core: add support for basic trig functions (#1589)

These can be useful for defining synthetic data when
demoing operations.

atlas-core/src/main/scala/com/netflix/atlas/core/model/MathExpr.scala

@@ -378,6 +378,13 @@ object MathExpr {
     def apply(v: Double): Double = -v
   }
 
+  case class Sine(expr: TimeSeriesExpr) extends UnaryMathExpr {
+
+    def name: String = "sin"
+
+    def apply(v: Double): Double = math.sin(v)
+  }
+
   case class Sqrt(expr: TimeSeriesExpr) extends UnaryMathExpr {
 
     def name: String = "sqrt"

atlas-core/src/main/scala/com/netflix/atlas/core/model/MathVocabulary.scala

@@ -40,6 +40,7 @@ object MathVocabulary extends Vocabulary {
     As,
     GroupBy,
     Const,
+    Pi,
     Random,
     SeededRandom,
     Time,
@@ -51,6 +52,7 @@ object MathVocabulary extends Vocabulary {
     ClampMax,
     Abs,
     Negate,
+    Sine,
     Sqrt,
     PerStep,
     Add,
@@ -231,7 +233,12 @@ object MathVocabulary extends Vocabulary {
       ),
       List("name,playback.startLatency,:eq")
     ),
-    Macro("median", List("(", "50", ")", ":percentiles"), List("name,requestLatency,:eq"))
+    Macro("median", List("(", "50", ")", ":percentiles"), List("name,requestLatency,:eq")),
+    Macro("cos", List(":pi", "2", ":div", ":swap", ":sub", ":sin")),
+    Macro("tan", List(":dup", ":sin", ":swap", ":cos", ":div")),
+    Macro("cot", List(":dup", ":cos", ":swap", ":sin", ":div")),
+    Macro("sec", List("1", ":swap", ":cos", ":div")),
+    Macro("csc", List("1", ":swap", ":sin", ":div"))
   )
 
   case object As extends SimpleWord {
@@ -324,6 +331,28 @@ object MathVocabulary extends Vocabulary {
     override def examples: List[String] = List("42")
   }
 
+  case object Pi extends SimpleWord {
+
+    override def name: String = "pi"
+
+    protected def matcher: PartialFunction[List[Any], Boolean] = {
+      case _ => true
+    }
+
+    protected def executor: PartialFunction[List[Any], List[Any]] = {
+      case stack => MathExpr.Constant(Math.PI) :: stack
+    }
+
+    override def summary: String =
+      """
+        |Generates a line where each datapoint has the value of the mathematical constant π.
+      """.stripMargin.trim
+
+    override def signature: String = " -- TimeSeriesExpr"
+
+    override def examples: List[String] = Nil
+  }
+
   case object Random extends SimpleWord {
 
     override def name: String = "random"
@@ -727,6 +756,19 @@ object MathVocabulary extends Vocabulary {
       """.stripMargin.trim
   }
 
+  case object Sine extends UnaryWord {
+
+    override def name: String = "sin"
+
+    def newInstance(t: TimeSeriesExpr): TimeSeriesExpr = MathExpr.Sine(t)
+
+    override def summary: String =
+      """
+        |Compute a new time series where each interval has the sine of the value from the
+        |input time series.
+      """.stripMargin.trim
+  }
+
   case object Sqrt extends UnaryWord {
 
     override def name: String = "sqrt"
@@ -1197,4 +1239,5 @@ object MathVocabulary extends Vocabulary {
       "name,requestLatency,:eq,(,25,50,90,)"
     )
   }
+
 }

atlas-core/src/test/scala/com/netflix/atlas/core/model/ModelExtractorsSuite.scala

@@ -34,7 +34,7 @@ class ModelExtractorsSuite extends FunSuite {
 
   completionTest("name", 8)
   completionTest("name,sps", 22)
-  completionTest("name,sps,:eq", 20)
-  completionTest("name,sps,:eq,app,foo,:eq", 41)
+  completionTest("name,sps,:eq", 21)
+  completionTest("name,sps,:eq,app,foo,:eq", 42)
   completionTest("name,sps,:eq,app,foo,:eq,:and,(,asg,)", 12)
 }

atlas-webapi/src/test/scala/com/netflix/atlas/webapi/ExprApiSuite.scala

@@ -163,7 +163,7 @@ class ExprApiSuite extends MUnitRouteSuite {
   testGet("/api/v1/expr/complete?q=name,sps,:eq,(,nf.cluster,)") {
     assertEquals(response.status, StatusCodes.OK)
     val data = Json.decode[List[ExprApiSuite.Candidate]](responseAs[String]).map(_.name)
-    assertEquals(data, List("by", "by", "cg", "offset", "palette"))
+    assertEquals(data, List("by", "by", "pi", "cg", "offset", "palette"))
   }
 
   // TODO: Right now these fail. As a future improvement suggestions should be possible within