#!/usr/bin/perl

use strict;
use warnings;
use POSIX qw(ceil);
use Getopt::Long;

sub usage() {
	print "Usage: git chart\n";
}

sub gather_data($) {
	my $options = shift;
	my @dataset;

	print "Gathering data ...\n";

	my $day=$options->{from};
	my $to =$options->{to};
	my $step=$options->{step};
	my $max=$options->{max} || 0;

	while ($day < $to) {
		my $next = $day + $step;
		my $val = `git log --pretty=%s --since="$next days ago" --until="$day days ago" | wc -l`;
		chomp $val;
		push @dataset, $val;
		$max = $val if $max < $val;
		$day = $next;
	}

	$options->{max} = $max;

	print "...done\n";

	return \@dataset;
}

# plot the dataset with google chart. the function can be called with either one or two parameters.
# when called with two parameters, the first is assumed to be the dataset, and the second the options
# (array and hash ref respectively).
# when called with a single parameter, it is assumed to be an options hash ref, and the dataset is 
# created by calling gather_data with the passed options.
sub google_chart($;$) {
	my $dataset = shift;
	my $options = shift;
	if (! defined $options) {
		$options = $dataset;
		$dataset = gather_data($options);
	}

	my $height=$options->{chart_height};
	my $max = $options->{max};
	my $from = $options->{from};
	my $to = $options->{to};
	my $step = $options->{step};
	my $width=($step < 20 ? 20 : $step)*@$dataset;

	my $url="https://chart.googleapis.com/chart?chs=${width}x${height}&cht=bvg&chd=t:%s&chds=0,$max&chbh=a&chxt=y,x&chxr=0,0,$max|1,$to,$from,-$step";

	my $launch = sprintf $url, join(",",reverse @$dataset);
	# print $launch, "\n";
	`git web--browse "$launch"`
}

sub parse_from($) {
	my $from = shift;
	if ($from =~/^\d+$/) {
		return 0 + $from;
	} else {
		# TODO
		warn "non-numeric from not supported yet\n";
	}
}

sub parse_to($) {
	my $to = shift;
	if ($to =~/^\d+$/) {
		return 0 + $to;
	} else {
		# TODO
		warn "non-numeric to not supported yet\n";
	}
}

sub parse_step($) {
	my $step = shift;
	if ($step =~/^\d+$/) {
		return 0 + $step;
	} else {
		return 1 if $step eq 'daily';
		return 7 if $step eq 'weekly';
		return 30 if $step eq 'monthly';
	}
}

# some defaults
my %options = (
	from => 0,
	to => 31,
	step => 1,
	chart_height => 144,
);

my $daily=0;
my $weekly=0;
my $monthly=0;

my $from=0;
my $to=0;
my $step=0;

GetOptions(
	daily => \$daily,
	weekly => \$weekly,
	monthly => \$monthly,
	'from=s' => \$from,
	'to=s' => \$to,
	'step=s' => \$step,
);

$options{from} = parse_from($from) if $from;

if ($monthly) {
	$options{to} = $options{from} + 365;
	$options{step} = 30;
} elsif ($weekly) {
	$options{to} = $options{from} + 6*30;
	$options{step} = 30;
} elsif ($daily) {
	$options{to} = $options{from} + 31;
	$options{step} = 1;
}

$options{to} = parse_to($to) if $to;
$options{step} = parse_step($step) if $step;

die "step must be strictly positive!" unless $options{step} > 0;

google_chart(\%options);