#ifndef epicsPV_h
#define epicsPV_h

#include <cadef.h>
#include <alarm.h>
#include <iostream>
#include <stdexcept>

// How epicsPVs work:
// A PV is a container for a remote named value provided via a so
// called EPICS "channel". It is "linked" to the channel in the
// constructor or later via the link() call.
// Because the original value is remote, the PV can only contain
// a copy of the original value.
// With the get() call, the PV is updated from the remote value.
// With the put() call, the remote value is updated from the PV.


// Channel Access datatypes (plus caTypeNative as default value)
// depending on the datatype of a PV, exporting the value
// to double, long or const char* may give different results
typedef enum {
    caTypeString,
    caTypeShort,
    caTypeFloat,
    caTypeEnum,
    caTypeChar,
    caTypeLong,
    caTypeDouble,
    caTypeNoAccess,
    caTypeNative
} caDatatype;

class epicsExceptionOutOfMemory {};
class epicsExceptionNoData {};
class epicsExceptionOutOfBounds {};
class epicsExceptionInvalidConversion {};

class epicsPV
{
public:
    // create PV and optionally link it to an EPICS channel
    // normally, you call the constructor with channelName but without
    // preferredDatatype to use the native datatype of the channel
    // you may read back datatype later
    epicsPV(const char* channelName=NULL, caDatatype preferredDatatype=caTypeNative);
    
    // destroy PV and free all resources
    virtual ~epicsPV();
    
    // explititely (re-)link PV to a (different) EPICS channel
    // it is normally called by the constructor and destructor.
    // note: linking does not yet send a search request to the
    // network until waitForConnect is called (probably implicitely)
    void link(const char* channelName, caDatatype preferredDatatype=caTypeNative);
    void unlink();
    
    // wait until all (or one) PVs are connected
    // timeoutSec = 0.0 just sends connect requests but does not wait
    // timeoutSec < 0.0 means wait forever
    // returns remaining seconds
    // calling this function is optional because it will be called
    // implicitely before the first get or put on an unconnected PV
    static double waitForConnect(double timeoutSec=5.0, epicsPV* pv=NULL);
    
    // these functions are called when the connection state changes
    // the default implementation does nothing
    // overwrite them if you want
    // connectionUpEvent is called after all data is initialized
    // connectionDownEvent is called before any data is deleted
    virtual void connectionUpEvent();
    virtual void connectionDownEvent();
    
    // get and put data
    epicsPV& get(double timeoutSec=2.0);
    static int getPVs(double timeoutSec, epicsPV* pv1, ...);
    
    epicsPV& put(const void* value, unsigned long elements, caDatatype datatype, double timeoutSec=0.0);
    epicsPV& put(long value, double timeoutSec=0.0)
        { return put(&value, 1, caTypeLong, timeoutSec); }
    epicsPV& put(double value, double timeoutSec=0.0)
        { return put(&value, 1, caTypeDouble, timeoutSec); }
    epicsPV& put(const char* value, double timeoutSec=0.0)
        { return put(value, 1, caTypeString, timeoutSec); }
    
    // read back channel name (what you provided to link or constuctor)
    const char* name() const
        { return channel ? ca_name(channel) : ""; }
        
    // find out connection state
    // see $(EPICS_BASE)/include/cadef.h for valid values
    channel_state connectionState() const
        { return channel ? ca_state(channel) : cs_never_conn; }
    const char* connectionStateStr() const
        { return connectionStateStrings[connectionState()]; }
    static const char* connectionStateStr(channel_state state)
        { return connectionStateStrings[state]; }
    
// The following methods return information which is available
// as soon as the PV is connected.
 
    // return currently used data type
    caDatatype datatype() const
        { return usedDatatype; }
    const char* datatypeStr() const
        { return dataTypeStrings[datatype()+1]; }
      
    // return number of elements (for array data)
    unsigned long elements() const
        { return channel ? 0 : ca_element_count(channel); }

    // return units and precision (.EGU and .PREC fields)
    const char* units() const;
    int precision() const;
    
    // return access rights (might change at run-time)
    bool hasReadAccess() const
        { return channel ? ca_read_access(channel) : false; }
    bool hasWriteAccess() const
        { return channel ? ca_write_access(channel) : false; }
    
// The following methods return information which is available
// after a successful get().
    
    // return alarm severity and status (.SEVR and .STAT fields)
    // see $(EPICS_BASE)/include/alarm.h for valid values
    // not conencted PV returns epicsSevInvalid/epicsAlarmNone
    epicsAlarmSeverity alarmSeverity() const
        { if (data)
          { epicsUInt16 sevr = static_cast<dbr_time_string*>(data)->severity;
            if (sevr <= lastEpicsAlarmSev)
                return static_cast<epicsAlarmSeverity>(sevr);
          }
          return epicsSevInvalid;
        }
    const char* alarmSeverityStr() const
        {  return epicsAlarmSeverityStrings[alarmSeverity()]; }
    static const char* alarmSeverityStr(epicsAlarmSeverity severity)
        {  return epicsAlarmSeverityStrings[severity]; }
    epicsAlarmCondition alarmStatus() const
        { if (data)
          { epicsUInt16 stat = static_cast<dbr_time_string*>(data)->status;
            if (stat <= lastEpicsAlarmCond)
                return static_cast<epicsAlarmCondition>(stat);
          }
          return epicsAlarmNone;
        }
    const char* alarmStatusStr() const
        {  return epicsAlarmConditionStrings[alarmStatus()]; }
    static const char* alarmStatusStr(epicsAlarmCondition status)
        {  return epicsAlarmConditionStrings[status]; }

    // return time of record processing
    // see $(EPICS_BASE)/include/epicsTime.h for class epicsTime
    epicsTime timestamp() const
        { if (data)
          { return epicsTime(static_cast<dbr_time_string*>(data)->stamp);
          }
          return epicsTime();
        }
    
    // return value of pv
    
    long toLong(unsigned long index = 0) const;
    double toDouble(unsigned long index = 0) const;
    enum { withUnits = 1 }; // flags for toStr()
    const char* toStr(int flags = 0, unsigned long index = 0);
    
    // conversion operators for convenience
    // We try not to be ambigous and define ops for all types.
    operator double() const
        { return toDouble(); }
    double operator [] (unsigned long index) const
        { return toDouble(index); }
       
    static const char* dataTypeStrings[9];
    static const char* connectionStateStrings[4];
private:
    chid channel;
    void* data;
    void* info;
    caDatatype usedDatatype;
    caDatatype requestedDatatype;
    int status;
    static unsigned long nconnecting;
    char stringrep[40];
  
    static void connectCallback(connection_handler_args);
    void connectionUp();
    void connectionDown();
};

inline std::ostream& operator << (std::ostream& o, epicsPV& pv)
{
    return o << pv.toStr(epicsPV::withUnits);
}

inline std::ostream& operator << (std::ostream& o, epicsAlarmSeverity sevr)
{
    return o << epicsAlarmSeverityStrings[sevr];
}

inline std::ostream& operator << (std::ostream& o, epicsAlarmCondition stat)
{
    return o << epicsAlarmConditionStrings[stat];
}

inline std::ostream& operator << (std::ostream& o, caDatatype type)
{
    return o << epicsPV::dataTypeStrings[type];
}

#define caget(pvs...) epicsPV::getPVs(2.0, pvs, NULL)

#endif