#=====================================================================
#
# Tax support module for LedgerSMB
# LedgerSMB::Tax
#  Default simple tax application
#
# LedgerSMB 
# Small Medium Business Accounting software
# http://www.ledgersmb.org/
# 
#
# Copyright (C) 2006
# This work contains copyrighted information from a number of sources all used
# with permission.  It is released under the GNU General Public License 
# Version 2 or, at your option, any later version.  See COPYRIGHT file for 
# details.
#
#
#======================================================================
# This package contains tax related functions:
#
# apply_taxes - applies taxes to the given subtotal
# extract_taxes - extracts taxes from the given total
# initialize_taxes - loads taxes from the database
# calculate_taxes - calculates taxes
#
#====================================================================
package Tax;

use Math::BigFloat;

sub init_taxes {
	my ($form, $taxaccounts) = @_;
	my $dbh = $form->{dbh};
	@taxes = ();
	my @accounts = split / /, $taxaccounts;
	my $query = qq|SELECT t.taxnumber, c.description,
			t.rate, t.chart_id, t.pass, m.taxmodulename
			FROM tax t INNER JOIN chart c ON (t.chart_id = c.id)
			INNER JOIN taxmodule m ON (t.taxmodule_id = m.taxmodule_id)
			WHERE c.accno = ?|;
	my $sth = $dbh->prepare($query);
	foreach $taxaccount (@accounts) {
		$sth->execute(int($taxaccount)) || $form->dberror($query);
		my $ref = $sth->fetchrow_hashref;

		my $module = $ref->{'taxmodulename'};
		require "LedgerSMB/Taxes/${module}.pm";
		$module =~ s/\//::/g;
		my $tax = (eval 'Taxes::'.$module)->new();

		$tax->pass($ref->{'pass'});
		$tax->account($taxaccount);
		$tax->rate(Math::BigFloat->new($ref->{'rate'}));
		$tax->taxnumber($ref->{'taxnumber'});
		$tax->chart($ref->{'chart'});
		$tax->description($ref->{'description'});
		$tax->value(Math::BigFloat->bzero());

		push @taxes, $tax;
		$sth->finish;
	}
	return @taxes;
}

sub calculate_taxes {
	my ($taxes, $form, $subtotal, $extract) = @_;
	my $total = Math::BigFloat->bzero();
	my %passes;
	foreach my $tax (@taxes) {
		push @{$passes{$tax->pass}}, $tax;
	}
	my @passkeys = sort keys %passes;
	@passkeys = reverse @passkeys if $extract;
	foreach my $pass (@passkeys) {
		my $passrate = Math::BigFloat->bzero();
		my $passtotal = Math::BigFloat->bzero();
		foreach my $tax (@{$passes{$pass}}) {
			$passrate += $tax->rate;
		}
		foreach my $tax (@{$passes{$pass}}) {
			$passtotal += $tax->apply_tax($form, $subtotal + $total) if not $extract;
			$passtotal += $tax->extract_tax($form, $subtotal - $total, $passrate) if $extract;
		}
		$total += $passtotal;
	}
	return $total;
}

sub apply_taxes {
	my ($taxes, $form, $subtotal) = @_;
	return $subtotal + calculate_taxes($taxes, $form, $subtotal, 0);
}

sub extract_taxes {
	my ($taxes, $form, $subtotal) = @_;
	return $subtotal - calculate_taxes($taxes, $form, $subtotal, 1);
}

1;