#!/usr/bin/perl -w

use POSIX;

# Data structures:
#  $loc{$id}{X}
#  $loc{$id}{Y}
#  $loc{$id}{A}  may be undef

#$debug=1;
open DEBUG, ($debug ? ">&2" : ">/dev/null") or die $!;

if ($debug) {
    select(DEBUG); $|=1;
    select(STDOUT); $|=1;
}

sub canf ($$) {
    my ($converter,$defaulter)=@_;
    my ($spec,$v);
    return &$defaulter unless @al;
    $spec= shift @al;
    $v= &$converter($spec);
    dv('canf ','$spec',$spec, '$v',$v);
    return $v;
}
sub can ($) { my ($c)=@_; canf($c, sub { die "too few args"; }); }
sub cano ($$) { my ($c,$def)=@_; canf($c, sub { return $def }); }

$pi= atan2(0,-1);

%units_len= qw(- mm  mm 1  cm 10  m 1000);
%units_ang= qw(- d   r 1); $units_ang{'d'}= 2*$pi / 360;

sub cva_len ($) { my ($sp)=@_; cva_units($sp,\%units_len); }
sub cva_ang ($) { my ($sp)=@_; cva_units($sp,\%units_ang); }
sub cva_units ($$) {
    my ($sp,$ua)=@_;
    my ($n,$u,$r);
    $sp =~ m/^([-0-9eE.]*[0-9.])([A-Za-z]*)$/
	or die "lexically invalid quantity";
    ($n,$u)= ($1,$2);
    $u=$ua->{'-'} unless length $u;
    defined $ua->{$u} or die "unknown unit $u";
    $r= $n * $ua->{$u};
    print DEBUG "cva_units($sp,)=$r ($n $u $ua->{$u})\n";
    return $r;
}
sub cva_idstr ($) {
    my ($sp)=@_;
    die "invalid id" unless $sp =~ m/^[-0-9a-z]+$/;
    return $&;
}
sub cva_idex ($) {
    my ($sp,$id)=@_;
    my ($r,$d,$k);
    $id=cva_idstr($sp);
    die "unknown $id" unless defined $loc{$id};
    $r= $loc{$id};
    $d= "idex $id";
    foreach $k (sort keys %$r) { $d .= " $k=$r->{$k}"; }
    printf DEBUG "%s\n", $d;
    return $r;
}
sub cva_idnew ($) {
    my ($sp,$id)=@_;
    $id=cva_idstr($sp);
    die "duplicate $id" if exists $loc{$id};
    exists $loc{$id}{X};
    return $loc{$id};
}
sub cva_cmd ($) {
    my ($sp)=@_;
    die "command lexically invalid" if $sp =~ m/[^-0-9a-z]/i;
    $sp =~ y/-/_/;
    return $sp;
}
sub cva__enum ($$) {
    my ($sp,$el)=@_;
    return $sp if grep { $_ eq $sp } @$el;
    die "invalid option (permitted: @$el)";
}
sub cvam_enum { my (@e) = @_; return sub { cva__enum($_[0],\@e); }; }

sub cmd_mark {
    $mark= 1;
    &cmd__do;
}

sub cmd_abs {
    $nl= can(\&cva_idnew);
    $nl->{X}= can(\&cva_len);
    $nl->{Y}= can(\&cva_len);
    $nl->{A}= cano(\&cva_ang, undef);
dv('cmd_abs ','$nl',$nl,'\\%loc',\%loc);
}

sub cmd_rel {
    $from= can(\&cva_idex);
    $to= can(\&cva_idnew);
    $len= can(\&cva_len);
    $right= can(\&cva_len);
    $turn= cano(\&cva_ang, 0);
    $to->{X}= $from->{X} + $len * cos($from->{A}) + $right * sin($from->{A});
    $to->{Y}= $from->{Y} + $len * sin($from->{A}) - $right * cos($from->{A});
    $to->{A}= $from->{A} + $turn;
dv('cmd_abs ','$to',$to);
}

