From fe72ce82234aca671d0992cdc41c77533ba8522a Mon Sep 17 00:00:00 2001
From: Gabriel Nelle <gabriel.nelle@gostudent.org>
Date: Sat, 12 Nov 2022 10:23:08 +0000
Subject: [PATCH] add declaration normalization

---
 representation/normalize.go      |  22 ++--
 representation/normalize_decl.go | 168 +++++++++++++++++++++++++++++++
 2 files changed, 181 insertions(+), 9 deletions(-)
 create mode 100644 representation/normalize_decl.go

diff --git a/representation/normalize.go b/representation/normalize.go
index 895b818..3bf1797 100644
--- a/representation/normalize.go
+++ b/representation/normalize.go
@@ -15,17 +15,20 @@ func (s *Representation) Normalize() error {
 		return errors.New("no Go package found")
 	}
 
-	pkg = s.normalize(pkg)
-	s.represent = pkg
-	return nil
-}
-
-func (s *Representation) normalize(pkg *ast.Package) *ast.Package {
 	f := ast.MergePackageFiles(pkg, ast.FilterImportDuplicates+ast.FilterUnassociatedComments)
 	pkg.Files = map[string]*ast.File{defaultFileName: f}
 
+	// register additional normalizations here
+	s.normalizeDeclarations(pkg)
+
 	s.sortInFile(f)
+	s.normalizeNaming(pkg)
 
+	s.represent = pkg
+	return nil
+}
+
+func (s *Representation) normalizeNaming(pkg *ast.Package) {
 	astutil.Apply(pkg, func(cursor *astutil.Cursor) bool {
 		node := cursor.Node()
 		if node == nil {
@@ -33,13 +36,14 @@ func (s *Representation) normalize(pkg *ast.Package) *ast.Package {
 		}
 
 		s.collectImport(node)
-		s.rename(node, cursor)
+		s.rename(cursor)
 		return true
 	}, nil)
-	return pkg
 }
 
-func (s *Representation) rename(node ast.Node, cursor *astutil.Cursor) {
+func (s *Representation) rename(cursor *astutil.Cursor) {
+	node := cursor.Node()
+
 	switch n := node.(type) {
 	default:
 		return
diff --git a/representation/normalize_decl.go b/representation/normalize_decl.go
new file mode 100644
index 0000000..0382ffa
--- /dev/null
+++ b/representation/normalize_decl.go
@@ -0,0 +1,168 @@
+package representation
+
+import (
+	"go/ast"
+	"go/token"
+	"strconv"
+	"strings"
+
+	"golang.org/x/tools/go/ast/astutil"
+)
+
+// TODO: test with more cases
+func (s *Representation) normalizeDeclarations(pkg *ast.Package) {
+	astutil.Apply(pkg, func(cursor *astutil.Cursor) bool {
+		node := cursor.Node()
+		if node == nil {
+			return true
+		}
+		var (
+			a    = "abc"
+			b, c = 1, "cde"
+		)
+		_, _, _ = a, b, c
+
+		switch n := node.(type) {
+		default:
+			return true
+		case *ast.DeclStmt:
+			genDecl, ok := n.Decl.(*ast.GenDecl)
+			if !ok {
+				return true
+			}
+			if genDecl.Tok.String() != "var" {
+				return true
+			}
+
+			var keep bool
+			for _, spec := range genDecl.Specs {
+				specNode, ok := spec.(*ast.ValueSpec)
+				if !ok {
+					keep = true
+					continue
+				}
+
+				for i, name := range specNode.Names {
+					val := getValue(specNode.Values, i)
+					if val == nil {
+						val = getDefaultLiteralForExpression(specNode.Type)
+					}
+					val = addTypeAsNeeded(val, specNode.Type)
+					newDecl := newAssignment(name.Name, val)
+					cursor.InsertBefore(newDecl)
+				}
+			}
+			if !keep {
+				cursor.Delete()
+			}
+		}
+
+		return true
+	}, nil)
+}
+
+func addTypeAsNeeded(val ast.Expr, typeExpr ast.Expr) ast.Expr {
+	if _, ok := val.(*ast.BasicLit); !ok {
+		return val
+	}
+	typeIdent, ok := typeExpr.(*ast.Ident)
+	if !ok {
+		return val
+	}
+	if !needsType(typeIdent.Name) {
+		return val
+	}
+
+	return &ast.CallExpr{
+		Fun:  typeIdent,
+		Args: []ast.Expr{val},
+	}
+}
+
+func needsType(ident string) bool {
+	switch ident {
+	case "string", "int", "float64", "complex128", "bool":
+		return false
+	}
+	return true
+}
+
+func newAssignment(name string, value ast.Expr) ast.Node {
+	return &ast.AssignStmt{
+		Lhs: []ast.Expr{&ast.Ident{Name: name}},
+		Tok: token.DEFINE,
+		Rhs: []ast.Expr{value},
+	}
+}
+
+func getValue(values []ast.Expr, i int) ast.Expr {
+	if len(values) > i {
+		return values[i]
+	}
+	return nil
+}
+
+func getDefaultLiteralForExpression(typeExpr ast.Expr) ast.Expr {
+	typeIdent, ok := typeExpr.(*ast.Ident)
+	if !ok {
+		return &ast.BasicLit{
+			Kind:  token.STRING,
+			Value: `"unimplemented case in representer: getDefaultLiteralForExpression: typeExpr is not *ast.Ident"`,
+		}
+	}
+
+	kind := typeLookup(typeIdent.Name)
+	switch kind {
+	case token.IDENT:
+		return &ast.CallExpr{
+			Fun: typeIdent,
+			Args: []ast.Expr{
+				&ast.BasicLit{
+					Kind:  token.INT,
+					Value: `0`,
+				},
+			},
+		}
+	}
+	return &ast.BasicLit{
+		Kind:  kind,
+		Value: getDefaultLiteral(kind),
+	}
+}
+
+// TODO: test this. Correct string names used?
+func typeLookup(name string) token.Token {
+	switch strings.ToLower(name) {
+	case "int":
+		return token.INT
+	case "float":
+		return token.FLOAT
+	case "imag":
+		return token.IMAG
+	case "char":
+		return token.CHAR
+	case "string":
+		return token.STRING
+	}
+	return token.IDENT
+}
+
+func getDefaultLiteral(kind token.Token) string {
+	switch kind {
+	case token.INT:
+		return `0`
+	case token.FLOAT:
+		return `0.0`
+	case token.IMAG:
+		return `0i`
+	case token.CHAR:
+		return `0`
+	case token.STRING:
+		return `""`
+	}
+	return `"unimplemented case in representer: getDefaultLiteral: unknown kind: ` + strconv.Itoa(int(kind)) + `"`
+}
+
+// *ast.AssignStmt: &{Lhs:[res] TokPos:110 Tok::= Rhs:[0x140001dc660]}
+// *ast.Ident: res
+// *ast.BasicLit: &{ValuePos:113 Kind:STRING Value:""}