1 files changed, 96 insertions, 0 deletions
diff --git a/range.go b/range.go
new file mode 100644
index 0000000..0ad5eab
--- /dev/null
+++ b/range.go
@@ -0,0 +1,96 @@
+// SPDX-FileCopyrightText: 2023 M. Shulhan <ms@kilabit.info>
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package awwan
+
+import (
+	"strconv"
+	"strings"
+)
+
+// lineRange contains the start and end of line number.
+// For single line, the Start and End must be equal.
+// For range that does not have an end, the End value must be zero.
+type lineRange struct {
+	list []linePosition
+}
+
+// parseLineRange parse a line range in the following format,
+//
+//	line-range = start ["-" [end]] *("," line-range)
+//
+// The start must be greater than zero.
+// The end is optional, if its exist it must be equal or greater than start.
+//
+// The next line-range must not overlap with previous range, otherwise it will
+// be skipped.
+func parseLineRange(raw string) (lr lineRange) {
+	raw = strings.TrimSpace(raw)
+	if len(raw) == 0 {
+		return lr
+	}
+
+	var (
+		listRange = strings.Split(raw, ",")
+
+		rawPos string
+		start  int64
+		end    int64
+		err    error
+		ok     bool
+	)
+	for _, rawPos = range listRange {
+		rawPos = strings.TrimSpace(rawPos)
+		if len(rawPos) == 0 {
+			continue
+		}
+
+		var pos = strings.Split(rawPos, "-")
+		if len(pos) > 2 {
+			// Invalid range.
+			continue
+		}
+
+		start, err = strconv.ParseInt(pos[0], 10, 64)
+		if err != nil || start <= 0 {
+			continue
+		}
+		if len(pos) == 1 {
+			lr.add(start, start)
+			continue
+		}
+
+		if len(pos[1]) == 0 {
+			ok = lr.add(start, 0)
+			if ok {
+				break
+			}
+			continue
+		}
+
+		end, err = strconv.ParseInt(pos[1], 10, 64)
+		if err != nil || end < start {
+			continue
+		}
+
+		lr.add(start, end)
+	}
+	return lr
+}
+
+// add new position to line range.
+// It will return true if new position is added to the list.
+func (lr *lineRange) add(start, end int64) bool {
+	var pos linePosition
+	for _, pos = range lr.list {
+		if start <= pos.start {
+			return false
+		}
+		if start <= pos.end {
+			return false
+		}
+		continue
+	}
+	lr.list = append(lr.list, linePosition{start: start, end: end})
+	return true
+}