#!/usr/bin/env perl
# SPDX-License-Identifier: GPL-2.0
#
# Treewide grep for references to files under Documentation, and report
# non-existing files in stderr.

use warnings;
use strict;
use Getopt::Long qw(:config no_auto_abbrev);

# NOTE: only add things here when the file was gone, but the text wants
# to mention a past documentation file, for example, to give credits for
# the original work.
my %false_positives = (
	"Documentation/scsi/scsi_mid_low_api.rst" => "Documentation/Configure.help",
	"drivers/vhost/vhost.c" => "Documentation/virtual/lguest/lguest.c",
);

my $scriptname = $0;
$scriptname =~ s,tools/docs/([^/]+/),$1,;

# Parse arguments
my $help = 0;
my $fix = 0;
my $warn = 0;

if (! -e ".git") {
	printf "Warning: can't check if file exists, as this is not a git tree\n";
	exit 0;
}

GetOptions(
	'fix' => \$fix,
	'warn' => \$warn,
	'h|help|usage' => \$help,
);

if ($help != 0) {
    print "$scriptname [--help] [--fix]\n";
    exit -1;
}

# Step 1: find broken references
print "Finding broken references. This may take a while...  " if ($fix);

my %broken_ref;

my $doc_fix = 0;

open IN, "git grep ':doc:\`' Documentation/|"
     or die "Failed to run git grep";
while (<IN>) {
	next if (!m,^([^:]+):.*\:doc\:\`([^\`]+)\`,);
	next if (m,sphinx/,);

	my $file = $1;
	my $d = $1;
	my $doc_ref = $2;

	my $f = $doc_ref;

	$d =~ s,(.*/).*,$1,;
	$f =~ s,.*\<([^\>]+)\>,$1,;

	if ($f =~ m,^/,) {
		$f = "$f.rst";
		$f =~ s,^/,Documentation/,;
	} else {
		$f = "$d$f.rst";
	}

	next if (grep -e, glob("$f"));

	if ($fix && !$doc_fix) {
		print STDERR "\nWARNING: Currently, can't fix broken :doc:`` fields\n";
	}
	$doc_fix++;

	print STDERR "$file: :doc:`$doc_ref`\n";
}
close IN;

open IN, "git grep 'Documentation/'|"
     or die "Failed to run git grep";
while (<IN>) {
	next if (!m/^([^:]+):(.*)/);

	my $f = $1;
	my $ln = $2;

	# On linux-next, discard the Next/ directory
	next if ($f =~ m,^Next/,);

	# Makefiles and scripts contain nasty expressions to parse docs
	next if ($f =~ m/Makefile/ || $f =~ m/\.(sh|py|pl|~|rej|org|orig)$/);

	# It doesn't make sense to parse hidden files
	next if ($f =~ m#/\.#);

	# Skip this script
	next if ($f eq $scriptname);

	# Ignore the dir where documentation will be built
	next if ($ln =~ m,\b(\S*)Documentation/output,);

	if ($ln =~ m,\b(\S*)(Documentation/[A-Za-z0-9\_\.\,\~/\*\[\]\?+-]*)(.*),) {
		my $prefix = $1;
		my $ref = $2;
		my $base = $2;
		my $extra = $3;

		# some file references are like:
		# /usr/src/linux/Documentation/DMA-{API,mapping}.txt
		# For now, ignore them
		next if ($extra =~ m/^{/);

		# Remove footnotes at the end like:
		# Documentation/devicetree/dt-object-internal.txt[1]
		$ref =~ s/(txt|rst)\[\d+]$/$1/;

		# Remove ending ']' without any '['
		$ref =~ s/\].*// if (!($ref =~ m/\[/));

		# Remove puntuation marks at the end
		$ref =~ s/[\,\.]+$//;

		my $fulref = "$prefix$ref";

		$fulref =~ s/^(\<file|ref)://;
		$fulref =~ s/^[\'\`]+//;
		$fulref =~ s,^\$\(.*\)/,,;
		$base =~ s,.*/,,;

		# Remove URL false-positives
		next if ($fulref =~ m/^http/);

		# Remove sched-pelt false-positive
		next if ($fulref =~ m,^Documentation/scheduler/sched-pelt$,);

		# Discard some build examples from Documentation/target/tcm_mod_builder.rst
		next if ($fulref =~ m,mnt/sdb/lio-core-2.6.git/Documentation/target,);

		# Check if exists, evaluating wildcards
		next if (grep -e, glob("$ref $fulref"));

		# Accept relative Documentation paths for tools/
		if ($f =~ m/tools/) {
			my $path = $f;
			$path =~ s,(.*)/.*,$1,;
			$path =~ s,testing/selftests/bpf,bpf/bpftool,;
			next if (grep -e, glob("$path/$ref $path/../$ref $path/$fulref"));
		}

		# Discard known false-positives
		if (defined($false_positives{$f})) {
			next if ($false_positives{$f} eq $fulref);
		}

		if ($fix) {
			if (!($ref =~ m/(scripts|Kconfig|Kbuild)/)) {
				$broken_ref{$ref}++;
			}
		} elsif ($warn) {
			print STDERR "Warning: $f references a file that doesn't exist: $fulref\n";
		} else {
			print STDERR "$f: $fulref\n";
		}
	}
}
close IN;

exit 0 if (!$fix);

# Step 2: Seek for file name alternatives
print "Auto-fixing broken references. Please double-check the results\n";

foreach my $ref (keys %broken_ref) {
	my $new =$ref;

	my $basedir = ".";
	# On translations, only seek inside the translations directory
	$basedir  = $1 if ($ref =~ m,(Documentation/translations/[^/]+),);

	# get just the basename
	$new =~ s,.*/,,;

	my $f="";

	# usual reason for breakage: DT file moved around
	if ($ref =~ /devicetree/) {
		# usual reason for breakage: DT file renamed to .yaml
		if (!$f) {
			my $new_ref = $ref;
			$new_ref =~ s/\.txt$/.yaml/;
			$f=$new_ref if (-f $new_ref);
		}

		if (!$f) {
			my $search = $new;
			$search =~ s,^.*/,,;
			$f = qx(find Documentation/devicetree/ -iname "*$search*") if ($search);
			if (!$f) {
				# Manufacturer name may have changed
				$search =~ s/^.*,//;
				$f = qx(find Documentation/devicetree/ -iname "*$search*") if ($search);
			}
		}
	}

	# usual reason for breakage: file renamed to .rst
	if (!$f) {
		$new =~ s/\.txt$/.rst/;
		$f=qx(find $basedir -iname $new) if ($new);
	}

	# usual reason for breakage: use dash or underline
	if (!$f) {
		$new =~ s/[-_]/[-_]/g;
		$f=qx(find $basedir -iname $new) if ($new);
	}

	# Wild guess: seek for the same name on another place
	if (!$f) {
		$f = qx(find $basedir -iname $new) if ($new);
	}

	my @find = split /\s+/, $f;

	if (!$f) {
		print STDERR "ERROR: Didn't find a replacement for $ref\n";
	} elsif (scalar(@find) > 1) {
		print STDERR "WARNING: Won't auto-replace, as found multiple files close to $ref:\n";
		foreach my $j (@find) {
			$j =~ s,^./,,;
			print STDERR "    $j\n";
		}
	} else {
		$f = $find[0];
		$f =~ s,^./,,;
		print "INFO: Replacing $ref to $f\n";
		foreach my $j (qx(git grep -l $ref)) {
			qx(sed "s\@$ref\@$f\@g" -i $j);
		}
	}
}