From dc7437a8c1e223e90b232a2d8790b9a26fab8066 Mon Sep 17 00:00:00 2001
From: Jeremy Wall <jeremy@marzhillstudios.com>
Date: Sun, 30 Jun 2019 22:21:28 -0500
Subject: [PATCH] DEV: Implement Jumping

---
 src/build/opcode/mod.rs  | 37 ++++++++++++++++++++++++++++++-------
 src/build/opcode/test.rs | 38 +++++++++++++++++++++++++++-----------
 2 files changed, 57 insertions(+), 18 deletions(-)

diff --git a/src/build/opcode/mod.rs b/src/build/opcode/mod.rs
index c6c5b5f..36005dc 100644
--- a/src/build/opcode/mod.rs
+++ b/src/build/opcode/mod.rs
@@ -62,13 +62,18 @@ pub enum Op {
     Sym(String),
     // Complex Type ops
     InitTuple,
-    FIELD,
+    Field,
     InitList,
     Element,
     // Operations
     Cp,
-    // record
-    InitThunk,
+    // Control Flow
+    Select,
+    Bang,
+    Jump(usize),
+    Noop,
+    // Pending Computation
+    InitThunk(usize),
     Return,
     // - Call
     // Runtime hooks
@@ -86,6 +91,7 @@ pub struct Error {}
 
 pub struct VM {
     stack: Vec<Value>,
+    // TODO(jwall): We may want to preserve order on these.
     symbols: BTreeMap<String, Value>,
     ops: OpPointer,
 }
@@ -114,13 +120,19 @@ impl VM {
                 Op::InitList => self.composite_push(List(Vec::new()))?,
                 // Add a composite tuple value to the stack
                 Op::InitTuple => self.composite_push(Tuple(Vec::new()))?,
-                Op::FIELD => self.op_field()?,
+                Op::Field => self.op_field()?,
                 Op::Element => self.op_element()?,
                 Op::Cp => self.op_copy()?,
-                Op::InitThunk => self.op_thunk(idx)?,
+                Op::Select => self.op_select()?,
+                Op::Bang => return Err(Error {}),
+                Op::InitThunk(jp) => self.op_thunk(idx, *jp)?,
+                Op::Noop => {
+                    // Do nothing
+                }
                 Op::Return => {
                     // TODO(jwall): This means we return back to the start of the frame.
                 }
+                Op::Jump(jp) => self.ops.jump(self.ops.ptr.map(|v| v + jp).unwrap_or(*jp))?,
                 Op::Pop => {
                     self.pop()?;
                 }
@@ -129,9 +141,20 @@ impl VM {
         Ok(())
     }
 
-    fn op_thunk(&mut self, idx: usize) -> Result<(), Error> {
-        // TODO(jwall): Record the position in the op codes.
+    fn op_thunk(&mut self, idx: usize, jp: usize) -> Result<(), Error> {
         self.push(Value::T(idx))?;
+        self.ops.jump(self.ops.ptr.map(|v| v + jp).unwrap_or(jp))?;
+        // TODO(jwall): Skip over the rest until we reach the return?
+        Ok(())
+    }
+
+    fn op_select(&mut self) -> Result<(), Error> {
+        // first get our compare value from the stack
+        let search_field = self.pop()?;
+        // next get our default value from the stack
+        let default_field = self.pop()?;
+        // finally get our fields from the stack
+        let fields = self.pop()?;
         Ok(())
     }
 
diff --git a/src/build/opcode/test.rs b/src/build/opcode/test.rs
index eaabbcb..309a8c9 100644
--- a/src/build/opcode/test.rs
+++ b/src/build/opcode/test.rs
@@ -13,9 +13,12 @@
 // limitations under the License.
 
 use super::Composite::{List, Tuple};
-use super::Op::{Add, Bind, Cp, Div, Element, InitList, InitTuple, Mul, Sub, Sym, Val, FIELD};
+use super::Op::{
+    Add, Bind, Cp, Div, Element, Field, InitList, InitThunk, InitTuple, Jump, Mul, Noop, Sub, Sym,
+    Val,
+};
 use super::Primitive::{Float, Int, Str};
-use super::Value::{C, P};
+use super::Value::{C, P, T};
 use super::VM;
 
 #[test]
@@ -118,7 +121,7 @@ fn test_tuple_ops() {
     let mut cases = vec![
         (vec![InitTuple], C(Tuple(Vec::new()))),
         (
-            vec![InitTuple, Val(Str("foo".to_owned())), Val(Int(1)), FIELD],
+            vec![InitTuple, Val(Str("foo".to_owned())), Val(Int(1)), Field],
             C(Tuple(vec![("foo".to_owned(), P(Int(1)))])),
         ),
         (
@@ -126,10 +129,10 @@ fn test_tuple_ops() {
                 InitTuple,
                 Sym("bar".to_owned()),
                 Val(Str("quux".to_owned())),
-                FIELD,
+                Field,
                 Val(Str("foo".to_owned())),
                 Val(Int(1)),
-                FIELD,
+                Field,
             ],
             C(Tuple(vec![
                 ("bar".to_owned(), P(Str("quux".to_owned()))),
@@ -141,14 +144,14 @@ fn test_tuple_ops() {
                 InitTuple,
                 Sym("bar".to_owned()),
                 Val(Str("quux".to_owned())),
-                FIELD,
+                Field,
                 Val(Str("foo".to_owned())),
                 Val(Int(1)),
-                FIELD,
+                Field,
                 Cp,
                 Val(Str("foo".to_owned())),
                 Val(Int(2)),
-                FIELD,
+                Field,
             ],
             C(Tuple(vec![
                 ("bar".to_owned(), P(Str("quux".to_owned()))),
@@ -162,14 +165,14 @@ fn test_tuple_ops() {
                 Val(Str("ux".to_owned())),
                 Val(Str("qu".to_owned())),
                 Add,
-                FIELD,
+                Field,
                 Val(Str("foo".to_owned())),
                 Val(Int(1)),
-                FIELD,
+                Field,
                 Cp,
                 Val(Str("foo".to_owned())),
                 Val(Int(2)),
-                FIELD,
+                Field,
             ],
             C(Tuple(vec![
                 ("bar".to_owned(), P(Str("quux".to_owned()))),
@@ -183,3 +186,16 @@ fn test_tuple_ops() {
         assert_eq!(vm.pop().unwrap(), case.1);
     }
 }
+
+#[test]
+fn test_jump_ops() {
+    let mut cases = vec![
+        (vec![InitThunk(1), Val(Int(1)), Noop], T(0)),
+        (vec![Jump(1), Val(Int(1)), Noop, Val(Int(1))], P(Int(1))),
+    ];
+    for case in cases.drain(0..) {
+        let mut vm = VM::new(case.0);
+        vm.run().unwrap();
+        assert_eq!(vm.pop().unwrap(), case.1);
+    }
+}