Add 'dirty' flag to document

editor/document.go

@@ -36,6 +36,8 @@ func (d *document) open(filename string) {
 	for scanner.Scan() {
 		d.appendRow(scanner.Text())
 	}
+
+	d.dirty = false
 }
 
 func (d *document) save() int {
@@ -67,6 +69,8 @@ func (d *document) save() int {
 		return size
 	}
 
+	d.dirty = false
+
 	return 0
 }
 
@@ -74,6 +78,8 @@ func (d *document) appendRow(s string) {
 	newRow := newRow(s)
 	newRow.update()
 	d.rows = append(d.rows, newRow)
+
+	d.dirty = true
 }
 
 func (d *document) toString() string {

editor/draw.go

@@ -114,8 +114,12 @@ func (e *editor) drawStatusBar(ab *buffer) {
 	if e.document.filename != "" {
 		fileName = e.document.filename
 	}
+	modified := ""
+	if e.document.dirty {
+		modified = "(modified)"
+	}
 
-	leftStatus := fmt.Sprintf("%.20s - %d lines", fileName, e.document.rowCount())
+	leftStatus := fmt.Sprintf("%.20s - %d lines %s", fileName, e.document.rowCount(), modified)
 	length := len(leftStatus)
 	if length > cols {
 		leftStatus = truncate(leftStatus, cols)

editor/editor.go

@@ -193,6 +193,7 @@ func (e *editor) insertChar(ch rune) {
 
 	e.document.rows[e.cursor.y].insertRune(ch, e.cursor.x)
 	e.cursor.x += 1
+	e.document.dirty = true
 }
 
 // Convert the raw ANSI escape sequences to the type of key input