Isolate import tracking functionality

import_tracker.go

@@ -0,0 +1,61 @@
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package gas
+
+import (
+	"go/ast"
+	"go/types"
+	"strings"
+)
+
+type ImportTracker struct {
+	Imported map[string]string
+	Aliased  map[string]string
+	InitOnly map[string]bool
+}
+
+func NewImportTracker() *ImportTracker {
+	return &ImportTracker{
+		make(map[string]string),
+		make(map[string]string),
+		make(map[string]bool),
+	}
+}
+
+func (t *ImportTracker) TrackPackages(pkgs ...*types.Package) {
+	for _, pkg := range pkgs {
+		for _, imp := range pkg.Imports() {
+			t.Imported[imp.Path()] = imp.Name()
+		}
+	}
+}
+
+func (t *ImportTracker) TrackImport(n ast.Node) {
+	if imported, ok := n.(*ast.ImportSpec); ok {
+		path := strings.Trim(imported.Path.Value, `"`)
+		if imported.Name != nil {
+			if imported.Name.Name == "_" {
+				// Initialization only import
+				t.InitOnly[path] = true
+			} else {
+				// Aliased import
+				t.Aliased[path] = imported.Name.Name
+			}
+		}
+
+		// unsafe is not included in Package.Imports()
+		if path == "unsafe" {
+			t.Imported[path] = path
+		}
+	}
+}