From 9b733cab78b9b475b2244203575f2f4c925dee92 Mon Sep 17 00:00:00 2001
From: brettlangdon <brett@blangdon.com>
Date: Sat, 26 Sep 2015 09:22:46 -0400
Subject: [PATCH] add start to compiler

---
 compiler/compiler.go  | 111 ++++++++++++++++++++++++++++++++++++++++++
 compiler/interface.go |  11 +++++
 compiler/scope.go     |   7 +++
 3 files changed, 129 insertions(+)
 create mode 100644 compiler/compiler.go
 create mode 100644 compiler/interface.go
 create mode 100644 compiler/scope.go

diff --git a/compiler/compiler.go b/compiler/compiler.go
new file mode 100644
index 0000000..d2464b9
--- /dev/null
+++ b/compiler/compiler.go
@@ -0,0 +1,111 @@
+package compiler
+
+import (
+	"fmt"
+
+	"github.com/brettlangdon/gython/ast"
+	"github.com/brettlangdon/gython/bytecode"
+)
+
+type Compiler struct {
+	nestLevel  int
+	scopeStack []*Scope
+}
+
+func NewCompiler() *Compiler {
+	return &Compiler{
+		nestLevel:  0,
+		scopeStack: make([]*Scope, 0),
+	}
+}
+
+func (compiler *Compiler) currentScope() *Scope {
+	length := len(compiler.scopeStack)
+	if length > 0 {
+		return compiler.scopeStack[length-1]
+	}
+	return nil
+}
+
+func (compiler *Compiler) enterScope() *Scope {
+	scope := NewScope()
+	compiler.scopeStack = append(compiler.scopeStack, scope)
+	compiler.nestLevel++
+	return scope
+}
+
+func (compiler *Compiler) exitScope() *Scope {
+	last := len(compiler.scopeStack) - 1
+	scope := compiler.scopeStack[last]
+	compiler.scopeStack = compiler.scopeStack[:last]
+	compiler.nestLevel--
+	return scope
+}
+
+func (compiler *Compiler) assemble(addNone bool) *bytecode.CodeObject {
+	if addNone {
+		compiler.addOp(bytecode.LOAD_CONST)
+		compiler.addOp(bytecode.RETURN_VALUE)
+	}
+
+	codeobject := bytecode.NewCodeObject()
+	return codeobject
+}
+
+func (compiler *Compiler) addOp(op bytecode.Opcode) bool {
+	fmt.Println(bytecode.Opnames[op])
+	return true
+}
+
+func (compiler *Compiler) visitExpression(expr ast.Expression) bool {
+	switch expr := expr.(type) {
+	case *ast.Num:
+		compiler.addOp(bytecode.LOAD_CONST)
+	case *ast.Name:
+		compiler.addOp(bytecode.STORE_NAME)
+	default:
+		fmt.Println(expr)
+	}
+
+	return true
+}
+
+func (compiler *Compiler) visitStatement(stmt ast.Statement) bool {
+	switch stmt := stmt.(type) {
+	case *ast.Assign:
+		compiler.visitExpression(stmt.Value)
+		length := len(stmt.Targets)
+		for i := 0; i < length; i++ {
+			if i < length-1 {
+				compiler.addOp(bytecode.DUP_TOP)
+			}
+			compiler.visitExpression(stmt.Targets[i])
+		}
+	}
+	return true
+}
+
+func (compiler *Compiler) compileBody(stmts []ast.Statement) bool {
+	// TODO: Check for docstring
+	for _, stmt := range stmts {
+		compiler.visitStatement(stmt)
+	}
+	return true
+}
+
+func (compiler *Compiler) CompileMod(root ast.Mod) *bytecode.CodeObject {
+	addNone := true
+	compiler.enterScope()
+	var codeobject *bytecode.CodeObject
+	switch root := root.(type) {
+	case *ast.Module:
+		if !compiler.compileBody(root.Body) {
+			compiler.exitScope()
+			return nil
+		}
+	}
+
+	codeobject = compiler.assemble(addNone)
+	compiler.exitScope()
+	return codeobject
+}
diff --git a/compiler/interface.go b/compiler/interface.go
new file mode 100644
index 0000000..46a9cab
--- /dev/null
+++ b/compiler/interface.go
@@ -0,0 +1,11 @@
+package compiler
+
+import (
+	"github.com/brettlangdon/gython/ast"
+	"github.com/brettlangdon/gython/bytecode"
+)
+
+func CompileAST(root ast.Mod) *bytecode.CodeObject {
+	compiler := NewCompiler()
+	return compiler.CompileMod(root)
+}
diff --git a/compiler/scope.go b/compiler/scope.go
new file mode 100644
index 0000000..13a2415
--- /dev/null
+++ b/compiler/scope.go
@@ -0,0 +1,7 @@
+package compiler
+
+type Scope struct{}
+
+func NewScope() *Scope {
+	return &Scope{}
+}