fix(simulator): Fix loss computation for UPS and PDU

This change fixes the loss computation for both the UPS and PDU
implementation that was broken due to the new pushing mechanism. We
implement a new class FlowMapper that can be used to map the flow pushed
by a `FlowSource` using a user-specified method.

10 files changed, 97 insertions, 35 deletions

diff --git a/opendc-simulator/opendc-simulator-compute/src/main/kotlin/org/opendc/simulator/compute/device/SimPsu.kt b/opendc-simulator/opendc-simulator-compute/src/main/kotlin/org/opendc/simulator/compute/device/SimPsu.kt
index 8400c225..62d91c0b 100644
--- a/opendc-simulator/opendc-simulator-compute/src/main/kotlin/org/opendc/simulator/compute/device/SimPsu.kt
+++ b/opendc-simulator/opendc-simulator-compute/src/main/kotlin/org/opendc/simulator/compute/device/SimPsu.kt
@@ -80,7 +80,7 @@ public class SimPsu(
         update()
     }
 
-    override fun createConsumer(): FlowSource = object : FlowSource {
+    override fun createSource(): FlowSource = object : FlowSource {
         override fun onStart(conn: FlowConnection, now: Long) {
             _ctx = conn
         }
diff --git a/opendc-simulator/opendc-simulator-flow/src/main/kotlin/org/opendc/simulator/flow/FlowMapper.kt b/opendc-simulator/opendc-simulator-flow/src/main/kotlin/org/opendc/simulator/flow/FlowMapper.kt
new file mode 100644
index 00000000..6867bcef
--- /dev/null
+++ b/opendc-simulator/opendc-simulator-flow/src/main/kotlin/org/opendc/simulator/flow/FlowMapper.kt
@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2021 AtLarge Research
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package org.opendc.simulator.flow
+
+/**
+ * A [FlowConsumer] that maps the pushed flow through [transform].
+ *
+ * @param source The source of the flow.
+ * @param transform The method to transform the flow.
+ */
+public class FlowMapper(
+    private val source: FlowSource,
+    private val transform: (FlowConnection, Double) -> Double
+) : FlowSource {
+
+    /**
+     * The current active connection.
+     */
+    private var _conn: Connection? = null
+
+    override fun onStart(conn: FlowConnection, now: Long) {
+        check(_conn == null) { "Concurrent access" }
+        val delegate = Connection(conn, transform)
+        _conn = delegate
+        source.onStart(delegate, now)
+    }
+
+    override fun onStop(conn: FlowConnection, now: Long, delta: Long) {
+        val delegate = checkNotNull(_conn) { "Invariant violation" }
+        _conn = null
+        source.onStop(delegate, now, delta)
+    }
+
+    override fun onPull(conn: FlowConnection, now: Long, delta: Long): Long {
+        val delegate = checkNotNull(_conn) { "Invariant violation" }
+        return source.onPull(delegate, now, delta)
+    }
+
+    override fun onConverge(conn: FlowConnection, now: Long, delta: Long) {
+        val delegate = _conn ?: return
+        source.onConverge(delegate, now, delta)
+    }
+
+    /**
+     * The wrapper [FlowConnection] that is used to transform the flow.
+     */
+    private class Connection(
+        private val delegate: FlowConnection,
+        private val transform: (FlowConnection, Double) -> Double
+    ) : FlowConnection by delegate {
+        override fun push(rate: Double) {
+            delegate.push(transform(this, rate))
+        }
+    }
+}
diff --git a/opendc-simulator/opendc-simulator-flow/src/main/kotlin/org/opendc/simulator/flow/internal/FlowConsumerContextImpl.kt b/opendc-simulator/opendc-simulator-flow/src/main/kotlin/org/opendc/simulator/flow/internal/FlowConsumerContextImpl.kt
index c235b9ae..55fa92df 100644
--- a/opendc-simulator/opendc-simulator-flow/src/main/kotlin/org/opendc/simulator/flow/internal/FlowConsumerContextImpl.kt
+++ b/opendc-simulator/opendc-simulator-flow/src/main/kotlin/org/opendc/simulator/flow/internal/FlowConsumerContextImpl.kt
@@ -127,6 +127,7 @@ internal class FlowConsumerContextImpl(
         engine.batch {
             source.onStart(this, _clock.millis())
             _state = State.Active
+
             pull()
         }
     }
diff --git a/opendc-simulator/opendc-simulator-power/src/main/kotlin/org/opendc/simulator/power/SimPdu.kt b/opendc-simulator/opendc-simulator-power/src/main/kotlin/org/opendc/simulator/power/SimPdu.kt
index c33f5186..d536f22d 100644
--- a/opendc-simulator/opendc-simulator-power/src/main/kotlin/org/opendc/simulator/power/SimPdu.kt
+++ b/opendc-simulator/opendc-simulator-power/src/main/kotlin/org/opendc/simulator/power/SimPdu.kt
@@ -57,17 +57,9 @@ public class SimPdu(
         mux.addOutput(forwarder)
     }
 
