Implement Glob matching for pass/drop filters

internal/internal.go

@@ -61,3 +61,59 @@ func ReadLinesOffsetN(filename string, offset uint, n int) ([]string, error) {
 
 	return ret, nil
 }
+
+// Glob will test a string pattern, potentially containing globs, against a
+// subject string. The result is a simple true/false, determining whether or
+// not the glob pattern matched the subject text.
+//
+// Adapted from https://github.com/ryanuber/go-glob/blob/master/glob.go
+// thanks Ryan Uber!
+func Glob(pattern, measurement string) bool {
+	// Empty pattern can only match empty subject
+	if pattern == "" {
+		return measurement == pattern
+	}
+
+	// If the pattern _is_ a glob, it matches everything
+	if pattern == "*" {
+		return true
+	}
+
+	parts := strings.Split(pattern, "*")
+
+	if len(parts) == 1 {
+		// No globs in pattern, so test for match
+		return pattern == measurement
+	}
+
+	leadingGlob := strings.HasPrefix(pattern, "*")
+	trailingGlob := strings.HasSuffix(pattern, "*")
+	end := len(parts) - 1
+
+	for i, part := range parts {
+		switch i {
+		case 0:
+			if leadingGlob {
+				continue
+			}
+			if !strings.HasPrefix(measurement, part) {
+				return false
+			}
+		case end:
+			if len(measurement) > 0 {
+				return trailingGlob || strings.HasSuffix(measurement, part)
+			}
+		default:
+			if !strings.Contains(measurement, part) {
+				return false
+			}
+		}
+
+		// Trim evaluated text from measurement as we loop over the pattern.
+		idx := strings.Index(measurement, part) + len(part)
+		measurement = measurement[idx:]
+	}
+
+	// All parts of the pattern matched
+	return true
+}