#!/usr/bin/perl
use strict;
use warnings;
use Math::Round;
use Geo::ShapeFile;
use Geo::ShapeFile::Shape;
use Geo::ShapeFile::Point;

# Declare variables
my $blockid;
my $bcount;
my $totalblocks;
my $progress;
my $shapefile; # used for loading the TIGER shapefile
my %attr; # used to read the dbf file
my $polygon; # used to read the shp file
my @points; # used to read the shape into an array of points
my $coor; # used to read the coordinates of each point
my $x;
my $y;
my $pcount; # counter for the coordinates being written into output
my $totalpoints; # total number of coordinates in each polygon

# Variables for time keeping
my $start = time;
my $duration;

# Prepare the TIGER spreadsheet.
open (TIGER, ">tiger.txt") or die "Failed to open";
print TIGER "BLOCKID\tPolygon\n"; # make a header

# Load the TIGER shapefile
$shapefile = 0;
$shapefile = Geo::ShapeFile->new ("tabblock2010_42_pophu"); # use the TIGER census block special release (population & housing units only)
$totalblocks = $shapefile->shapes();
for (1 .. $totalblocks) {
	%attr = $shapefile->get_dbf_record($_);
	$blockid = $attr{BLOCKID10};
	$bcount++;
	print TIGER "$blockid\t\"geometry\":{\"type\":\"Polygon\",\"coordinates\":[["; # The polygon column is in the GEOJSON format
	$polygon = $shapefile->get_shp_record($_);
	@points = $polygon->points();
	$pcount = 0;
	$totalpoints = scalar (@points);
	foreach $coor (@points) {
		$x = $coor->get_x();
		$y = $coor->get_y();
		print TIGER "[$x,$y]";
		$pcount++;
		if ($pcount != $totalpoints) { # All but the last coordinate should be followed by a comma
			print TIGER ",";
		}
	}
	print TIGER "]]}\n"; # finish the entry
	print "Done $bcount out of $totalblocks.\n";
	
	%attr = ();
	$blockid = 0;
	$polygon = 0;
	@points = ();
	$totalpoints = 0;
}

close (TIGER);
$shapefile = 0;
select()->autoflush(1);

# Show stopwatch
$duration = time - $start;
$duration = round ($duration / 60);
print "\n\nThis script took $duration minutes\n\n";

exit;