/**
 * @file   iodevice.h
 * @brief  Declaration of the IODevice class.
 * @author Andreas Aardal Hanssen
 * @date   2002, 2003
 */

#ifndef iodevice_h_included
#define iodevice_h_included

#include "convert.h"  // BincStream

#include <string>

#include <unistd.h>  // ::write

const char CMS_END_OF_LINE[4] = {0x0d, '\n', 0x00, 0x00};

namespace Binc {

  /**
   * @class IODevice
   * @brief The IODevice class provides a framework for reading and writing to device.
   *
   * Implement new devices by inheriting this class and overloading all
   * virtual methods.
   *
   * service() returns the service that the specific device is used
   * for. Two values are "log" and "client".
   *
   * @sa IOFactory, MultilogDevice, SyslogDevice, StdIODevice, SSLDevice
   */
  class IODevice {
  public:
    /// Standard options for an IODevice.
    enum Flags {
      None = 0,
      FlushesOnEndl = 1 << 0,
      HasInputLimit = 1 << 1,
      HasOutputLimit = 1 << 2,
      IsEnabled = 1 << 3,
      HasTimeout = 1 << 4
    };

    /// Errors from when an operation returned false.
    enum class Error { Unknown, Timeout };

    /**
     * Constructs an invalid IODevice.
     *
     * Instances of IODevice perform no operations, and all boolean
     * functions always return false. This constructor is only useful
     * if called from a subclass that reimplements all virtual methods.
     */
    IODevice(int f = 0);

    /// Destructs an IODevice; does nothing.
    virtual ~IODevice();

    /// Clears all data in the input and output buffers.
    void clear();

    /**
     * Sets one or more flags.
     * @param f A bitwise OR of flags from the Flags enum.
     */
    void setFlags(unsigned int f);

    /*!
     * Clears one or more flags.
     * @param f A bitwise OR of flags from the Flags enum.
     */
    void clearFlags(unsigned int f);

    /**
     * Sets the maximum allowed input buffer size. If this size is
     * non-zero and exceeded, reading from the device will fail. This
     * functionality is used to prevent clients from forcing this class
     * to consume so much memory that the program crashes.
     *
     * Setting the max input buffer size to 0 disables the input size
     * limit.
     *
     * @param max The maximum input buffer size in bytes.
     */
    void setMaxInputBufferSize(unsigned int max);

    /**
     * Sets the maximum allowed output buffer size. If this size is
     * non-zero and exceeded, flush() is called implicitly.
     *
     * Setting the max output buffer size to 0 disables the output size
     * limit. This is generally discouraged.
     *
     * As a contrast to setMaxInputBufferSize(), this function is used
     * to bundle up consequent write calls, allowing more efficient use
     * of the underlying device as larger blocks of data are written at
     * a time.
     *
     * @param max The maximum output buffer size in bytes.
     */
    void setMaxOutputBufferSize(unsigned int max);

    /**
     * Sets the device's internal timeout in seconds. This timeout is
     * used both when waiting for data to read and for waiting for the
     * ability to write.
     *
     * If this timeout is exceeded, the read or write function that
     * triggered the timeout will fail.
     *
     * Setting the timeout to 0 disables the timeout.
     *
     * @param t The timeout in seconds.
     * @sa getTimeout()
     */
    void setTimeout(unsigned int t);

    /**
     * Returns the timeout in seconds, or 0 if there is no timeout.
     *
     * @sa setTimeout()
     */
    unsigned int getTimeout() const;

    enum class LogLevel { ErrorLevel, InfoLevel, WarningLevel, DebugLevel };

    /**
     * Sets the output level for the following write operations on this
     * device.
     *
     * The output level is a number which gives the following write
     * operations a priority. You can use setOutputLevelLimit() to
     * filter the write operations valid for different operating modes.
     * This enables you to have certain write operations ignored.
     *
     * For instance, if the output level is set to 0, then "Hello" is
     * written, and the output level is set to 1, followed by writing
     * "Daisy", the output level limit value will decide whether only
     * "Hello" is written, or if also "Daisy" is written.
     *
     * A low value of the level gives higher priority, and a high level
     * will give low priority. The default value is 0, and write
     * operations that are done with output level 0 are never ignored.
     *
     * @param level The output level
     * @sa getOutputLevel(), setOutputLevelLimit()
     */
    void setOutputLevel(LogLevel level);

    /**
     * Returns the current output level.
     *
     * @sa setOutputLevel()
     */
    LogLevel getOutputLevel() const;

    /**
     * Sets the current output level limit. Write operations with a
     * level higher than the output level limit are ignored.
     *
     * @param level The output level limit
     * @sa setOutputLevel()
     */
    void setOutputLevelLimit(LogLevel level);

