Unit System v2 (#243)

* Separated `Time` unit into `TimeDelta` and `TimeStamp` + small fixes

Addition and subtruction between `Timestamp`s is not allowed, but any
other `Unit` operation/comparison is. `TimeDelta`s can be
added/subtructed to/form `Timestamp`s.

Deserialization of `Timestamp`:
- `Number` -> interpreted as millis from Epoch
- `Instant` (string representation) -> converted to Timestamp
- `Duration` (string representation) -> interpreted as duration since
  Epoch (warn msg is logged)

Deserialization of `TimeDelta` is the same as `Time` was before, with the
diference that when an `Instant` is converted to an timedelta since Epoch
a warning message is logged.

* Unit System v2

- Merged `BoundedPercentage` and `UnboundedPercentage`
- Overrided all operation defined in `Unit` in all subclasses to avoid
  as much as possible value classes being boxed in bytecode. If units are used as generics
  (hence also functions defined in Unit<T>) they are boxed (as double would if used as generic).
- All units companions now subclass `UnitId`, and can be used as keys
  (e.g `Map<UnitId, idk>`), while offering `max` `min` and `zero`
  methods.
- Division between the same unit now returns `Percentage`
- Added `Iterable<T>.averageOfUnitOrNull(selector (T) -> <specific unit>)`
- `ifNeg0ThenPos0()` now is optional and not invoked on every
  constructor
- Now methods in `Unit<T>` are all abstract, forcing override and avoid
  boxing in some cases
- Added `@UnintendedOperation` and `UnitOperationException` for methods
  that must be defined but are not intended for use (e.g. `Timestamp` +
  `Timestamp`)

