#!/bin/bash

TMP=/tmp/stack  # Scratch directory for time-shifted files
mkdir -p $TMP
rm -f $TMP/*

# A -p option means normalise by power instead of amplitude

PFLAG=""
[ "$1" = "-p" ] && {
   PFLAG=1
   shift 1
}

# List of input files on the command line
list=$*

# Mixer coefficient strings
c1=""
c2=""

N=0
for src in $list
do

  set `vtstat -i $src | sed 's/,/ /g' |
       awk '($1 == "start:"){ start=$2}
            ($1 == "mean"){ amps += $6 }
            END{printf( "%s %.3e %.3e\n", start, 1/amps, 1/(amps*amps))}'`
  offset=`vtdate -n $1`
  gain1=$2
  gain2=$3
  [ "$PFLAG" = 1 ] && gain=$gain2 || gain=$gain1

  [ "$c1" = "" ] && c1=$gain,0 || c1=${c1},$gain,0
  [ "$c2" = "" ] && c2=0,$gain || c2=${c2},0,$gain

  echo "$src $offset $gain1 $gain2" >&2
  vtcat -a-$offset $src $TMP/$N 

  jlist="$jlist $TMP/$N"

  N=$((N+1))
done

vtjoin $jlist - | vtmix -c $c1 -c $c2
rm -f $TMP/*