#!/bin/sh
#
############################################################################
#
# MODULE:       v.line.center
#
# AUTHOR(S):    Maciej Sieczka, sieczka@biol.uni.wroc.pl
#		Intitute of Plant Biology, Wroclaw University, Poland
#
# PURPOSE:      Create a vector map of points, each located in the center of
#		one input line.
#
# VERSION:	1.0.1, developed over Grass 6.3 CVS 2007.01.24
#
# COPYRIGHT:    (c) 2007 Maciej Sieczka
#
# NOTES:	Developed within the course and for the purpose of the CAVES
#		project http://caves.cfpm.org, funded under the EU 6FP NEST
#		programme.
#
#               This program is free software under the GNU General Public
#               License (>=v2). Read the file COPYING that comes with GRASS
#               for details.
#
#############################################################################

# CHANGELOG:
#
# 1.0.1: first public release

#%Module
#%  description: Create a points vector map with each point located in the center of one input line.
#%END

#%option
#% key: input
#% type: string
#% gisprompt: old,vector,vector
#% description: Input lines vector
#% required : yes
#%END

#%option
#% key: layer
#% type: integer
#% answer: 1
#% description: Input layer number
#% required : yes
#%END

#%option
#% key: output
#% type: string
#% gisprompt: new,dig,vector
#% description: Output points vector
#% required : yes
#%END

# called from Grass?
if test "$GISBASE" = ""; then
 echo "ERROR: You must be in GRASS GIS to run this program." >&2
 exit 1
fi

if [ "$1" != "@ARGS_PARSED@" ] ; then
  exec g.parser "$0" "$@"
fi

# check if we have awk
if [ ! -x "`which awk`" ] ; then
    echo "ERROR: awk required, please install awk or gawk first." 1>&2
    exit 1
fi

# set environment so that awk works properly in all languages
unset LC_ALL
LC_NUMERIC=C
export LC_NUMERIC

INPUT="$GIS_OPT_INPUT"
OUTPUT="$GIS_OPT_OUTPUT"
LAYER="$GIS_OPT_LAYER"

# check if output vector exists
#eval `g.gisenv`
#g.findfile elem=vector file="$OUTPUT" mapset="$MAPSET" > /dev/null
# if [ $? -eq 0 ] ; then
#  echo "ERROR: The output vector <"$OUTPUT"> already exists in current mapset." 1>&2
#  exit 1
# fi

# set up temporary files
TMP="`g.tempfile pid=$$`"
if [ $? -ne 0 ] || [ -z "$TMP" ] ; then
    echo "ERROR: Unable to create temporary files." 1>&2
    exit 1
fi

PROG=`basename $0 | sed 's/\./_/g'`
# UNQ=`basename $TMP | sed 's/\./_/g'`"_${PROG}"

# define the cleanup procedure
cleanup()
{
 \rm -f $TMP
 \rm -f $TMP.${PROG}.offsets
}

# what to do in case of user break:
exitprocedure()
{
 echo "User break!" 1>&2
 cleanup
 exit 1
}
# shell check for user break (signal list: trap -l)
trap "exitprocedure" 2 3 15



### DO IT ###

# Prepare the input for v.segment that will extract center points of each line,
# excluding the first and the last offset.

v.to.db -p map="$INPUT" layer=$LAYER type=line option=length units=me column=dummy | awk -F "|" 'NR>1 {printf "%s","P "$1" "$1" "; printf "%.16f\n",$2/2}' > $TMP.${PROG}.offsets

# Pipe offsets into v.segment. The output are points located exactly in the
# center of the input lines.

cat $TMP.${PROG}.offsets | v.segment llayer=$LAYER input="$INPUT" output="$OUTPUT" > /dev/null



### ALL DONE ###

cleanup

echo 1>&2
echo "Done." 1>&2
echo 1>&2