sub evreff ($) {
    my ($pfx) = @_;
    $pfx . ($pfx =~ m/\}$|\]$/ ? '' : '->');
}
sub evr ($) {
    my ($v) = @_;
    return $v if $v !~ m/\W/ && $v =~ m/[A-Z]/ && $v =~ m/^[a-z_]/i;
    return $v if $v eq ($v+0.0);
    $v =~ s/[\\\']/\\$&/g;
    return "'$v'";
}
sub dv1 ($$$);
sub dv1_kind ($$$$$$$) {
    my ($pfx,$expr,$ref,$ref_exp,$ixfmt,$ixesfn,$ixmapfn) = @_;
    my ($ix,$any);
    return 0 if $ref ne $ref_exp;
    $any=0;
    foreach $ix (&$ixesfn) {
	$any=1;
	my ($v)= &$ixmapfn($ix);
#print STDERR "dv1_kind($pfx,$expr,$ref,$ref_exp,$ixmapfn) ix=$ix v=$v\n";
	dv1($pfx,$expr.sprintf($ixfmt,evr($ix)),$v);
    }
    if (!$any) {
	printf DEBUG "%s%s= $ixfmt\n", $pfx, $expr, ' ';
    }
    1;
}    
sub dv1 ($$$) {
    return ;0 unless $debug;
    my ($pfx,$expr,$v) = @_;
    $ref= ref $v;
#print STDERR "dv1 >$pfx|$ref<\n";
    if (!$ref) {
	printf DEBUG "%s%s= %s\n", $pfx,$expr, evr($v);
	return;
    } elsif ($ref eq 'SCALAR') {
	dv1($pfx, ($expr =~ m/^\$/ ? "\$$expr" : '${'.$expr.'}'), $$v);
	return;
    }
    $expr.='->' unless $expr =~ m/\]$|\}$/;
    return if dv1_kind($pfx,$expr,$ref,'ARRAY','[%s]',
                       sub { ($[ .. $#$v) },
                       sub { $v->[$_[0]] });
    return if dv1_kind($pfx,$expr,$ref,'HASH','{%s}',
                       sub { sort keys %$v },
                       sub { $v->{$_[0]} });
    printf DEBUG "%s%s is %s\n", $pfx, $expr, $ref;
}
    
sub dv {
    my ($pfx,@l) = @_;
    my ($expr,$v,$ref);
    while (@l) {
	($expr,$v,@l)=@l;
	dv1($pfx,$expr,$v);
    }
}		    

sub loc_lin_comb ($$$) {
    my ($a,$b,$p) = @_;
    my ($q,$r) = 1.0-$p;
    map { $r->{$_} = $q * $a->{$_} + $p * $b->{$_} } qw(X Y A);
#    dv("loc_lin_comb ",'$a',$a,'$b',$b,'$p',$p,'$r',$r);
    return $r;
}

$psu_ulen= 4.5;
$psu_edgelw= 0.5;
$psu_ticklw= 0.1;
$psu_ticksperu= 3;
$psu_ticklen= 3.0;
$psu_allwidth= 37.0/2;
$psu_gauge= 9;
$psu_sleeperlen= 17;
$psu_sleeperlw= 15;
$psu_raillw= 1.0;

sub o ($) {
    # fixme optional marking
    print "$_[0]" or die $!;
}

sub o_path_begin () {
    o("      newpath\n");
    $o_path_verb= 'moveto';
}
sub o_path_point ($) {
    my ($pt)=@_;
    o("        $pt $o_path_verb\n");
    $o_path_verb= 'lineto';
}
sub o_path_stroke ($) {
    my ($width)=@_;
    o("        $width setlinewidth stroke\n");
}    

sub o_line ($$$) {
    my ($a,$b,$width)=@_;
    o_path_begin();
    o_path_point($a);
    o_path_point($b);
    o_path_stroke($width);
}