1 files changed, 273 insertions, 0 deletions

diff --git a/opendc-common/src/main/kotlin/org/opendc/common/units/Timestamp.kt b/opendc-common/src/main/kotlin/org/opendc/common/units/Timestamp.kt
new file mode 100644
index 00000000..2706e07c
--- /dev/null
+++ b/opendc-common/src/main/kotlin/org/opendc/common/units/Timestamp.kt
@@ -0,0 +1,273 @@
+/*
+ * Copyright (c) 2024 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.
+ */
+
+@file:OptIn(InternalUse::class, NonInlinableUnit::class)
+
+package org.opendc.common.units
+
+import kotlinx.serialization.Serializable
+import org.opendc.common.annotations.InternalUse
+import org.opendc.common.units.TimeDelta.Companion.toTimeDelta
+import org.opendc.common.utils.DFLT_MIN_EPS
+import org.opendc.common.utils.approx
+import org.opendc.common.utils.approxLarger
+import org.opendc.common.utils.approxLargerOrEq
+import org.opendc.common.utils.approxSmaller
+import org.opendc.common.utils.approxSmallerOrEq
+import org.opendc.common.utils.ifNeg0thenPos0
+import java.time.Duration
+import java.time.Instant
+
+/**
+ * Represents timestamp values.
+ * @see[Unit]
+ */
+@JvmInline
+@Serializable(with = Timestamp.Companion.TimeStampSerializer::class)
+public value class Timestamp private constructor(
+    // In milliseconds since the Epoch.
+    public override val value: Double,
+) : Unit<Timestamp> {
+    override fun toString(): String = fmtValue()
+
+    /**
+     * @return the [Instant] [toString] result of this [Timestamp] value.
+     * @param[fmt] no ops.
+     */
+    override fun fmtValue(fmt: String): String = toInstant().toString()
+
+    // //////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+    // Conversions to Double
+    // //////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
+    public fun toEpochNs(): Double = value * 1e6
+
+    public fun toEpochMicros(): Double = value * 1e3
+
+    public fun toEpochMs(): Double = value
+
+    public fun toEpochSec(): Double = value / 1000.0
+
+    public fun toEpochMin(): Double = toEpochSec() / 60
+
+    public fun toEpochHours(): Double = toEpochMin() / 60
+
+    public fun toEpochDays(): Double = toEpochHours() / 24
+
+    // //////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+    // Operation Override (to avoid boxing of value classes in byte code)
+    // //////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
+    public override fun ifNeg0ThenPos0(): Timestamp = Timestamp(value.ifNeg0thenPos0())
+
+    @UnintendedOperation
+    public override operator fun plus(other: Timestamp): Timestamp = throw UnitOperationException()
+
+    @UnintendedOperation
+    public override operator fun minus(other: Timestamp): Timestamp = throw UnitOperationException()
+
+    public override operator fun div(scalar: Number): Timestamp = Timestamp(value / scalar.toDouble())
+
+    public override operator fun div(other: Timestamp): Percentage = Percentage.ofRatio(value / other.value)
+
+    public override operator fun times(scalar: Number): Timestamp = Timestamp(value * scalar.toDouble())
+
+    @UnintendedOperation
+    public override operator fun times(percentage: Percentage): Timestamp = throw UnitOperationException()
+
+    @UnintendedOperation
+    public override operator fun unaryMinus(): Timestamp = throw UnitOperationException()
+
+    public override operator fun compareTo(other: Timestamp): Int = this.value.compareTo(other.value)
+
+    public override fun isZero(): Boolean = value == .0
+
+    public override fun approxZero(epsilon: Double): Boolean = value.approx(.0, epsilon = epsilon)
+
+    public override fun approx(
+        other: Timestamp,
+        minEpsilon: Double,
+        epsilon: Double,
+    ): Boolean = this == other || this.value.approx(other.value, minEpsilon, epsilon)
+
+    public override infix fun approx(other: Timestamp): Boolean = approx(other, minEpsilon = DFLT_MIN_EPS)
+
+    public override fun approxLarger(
+        other: Timestamp,
+        minEpsilon: Double,
+        epsilon: Double,
+    ): Boolean = this.value.approxLarger(other.value, minEpsilon, epsilon)
+
+    public override infix fun approxLarger(other: Timestamp): Boolean = approxLarger(other, minEpsilon = DFLT_MIN_EPS)
+
+    public override fun approxLargerOrEq(
+        other: Timestamp,
+        minEpsilon: Double,
+        epsilon: Double,
+    ): Boolean = this.value.approxLargerOrEq(other.value, minEpsilon, epsilon)
+
+    public override infix fun approxLargerOrEq(other: Timestamp): Boolean = approxLargerOrEq(other, minEpsilon = DFLT_MIN_EPS)
+
+    public override fun approxSmaller(
+        other: Timestamp,
+        minEpsilon: Double,
+        epsilon: Double,
+    ): Boolean = this.value.approxSmaller(other.value, minEpsilon, epsilon)
+
+    public override infix fun approxSmaller(other: Timestamp): Boolean = approxSmaller(other, minEpsilon = DFLT_MIN_EPS)
+
+    public override fun approxSmallerOrEq(
+        other: Timestamp,
+        minEpsilon: Double,
+        epsilon: Double,
+    ): Boolean = this.value.approxSmallerOrEq(other.value, minEpsilon, epsilon)
+
