!/usr/bin/perl

use strict; use warnings; use IPC::Open2;

# An example hook script to integrate Watchman # (facebook.github.io/watchman/) with git to speed up detecting # new and modified files. # # The hook is passed a version (currently 2) and last update token # formatted as a string and outputs to stdout a new update token and # all files that have been modified since the update token. Paths must # be relative to the root of the working tree and separated by a single NUL. # # To enable this hook, rename this file to “query-watchman” and set # ‘git config core.fsmonitor .git/hooks/query-watchman’ # my ($version, $last_update_token) = @ARGV;

# Uncomment for debugging # print STDERR “$0 $version $last_update_tokenn”;

# Check the hook interface version if ($version ne 2) {

die "Unsupported query-fsmonitor hook version '$version'.\n" .
    "Falling back to scanning...\n";

}

my $git_work_tree = get_working_dir();

my $retry = 1;

my $json_pkg; eval {

require JSON::XS;
$json_pkg = "JSON::XS";
1;

} or do {

require JSON::PP;
$json_pkg = "JSON::PP";

};

launch_watchman();

sub launch_watchman {

my $o = watchman_query();
if (is_work_tree_watched($o)) {
        output_result($o->{clock}, @{$o->{files}});
}

}

sub output_result {

my ($clockid, @files) = @_;

# Uncomment for debugging watchman output
# open (my $fh, ">", ".git/watchman-output.out");
# binmode $fh, ":utf8";
# print $fh "$clockid\n@files\n";
# close $fh;

binmode STDOUT, ":utf8";
print $clockid;
print "\0";
local $, = "\0";
print @files;

}

sub watchman_clock {

my $response = qx/watchman clock "$git_work_tree"/;
die "Failed to get clock id on '$git_work_tree'.\n" .
        "Falling back to scanning...\n" if $? != 0;

return $json_pkg->new->utf8->decode($response);

}

sub watchman_query {

my $pid = open2(\*CHLD_OUT, \*CHLD_IN, 'watchman -j --no-pretty')
or die "open2() failed: $!\n" .
"Falling back to scanning...\n";

# In the query expression below we're asking for names of files that
# changed since $last_update_token but not from the .git folder.
#
# To accomplish this, we're using the "since" generator to use the
# recency index to select candidate nodes and "fields" to limit the
# output to file names only. Then we're using the "expression" term to
# further constrain the results.
my $last_update_line = "";
if (substr($last_update_token, 0, 1) eq "c") {
        $last_update_token = "\"$last_update_token\"";
        $last_update_line = qq[\n"since": $last_update_token,];
}
my $query = <<" END";
        ["query", "$git_work_tree", {$last_update_line
                "fields": ["name"],
                "expression": ["not", ["dirname", ".git"]]
        }]
END

# Uncomment for debugging the watchman query
# open (my $fh, ">", ".git/watchman-query.json");
# print $fh $query;
# close $fh;

print CHLD_IN $query;
close CHLD_IN;
my $response = do {local $/; <CHLD_OUT>};

# Uncomment for debugging the watch response
# open ($fh, ">", ".git/watchman-response.json");
# print $fh $response;
# close $fh;

die "Watchman: command returned no output.\n" .
"Falling back to scanning...\n" if $response eq "";
die "Watchman: command returned invalid output: $response\n" .
"Falling back to scanning...\n" unless $response =~ /^\{/;

return $json_pkg->new->utf8->decode($response);

}

sub is_work_tree_watched {

my ($output) = @_;
my $error = $output->{error};
if ($retry > 0 and $error and $error =~ m/unable to resolve root .* directory (.*) is not watched/) {
        $retry--;
        my $response = qx/watchman watch "$git_work_tree"/;
        die "Failed to make watchman watch '$git_work_tree'.\n" .
            "Falling back to scanning...\n" if $? != 0;
        $output = $json_pkg->new->utf8->decode($response);
        $error = $output->{error};
        die "Watchman: $error.\n" .
        "Falling back to scanning...\n" if $error;

        # Uncomment for debugging watchman output
        # open (my $fh, ">", ".git/watchman-output.out");
        # close $fh;

        # Watchman will always return all files on the first query so
        # return the fast "everything is dirty" flag to git and do the
        # Watchman query just to get it over with now so we won't pay
        # the cost in git to look up each individual file.
        my $o = watchman_clock();
        $error = $output->{error};

        die "Watchman: $error.\n" .
        "Falling back to scanning...\n" if $error;

        output_result($o->{clock}, ("/"));
        $last_update_token = $o->{clock};

        eval { launch_watchman() };
        return 0;
}

die "Watchman: $error.\n" .
"Falling back to scanning...\n" if $error;

return 1;

}

sub get_working_dir {

my $working_dir;
if ($^O =~ 'msys' || $^O =~ 'cygwin') {
        $working_dir = Win32::GetCwd();
        $working_dir =~ tr/\\/\//;
} else {
        require Cwd;
        $working_dir = Cwd::cwd();
}

return $working_dir;

}