-    override fun createConsumer(): FlowSource = object : FlowSource by forwarder {
-        override fun onPull(conn: FlowConnection, now: Long, delta: Long): Long {
-            val duration = forwarder.onPull(conn, now, delta)
-            val loss = computePowerLoss(conn.demand)
-            val newLimit = conn.demand + loss
-
-            conn.push(newLimit)
-            return duration
-        }
-
-        override fun toString(): String = "SimPdu.Consumer"
+    override fun createSource(): FlowSource = FlowMapper(forwarder) { _, rate ->
+        val loss = computePowerLoss(rate)
+        rate + loss
     }
 
     override fun toString(): String = "SimPdu"
@@ -85,7 +77,7 @@ public class SimPdu(
      */
     public class Outlet(private val switch: FlowMultiplexer, private val provider: FlowConsumer) : SimPowerOutlet(), AutoCloseable {
         override fun onConnect(inlet: SimPowerInlet) {
-            provider.startConsumer(inlet.createConsumer())
+            provider.startConsumer(inlet.createSource())
         }
 
         override fun onDisconnect(inlet: SimPowerInlet) {
diff --git a/opendc-simulator/opendc-simulator-power/src/main/kotlin/org/opendc/simulator/power/SimPowerInlet.kt b/opendc-simulator/opendc-simulator-power/src/main/kotlin/org/opendc/simulator/power/SimPowerInlet.kt
index 851b28a5..de587b7f 100644
--- a/opendc-simulator/opendc-simulator-power/src/main/kotlin/org/opendc/simulator/power/SimPowerInlet.kt
+++ b/opendc-simulator/opendc-simulator-power/src/main/kotlin/org/opendc/simulator/power/SimPowerInlet.kt
@@ -44,5 +44,5 @@ public abstract class SimPowerInlet {
     /**
      * Create a [FlowSource] which represents the consumption of electricity from the power outlet.
      */
-    public abstract fun createConsumer(): FlowSource
+    public abstract fun createSource(): FlowSource
 }
diff --git a/opendc-simulator/opendc-simulator-power/src/main/kotlin/org/opendc/simulator/power/SimPowerSource.kt b/opendc-simulator/opendc-simulator-power/src/main/kotlin/org/opendc/simulator/power/SimPowerSource.kt
index 7faebd75..07e9f52e 100644
--- a/opendc-simulator/opendc-simulator-power/src/main/kotlin/org/opendc/simulator/power/SimPowerSource.kt
+++ b/opendc-simulator/opendc-simulator-power/src/main/kotlin/org/opendc/simulator/power/SimPowerSource.kt
@@ -43,7 +43,7 @@ public class SimPowerSource(engine: FlowEngine, public val capacity: Double) : S
         get() = source.rate
 
     override fun onConnect(inlet: SimPowerInlet) {
-        source.startConsumer(inlet.createConsumer())
+        source.startConsumer(inlet.createSource())
     }
 
     override fun onDisconnect(inlet: SimPowerInlet) {
diff --git a/opendc-simulator/opendc-simulator-power/src/main/kotlin/org/opendc/simulator/power/SimUps.kt b/opendc-simulator/opendc-simulator-power/src/main/kotlin/org/opendc/simulator/power/SimUps.kt
index 5eaa91af..312f1d0f 100644
--- a/opendc-simulator/opendc-simulator-power/src/main/kotlin/org/opendc/simulator/power/SimUps.kt
+++ b/opendc-simulator/opendc-simulator-power/src/main/kotlin/org/opendc/simulator/power/SimUps.kt
@@ -59,17 +59,13 @@ public class SimUps(
     }
 
     override fun onConnect(inlet: SimPowerInlet) {
-        val consumer = inlet.createConsumer()
-        provider.startConsumer(object : FlowSource by consumer {
-            override fun onPull(conn: FlowConnection, now: Long, delta: Long): Long {
-                val duration = consumer.onPull(conn, now, delta)
-                val loss = computePowerLoss(conn.demand)
-                val newLimit = conn.demand + loss
+        val source = inlet.createSource()
+        val mapper = FlowMapper(source) { _, rate ->
+            val loss = computePowerLoss(rate)
+            rate + loss
+        }
 
-                conn.push(newLimit)
-                return duration
-            }
-        })
+        provider.startConsumer(mapper)
     }
 
     override fun onDisconnect(inlet: SimPowerInlet) {
@@ -88,7 +84,7 @@ public class SimUps(
      * A UPS inlet.
      */
     public inner class Inlet(private val forwarder: FlowForwarder) : SimPowerInlet(), AutoCloseable {
-        override fun createConsumer(): FlowSource = forwarder
+        override fun createSource(): FlowSource = forwarder
 
