From a728570c893e1a1354728570b049df597f345aed Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicol=C3=A1s=20Ortega=20Froysa?= <nicolas@ortegas.org>
Date: Sat, 24 Feb 2024 13:57:09 +0100
Subject: [PATCH] Implement log search to find transactions.
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Signed-off-by: Nicolás Ortega Froysa <nicolas@ortegas.org>
---
 README.md  |  7 +++++++
 pacundo.pl | 42 +++++++++++++++++++++++++++++++++++-------
 2 files changed, 42 insertions(+), 7 deletions(-)

diff --git a/README.md b/README.md
index c8eb9f0..b1db337 100644
--- a/README.md
+++ b/README.md
@@ -5,6 +5,13 @@ system, and now you have to go in and downgrade those packages? It's a pain
 ain't it? Well, this should make it slightly less of a pain (you may still have
 to boot from a USB depending on just how broken it is).
 
+## Installation
+
+Dependencies:
+
+- Perl 5
+- `File::ReadBackwards` module
+
 ## License
 
 This project is licensed under the terms & conditions of the Zlib license.
diff --git a/pacundo.pl b/pacundo.pl
index 192f7c2..d93352a 100755
--- a/pacundo.pl
+++ b/pacundo.pl
@@ -26,12 +26,14 @@ use strict;
 use warnings;
 
 use Getopt::Std;
+use File::ReadBackwards;
 
 my $VERSION = "1.0";
 my $PROG_NAME = "pacundo";
 
 my $r_flag = 0;
 my $dry_run = 0;
+my $num_txs = 1;
 
 sub print_version {
 	print("$PROG_NAME v$VERSION\n");
@@ -41,19 +43,20 @@ sub print_help {
 	&print_version();
 	print("A time machine to return your ArchLinux machine back to a working state.\n");
 	print("\nUSAGE:
-	$PROG_NAME [-i|-r] [-d]
+	$PROG_NAME [-i|-r] [-t <num>] [-d]
 	$PROG_NAME -h
 	$PROG_NAME -v
 
 OPTIONS:
-	-i   Enter interactive mode to select packages to downgrade [default behavior]
-	-r   Automatically downgrade all packages from last upgrade
-	-d   Dry run, i.e. don't actually do anything
-	-h   Show this help information
-	-v   Print program version\n");
+	-i         Enter interactive mode to select packages to downgrade [default behavior]
+	-r         Automatically downgrade all packages from last upgrade
+	-t <num>   Specify the number of transactions to include for undoing selection [default 1]
+	-d         Dry run, i.e. don't actually do anything
+	-h         Show this help information
+	-v         Print program version\n");
 }
 
-getopts("irdvh", \my %opts);
+getopts("irt:dvh", \my %opts);
 
 if ($opts{'v'}) {
 	&print_version();
@@ -69,3 +72,28 @@ if ($opts{'v'}) {
 
 $r_flag = 1 if ($opts{'r'});
 $dry_run = 1 if ($opts{'d'});
+$num_txs = $opts{'t'} if ($opts{'t'});
+
+my $pacman_log = File::ReadBackwards->new("/var/log/pacman.log") or
+die("Failed to load pacman log file.\n$!");
+
+my $found_txs = 0;
+my $in_tx = 0;
+
+while ($found_txs < $num_txs && defined(my $line = $pacman_log->readline)) {
+	# Remeber that we're reading this in reverse order
+	if (!$in_tx && $line =~ /\[ALPM\] transaction completed/) {
+		$in_tx = 1;
+	} elsif ($in_tx) {
+		if ($line =~ /\[ALPM\] transaction started/) {
+			$found_txs++;
+			$in_tx = 0;
+		} elsif ($line =~ /\[ALPM\] (upgraded|downgraded)/) {
+			my ($action, $package, $oldver, $newver) = $line =~ /\[ALPM\] (upgraded|downgraded) ([^\s]+) \((.*) -> (.*)\)/;
+			print("$action $package $oldver -> $newver\n");
+		} elsif ($line =~ /\[ALPM\] (installed|removed)/) {
+			my ($action, $package) = $line =~ /\[ALPM\] (installed|removed) ([^\s]+)/;
+			print("$action $package\n");
+		}
+	}
+}