sub psu_coords ($$$) {
    my ($ends,$inunit,$across)=@_;
    # $ends->[0]{X} etc.; $inunit 0 to 1 (but go to 1.5);
    # $across in mm, +ve to right.
    my (%ea_zo);
    $ea_zo{X}=$ea_zo{Y}=0;
    foreach $zo (qw(0 1)) {
	$prop= $zo ? $inunit : (1.0 - $inunit);
	$ea_zo{X} += $prop * ($ends->[$zo]{X} - $across * sin($ends->[0]{A}));
	$ea_zo{Y} += $prop * ($ends->[$zo]{Y} + $across * cos($ends->[0]{A}));
    }
#    dv("psu_coords ", '$ends',$ends, '$inunit',$inunit, '$across',$across,
#       '\\%ea_zo', \%ea_zo);
    return $ea_zo{X}." ".$ea_zo{Y};
}

sub parametric_segment ($$$$$) {
    my ($endstatuses,$p0,$p1,$lenperp,$calcfn) = @_;
    # makes $p (global) go from $p0 to $p1  ($p1>$p0)
    # $ends is II, SI, IS, SS (I=actual lineobj end, S=in mid of lineobj)
    # $lenperp is the length of one unit p, ie the curve
    # must have a uniform `density' in parameter space
    # $calcfn is invoked with $p set and should return a loc
    # (ie, ref to X =>, Y =>, A =>).
    my ($pa,$pb,@ends,$side,$ppu,$e,$v,$tick);
    $ppu= $psu_ulen/$lenperp;
    my ($railctr)=($psu_gauge + $psu_raillw)*0.5;
    my ($tickend)=($psu_allwidth - $psu_ticklen);
    my ($tickpitch)=($psu_ulen / $psu_ticksperu);
    my ($sleeperctr)=($psu_ulen*0.5);
    my ($sleeperend)=($psu_sleeperlen*0.5);
print DEBUG "ps $p0 $p1 $lenperp ($ppu)\n";
    for ($pa= $p0; $pa<$p1; $pa=$pb) {
	$pb= $pa + $ppu;
	$p= $pa; $ends[0]= @ends ? $ends[1] : &$calcfn;
	$p= $pb; $ends[1]= &$calcfn;
#print DEBUG "pa $pa $ends[0]{X} $ends[0]{Y} $ends[0]{A}\n";
#print DEBUG "pb $pb $ends[1]{X} $ends[1]{Y} $ends[1]{A}\n";
	$e= $pb<=$p1 ? 1.0 : ($p1-$pa)/$ppu;
	o("    gsave\n");
	o_path_begin();
	o_path_point(psu_coords(\@ends,0,-$psu_allwidth));
	o_path_point(psu_coords(\@ends,0,$psu_allwidth));
	o_path_point(psu_coords(\@ends,$e,$psu_allwidth));
	o_path_point(psu_coords(\@ends,$e,-$psu_allwidth));
	o("        closepath clip\n");
	foreach $side qw(-1 1) {
	    o_line(psu_coords(\@ends,0,$side*$psu_allwidth),
		   psu_coords(\@ends,1.5,$side*$psu_allwidth),
		   $psu_edgelw);
	    o_line(psu_coords(\@ends,0,$side*$railctr),
		   psu_coords(\@ends,1.5,$side*$railctr),
		   $psu_raillw);
	    for ($tick=0; $tick<1.5; $tick+=$tickpitch/$psu_ulen) {
		o_line(psu_coords(\@ends,$tick,$side*$psu_allwidth),
		       psu_coords(\@ends,$tick,$side*$tickend),
		       $psu_ticklw);
	    }
	}
	o_line(psu_coords(\@ends,$sleeperctr,-$sleeperend),
	       psu_coords(\@ends,$sleeperctr,+$sleeperend),
	       $psu_sleeperlw);
	o("      grestore\n");
    }
}

