#!/usr/bin/perl -w
#
# usage:
#   ./distort-stl <INPUT >OUTPUT DISTORTION [PARAMS...] ...
#
# DISTORTIONs:
#
#   project-cylinder RADIUS
#       projects the X-Z plane onto the cylinder of
#           radius RADIUS with axis [0, 0, t]
#       origin becomes [0, -RADIUS, 0]
#       other planes of the input are projected onto smaller
#           or larger cylinders accordingly
#       probably a bad idea if
#           object has any Y > RADIUS
#           object has any |X| > tau / RADIUS
#       technically, treats input as if it were
#       polar-rectangular coords:
#          Z' = Z; R' = Y + RADIUS; theta' = X / RADIUS
#       and then converts back into cartesian
#       honours fa but not fs or fn
#
#   set-fa $FA

use strict;
use autodie;

use File::Temp;
use List::Util;

our $fa = 10;

our @triangles;

sub shift_arg () {
    die unless @ARGV;
    scalar shift @ARGV;
}

sub subdivide_triangle ($$) {
    my ($it, $fn) = @_;
    my @mids;
    foreach my $ix (0..2) {
	my $jx = ($ix+1) % 3;
	my @midp;
	foreach my $ci (0..2) {
	    push @midp, 0.5 * ($it->[$ix][$ci] + $it->[$jx][$ci]);
	}
	push @mids, @midp;
    }
    foreach my $ix (0..2) {
	my $kx = ($ix+2) % 3;
	$fn->([ $it->[$ix], $mids[$ix], $it->[$kx] ]);
    }
    $fn->(\@mids);
}

#---------- project-cylinder ----------

our $project_cylinder_radius;
our $project_cylinder_max_d_theta;

sub project_cylinder_tri {
    my ($it) = @_;

    my $radius = project_cylinder_radius;

    my @thetas = map { $_->[0] / $radius } @$it;

    foreach my $ix (0..2) {
	if (abs($thetas[$ix] - $thetas[($ix+1)%3])
	    > $project_cylinder_max_d_theta) {
	    subdivide_triangle $it, \&project_cylinder_tri;
	    return;
	}
    }

    my @ot;
    foreach my $p (@it) {
	my ($x,$y,$z) = @$p;
	my $r = $radius - $y;
	my $theta = $x / $radius;
	push @ot, [ $r * sin($theta),
		    -$r * cos($theta),
		    $z ];
    }
    push @triangles, \@ot;
}

sub op__project_cylinder () {
    $project_cylinder_radius = shift_arg;
    $project_cylinder_max_d_theta = $fa * TAU/360;

    my @input = (@triangles);
    @triangles = ();

    project_cylinder_tri $_ foreach @input;
}

#---------- main program ----------

if (@ARGV && $ARGV[0] =~ m/^-/) {
    die "no options supported\n";
}

my $itmp = new File::Temp;
my $otmp = new File::Temp;

system "cat >$itmp";

my $admesh_stdout = '--write-ascii-stl /dev/fd/3 3>&1 >/dev/null';

open I, "admesh $admesh_stdout $itmp |";

my $triangle;

while (<I>) {
    if (m/^\s+outer\s+loop/) {
	die if $triangle;
	$triangle = [];
    } elsif (s/^\s+vertex\s+//) {
	my $lhs = $&;
	s/\s+$//;
	my @xyz = split /\s+/, $_;
	die unless $triangle;
	push @$triangle, \@xya;
    } elsif (m/^\s+endloop/) {
	die unless @$triangle == 3;
	push @triangles, $triangle;
    } elsif (m/^\s+(?:solid|facet\s+normal|endfacet|endsolid)\s/) {
    } else {
	die "$_ ?";
    }
}

close I;
<I> if 0; # suppresses Name "main::I" used only once

while (@ARGV) {
    my $op = shift_arg;
    $op =~ y/-/_/;
    &{ ${*::}{"op__$op"} };
}

select $otmp;

print "solid distort-stl\n";

foreach my $t (@triangles) {
    print "  facet normal 0 0 0\n";
    print "    outer loop\n";
    print "      vertex";
    printf " %.18g", $_ foreach @$t;
    print "\n";
    print "    endloop\n";
    print "  endfacet\n";
}

print "endsolid distort-stl\n";

flush $otmp;

system "admesh --normal-values $admesh_stdout $otmp";