#!/usr/bin/perl

use warnings;
use strict;

use Getopt::Long qw{:config gnu_getopt posix_default};
use POSIX;
use Term::ReadKey;

$0 =~ s{^.*/([^/]+)$}{$1};

my %opt;
GetOptions(\%opt, qw{
	cancel|c
	height|h=i
	overlay|o
	stack|s
	width|w=i
}) or do {
	print STDERR <<END;
usage: git-graph [options]
	-c | --cancel	+/- counts cancel out
	-o | --overlay	+/- counts are overlaid as # (default)
	-s | --cancel	+/- counts are stacked
	--height [n]	Set height of graph
	-h [n]		(height of terminal is default)
	--width [n]	Set horizontal scale
	-w [n]		(fit to width of terminal by default)
END
	exit 1;
};

$opt{overlay} = 1 unless $opt{cancel} or $opt{stack};

my @terminal = GetTerminalSize;
my $width = $terminal[0] - 11;
my $height = $opt{height} // $terminal[1] - 2;

my %add;
my %del;

my $addmax = 0;
my $delmax = 0;
my $canmax = 0;

my $date;

for (qx{git log --find-renames --shortstat --pretty=format:%ct --since='$height days ago'}) {
	next if m{^\s*$};
	if (m{^(\d{10})\n$}) {
		$date = int ($1 / 86400);
		next;
	}
	m{^\ \d+\ files?\ changed
	  (?:,\ (\d+)\ insertion[s()+]+)?
	   (?:,\ (\d+)\ deletion[s()-]+)?$}x
	    or die "$0: bad stats $_";
	my ($add,$del) = ($1 || 0, $2 || 0);
	$add{$date} += $add;
	$del{$date} += $del;
	$addmax = $add{$date} if $addmax < $add{$date};
	$delmax = $del{$date} if $delmax < $del{$date};
	my $can = abs $add{$date} - $del{$date};
	$canmax = $can if $canmax < $can;
}

my $max = $opt{width} ? $opt{width} :
    $opt{cancel} ? $canmax :
    $opt{stack} ? $addmax + $delmax :
    $addmax > $delmax ? $addmax : $delmax;
my $scale = $width / $max;

my $today = int (time / 86400);

for my $date ($today - $height .. $today) {
	my $add = 0;
	my $del = 0;
	my $mod = 0;
	$add{$date} //= 0;
	$del{$date} //= 0;
	if ($opt{cancel} or $opt{overlay}) {
		if ($add{$date} > $del{$date}) {
			$add = $add{$date} - $del{$date};
		} else {
			$del = $del{$date} - $add{$date};
		}
	}
	if ($opt{overlay}) {
		$mod = $add{$date} < $del{$date} ?
		       $add{$date} : $del{$date};
	}
	if ($opt{stack}) {
		$add = $add{$date};
		$del = $del{$date};
	}
	my $greg = strftime "%b %d %w", localtime $date * 86400;
	$greg =~ s{(\d)$}{substr "sMTWTFs", $1, 1}e;
	my $line = sprintf "$greg \e[33m%s\e[32m%s\e[31m%s\e[0m\n",
	    "#" x ($mod && 1 + $mod * $scale),
	    "+" x ($add && 1 + $add * $scale),
	    "-" x ($del && 1 + $del * $scale);
	if (length $line > $width + 30) {
		$line = sprintf "## %d ##\e[32m++ %d ++\e[31m-- %d --\e[0m\n",
		    $mod, $add, $del;
		$line = "$greg \e[33m" . "#"x($width + 16 - length $line) . $line;
	}
	print $line;
}
printf "         \e[33m#\e[0m <- %-8.1f %s %8d ->\n",
    1/$scale, " " x ($width - 25), $max;