From fbb75b2f43f672db61c906e2f0f5add11db1a594 Mon Sep 17 00:00:00 2001
From: vbergeron <valentin.bergeron@ledger.fr>
Date: Thu, 23 Nov 2023 14:49:41 +0100
Subject: [PATCH] Added switch conditional implementation

---
 src/main/scala/sail/main.scala   | 16 ++++++++++++++++
 src/main/scala/sail/model.scala  |  2 ++
 src/main/scala/sail/parser.scala | 27 ++++++++++++++++++++++-----
 src/test/scala/parser.test.scala | 24 ++++++++++++++++++++++++
 4 files changed, 64 insertions(+), 5 deletions(-)

diff --git a/src/main/scala/sail/main.scala b/src/main/scala/sail/main.scala
index 80a6e01..40460a4 100644
--- a/src/main/scala/sail/main.scala
+++ b/src/main/scala/sail/main.scala
@@ -53,6 +53,7 @@ def show(expr: Expr): String =
       s"<container from ${show(from)} - ${showInstr(build)}>"
     case Expr.Module(name, source)       =>
       s"<module ${show(name)} - ${show(source)}"
+    case Expr.Switch(_, _)               => "<switch TODO>"
 
 def render(expr: Expr): String =
   expr match
@@ -195,6 +196,21 @@ def reduce(cmd: Args, env: Env, expr: Expr): (Env, Expr) =
         (sym, expr) => sym.copy(module = Some(mod.name.value)) -> expr
       (env, Expr.Unit)
 
+    case switch: Expr.Switch =>
+      import BooleanExpr.*
+      val branch = switch.clauses.find: (cond, _) =>
+        val reduced = reduce(cmd, env, cond)._2 match
+          case x: (True.type | False.type) =>
+            x
+          case e                           =>
+            throw Exception(
+              s"Expression did not reduce to boolean: $cond (reduced: $e)"
+            )
+        reduced == True
+      (branch.map(_._2) orElse switch.default)
+        .fold(throw Exception(s"Non exhaustive switch: $switch")): expr =>
+          reduce(cmd, env, expr)
+
 def reduceFile(cmd: Args, exprs: Seq[Expr]): Env =
   exprs.foldLeft(Map.empty[Expr.Sym, Expr])(reduce(cmd, _, _)._1)
 
diff --git a/src/main/scala/sail/model.scala b/src/main/scala/sail/model.scala
index 672dbe2..319a8a8 100644
--- a/src/main/scala/sail/model.scala
+++ b/src/main/scala/sail/model.scala
@@ -13,6 +13,8 @@ object Expr:
   case class FuncCall(name: Sym, args: Seq[Expr])           extends Expr
   case class Container(from: Str, build: Instr)             extends Expr
   case class Scope(bindings: Seq[FuncDef], body: Expr)      extends Expr
+  case class Switch(clauses: Seq[(Expr, Expr)], default: Option[Expr])
+      extends Expr
 
   case class Module(name: Expr.Sym, sourcePath: Expr.Str) extends Expr
 
diff --git a/src/main/scala/sail/parser.scala b/src/main/scala/sail/parser.scala
index 96fef8f..eed3693 100644
--- a/src/main/scala/sail/parser.scala
+++ b/src/main/scala/sail/parser.scala
@@ -18,7 +18,7 @@ def part[$: P]: P[Part] =
   capture | content
 
 def expr[$: P]: P[Expr] =
-  scope | container | module | funcDef | instr | template | str | num | funcCall | sym | boolean.apply
+  cond.apply | scope | container | module | funcDef | instr | template | str | num | funcCall | sym | boolean.apply
 
 object boolean:
   def t[$: P]: P[BooleanExpr.True.type] =
@@ -28,22 +28,25 @@ object boolean:
     P("false").map(_ => BooleanExpr.False)
 
   def and[$: P]: P[BooleanExpr.And] =
-    P(expr ~ ws ~ "and" ~/ ws ~ expr)
+    val inner = eq | expr
+    P(inner ~ ws ~ "and" ~ ws ~ inner)
       .map(BooleanExpr.And.apply)
 
   def or[$: P]: P[BooleanExpr.Or] =
-    P(expr ~ ws ~ "or" ~/ ws ~ expr)
+    val inner = expr
+    P(inner ~ ws ~ "or" ~ ws ~ inner)
       .map(BooleanExpr.Or.apply)
 
   def not[$: P]: P[BooleanExpr.Not] =
     P("not" ~ ws ~ expr).map(BooleanExpr.Not.apply)
 
   def eq[$: P]: P[BooleanExpr.Eq] =
-    P(expr ~ ws ~ "==" ~/ ws ~ expr)
+    val inner = expr
+    P(inner ~ ws ~ "==" ~ ws ~ inner)
       .map(BooleanExpr.Eq.apply)
 
   def apply[$: P]: P[BooleanExpr] =
-    eq | and | or | not | t | f
+    and | or | eq | not | t | f
 
 def instr[$: P]: P[Instr] =
   def run[$: P]: P[Instr.Run] =
@@ -69,6 +72,20 @@ def instr[$: P]: P[Instr] =
 
   rec
 
+object cond:
+  def clause[$: P]: P[(Expr, Expr)] =
+    P("when" ~ ws ~ expr ~ ws ~ "then" ~ ws ~ expr)
+
+  def default[$: P]: P[Expr] =
+    P("else" ~ ws ~ expr)
+
+  def apply[$: P]: P[Expr.Switch] =
+    P(clause.rep ~ ws ~ default.?)
+      .filter: (clauses, _) =>
+        clauses.size > 0
+      .map: (clauses, default) =>
+        Expr.Switch(clauses, default)
+
 def scope[$: P]: P[Expr.Scope] =
   P("let" ~ ws ~ (funcDef ~ ws).rep ~ "in" ~ ws ~ expr).map(Expr.Scope.apply)
 
diff --git a/src/test/scala/parser.test.scala b/src/test/scala/parser.test.scala
index 207b9a3..35e6f11 100644
--- a/src/test/scala/parser.test.scala
+++ b/src/test/scala/parser.test.scala
@@ -107,5 +107,29 @@ class ParserTest extends FunSuite:
   passing("Boolean", "false", boolean(_))
   passing("Boolean", "bar or bar", boolean(_))
   passing("Boolean", "f(x) and g(y)", boolean(_))
+  // passingT("Boolean", "foo == bar and foo == baz", boolean.and(_)): expr =>
+  //  import BooleanExpr.*
+  //  import Expr.*
+  //  assertEquals(
+  //    expr,
+  //    And(
+  //      Eq(Sym(None, "foo"), Sym(None, "bar")),
+  //      Eq(Sym(None, "foo"), Sym(None, "bar"))
+  //    )
+  //  )
+
   passing("Boolean", "f(x) == g(y)", boolean(_))
   passing("Boolean", "not f(x)", boolean(_))
+
+  passing("Switch", "when foo then bar", cond.apply)
+  passing("Switch", "when foo then bar when foobar then barbar", cond.apply)
+
+  passing("Switch", "when foo then bar else baz", cond.apply)
+  passing(
+    "Switch",
+    """when foo then bar
+      |when foo == bar then barbar
+      |else baz
+      |""".stripMargin,
+    cond.apply
+  )