Complete step 164 in Chapter 7 of Kilo tutorial

editor/Editor.go

@@ -74,9 +74,13 @@ func (e *Editor) save() {
 		e.doc.Filename = e.prompt("Save as: %s (ESC to cancel)", nil)
 		if e.doc.Filename == "" {
 			e.SetStatusMessage("Save aborted")
+			return
 		}
 	}
 
+	// Set the syntax highlighting type, now that we now the file extension
+	e.doc.SelectSyntaxHighlight()
+
 	size := e.doc.Save()
 
 	if size > 0 {

editor/document/document.go

@@ -34,6 +34,8 @@ func (d *Document) Open(filename string) {
 	defer file.Close()
 
 	d.Filename = filename
+	d.SelectSyntaxHighlight()
+
 	scanner := bufio.NewScanner(file)
 	scanner.Split(bufio.ScanLines)
 
@@ -175,3 +177,12 @@ func (d *Document) delRow(at int) {
 	d.rows = newSlice
 	d.dirty = true
 }
+
+func (d *Document) SelectSyntaxHighlight() {
+	d.Syntax = highlight.GetSyntaxByFilename(d.Filename)
+
+	// Update syntax highlighting when syntax type changes
+	for _, row := range d.rows {
+		row.updateSyntax()
+	}
+}

editor/document/document_test.go

@@ -1,6 +1,9 @@
 package document
 
-import "testing"
+import (
+	"testing"
+	"timshome.page/gilo/editor/highlight"
+)
 
 func TestNewDocument(t *testing.T) {
 	d := NewDocument()

editor/highlight/constants.go

@@ -10,13 +10,3 @@ const (
 )
 
 const HighlightNumbers = (1 << 0)
-
-var HLDB = []*Syntax{{
-	"c",
-	[]string{".c", ".h", ".cpp"},
-	HighlightNumbers,
-}, {
-	"go",
-	[]string{".go"},
-	HighlightNumbers,
-}}

editor/highlight/syntax.go

@@ -1,7 +1,44 @@
 package highlight
 
+import "strings"
+
 type Syntax struct {
 	FileType  string
 	FileMatch []string
 	Flags     int
 }
+
+// HLDB - The "database" of syntax types
+var HLDB = []*Syntax{{
+	"c",
+	[]string{".c", ".h", ".cpp"},
+	HighlightNumbers,
+}, {
+	"go",
+	[]string{".go", "go.mod"},
+	HighlightNumbers,
+}, {
+	"makefile",
+	[]string{"Makefile", "makefile"},
+	0,
+}}
+
+func GetSyntaxByFilename(filename string) *Syntax {
+	if filename == "" {
+		return nil
+	}
+
+	extInd := strings.LastIndex(filename, ".")
+	ext := filename[extInd:len(filename)]
+
+	for i := 0; i < len(HLDB); i++ {
+		s := HLDB[i]
+		for j := range s.FileMatch {
+			if s.FileMatch[j] == ext || strings.Contains(filename, s.FileMatch[j]) {
+				return s
+			}
+		}
+	}
+
+	return nil
+}

editor/highlight/syntax_test.go

@@ -0,0 +1,34 @@
+package highlight
+
+import "testing"
+
+func TestGetSyntaxByFilename(t *testing.T) {
+	var s *Syntax = nil
+
+	t.Run("returns nil on empty filename", func(t *testing.T) {
+		got := GetSyntaxByFilename("")
+		want := s
+
+		if got != want {
+			t.Errorf("got %q want 'nil'", got.FileType)
+		}
+	})
+
+	t.Run("returns nil on undefined file type", func(t *testing.T) {
+		got := GetSyntaxByFilename("foo.bar")
+		want := s
+
+		if got != want {
+			t.Errorf("got %q want 'nil'", got.FileType)
+		}
+	})
+
+	t.Run("returns c on .c file", func(t *testing.T) {
+		got := GetSyntaxByFilename("kilo.c")
+		want := "c"
+
+		if got.FileType != want {
+			t.Errorf("got %q want %q", got.FileType, want)
+		}
+	})
+}