From 13ca954072bf343aa8bdb5c1ca32e76625ab747d Mon Sep 17 00:00:00 2001
From: Aadhavan Srinivasan <aadhavan@twomorecents.org>
Date: Thu, 19 Dec 2024 04:29:05 -0500
Subject: [PATCH] Started working on '-m num' flag : print the <num>th match

---
 main.go | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/main.go b/main.go
index 8e99179..53ff644 100644
--- a/main.go
+++ b/main.go
@@ -606,7 +606,8 @@ func main() {
 	multiLineFlag := flag.Bool("t", false, "Multi-line mode. Treats newline just like any character.")
 	printMatchesFlag := flag.Bool("p", false, "Prints start and end index of each match. Can only be used with '-t' for multi-line mode.")
 	caseInsensitiveFlag = flag.Bool("i", false, "Case-insensitive. Disregard the case of all characters.")
-	substituteText := flag.String("s", "", "Substitute the contents  of each match with the given string. Overrides -o and -v")
+	matchNum := flag.Int("m", 0, "Print the match with the given index. Eg. -m 3 prints the third match.")
+	substituteText := flag.String("s", "", "Substitute the contents of each match with the given string. Overrides -o and -v")
 	flag.Parse()
 
 	// In multi-line mode, 'dot' metacharacter also matches newline
@@ -619,14 +620,23 @@ func main() {
 	if *onlyFlag {
 		*lineFlag = false
 	}
-	// Check if substitute text has been enabled
+	// Check if substitute and matchNum flags have been enabled
 	substituteFlagEnabled := false
+	matchNumFlagEnabled := false
 	flag.Visit(func(f *flag.Flag) {
 		if f.Name == "s" {
 			substituteFlagEnabled = true
 		}
+		if f.Name == "m" {
+			matchNumFlagEnabled = true
+		}
 	})
 
+	// Validate matchNumFlag - must be positive integer
+	if matchNumFlagEnabled && *matchNum < 1 {
+		panic("Invalid match number to print.")
+	}
+
 	// Process:
 	// 1. Convert regex into postfix notation (Shunting-Yard algorithm)
 	// 		a. Add explicit concatenation operators to facilitate this