#!/usr/bin/perl -lw
#
# Copyright (C) 2003 Don Stewart - http://www.cse.unsw.edu.au/~dons
#       (see http://www.gnu.org/copyleft/gpl.html)
# 
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License as
# published by the Free Software Foundation; either version 2 of
# the License, or (at your option) any later version.
# 
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
# 02111-1307, USA.
#

# Maintain a record of hours worked

sub main();
sub usage();
sub logpath();
sub getargs();
sub subtract($$);
sub readlog($);

# valid command line flags, and their long forms
%ARGS = (
    "s"  => "start",
    "bs" => "break start",
    "be" => "break end",
    "e"  => "end",
    "nl" => "no lunch",
    "new" => "insert delimiter",
);

# functions to execute, by key
%function = (
    "s"  => \&start,
    "bs" => \&break,
    "be" => \&break,
    "e"  => \&end,
    "nl" =>  \&no_lunch,
    "new" => \&new_delim,
);

main();


## subroutines ##

# entry point
sub main() {

    my ($mode,$write) = getargs();

    my $log = logpath();

    my $string = &{$function{$mode}}();

}

# parse the command line args, returning the function we want
sub getargs() {

    my $mode = "";
    my $write = 0;

    # must be at least 1 argument
    if (not @ARGV) {
            usage();
            exit 1;
    }

    # always at least 1 arg
    $mode = shift;

    # if using the -w flag, then find the real mode 
    if ($mode eq "-w") {

        # must be another argument then
        if (not @ARGV) {
                usage();
                exit 1;
        }
        $write = 1;
        $mode = shift;
    }

    # sanity check the arguments
    if (not defined $ARGS{$mode})) {
            usage();
            exit 1;
    }

    return ($mode,$write);
}

# generate the current time, in "start" format
sub start() {
    my $s;
    $s = `date '+%a %d.%m.%y#%H:%M'`;
    $s =~ s/#/\n\t/;
    return $s;
}

# return current time in "break" format
sub break() {
    return "\t" . `date '+%H:%M'`;
}

# end: total up the previous 3 entries, producing a sum
sub end($) {

    my $valid = 0;
    my $log = shift;
    my $s;

    my @entries = readlog($log);

    # grab current time ( I have no idea what I'm doing here )
    $s = `date '+%d.%m.%y'`;
    push (@entries, `date '+%H:%M'`);
    chomp $entries[-1];
    $s .= "\t$entries[-1] =";

    # normalise numbers
    for $i (0 .. $#entries) {
        $entries[$i] =~ s/\s+//g;
    }   

    if (not $empty) {
        # calculate in minutes, to work out the number of hours worked
        $morn = subtract($day[1],$day[0]);
        $aft  = subtract($day[3],$day[2]);

        $hour = int(($morn+$aft)/60);
        $mins = int(($morn+$aft)%60);

    # didn't go to lunch, so operate on the whole day
    } else {
        $morn = subtract($day[3],$day[0]);
        $hour = int($morn/60);
        $mins = int($morn%60);
    }

    $s = sprintf("%s %d:%02d",$s,$hour,$mins);

    # sanity test: mustn't be negative
    if ($s =~ /-/) {
        print "Error parsing log file: hours worked are negative!";
        exit 1;
    }

    return $s;
}

# does some IO: open the log readonly, and return the last 3 lines?
sub readlog($) {

    my @tmp = ();
    my $t = "";
    my $empty = 0;
    my $valid = 0;

    open LOGRO, "<$log" or die "$0 : couldn't open $log for RO : $!";
    @tmp = <LOGRO>; # urgh
    close LOGRO; 

    # find the last 3 entries in the file
    for (;;) {

        # sanity test  : must be some content in file
        $valid = 0;
        for my $d (@tmp) {
            $valid = 1 if ($d !~ /^\s*$/);
        }
        if (not $valid) {
            print "Error parsing log file: empty file";
            exit 1;
        }

        # last line
        $t = pop @tmp;

        # i.e. didn't go to lunch
        $empty = 1 if ($t =~ /-/);

        # $t must be in normal form
        if ($t =~ /^\s+\d\d:\d\d$|^\s+-$/) {
            unshift(@day, $t);

        # otherwise it is an error
        } else {
            chomp $t;
            print "Error parsing log file: bogus entry: \"$t\"";
            exit 1;
        }

        # only read 3 lines
        last if ($#day == 2); # this will also force 3 entries to appear
    }

    # two constraints:
    # (1) if there is a '-' in the last entry,
    #     it must also be the second last
    if ($day[2] =~ /^\s+-$/) {
        # then $day[1] must also
        if ($day[1] !~ /^\s+-$/) {
            print "Error parsing log file: missing \"-\" field";
            exit 1;
        }

    # (2) there must be no '-' entries, otherwise
    } else {
        for my $d (@day) {
            if ($d =~ /^\s+-$/) {
                print "Error parsing log file: unexpected \"-\" field";
                exit 1;
            }
        }
    }

    return @day;
}



sub new() {
    return "# a new fortnight";
}

sub nolunch() {
    return "\t-\n\t-";
}

sub write($$$) {

    my $string = shift;
    my $log = shift;
    my $write = shift;

    # please try to run these in order!
    open LOG, ">>$log" or die "$0 : couldn't open $log : $!";

    chomp $s;

    if ($write) {
        print LOG $s;
        print LOG "" if (/^e$/); # newline if end of the day
        close LOG;
    }
    print "$s";
}


# takes 2 strings of the from "hh:mm", and subtracts them, giving 
# a time in minutes
sub subtract($$) {

    my ($ah,$am) = split /:/, shift;
    my ($bh,$bm) = split /:/, shift;

    # convert to minutes and subtract
    return  (($ah * 60) + $am) -  (($bh * 60) + $bm);
}

# usage message
sub usage() {
    print "\nusage: $0 [-w] [s bs be e nl new]" ;
    print "
            -w  : write to file

         s  : start of day
         bs : start break
         be : end break
         e  : end day
         nl : no lunch
         new: new fortnight"
}

# find the home directory, this should be portable
sub logpath() {
    my $h = $ENV{"HOME"};
    return "$home/.timesheet";
}