feat: added support for case-when and if-else in composed metrics (#69)

checkita-core/src/main/scala/org/checkita/dqf/utils/FormulaParser.scala

@@ -17,6 +17,8 @@ trait FormulaParser extends JavaTokenParsers {
   case class BoolBinaryFunc(t1: Tree, t2: Tree, f: (Boolean, Boolean) => Boolean) extends Tree
   case class BoolCompareFunc(t1: Tree, t2: Tree, f: (Double, Double) => Boolean) extends Tree
   case class Bool(t: Boolean) extends Tree
+  case class CaseWhen(cases: Seq[(Tree, Tree)], elseBranch: Tree) extends Tree
+  case class IfElse(condition: Tree, ifBranch: Tree, elseBranch: Tree) extends Tree
 
   /**
    * API to parse and evaluate arithmetic expression.
@@ -61,6 +63,10 @@ trait FormulaParser extends JavaTokenParsers {
     case UnaryFunc(t1, f) => f(eval(t1))
     case BinaryFunc(t1, t2, f) => f(eval(t1), eval(t2))
     case Num(t) => t
+    case CaseWhen(cases, elseBranch) =>
+      cases.collectFirst { case (cond, branch) if boolEval(cond) => eval(branch) }.getOrElse(eval(elseBranch))
+    case IfElse(cond, ifBranch, elseBranch) =>
+      if (boolEval(cond)) eval(ifBranch) else eval(elseBranch)
     case other => throw new MatchError(s"Illegal operation for arithmetic expression: ${other.getClass.getSimpleName}")
   }
 
@@ -161,7 +167,7 @@ trait FormulaParser extends JavaTokenParsers {
 
   private lazy val bool: Parser[Bool] = "true" ^^ (_ => Bool(true)) | "false" ^^ (_ => Bool(false))
 
-  private lazy val expr: Parser[Tree] = opt("[+-]".r) ~ term ~ rep("[+-]".r ~ term) ^^ {
+  private lazy val expr: Parser[Tree] = caseWhenExpr | ifElseExpr | opt("[+-]".r) ~ term ~ rep("[+-]".r ~ term) ^^ {
     case s ~ t ~ ts =>
       val signed = s match {
         case None => t
@@ -208,4 +214,20 @@ trait FormulaParser extends JavaTokenParsers {
   }
 
   private lazy val num: Parser[Num] = floatingPointNumber ^^ (t => Num(t.toDouble))
+
+  private lazy val whenExpr: Parser[(Tree, Tree)] =
+    "(?i)when".r ~> boolExpr ~ ("(?i)then".r ~> expr) ^^ {
+      case condExpr ~ thenExpr => (condExpr, thenExpr)
+  }
+
+  private lazy val caseWhenExpr: Parser[Tree] =
+    "(?i)case".r ~> rep1(whenExpr) ~ opt("(?i)else".r ~> expr) <~ "(?i)end".r ^^ {
+    case conditions ~ Some(elseExpr) => CaseWhen(conditions, elseExpr)
+    case conditions ~ None           => CaseWhen(conditions, Num(0.0))
+  }
+
+  private lazy val ifElseExpr: Parser[Tree] =
+    "(?i)if".r ~> boolExpr ~ expr ~ ("(?i)else".r ~> expr) ^^ {
+      case condition ~ thanBranch ~ elseBranch => IfElse(condition, thanBranch, elseBranch)
+    }
 }

checkita-core/src/test/scala/org/checkita/dqf/utils/FormulaParserSpec.scala

@@ -28,6 +28,21 @@ class FormulaParserSpec extends AnyWordSpec with Matchers with FormulaParser {
         "(1 < 0) || (3.14 * (2.77 - 1.31) ^ 0.5 > 3.5) && not(-3.14 * ln(max((2.77 - 1.31) ^ 0.5, - 5.55)) + 0.99 < 0)" -> true
       ).foreach{ case (f, r) => checkBoolean(f, r) }
     }
+    "correctly parse case-when expressions" in {
+      Seq(
+        "CASE WHEN 1 > 0 THEN 777.7 ELSE 0 END" -> 777.7,
+        "case when 1 < 0 then 777.7 when 2 > 1 then 17 else 0 end" -> 17.0,
+        "case when 1 < 0 THEN 777.7 else 0 END" -> 0.0
+      ).foreach { case (f, r) => checkArithmetic(f, r) }
+    }
+
+    "correctly parse if-else expressions" in {
+      Seq(
+        "IF 1 > 0 777.7 ELSE 0" -> 777.7,
+        "if 1 < 0 777.7 else 0" -> 0.0,
+        "if (3.14 > 2.0) (2.71 * 2) ELSE (1.41 + 0.5)" -> (2.71 * 2)
+      ).foreach { case (f, r) => checkArithmetic(f, r) }
+    }
     "throw error when arithmetic expression is invalid" in {
       Seq(
         "sin(3.14)",
@@ -43,5 +58,17 @@ class FormulaParserSpec extends AnyWordSpec with Matchers with FormulaParser {
         "(1.41 > 0) == (-3.14 < 0)"
       ).foreach(f => an [RuntimeException] should be thrownBy evalBoolean(f))
     }
+    "throw error when case-when expression is invalid" in {
+      Seq(
+        "case when true then 3.14 else true end"
+      ).foreach(f => an[RuntimeException] should be thrownBy evalArithmetic(f))
+    }
+
+    "throw error when if-else expression is invalid" in {
+      Seq(
+        "IF 1 3.14 ELSE 0",
+        "if true 3.14 else true"
+      ).foreach(f => an[RuntimeException] should be thrownBy evalArithmetic(f))
+    }
   }
 }