sub cmd_extend {
    my ($from,$to,$radius,$ctr,$beta,$ang,$how,$signum);
    $from= can(\&cva_idex);
    $to= can(\&cva_idnew);
    printf DEBUG "from $from->{X} $from->{Y} $from->{A}\n";
    die "no ang" unless defined $from->{A};
    $how= can(cvam_enum(qw(len upto ang uptoang parallel)));
    if ($how eq 'len') { $len= can(\&cva_len); }
    elsif ($how =~ m/ang$/) { $ang= can(\&cva_ang); }
    elsif ($how eq 'parallel' || $how eq 'upto') { $upto= can(\&cva_idex); }
    $radius= cano(\&cva_len, 'Inf'); # +ve is right hand bend
    if ($radius eq 'Inf') {
	print DEBUG "extend inf $len\n";
	if ($how eq 'ang') { die "len of straight spec by angle"; }
	if ($how eq 'upto') {
	    $len= ($upto->{X} - $from->{X}) * cos($from->{A})
		+ ($upto->{Y} - $from->{Y}) * sin($from->{A});
	}
	printf DEBUG "len $len\n";
	$to->{X}= $from->{X} + $len * cos($from->{A});
	$to->{Y}= $from->{Y} + $len * sin($from->{A});
	$to->{A}= $from->{A};
	parametric_segment(II, 0.0, 1.0, $len, sub {
	    loc_lin_comb($from, $to, $p);
	});
    } else {
	print DEBUG "radius >$radius<\n";
	$signum= $radius / abs($radius);
	$ctr->{X}= $from->{X} + $radius * sin($from->{A});
	$ctr->{Y}= $from->{Y} - $radius * cos($from->{A});
	if ($how eq 'upto') {
	    $beta= atan2(-$signum * ($upto->{X} - $ctr->{X}),
			 $signum * ($upto->{Y} - $ctr->{Y}));
	    $beta_interval= 1.0;
	} elsif ($how eq 'parallel') {
	    $beta= $upto->{A};
	    $beta_interval= 1.0;
	} elsif ($how eq 'uptoang') {
	    $beta= $ang;
	    $beta_interval= 2.0;
	} elsif ($how eq 'len') {
	    $beta= $from->{A} - $signum * $len / abs($radius);
	    $beta_interval= 2.0;
	} else {
	    $beta= $from->{A} - $signum * $ang;
	    $beta_interval= 2.0;
	}
    printf DEBUG "ctr->{Y}=$ctr->{Y} radius=$radius beta=$beta\n";
	$beta += $signum * 4.0 * $pi;
	for (;;) {
	    $delta= $beta - $from->{A};
	    last if $signum * $delta <= 0;
	    $beta -= $signum * $beta_interval * $pi;
	}	
    printf DEBUG "ctr->{Y}=$ctr->{Y} radius=$radius beta=$beta\n";
	$to->{A}= $beta;
	$to->{X}= $ctr->{X} - $radius * sin($beta);
	$to->{Y}= $ctr->{Y} + $radius * cos($beta);
	parametric_segment(II, 0.0, 1.0, abs($radius*$delta), sub {
	    my ($beta) = $from->{A} + $delta * $p;
	    return { X => $ctr->{X} - $radius * sin($beta),
		     Y => $ctr->{Y} + $radius * cos($beta),
		     A => $beta }
	});
    }
    printf DEBUG "to $to->{X} $to->{Y} $to->{A}\n";
}

sub cmd__do {
    $cmd= can(\&cva_cmd);
    &{ "cmd_$cmd" };
}	

$ptscale= 72/25.4 / 5.0;

o("%!\n".
  "  $ptscale $ptscale scale\n");

while (<>) {
    next if m/^\s*\#/;
    chomp; s/^\s+//; s/\s+$//;
    @al= split /\s+/, $_;
    next unless @al;
    print DEBUG "=== @al\n";
    $mark= 0;
    cmd__do();
}
dv('','\\%loc',\%loc);