From 6162d05b6064cb743b085c0006b556a031c640b5 Mon Sep 17 00:00:00 2001
From: Greg Shuflin <greg.shuflin@protonmail.com>
Date: Mon, 25 Oct 2021 21:19:26 -0700
Subject: [PATCH] Starting on case-matching

---
 schala-lang/language/src/reduced_ast/mod.rs   |  5 +-
 schala-lang/language/src/reduced_ir/mod.rs    | 87 ++++++++++++++++++-
 schala-lang/language/src/reduced_ir/types.rs  | 18 ++++
 .../language/src/tree_walk_eval/mod.rs        |  3 +
 4 files changed, 108 insertions(+), 5 deletions(-)

diff --git a/schala-lang/language/src/reduced_ast/mod.rs b/schala-lang/language/src/reduced_ast/mod.rs
index 12ac4cd..107e29b 100644
--- a/schala-lang/language/src/reduced_ast/mod.rs
+++ b/schala-lang/language/src/reduced_ast/mod.rs
@@ -243,9 +243,8 @@ impl<'a> Reducer<'a> {
                         item: else_clause,
                     },
                 ];
-
-                Expr::CaseMatch { cond, alternatives }
-            }
+                Expression::CaseMatch { cond, alternatives }
+            },
             IfExpressionBody::CondList(ref condition_arms) => {
                 let mut alternatives = vec![];
                 for arm in condition_arms {
diff --git a/schala-lang/language/src/reduced_ir/mod.rs b/schala-lang/language/src/reduced_ir/mod.rs
index c203563..13f0333 100644
--- a/schala-lang/language/src/reduced_ir/mod.rs
+++ b/schala-lang/language/src/reduced_ir/mod.rs
@@ -148,12 +148,14 @@ impl<'a> Reducer<'a> {
     }
 
     fn reduce_if_expression(&mut self, discriminator: Option<&ast::Expression>, body: &ast::IfExpressionBody) -> Expression {
+        use  ast::IfExpressionBody::*;
+
         let cond = Box::new(match discriminator {
             Some(expr) => self.expression(expr),
             None => return Expression::ReductionError("blank cond if-expr not supported".to_string()),
         });
         match body {
-            ast::IfExpressionBody::SimpleConditional {
+            SimpleConditional {
                 then_case,
                 else_case,
             } => {
@@ -168,7 +170,34 @@ impl<'a> Reducer<'a> {
                     else_clause,
                 }
             },
-            _ => Expression::ReductionError("if expr".to_string())
+            SimplePatternMatch {
+                pattern,
+                then_case,
+                else_case,
+            } => {
+                let alternatives = vec![
+                    Alternative {
+                        matchable: pattern.to_subpattern(self.symbol_table),
+                        item: self.function_internal_block(then_case),
+                    },
+                    Alternative {
+                        matchable: Subpattern {
+                            tag: None,
+                            subpatterns: vec![],
+                            guard: None,
+                        },
+                        item: match else_case.as_ref() {
+                            Some(else_case) => self.function_internal_block(else_case),
+                            None => vec![],
+                        },
+                    },
+                ];
+
+                Expression::CaseMatch { cond, alternatives }
+            },
+            CondList(ref condition_arms) => {
+                Expression::ReductionError("if expr".to_string())
+            }
         }
     }
 
@@ -258,3 +287,57 @@ impl<'a> Reducer<'a> {
         }
     }
 }
+
+impl ast::Pattern {
+
+    fn to_subpattern(&self, symbol_table: &SymbolTable) -> Subpattern {
+        Subpattern {
+            tag: None,
+            subpatterns: vec![],
+            guard: None,
+        }
+        /*
+        use self::Pattern::*;
+        match self {
+            TupleStruct(QualifiedName { components, id }, inner_patterns) => {
+                match symbol_table.lookup_symbol(id) {
+                    Some(symbol) => handle_symbol(Some(symbol), inner_patterns, symbol_table),
+                    None => panic!("Symbol {:?} not found", components),
+                }
+            }
+            TuplePattern(inner_patterns) => handle_symbol(None, inner_patterns, symbol_table),
+            Record(_name, _pairs) => {
+                unimplemented!()
+            }
+            Ignored => Subpattern {
+                tag: None,
+                subpatterns: vec![],
+                guard: None,
+                bound_vars: vec![],
+            },
+            Literal(lit) => lit.to_subpattern(symbol_table),
+            VarOrName(QualifiedName { components, id }) => {
+                // if symbol is Some, treat this as a symbol pattern. If it's None, treat it
+                // as a variable.
+                match symbol_table.lookup_symbol(id) {
+                    Some(symbol) => handle_symbol(Some(symbol), &[], symbol_table),
+                    None => {
+                        println!("Components: {:?}", components);
+                        let name = if components.len() == 1 {
+                            components[0].clone()
+                        } else {
+                            panic!("check this line of code yo");
+                        };
+                        Subpattern {
+                            tag: None,
+                            subpatterns: vec![],
+                            guard: None,
+                            bound_vars: vec![Some(name)],
+                        }
+                    }
+                }
+            }
+        }
+        */
+    }
+}
diff --git a/schala-lang/language/src/reduced_ir/types.rs b/schala-lang/language/src/reduced_ir/types.rs
index 9e0dca7..f046971 100644
--- a/schala-lang/language/src/reduced_ir/types.rs
+++ b/schala-lang/language/src/reduced_ir/types.rs
@@ -66,6 +66,10 @@ pub enum Expression {
         then_clause: Vec<Statement>,
         else_clause: Vec<Statement>,
     },
+    CaseMatch {
+        cond: Box<Expression>,
+        alternatives: Vec<Alternative>,
+    },
     ReductionError(String),
 }
 
@@ -111,3 +115,17 @@ pub enum Literal {
     Bool(bool),
     StringLit(Rc<String>),
 }
+
+#[derive(Debug, Clone)]
+pub struct Alternative {
+    pub matchable: Subpattern,
+    pub item: Vec<Statement>,
+}
+
+#[derive(Debug, Clone)]
+pub struct Subpattern {
+    pub tag: Option<usize>,
+    pub subpatterns: Vec<Option<Subpattern>>,
+    //pub bound_vars: BoundVars,
+    pub guard: Option<Expression>,
+}
diff --git a/schala-lang/language/src/tree_walk_eval/mod.rs b/schala-lang/language/src/tree_walk_eval/mod.rs
index 3d59b9c..7afe402 100644
--- a/schala-lang/language/src/tree_walk_eval/mod.rs
+++ b/schala-lang/language/src/tree_walk_eval/mod.rs
@@ -270,6 +270,9 @@ impl<'a> State<'a> {
                   v => return Err(format!("Non-boolean value {:?} in if-statement", v).into())
               }
           },
+          Expression::CaseMatch { cond, alternatives } => {
+              panic!()
+          },
           Expression::ReductionError(e) => return Err(e.into()),
       })
   }