const NUM_CHANNELS = instrument.properties.channels.length;

connection.acquire();

var displayedChannels = [];

connection.command(`:KEY:LOCK ENABle`);

for (var iChannel = 1; iChannel <= NUM_CHANNELS; ++iChannel) { //figure out active channels (MATH, DIGI and FFT not supported yet)
    var displayed = await connection.query(`:CHANnel${iChannel}:DISPlay?`);
    if (displayed) {
        displayedChannels.push(iChannel);
    }
}

if (displayedChannels.length > 0) {
    connection.command(`:STOP`); //measurement has to be stopped, otherwise only contents of screen can be read
    //connection.command(`:WAVeform:POINTs:MODE NORMal`); //read only contents of screen (600 points)
    connection.command(`:WAVeform:POINTs:MODE MAXimum`); //read whole memory (5k/10K)
    
    var timeScale = parseFloat(await connection.query(`:TIMebase:SCALe?`));

    for (var iDisplayedChannel = 0; iDisplayedChannel < displayedChannels.length; ++iDisplayedChannel) {
        var iChannel = displayedChannels[iDisplayedChannel];
        var samplingRate = await connection.query(`:ACQuire:SAMPlingrate? CHANnel${iChannel}`);
        
        var channelScale = parseFloat(await connection.query(`:CHANnel${iChannel}:SCALe?`));
        var channelOffset = parseFloat(await connection.query(`:CHANnel${iChannel}:OFFSet?`));
        
        var color = instrument.properties.channels[iChannel - 1].color;
        var colorInverse = instrument.properties.channels[iChannel - 1].colorInverse;
        var label = `Channel ${iChannel}`;
       
        var description = `Channel: ${iChannel}, Sampling rate: ${samplingRate}, Timebase: ${timeScale}s, Vertical scale: ${channelScale} V, Offset: ${channelOffset} V`;
        notify.info(description);

        var data = [];
        //var waveform = await connection.query(`:WAVeform:DATA? CHANnel${iChannel}`); //reads contents of screen
        var waveform = await connection.query(`:WAVeform:MEMORYDATA? CHANnel${iChannel}`);  //reads contents of screen/memory, undocumented in prog. manual
        data.push(waveform.data);
        waveform.deleteLog();
         
        channelScaleResized=10*channelScale/250; //data mangling for proper display of data - oscilloscope provides data in very strange format 0-199, inverted 
        pixelHalfWidth=8*channelScale/200/2;
        channelOffsetResized=-4*channelScale-channelOffset;//+pixelHalfWidth;
        samplingRateResized=samplingRate/2;
        for (var i=0; i < data[0].length; ++i) {
            data[0][i]=199-data[0][i]; //invert data
        }
        //console.log(pixelHalfWidth);
        
        session.addChart({
            description,
            data,
            samplingRate: samplingRateResized,
            offset: channelOffsetResized,
            scale: channelScaleResized,
            format: 2,
            unit: "Voltage",
            color,
            colorInverse,
            label
        });
    }
    
    
    connection.command(`:RUN`);
}

connection.command(`:KEY:LOCK DISable`);
connection.release();