#!/bin/bash

WORKDIR=/tmp/sense-voltage-plot
EVENTS=/m/data/home/sense/realtime.csv
interval="$1"
if [ -z "$interval" ]; then
  interval=$((60 * 60 * 8))
fi

mkdir -p "$WORKDIR"
cd "$WORKDIR" || exit

now="$(date +'%s')"
begin="$((now - interval))"

# Select just the timestamp and voltage data from our events, then filter it
# to only look at the past interval and exclude any blips that didn't log
# voltage data. Finally, subtract our timezone offset since gnuplot doesn't
# handle timezones.
#
# For the CONVFMT trick, see:
# https://unix.stackexchange.com/questions/57006/awk-high-precision-arithmetic
# Without it, awk prints the result of floating point arithmetic like this
#
#   1.61866e+09
#
# instead of the desired
#
#   1618658551.1843472
xsv select ts,volt "$EVENTS" \
  | awk -F, '$2 > 0 && $1 > '$begin' { print $0 }' \
  | awk -v CONVFMT=%.17g -F, '{ print ($1 - (60 * 60 * 4))","$2 }' \
  > plot.csv

cat > voltage-over-time.gnuplot <<EOF
set datafile separator ','
set xdata time # tells gnuplot the x axis is time data
set timefmt "%s.%N" # specify our time string format
set format x "%b %d %H:%M" # otherwise it will show only MM:SS
set xtics rotate by -45
plot 'plot.csv' using 1:2 with lines, '' using 1:3 with lines
EOF
gnuplot -p voltage-over-time.gnuplot