#!/bin/bash

echo "parsing POSCAR file ..."

trg=POSCAR.transformed

theta=$1

sicnt=`sed -n 6p POSCAR | awk '{ print $1 }'`
ccnt=`sed -n 6p POSCAR | awk '{ print $2 }'`

lc=`sed -n 2p POSCAR | awk '{ print $1 }'`

x1=`sed -n 3p POSCAR | awk '{ print $1 }'`
x2=`sed -n 3p POSCAR | awk '{ print $2 }'`
x3=`sed -n 3p POSCAR | awk '{ print $3 }'`

y1=`sed -n 4p POSCAR | awk '{ print $1 }'`
y2=`sed -n 4p POSCAR | awk '{ print $2 }'`
y3=`sed -n 4p POSCAR | awk '{ print $3 }'`

z1=`sed -n 5p POSCAR | awk '{ print $1 }'`
z2=`sed -n 5p POSCAR | awk '{ print $2 }'`
z3=`sed -n 5p POSCAR | awk '{ print $3 }'`

((total=sicnt+ccnt))

echo "  Si: $sicnt, C: $ccnt, total: $total"
echo "  Lattice constant: $lc A"
echo "  Basis:"
echo "      $x1      $y1      $z1"
echo "  x = $x2  y = $y2  z = $z2"
echo "      $x3      $y3      $z3"
echo
echo "  -----"
echo "  Trafo: x axis, $theta degree"
echo "  -----"

costheta=`echo $theta | awk '{ print cos($1*3.1415927/180.0) }'`
sintheta=`echo $theta | awk '{ print sin($1*3.1415927/180.0) }'`

X1=$x1
X2=`echo $x2 $x3 $costheta $sintheta | awk '{ print $3*$1-$4*$2 }'`
X3=`echo $x2 $x3 $costheta $sintheta | awk '{ print $4*$1+$3*$2 }'`

Y1=$y1
Y2=`echo $y2 $y3 $costheta $sintheta | awk '{ print $3*$1-$4*$2 }'`
Y3=`echo $y2 $y3 $costheta $sintheta | awk '{ print $4*$1+$3*$2 }'`

Z1=$z1
Z2=`echo $z2 $z3 $costheta $sintheta | awk '{ print $3*$1-$4*$2 }'`
Z3=`echo $z2 $z3 $costheta $sintheta | awk '{ print $4*$1+$3*$2 }'`

echo
echo "  Transformed basis:"
echo "      $X1      $Y1      $Z1"
echo "  x = $X2  y = $Y2  z = $Z2"
echo "      $X3      $Y3      $Z3"
echo

cnt=0
tcnt=0

cx=1.0
cy=1.0
cz=0.8

# header
sed -n 1p POSCAR > $trg
echo " $lc" >> $trg
echo " $X1 $X2 $X3" >> $trg
echo " $Y1 $Y2 $Y3" >> $trg
echo " $Z1 $Z2 $Z3" >> $trg
echo " $sicnt $ccnt" >> $trg
echo "selective dynamics" >> $trg
echo "direct" >> $trg

tail -${total} POSCAR | \
	while read x y z fx fy fz; do
		Y=`echo $y $z $costheta $sintheta | \
			awk '{ print $3*$1+$4*$2 }'`
		Z=`echo $y $z $costheta $sintheta | \
			awk '{ print $3*$2-$4*$1 }'`
		echo " $x $Y $Z $fx $fy $fz" >> $trg
	done

echo "done"