feat: statistics flag, commented some more

internal/config/source.go

@@ -5,21 +5,21 @@ import (
 	"os"
 )
 
-// Defines the consumption of different types of input sources.
+// A method of extracting input from the user.
 type Source interface {
-	// Get the data.
-	Pull() (string, error)
+	// Fetch data from this source.
+	Extract() (string, error)
 }
 
-// A source coming from a string.
-type StringSource struct{ data string }
+// A source defined by a string.
+type StringSource struct{ Data string }
 
-func (s StringSource) Pull() (string, error) { return s.data, nil }
+func (s StringSource) Extract() (string, error) { return s.Data, nil }
 
-// A source coming from standard input.
+// A source pulling from standard input.
 type StdinSource struct{}
 
-func (s StdinSource) Pull() (string, error) {
+func (s StdinSource) Extract() (string, error) {
 	data, err := io.ReadAll(os.Stdin)
 	if err != nil {
 		return "", err