#!/bin/bash

#  Scales of Truth
#
#  (c) 2011 Thomas White <taw@bitwiz.org.uk>
#
#  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 3 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, see <http://www.gnu.org/licenses/>.

# Prerequisites: "git", "perl", "bash" and "gnuplot"
#
# Setup instructions:
#
# Save this script somewhere sensible like your home directory's "bin" folder
#  and make sure it's in your PATH and marked as executable.
# Edit the variables below.
# Run "sot" on its own.
# Put your height in metres into $SOTDIR/height_in_metres.
# Run "sot <weight>" to input your first weight reading.
# Go into your "SOTDIR", and push the "master" branch to a suitable remote
#  repository, and set up tracking.
#
# The final step is optional, but it'll complain at you until you do it.

# Directory in which data will be stored, backed up by Git
SOTDIR=~/.sot

# Filename for raw data
LOGFILE=${SOTDIR}/data

# File containing your height in metres
HEIGHTFILE=${SOTDIR}/height_in_metres

# Units of measurement
UNITS=kg

# Number of kilojoules per "unit" of fat
KJ_PER_UNIT=29288

# A conversion factor (don't touch this)
KCAL_PER_KJ=4.184

# Graph vertical axis minimum and maximum
G_MIN=40
G_MAX=200

function write_perl ()
{
cat > $SOTDIR/add-reading.pl << EOF
#!/usr/bin/perl -w

use strict;

use constant SECONDS_TO_DAYS => (60.0*60.0*24.0);

my \$new_weight = \$ARGV[0];
my \$old_trend = \$ARGV[1];
my \$newtime = \$ARGV[2];
my \$oldtime = \$ARGV[3];
my \$file = \$ARGV[4];
my \$old_weight = \$ARGV[5];
my \$weightdiff = \$new_weight-\$old_weight;

open(FH, ">> \$file") or die("Couldn't open \$file\n");

my \$timediff = int(((\$newtime - \$oldtime)/SECONDS_TO_DAYS)+0.5);

if ( \$timediff > 1 ) {

	printf("%i days since last reading, interpolating...\n", \$timediff);

	my \$day;
	my \$wd = \$weightdiff / \$timediff;

	for ( \$day=\$timediff-1; \$day>=0; \$day-- ) {

		my \$this_weight = \$new_weight-\$wd*\$day;
		my \$this_trend = \$old_trend + 0.1*(\$this_weight-\$old_trend);

		printf(FH "%i %.2f %.2f %.2f\n",
		       \$newtime-\$day*SECONDS_TO_DAYS, \$this_weight,
		       \$this_trend, \$this_trend - \$old_trend);
		\$old_trend = \$this_trend;
	}

} else {

	my \$this_trend = \$old_trend + 0.1*(\$new_weight-\$old_trend);

	printf(FH "%i %.2f %.2f %.2f\n", \$newtime, \$new_weight, \$this_trend,
	                                 \$this_trend - \$old_trend);

}

close(FH);
exit 0;
EOF
chmod +x $SOTDIR/add-reading.pl
}


function check_setup ()
{
	# Check git is installed
	git --help > /dev/null 2>&1
	if [ $? -ne 0 ]; then
		echo "Git is not installed"
		exit 1
	fi

	# Check bc is installed
	bc --help > /dev/null 2>&1
	if [ $? -ne 0 ]; then
		echo "bc is not installed"
		exit 1
	fi

	# Check dir exists, create it if not
	if [ ! -d $SOTDIR ]; then
		if [ -e $SOTDIR ]; then
			echo "$SOTDIR exists, but isn't a directory!"
			exit 1
		fi
		mkdir $SOTDIR
		echo "Created $SOTDIR."
		cd $SOTDIR
		git init
	fi

	if [ ! -f $SOTDIR/add-reading.pl ]; then
		write_perl
	fi

	if [ ! -f $HEIGHTFILE ]; then
		echo "Now put your height in metres into $HEIGHTFILE:"
		echo "\$ echo 1.82 > $HEIGHTFILE"
		exit 1;
	fi
}


function show_change ()
{
	local CUR_TREND OLD_TREND CHANGE

	if [ "`wc -l $LOGFILE | cut -d" " -f 1`" -lt $1 ]; then
		echo "Not enough readings for $1 day statistics yet."
	else

		CUR_TREND=`tail -n 1 $LOGFILE | cut -d" " -f 3`
		OLD_TREND=`tail -n $1 $LOGFILE | head -n 1 | cut -d" " -f 3`

