use strict;
use warnings;

use CGI qw(:standard);
use Date::Simple;

sub NiceDateFormat {
    Date::Simple->new($_[0])->format("%d %b %Y"); 
}

my ($fday,$fmonth,$fyear) = (param('fday'),param('fmonth'),param('fyear'));
my ($tday,$tmonth,$tyear) = (param('tday'),param('tmonth'),param('tyear'));

die &Template("DevMgr/GenericError",{message => 'missing some or all of the FROM date'}) 
    unless ($fday and $fmonth and $fyear);
die &Template("DevMgr/GenericError",{message => 'missing some or all of the TO date'}) 
    unless ($tday and $tmonth and $tyear);

my $start = "$fyear-$fmonth-$fday"; 
my $end   = "$tyear-$tmonth-$tday";

my $s = &db_Staff_On_Site_Between_Two_Dates($start,$end);

my (%days, $hc, @previnits, $thisline, $from, @people, @prevpeople, $prevdate);

push @{$days{$$_[1]}}, $$_[2] for @$s;

# loop through each date (up to the end of range)
# looking for changes in head count
for my $date (sort keys %days) {

    @people = sort @{$days{$date}}; 

    # initialise values for the 'previous' day
    @prevpeople = @people unless @prevpeople;
    $from     ||= $date;
    $prevdate ||= $date;

    if ("@prevpeople" ne "@people") {

        # work out who has arrived, who has departed
        my (@arriving,@departing);

        my %prevpeople = map {$_ => undef} @prevpeople;
        my %people     = map {$_ => undef} @people;

        for (@people) { push @arriving, $_ unless exists $prevpeople{$_}; }
            
        for (@prevpeople) { push @departing, $_ unless exists $people{$_}; }

        # then deal with arrivals and departures
        my $arriving = @arriving ? &Template("DevMgr/SingleHeadCountArrivalLine",{ 
            date   => NiceDateFormat($date), 
            change => join(", ", sort @arriving)}) : ' ';
            
        my $departing = @departing ? &Template("DevMgr/SingleHeadCountDepartureLine",{ 
            date   => NiceDateFormat($prevdate), 
            change => join(", ", sort @departing)}) : ' ';
            
        # output the headcount as at the previous day
        $hc .= &Template("DevMgr/SingleHeadCountLine", {
                datefrom    => NiceDateFormat($from),
                dateto      => NiceDateFormat($prevdate),
                headcount   => scalar(@prevpeople),
                staffonsite => join (', ', sort values %{UniqInits(@prevpeople)}),
                arriving    => $arriving,
                departing   => $departing
            }
        );

            
        $from = $date;
        @prevpeople = @people;
    } 

    $prevdate = $date;
}

# we drop out of the loop when we hit the end of the range,
# so it is now necessary to output a final line of head count
$hc .= &Template("DevMgr/SingleHeadCountLine", {
        datefrom    => NiceDateFormat($from),
        dateto      => NiceDateFormat((reverse sort keys %days)[0]),
        headcount   => scalar(@people),
        staffonsite => join(', ', sort values %{UniqInits(@people)}),
        arriving    => ' ',
        departing   => ' '
    }
);

print &Template("DevMgr/ShowHeadCount",{ headcount_html => $hc });