#!/usr/bin/perl

# Author: <quentin@mit.edu>

use strict;
use warnings;

use File::Spec::Functions;
use Getopt::Long;

use constant {
    CRON_DIR => "cron_scripts",
    CRONTAB_FILE => "crontab",
    AUTO_DIR => "AUTO",
    SPOOL_DIR => "/mit/scripts/cron/crontabs",
};

my $force = 0;
my $list = 0;
my $pretend = 0;

sub get_crontabs() {
    my $crontab = catfile($ENV{"HOME"}, CRON_DIR, CRONTAB_FILE);
    my $crontabdir = catdir($ENV{"HOME"}, CRON_DIR, AUTO_DIR);
    
    my @crontabs;
    
    opendir(CRONTABS, $crontabdir) or print "You don't have a ".CRON_DIR."/".AUTO_DIR."/ directory\n";
    push(@crontabs, grep { -r $_ } map { catfile($crontabdir, $_) } grep { !/^[\.#]/ } readdir(CRONTABS));
    closedir(CRONTABS);
    
    push (@crontabs, $crontab) if (-r $crontab);
    return @crontabs;
}

sub read_crontab($) {
    my ($file) = @_;
    # local $/;
    
    open(CRONTAB, $file) or die "Couldn't read crontab $file!";
    my @lines = <CRONTAB>;
    close(CRONTAB);
    
    return @lines;
}

sub check_crontab(@) {
    my (@lines) = @_;
    
    my @errors;
    
    foreach my $line (@lines) {
        $line =~ s|#.*$||; # Remove comments
        $line =~ s|^\s*(.*?)\s*$|$1|; # Remove whitespace
        
        if ($line =~ m|^\w[\w\d]*=|) {
            # Comment
            next;
        } elsif ($line =~ m|^(?:(\S+)\s+){5}(.*)|) {
            # Crontab line
            my ($minute, $hour, $day, $month, $dow) = ($1,$2,$3,$4,$5);
            # FIXME: Validate the time fields.
            next;
        } elsif ($line =~ m|^\s*$|) {
            # Whitespace
            next;
        } else {
            push(@errors, "Unrecognized crontab line:\n$line\n");
        }
    }
    return @errors;
}



GetOptions("force|f+" => \$force,
	   "list|l" => \$list,
	   "pretend|p" => \$pretend);

if ($list) {
    my $file = catfile(SPOOL_DIR, $ENV{"USER"});
    local $/;
    open (CRONTAB, $file) or die "No crontab installed.\n";
    print <CRONTAB>;
    close (CRONTAB);
    exit;
}

my @crontabs = get_crontabs();
my @all_errors;
my @final_crontab;
my ($numvalid, $numinvalid) = (0,0);

foreach my $crontab (@crontabs) {
    push(@final_crontab, "### $crontab\n");
    my @crontab = read_crontab($crontab);
    my @errors = check_crontab(@crontab);
    if (@errors == 0) {
        print "$crontab is a valid crontab\n";
        push(@final_crontab, @crontab);
        $numvalid++;
    } else {
        print "$crontab has errors:\n";
        push(@all_errors, scalar(@errors)." errors in $crontab:\n", @errors);
        print join("\n", @errors);
        $numinvalid++;
        if ($force >= 2) {
            push(@final_crontab, @crontab);
        } else {
            my $errors = join("\n", @errors);
            $errors =~ s|^|# |mg;
            push(@final_crontab, "## $crontab was not installed due to errors:\n", $errors);
        }
    }
}
if ($pretend) {
    print "Would install this crontab:\n";
    print @final_crontab;
    exit;
}

if ($force < 1 && @all_errors) {
    print "Not loading new crontab. Use -f to force.\n";
    exit;
}
if ($force >= 2 && @all_errors) {
    print "Loading $numvalid crontab ($numinvalid BROKEN!) files...\n";
} else {
    print "Loading $numvalid crontab files...\n";
}

# FIXME
# Load @final_crontab somehow

print "done.\n";