+    public override infix fun approxSmallerOrEq(other: Timestamp): Boolean = approxSmallerOrEq(other, minEpsilon = DFLT_MIN_EPS)
+
+    public override infix fun max(other: Timestamp): Timestamp = if (this.value > other.value) this else other
+
+    public override infix fun min(other: Timestamp): Timestamp = if (this.value < other.value) this else other
+
+    public override fun abs(): Timestamp = Timestamp(kotlin.math.abs(value))
+
+    public override fun roundToIfWithinEpsilon(
+        to: Timestamp,
+        epsilon: Double,
+    ): Timestamp =
+        if (this.value in (to.value - epsilon)..(to.value + epsilon)) {
+            to
+        } else {
+            this
+        }
+
+    public fun max(
+        a: Timestamp,
+        b: Timestamp,
+    ): Timestamp = if (a.value > b.value) a else b
+
+    public fun min(
+        a: Timestamp,
+        b: Timestamp,
+    ): Timestamp = if (a.value < b.value) a else b
+
+    // //////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+    // Unit Specific Operations
+    // //////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
+    public operator fun minus(timeDelta: TimeDelta): Timestamp = Timestamp(value - timeDelta.value)
+
+    public operator fun plus(timeDelta: TimeDelta): Timestamp = Timestamp(value + timeDelta.value)
+
+    /**
+     * @return the [TimeDelta] between *this* and [other]. Be aware that this is not the absolute value, it can be negative.
+     */
+    public infix fun timeDelta(other: Timestamp): TimeDelta = this.toTimeDeltaFromEpoch() - other.toTimeDeltaFromEpoch()
+
+    public fun toInstant(): Instant =
+        if (toEpochMs() > Long.MAX_VALUE) {
+            Instant.ofEpochSecond(toEpochSec().toLong())
+        } else {
+            Instant.ofEpochMilli(toEpochMs().toLong())
+        }
+
+    public fun toTimeDeltaFromEpoch(): TimeDelta = TimeDelta.ofMillis(toEpochMs())
+
+    // //////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+    // Companion
+    // //////////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
+    public companion object : UnitId<Timestamp> {
+        @JvmStatic override val zero: Timestamp = Timestamp(.0)
+
+        @JvmStatic override val max: Timestamp = Timestamp(Double.MAX_VALUE)
+
+        @JvmStatic override val min: Timestamp = Timestamp(Double.MIN_VALUE)
+
+        public operator fun Number.times(unit: Timestamp): Timestamp = unit * this
+
+        @JvmStatic
+        @JvmName("ofEpochNs")
+        public fun ofEpochNs(nanos: Number): Timestamp = Timestamp(nanos.toDouble() / 1e6)
+
+        @JvmStatic
+        @JvmName("ofEpochMicros")
+        public fun ofEpochMicros(micros: Number): Timestamp = Timestamp(micros.toDouble() / 1e3)
+
+        @JvmStatic
+        @JvmName("ofEpochMs")
+        public fun ofEpochMs(ms: Number): Timestamp = Timestamp(ms.toDouble())
+
+        @JvmStatic
+        @JvmName("ofEpochSec")
+        public fun ofEpochSec(sec: Number): Timestamp = ofEpochMs(sec.toDouble() * 1000.0)
+
+        @JvmStatic
+        @JvmName("ofEpochMin")
+        public fun ofEpochMin(sec: Number): Timestamp = ofEpochSec(sec.toDouble() * 60)
+
+        @JvmStatic
+        @JvmName("ofEpochHours")
+        public fun ofEpochHours(sec: Number): Timestamp = ofEpochMin(sec.toDouble() * 60)
+
+        @JvmStatic
+        @JvmName("ofInstant")
+        public fun ofInstant(instant: Instant): Timestamp = ofEpochMs(instant.toEpochMilli())
+
+        @JvmStatic
+        @JvmName("toTimestamp")
+        public fun Instant.toTimestamp(): Timestamp = ofEpochMs(toEpochMilli())
+
+        // //////////////////////////////////////////////////////////////////////////////////////////////////////////////
+        // Serializer
+        // //////////////////////////////////////////////////////////////////////////////////////////////////////////////
+
+        /**
+         * Serializer for [Timestamp] value class. It needs to be a compile
+         * time constant to be used as serializer automatically,
+         * hence `object :` instead of class instantiation.
+         *
+         * ```json
+         * // e.g.
+         * "timestamp": "10000" // 10,000 ms since Epoch
+         * "timestamp": "2001-09-09T01:48:19Z"
+         * // etc.
+         * ```
+         */
+        internal object TimeStampSerializer : UnitSerializer<Timestamp>(
+            ifNumber = {
+                LOG.warn(
+                    "deserialization of number with no unit of measure, assuming it is in milliseconds since Epoch." +
+                        "Keep in mind that you can also specify the value with timestamp representation (e.g. '2001-09-09T01:48:19Z')",
+                )
+                ofEpochMs(it.toDouble())
+            },
+            serializerFun = { this.encodeString(it.toString()) },
+            ifNoExc { ofInstant(Instant.parse(this)) },
+            ifNoExc {
+                val duration = Duration.parse(this)
+                LOG.warn("timestamp value was expected but duration string representation found. Assuming it is a duration since Epoch.")
+
+                ofEpochMs(duration.toTimeDelta().toMs())
+            },
+        )
+    }
+}