$maxtechno =0;

@targv=@ARGV;

# First, get the list of technologies.
while (($line = <>)) {
    if ($line =~ m/TECH *(\d+) *(\w+)/i) {
	$techno = $1;
	if ($1>$maxtechno) {
	    $maxtechno = $1;
	}
	$current_tech = $2;
	
	if ($techno != 999) {
	    $techlist[$techno] = $current_tech;
	    $techhash{$current_tech} = $techno;
	}
    }
    
}

@ARGV = @targv;

# Build the Technology list tree.
while ($line = <>) {
    if ($line =~ m/TECH *(\d+) *(\w+)/i) {
	$techno = $1;
	$current_tech = $2;
	$reqsize=0;
	
    }
    
    if ($techno != 999) {
	if ($line =~ m/Tech_Requirement *\"(\w+)/i) {
	    $requires[$techno][$reqsize] = $techhash{$1};
	    $reqsize++;	
	    $refcount[$techhash{$1}]++;
	}
	if ($line =~ m/Tech_Requirement_ID *(\d+)/i) {
	    $requires[$techno][$reqsize] = $1;
	    $reqsize++;
	    $refcount[$1]++;
	}
	if ($line =~ m/Research_Cost *(\d+)/i) {
	    $cost[$techlist]=$1;
	}
    }
}

# Now, strip away unneeded techs.
for ($i=0; $i<$maxtechno; $i++) {
    if ($refcount[$i]==0 && $techlist[$i]) {
	if ($techlist[$i] ne "FinalFrontier") {
	    $j = $i + 1;
 	    for ($k=0; $requires[$i][$k] != 0; $k++) {
		$refcount[$requires[$i][$k]]--;
		if ($requires[$i][$k]-1< $j ) {
		    $j=$requires[$i][$k] - 1;
		}
	    }
	    undef $techlist[$i];
	    $i = $j;
	}
    }

}

# Now, dump the list of technologies.
display_tech ($techhash{"FinalFrontier"},0);

sub display_tech {
    my $k;
    if ($shown[$_[0]] != 1) {
	#$shown[$_[0]]=1; #Uncomment line to compress tech tree
	for ($k=0; $requires[$_[0]][$k] != 0; $k++) {
	    display_tech ($requires[$_[0]][$k], $_[1]+1);
	}
	for ($i=0; $i<$_[1]; $i++) {
	    if ($i % 2) {
		print " ";
	    } else {
		print "|";
	    }
	}
	print "$techlist[$_[0]] ($_[0])\n";
    }
}