBytes);

    static SlangResult setStreamBufferStyle(StdStreamType stdStream, StreamBufferStyle style);
};


} // namespace Slang

#endif