#!/usr/local/bin/perl -w
#
# Example 4-5. biorhythm.cgi

use GD::Graph::bars;
use Date::Calc;
use CGI;

# We'll need a good value for Pi later

my $pi = 4 * atan2(1,1);

my $query = new CGI;
my @dob = Date::Calc::Decode_Date_US($query->param('dob')); 
my @start = Date::Calc::Decode_Date_US($query->param('start')); 
my @end = Date::Calc::Decode_Date_US($query->param('end')); 

my $days = Date::Calc::Delta_Days(@start, @end);
my $dobdiff = Date::Calc::Delta_Days(@dob, @start);

my @xvalues;

foreach my $day (0..$days) {
    # Add_Delta_days returns a date offset from the start date.
    # It returns a list in the form (yyyy, mm, dd)
    
    push @xvalues, (Date::Calc::Add_Delta_Days(@start,$day))[2];
}

my (@pvalues, @evalues, @ivalues);

foreach my $count (0..$days) {
    push @pvalues, sin((($count+($dobdiff % 23))/23) * 2 * $pi);
    push @evalues, sin((($count+($dobdiff % 28))/28) * 2 * $pi);
    push @ivalues, sin((($count+($dobdiff % 33))/33) * 2 * $pi);
}

# Create a new bar graph

my $graph = new GD::Graph::bars(500,300);

# Set the attributes for the graph

$graph->set(
    x_label           => '',          # No labels
    y_label           => '',
    title             => 'Your Biorhythm',
    y_plot_values     => 0,
    y_max_value       => 1,           # sine range is -1 to 1
    y_min_value       => -1,
    y_tick_number     => 8,
    long_ticks        => 0,           # use short ticks on axes
    x_label_skip      => 3,           # print every third x label
    zero_axis         => 0,
    zero_axis_only    => 0,
);

# Add the legend to the graph

$graph->set_legend('Physical', 'Emotional', 'Intellectual');

# Plot the graph and write it to STDOUT

print STDOUT $query->header(-type => 'image/png');
binmode STDOUT;                      # switch to binary mode
my $gd = $graph->plot( [ \@xvalues,
                         \@pvalues,
                         \@evalues,
                         \@ivalues ] );
print STDOUT $gd->png;