1 files changed, 58 insertions, 0 deletions
diff --git a/tagpreprocessor.go b/tagpreprocessor.go
new file mode 100644
index 0000000..2be8846
--- /dev/null
+++ b/tagpreprocessor.go
@@ -0,0 +1,58 @@
+// Copyright 2019, M. Shulhan (ms@kilabit.info).  All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package haminer
+
+import (
+	"errors"
+	"regexp"
+	"strings"
+)
+
+type tagPreprocessor struct {
+	name  string
+	regex *regexp.Regexp
+	repl  string
+}
+
+//
+// newTagPreprocessor create and initialize replace tag pre-processing.
+// The regex and repl strings must be enclosed with double-quote, except for
+// repl it can be empty.
+//
+func newTagPreprocessor(name, regex, repl string) (
+	retag *tagPreprocessor, err error,
+) {
+	name = strings.TrimSpace(name)
+	regex = strings.TrimSpace(regex)
+	repl = strings.TrimSpace(repl)
+
+	if len(name) == 0 {
+		return nil, errors.New("newTagPreprocessor: empty name parameter")
+	}
+	if len(regex) == 0 {
+		return nil, errors.New("newTagPreprocessor: empty regex parameter")
+	}
+
+	re, err := regexp.Compile(regex)
+	if err != nil {
+		return nil, err
+	}
+
+	retag = &tagPreprocessor{
+		name:  name,
+		regex: re,
+		repl:  repl,
+	}
+
+	return retag, nil
+}
+
+func (tagp *tagPreprocessor) preprocess(name, value string) string {
+	if tagp.name != name {
+		return value
+	}
+	out := tagp.regex.ReplaceAllString(value, tagp.repl)
+	return out
+}