#!/usr/bin/env perl
#-----------------------------------------------------------------------
# Usage: perl REGRID.pl RESLN
#        where RESLN denotes the resolution desired.
#        Supported resolutions are:
#        T5, T21, T31, T42, T63, T85, T170,
#        10by15, 4by5, 2by2.5, 1by1.25
#-----------------------------------------------------------------------

@ARGV;

$resln = $ARGV[0];

#-----------------------------------------------------
# Assign necessary dimensions given the resolution
#-----------------------------------------------------

if( $resln eq "T42" ) {
    $nlat = 64;
    $nlon = 128;

} elsif ( $resln eq "T63" ) {
    $nlat = 96;
    $nlon = 192;

} elsif ( $resln eq "T85" ) {
    $nlat = 128;
    $nlon = 256;

} elsif ( $resln eq "T170" ) {
    $nlat = 256;
    $nlon = 512;

} elsif ( $resln eq "T31" ) {
    $nlat = 48;
    $nlon = 96;

} elsif ( $resln eq "T21" ) {
    $nlat = 32;
    $nlon = 64;

} elsif ( $resln eq "T5" ) {
    $nlat = 8;
    $nlon = 16;

} elsif ( $resln eq "10by15" ) {
    $nlat = 19;
    $nlon = 24;

    $blat = "-90.0";
    $blon = "0.0";
    $elat = "90.0";
    $elon = "345.0";

} elsif ( $resln eq "4by5" ) {
    $nlat = 46;
    $nlon = 72;

    $blat = "-90.0";
    $blon = "0.0";
    $elat = "90.0";
    $elon = "355.0";

} elsif ( $resln eq "2by2.5" ) {
    $nlat = 91;
    $nlon = 144;
    $blat = "-90.0";
    $blon = "0.0";
    $elat = "90.0";
    $elon = "357.5";

} elsif ( $resln eq "1.9by2.5" ) {
    $nlat = 96;
    $nlon = 144;
    $blat = "-90.0";
    $blon = "0.0";
    $elat = "90.0";
    $elon = "357.5";

} elsif ( $resln eq "1by1.25" ) {
    $nlat = 181;
    $nlon = 288;
    $blat = "-90.0";
    $blon = "0.0";
    $elat = "90.0";
    $elon = "358.75";

} else {

  die "FATAL: Invalid or unsupported resolution specified. Aborting."

}


#---------------------------------------------
# determine grid type (gaussian or regular)
#---------------------------------------------

$leadchar = substr($resln,0,1);

  if( $leadchar eq "T" ) {

       $indic = "GAUS";
       $infile = "CREATE_DIMS_GAU.ncl";

  }else{

       $indic = "REG";
       $infile = "CREATE_DIMS_REG.ncl";

  }

#------------------------------------------------------------------
# Set up NCL script to create netCDF file for requested resolution
#------------------------------------------------------------------

$keyword1 = "RESLN =";
$keyword2 = "NLAT =";
$keyword3 = "NLON =";
$keyword4 = "BEGLAT =";
$keyword5 = "BEGLON =";
$keyword6 = "ENDLAT =";
$keyword7 = "ENDLON =";

$resexpr = qq!"$resln"!;
  
$outfile = "CREATE_DIMS_$resln.ncl";

       open(INF, "$infile");
       open(OUTF,">$outfile");

       while(<INF>){

        if(/$keyword1/){
  	  print OUTF "RESLN = $resexpr\n";
        } elsif (/$keyword2/) {
   	  print OUTF "NLAT = $nlat\n";
        } elsif (/$keyword3/) {
   	  print OUTF "NLON = $nlon\n";
        } elsif (/$keyword4/) {
   	  print OUTF "BEGLAT = $blat\n";
        } elsif (/$keyword5/) {
   	  print OUTF "BEGLON = $blon\n";
        } elsif (/$keyword6/) {
   	  print OUTF "ENDLAT = $elat\n";
        } elsif (/$keyword7/) {
   	  print OUTF "ENDLON = $elon\n";
        } else {
          print OUTF "$_";
        }


       }

      close(INF);
      close(OUTF);


#------------------------------------------
# Run NCL script
#------------------------------------------

    print("CREATING DIMENSION FILE FOR $resln GRID\n");
    system( "ncl < CREATE_DIMS_$resln.ncl" );


exit;