		CHANGE=`echo "scale=1; $CUR_TREND - $OLD_TREND" | bc`
		ENERGY_KJ=`echo "scale=1; ($CHANGE * $KJ_PER_UNIT)/$1" | bc`
		ENERGY_KCAL=`echo "scale=1; $ENERGY_KJ / $KCAL_PER_KJ" | bc`

		echo -n "$1-day change: $CHANGE $UNITS"
		echo " ($ENERGY_KJ kJ or $ENERGY_KCAL kcal per day)"

	fi
}


function show_stats ()
{
	local CUR_TREND OLD_TREND CHANGE BMI HEIGHT CUR_VAL

	CUR_TREND=`tail -n 1 $LOGFILE | cut -d" " -f 3`
	CUR_VAL=`tail -n 1 $LOGFILE | cut -d" " -f 2`
	HEIGHT=`cat $HEIGHTFILE`
	BMI=`echo "scale=1; $CUR_VAL / ($HEIGHT * $HEIGHT)" | bc`
	BMI="$BMI $UNITS/m^2"

	echo "Current mass estimate: $CUR_TREND $UNITS (instantaneous BMI $BMI)"

	show_change 7
	show_change 30
}


function do_backup ()
{
	cd $SOTDIR

	git push > /dev/null 2>&1
	if [ $? -ne 0 ]; then
		echo "'git push' failed."
		echo -n "You need to manually set up the remote repository and"
		echo -n " branch tracking, otherwise you might lose data, which"
		echo "would suck."
	fi
}


function add_reading ()
{
	local NEW_WEIGHT OLD_TREND NEW_TREND DELTA OLD_DATETIME OLD_WEIGHT
	NEW_WEIGHT=`eval echo $1`

	# Get date/time
	DATETIME=`date +%s`

	if [ -f $LOGFILE ]; then

		# Get the most recent trend value
		OLD_TREND=`tail -n 1 $LOGFILE | cut -d" " -f 3`
		OLD_WEIGHT=`tail -n 1 $LOGFILE | cut -d" " -f 2`
		OLD_DATETIME=`tail -n 1 $LOGFILE | cut -d" " -f 1`

		${SOTDIR}/add-reading.pl $NEW_WEIGHT $OLD_TREND \
		                         $DATETIME $OLD_DATETIME \
		                         $LOGFILE $OLD_WEIGHT

		# Calculate new trend
		NEW_TREND=`echo "$OLD_TREND+0.1*($NEW_WEIGHT-$OLD_TREND)" | bc`

	else

		NEW_TREND=$NEW_WEIGHT
		echo "${DATETIME} ${NEW_WEIGHT} ${NEW_TREND}" >> $LOGFILE

	fi

	cd $SOTDIR
	git add $LOGFILE
	if [ $? -ne 0 ]; then
		echo "'git add' failed!"
		exit 1
	fi
	git commit -m "New measurement, time = $DATETIME" > /dev/null
	if [ $? -ne 0 ]; then
		echo "'git commit' failed!"
		exit 1
	fi

	do_backup
}


function draw_graph ()
{
	echo 'set xdata time' > $SOTDIR/plot.gp
	echo 'set xlabel "Date"' >> $SOTDIR/plot.gp
	echo "set ylabel \"Mass / $UNITS\"" >> $SOTDIR/plot.gp
	echo "set y2label \"Energy surplus / kCal [red, thin]\"" \
	                                                      >> $SOTDIR/plot.gp
	echo 'set timefmt "%s"' >> $SOTDIR/plot.gp
	echo 'set format x "%d %b %Y"' >> $SOTDIR/plot.gp
	echo 'set xtics nomirror rotate by -60' >> $SOTDIR/plot.gp
	echo 'set ytics nomirror' >> $SOTDIR/plot.gp
	echo 'unset key' >> $SOTDIR/plot.gp
	echo 'set grid' >> $SOTDIR/plot.gp
	echo 'set ytics' >> $SOTDIR/plot.gp
	echo 'set y2tics' >> $SOTDIR/plot.gp
	echo 'set y2range [-2000:+500]' >> $SOTDIR/plot.gp
	echo -n "plot [] [$G_MIN:$G_MAX] \"$LOGFILE\" ">> $SOTDIR/plot.gp
	echo "using 1:2 w lp pt 5 lc 0 axis x1y1" >> $SOTDIR/plot.gp
	echo "replot \"$LOGFILE\" using 1:3 w l lw 2 lc 3 axis x1y1" \
	                                                      >> $SOTDIR/plot.gp
	echo -n "replot \"$LOGFILE\" using 1:(\$4*$KJ_PER_UNIT/$KCAL_PER_KJ)" \
	                                                      >> $SOTDIR/plot.gp
	echo " w l lw 1 lc 8 axis x1y2" >> $SOTDIR/plot.gp
#	echo "fit a*x+b '$LOGFILE' using 1:3 via a,b" >> $SOTDIR/plot.gp
#	echo "replot a*x+1000" >> $SOTDIR/plot.gp

	gnuplot -persist < $SOTDIR/plot.gp
}


function show_help ()
{
	echo "`basename $0`: A dodgy shell script"
}


READING=false
check_setup

for OPT in `getopt -lhelp,graph,stats,backup -o hgs -- $@`; do

	if [ x$READING = "xtrue" ]; then
		add_reading $OPT
		show_stats
	fi

	if [ $OPT = "--help" -o $OPT = "-h" ]; then
		show_help
		exit 0
	fi

	if [ $OPT = "--graph" -o $OPT = "-g" ]; then
		draw_graph
		exit 0
	fi

	if [ $OPT = "--stats" -o $OPT = "-s" ]; then
		show_stats
		exit 0
	fi

	if [ $OPT = "--backup" ]; then
		do_backup
		exit 0
	fi

	if [ $OPT = "--" ]; then
		READING=true
	fi

done

exit 0