    /**
     * Returns the current output level limit.
     *
     * @sa setOutputLevelLimit()
     */
    LogLevel getOutputLevelLimit() const;

    /**
     * Returns the number of bytes that have been read from this device
     * since it was created.
     */
    unsigned int getReadCount() const;

    /**
     * Returns the number of bytes that have been written to this
     * device since it was created.
     */
    unsigned int getWriteCount() const;

    /**
     * Calling this function enables the built-in protocol dumping feature in
     * the device. All input and output to this device will be dumped to a file
     * in /tmp.
     */
    void enableProtocolDumping();

    /**
     * Writes data to the device. Depending on the value of the max
     * output buffer size, the data may not be written immediately.
     *
     * @sa setMaxOutputBufferSize()
     */
    template<class T> IODevice &operator<<(const T &source);

    /**
     * Writes data to the device. This function specializes on standard
     * ostream derivatives, such as std::endl.
     */
    IODevice &operator<<(std::ostream &(*source)(std::ostream &));

    /**
     * Returns true if data can be read from the device; otherwise
     * returns false.
     */
    virtual bool canRead() const;

    /**
     * Reads data from the device, and stores this in a string. Returns
     * true on success; otherwise returns false.
     *
     * @param dest The incoming data is stored in this string.
     * @param max No more than this number of bytes is read from the
     * device.
     */
    bool readStr(std::string *dest, unsigned int max = 0);

    /**
     * Reads exactly one byte from the device and stores this in a
     * char. Returns true on success; otherwise returns false.
     *
     * @param dest The incoming byte is stored in this char.
     */
    bool readChar(char *dest = nullptr);

    /*!
      FIXME: add docs
    */
    void unreadChar(char c);

    /*!
      FIXME: add docs
    */
    void unreadStr(const std::string &s);

    /**
     * Reads characters from the device, until and including one
     * certain character is found. All read characters are discarded.
     *
     * This function can be used to skip to the beginning of a line,
     * with the terminating character being '\n'.
     *
     * @param The certain character.
     */
    bool skipTo(char c);

    /**
     * Flushes the output buffer. Writes all data in the output buffer
     * to the device.
     */
    bool flush();

    /**
     * Returns the type of error that most recently occurred.
     */
    Error getLastError() const;

    /**
     * Returns a human readable description of the error that most
     * recently occurred. If no known error has occurred, this method
     * returns "Unknown error".
     */
    std::string getLastErrorString() const;

    /**
     * Returns the type of service provided by this device. Two valid
     * return values are "client" and "log".
     */
    virtual std::string service() const;

  protected:
    /**
     * Waits until data can be written to the device. If the timeout is
     * 0, this function waits indefinitely. Otherwise, it waits until
     * the timeout has expired.
     *
     * If this function returns true, data can be written to the
     * device; otherwise, getLastError() must be checked to determine
     * whether a timeout occurred or whether an error with the device
     * prevents further writing.
     */
    virtual bool waitForWrite() const;

    /**
     * Waits until data can be read from the device.
     *
     * \sa waitForWrite()
     */
    virtual bool waitForRead() const;

    /// Types of results from a write.
    enum WriteResult { WriteWait = 0, WriteDone = 1 << 0, WriteError = 1 << 1 };

    /**
     * Writes as much data as possible to the device. If some but not
     * all data was written, returns WriteWait. If all data was
     * written, returns WriteDone.  If an error occurred, returns
     * WriteError.
     */
    virtual WriteResult write();

    /**
     * Reads data from the device, and stores it in the input buffer.
     * Returns true on success; otherwise returns false.
     *
     * This method will fail if there is no more data available, if a
     * timeout occurred or if an error with the device prevents more
     * data from being read.
     *
     * The number of bytes read from the device is undefined.
     */
    virtual bool fillInputBuffer();

    BincStream inputBuffer;
    BincStream outputBuffer;

    unsigned int flags;
    unsigned int maxInputBufferSize;
    unsigned int maxOutputBufferSize;

    unsigned int timeout;

    size_t readCount;
    size_t writeCount;

    LogLevel outputLevel;
    LogLevel outputLevelLimit;

    mutable Error error;
    mutable std::string errorString;

    int dumpfd;
  };

  template<class T> IODevice &IODevice::operator<<(const T &source)
  {
    if ((flags & IsEnabled) && outputLevel <= outputLevelLimit) {
      outputBuffer << source;

      if (dumpfd) {
        BincStream ss;
        ss << source;
        ::write(dumpfd, ss.str().c_str(), ss.getSize());
      }

      if (flags & HasInputLimit) {
        if (outputBuffer.getSize() > maxOutputBufferSize) flush();
      }
    }

    return *this;
  }
}

#endif