         /**
          * Remove the inlet from the PSU.
diff --git a/opendc-simulator/opendc-simulator-power/src/test/kotlin/org/opendc/simulator/power/SimPduTest.kt b/opendc-simulator/opendc-simulator-power/src/test/kotlin/org/opendc/simulator/power/SimPduTest.kt
index 85b9ab01..eb823eb1 100644
--- a/opendc-simulator/opendc-simulator-power/src/test/kotlin/org/opendc/simulator/power/SimPduTest.kt
+++ b/opendc-simulator/opendc-simulator-power/src/test/kotlin/org/opendc/simulator/power/SimPduTest.kt
@@ -25,7 +25,6 @@ package org.opendc.simulator.power
 import io.mockk.spyk
 import io.mockk.verify
 import org.junit.jupiter.api.Assertions.assertEquals
-import org.junit.jupiter.api.Disabled
 import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.assertThrows
 import org.opendc.simulator.core.runBlockingSimulation
@@ -79,7 +78,7 @@ internal class SimPduTest {
         source.connect(pdu)
         val consumer = spyk(FixedFlowSource(100.0, utilization = 1.0))
         val inlet = object : SimPowerInlet() {
-            override fun createConsumer(): FlowSource = consumer
+            override fun createSource(): FlowSource = consumer
         }
 
         val outlet = pdu.newOutlet()
@@ -90,7 +89,6 @@ internal class SimPduTest {
     }
 
     @Test
-    @Disabled
     fun testLoss() = runBlockingSimulation {
         val engine = FlowEngine(coroutineContext, clock)
         val source = SimPowerSource(engine, capacity = 100.0)
@@ -116,6 +114,6 @@ internal class SimPduTest {
     }
 
     class SimpleInlet : SimPowerInlet() {
-        override fun createConsumer(): FlowSource = FixedFlowSource(100.0, utilization = 0.5)
+        override fun createSource(): FlowSource = FixedFlowSource(100.0, utilization = 0.5)
     }
 }
diff --git a/opendc-simulator/opendc-simulator-power/src/test/kotlin/org/opendc/simulator/power/SimPowerSourceTest.kt b/opendc-simulator/opendc-simulator-power/src/test/kotlin/org/opendc/simulator/power/SimPowerSourceTest.kt
index 20677633..76142103 100644
--- a/opendc-simulator/opendc-simulator-power/src/test/kotlin/org/opendc/simulator/power/SimPowerSourceTest.kt
+++ b/opendc-simulator/opendc-simulator-power/src/test/kotlin/org/opendc/simulator/power/SimPowerSourceTest.kt
@@ -79,7 +79,7 @@ internal class SimPowerSourceTest {
         val source = SimPowerSource(engine, capacity = 100.0)
         val consumer = spyk(FixedFlowSource(100.0, utilization = 1.0))
         val inlet = object : SimPowerInlet() {
-            override fun createConsumer(): FlowSource = consumer
+            override fun createSource(): FlowSource = consumer
         }
 
         source.connect(inlet)
@@ -95,7 +95,7 @@ internal class SimPowerSourceTest {
         val inlet = mockk<SimPowerInlet>(relaxUnitFun = true)
         every { inlet.isConnected } returns false
         every { inlet._outlet } returns null
-        every { inlet.createConsumer() } returns FixedFlowSource(100.0, utilization = 1.0)
+        every { inlet.createSource() } returns FixedFlowSource(100.0, utilization = 1.0)
 
         source.connect(inlet)
 
@@ -131,6 +131,6 @@ internal class SimPowerSourceTest {
     }
 
     class SimpleInlet : SimPowerInlet() {
-        override fun createConsumer(): FlowSource = FixedFlowSource(100.0, utilization = 1.0)
+        override fun createSource(): FlowSource = FixedFlowSource(100.0, utilization = 1.0)
     }
 }
diff --git a/opendc-simulator/opendc-simulator-power/src/test/kotlin/org/opendc/simulator/power/SimUpsTest.kt b/opendc-simulator/opendc-simulator-power/src/test/kotlin/org/opendc/simulator/power/SimUpsTest.kt
index c6e0605a..a764a368 100644
--- a/opendc-simulator/opendc-simulator-power/src/test/kotlin/org/opendc/simulator/power/SimUpsTest.kt
+++ b/opendc-simulator/opendc-simulator-power/src/test/kotlin/org/opendc/simulator/power/SimUpsTest.kt
@@ -86,7 +86,7 @@ internal class SimUpsTest {
         source2.connect(ups.newInlet())
         val consumer = spyk(FixedFlowSource(100.0, utilization = 1.0))
         val inlet = object : SimPowerInlet() {
-            override fun createConsumer(): FlowSource = consumer
+            override fun createSource(): FlowSource = consumer
         }
 
         ups.connect(inlet)
@@ -96,6 +96,6 @@ internal class SimUpsTest {
     }
 
     class SimpleInlet : SimPowerInlet() {
-        override fun createConsumer(): FlowSource = FixedFlowSource(100.0, utilization = 0.5)
+        override fun createSource(): FlowSource = FixedFlowSource(100.0, utilization = 0.5)
     }
 }