Add editor packages

internal/editor/buffer/save.go

@@ -0,0 +1,66 @@
+package buffer
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"time"
+)
+
+// TODO: save to temporary file, then move over current file.
+// TODO: autosave; track dirty buffer.
+func (b *Buffer) Save() error {
+	var buf bytes.Buffer
+	switch len(b.lines) {
+	case 1:
+		if l := b.lines[0]; l.Length() != 0 {
+			if _, err := buf.WriteString(l.String()); err != nil {
+				return fmt.Errorf(
+					"failed to write to buffer: %v", err,
+				)
+			}
+			if _, err := buf.WriteRune('\n'); err != nil {
+				return fmt.Errorf(
+					"failed to write to buffer: %v", err,
+				)
+			}
+		}
+	default:
+		for _, l := range b.lines {
+			if _, err := buf.WriteString(l.String()); err != nil {
+				return fmt.Errorf(
+					"failed to write to buffer: %v", err,
+				)
+			}
+			if _, err := buf.WriteRune('\n'); err != nil {
+				return fmt.Errorf(
+					"failed to write to buffer: %v", err,
+				)
+			}
+		}
+	}
+
+	if err := os.WriteFile(
+		b.name,
+		buf.Bytes(),
+		0666,
+	); err != nil {
+		return fmt.Errorf("failed to write file: %v", err)
+	}
+
+	b.saved = time.Now()
+
+	return nil
+}
+
+func (b *Buffer) SaveAs(name string) error {
+	old := b.name
+	b.name = name
+
+	if err := b.Save(); err != nil {
+		b.name = old
+		return fmt.Errorf("failed to save file as %s: %w", name, err)
+	}
+
+	return nil
+}