Adding a system time pv, with an offset and multiple format options

Author: shroffk

core/pv/doc/index.rst

@@ -135,5 +135,19 @@ If the VType is omitted, 'double' is assumed. Examples::
     mqtt://some_topic<VString>
     mqtt://some/nested/topic
 
+System
+------
+System process variables are useful for representing some system attributes. They do not communicate with the control system.::
 
+    * sys://time
+    * sys://timeOffset(offset, format, update_seconds)
 
+The `timeOffset` pv allows you to represent a time instant offset from `now`. The optional parameters are:
+*offset* which is described as 1 min, 1 hour, 1 day prior to the current instant.
+*format* which describes how to represent the instance, the supported formats are full, milli, seconds, datetime, date, or time.
+*update_seconds* the update rate / period.
+
+Examples ::
+
+    sys://timeOffset(12 hours)
+    sys://timeOffset(1hour, time, 1)

core/pv/src/main/java/org/phoebus/pv/sys/SysPVFactory.java

@@ -10,6 +10,9 @@
 import org.phoebus.pv.PV;
 import org.phoebus.pv.PVFactory;
 
+import java.util.List;
+import java.util.stream.Collectors;
+
 /** PV Factory for system PVs
  *  @author Kay Kasemir
  */
@@ -28,8 +31,27 @@ public String getType()
     @Override
     public PV createPV(final String name, final String base_name) throws Exception
     {
-        if (base_name.equals("time"))
+        // Determine simulation function name and (optional) parameters
+        final String func, parameters;
+        int sep = base_name.indexOf('(');
+        if (sep < 0)
+        {
+            func = base_name;
+            parameters = "";
+        }
+        else
+        {
+            final int end = base_name.lastIndexOf(')');
+            if (end < 0)
+                throw new Exception("Missing closing bracket for parameters in '" + name + "'");
+            func = base_name.substring(0, sep);
+            parameters = base_name.substring(sep+1, end);
+        }
+
+        if (func.equals("time"))
             return new TimePV(name);
+        else if (func.equals("timeOffset"))
+            return TimeOffsetPV.forParameters(name, List.of(parameters.split(",")).stream().map(String::strip).collect(Collectors.toList()));
         else
             throw new Exception("Unknown system PV " + base_name);
     }

core/pv/src/main/java/org/phoebus/pv/sys/TimeOffsetPV.java

@@ -0,0 +1,89 @@
+/*******************************************************************************
+ * Copyright (c) 2019 Oak Ridge National Laboratory.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ ******************************************************************************/
+package org.phoebus.pv.sys;
+
+import org.phoebus.pv.sim.SimulatedStringPV;
+import org.phoebus.util.time.TimeParser;
+import org.phoebus.util.time.TimestampFormats;
+
+import java.time.Instant;
+import java.time.Period;
+import java.time.format.DateTimeFormatter;
+import java.time.temporal.TemporalAmount;
+import java.util.List;
+import java.util.Locale;
+
+/** System "time" PV
+ *  @author Kay Kasemir, based on similar code in diirt
+ */
+public class TimeOffsetPV extends SimulatedStringPV
+{
+    private DateTimeFormatter formatter;
+    private TemporalAmount temporalAmount;
+    private double updateRate;
+
+    /**
+     * Factory method for creating a time pv with user defined offset, format, and update rate.
+     *
+     * @param name pv name
+     * @param parameters a list of optional parameters defining timeoffset, format, update rate
+     * @return a new TimeOffsetPV
+     */
+    public static TimeOffsetPV forParameters(final String name, final List<String> parameters) throws Exception {
+        if(parameters != null && !parameters.isEmpty()) {
+            if(parameters.size() == 1) {
+                return new TimeOffsetPV(name, parameters.get(0), TimestampFormats.SECONDS_FORMAT, 1.0);
+            } else if (parameters.size() == 2) {
+                return new TimeOffsetPV(name, parameters.get(0), TimestampFormats.SECONDS_FORMAT, Double.valueOf(parameters.get(1)));
+            } else if (parameters.size() == 3) {
+                DateTimeFormatter formatter;
+                switch (parameters.get(1).toLowerCase()) {
+                    case "full":
+                        formatter = TimestampFormats.FULL_FORMAT;
+                        break;
+                    case "milli":
+                        formatter = TimestampFormats.MILLI_FORMAT;
+                        break;
+                    case "seconds":
+                        formatter = TimestampFormats.SECONDS_FORMAT;
+                        break;
+                    case "datetime":
+                        formatter = TimestampFormats.DATETIME_FORMAT;
+                        break;
+                    case "date":
+                        formatter = TimestampFormats.DATE_FORMAT;
+                        break;
+                    case "time":
+                        formatter = TimestampFormats.TIME_FORMAT;
+                        break;
+                    default:
+                        formatter = TimestampFormats.SECONDS_FORMAT;
+                        break;
+                }
+                return new TimeOffsetPV(name, parameters.get(0), formatter, Double.valueOf(parameters.get(2)));
+            }
+        } else {
+            return new TimeOffsetPV(name, "now", TimestampFormats.SECONDS_FORMAT, 1.0);
+        }
+        throw new Exception("sim://timeOffset needs no parameters or (offset, update_seconds) or (offset, format, update_seconds)");
+    }
+
+    public TimeOffsetPV(final String name, final String offset, final DateTimeFormatter formatter, final double updateRate) {
+        super(name);
+        this.temporalAmount = TimeParser.parseTemporalAmount(offset);
+        this.formatter = formatter;
+        this.updateRate = updateRate;
+        start(updateRate);
+    }
+
+    @Override
+    public String compute()
+    {
+        return formatter.format(Instant.now().minus(temporalAmount));
+    }
+}