#!/usr/bin/perl -w

use POSIX;

# Data structures:
#  $ctx->{CmdLog}= undef                  } not in defobj
#  $ctx->{CmdLog}[]= [ command args ]     } in defobj
#  $ctx->{LocsMade}[]= $id
#  $ctx->{Loc}{$id}{X}
#  $ctx->{Loc}{$id}{Y}
#  $ctx->{Loc}{$id}{A}  may be undef
#  $ctx->{Trans}{X0}                  } transformation
#  $ctx->{Trans}{Y0}                  }  matrix
#  $ctx->{Trans}{XY}                  }
#  $ctx->{Trans}{YX}                  }
#  $ctx->{Trans}{XX}                  }
#  $ctx->{Trans}{YY}                  }
#  $ctx->{Trans}{AA}                  }
#  $ctx->{Trans}{AS}                  }
#
#  $objs{$id}{CmdLog}
#  $objs{$id}{Loc}

$debug=1;
open DEBUG, ($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_absang ($) { input_absang(cva_ang($_[0])) }
sub cva_units ($$) {
    my ($sp,$ua)=@_;
    my ($n,$u,$r);
    $sp =~ m/^([-0-9eE.]*[0-9.])([A-Za-z]*)$/
	or die "lexically invalid quantity";
    ($n,$u)= ($1,$2);
    $u=$ua->{'-'} unless length $u;
    defined $ua->{$u} or die "unknown unit $u";
    $r= $n * $ua->{$u};
    print DEBUG "cva_units($sp,)=$r ($n $u $ua->{$u})\n";
    return $r;
}
sub cva_idstr ($) {
    my ($sp)=@_;
    die "invalid id" unless $sp =~ m/^[a-z][_0-9A-Za-z]*$/;
    return $&;
}
sub cva_idex ($) {
    my ($sp,$id)=@_;
    my ($r,$d,$k);
    $id=cva_idstr($sp);
    die "unknown $id" unless defined $ctx->{Loc}{$id};
    $r= $ctx->{Loc}{$id};
    $d= "idex $id";
    foreach $k (sort keys %$r) { $d .= " $k=$r->{$k}"; }
    printf DEBUG "%s\n", $d;
    return $r;
}
sub cva_idnew ($) {
    my ($sp)=@_;
    my ($id);
    $id=cva_idstr($sp);
    die "duplicate $id" if exists $ctx->{Loc}{$id};
    exists $ctx->{Loc}{$id}{X};
    push @{ $ctx->{LocsMade} }, $id;
    return $ctx->{Loc}{$id};
}
sub cva_cmd ($) { return cva_idstr($_[0]); }
sub cva__enum ($$) {
    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_abs {
    my ($x,$y);
    $nl= can(\&cva_idnew);
    $x= can(\&cva_len);
    $y= can(\&cva_len);
    ($nl->{X}, $nl->{Y})= input_abscoords($x,$y);
    $nl->{A}= cano(\&cva_absang, undef);
}

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;
}

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 =~ m/^[0-9.]+/;
    $v =~ s/[\\\']/\\$&/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= 1;
$psu_ticklen= 5.0;
$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);
    return if defined $ctx->{InDefObj};
    $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";
	$radius *= $ctx->{Trans}{AA};
	$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') {
	    $beta= input_absang($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 {
    my ($id, $cmd, $loc);
    $ctx->{LocsMade}= [ ];
    $cmd= can(\&cva_cmd);
    &{ "cmd_$cmd" };
    die "too many args" if @al;
    foreach $id (@{ $ctx->{LocsMade} }) {
	$loc= $ctx->{Loc}{$id};
	o("%  point $id $loc->{X} $loc->{Y} ".ang2deg($loc->{A})."\n");
    }
}

sub cmd__one {
    cmd__do();
}

sub ang2deg ($) {
    return $_[0] * 180 / $pi;
}
sub input_absang ($) {
    return $_[0] * $ctx->{Trans}{AA} + $ctx->{Trans}{A0};
}
sub input_abscoords ($$) {
    my ($in,$out, $i);
    ($in->{X}, $in->{Y})= @_;
    foreach $o (qw(X Y)) {
	$out->{$o}= $ctx->{Trans}{$o.0};
	foreach $i (qw(X Y)) {
	    $out->{$o} += $ctx->{Trans}{"$i$o"} * $in->{$i};
	}
    }
    return ($out->{X}, $out->{Y});
}

sub newctx () {
    $ctx= { Trans => { X0 => 0.0, Y0 => 0.0,
		       XY => 0.0, YX => 0.0,
		       A0 => 0.0, AA => 1.0,
		       XX => 1.0, YY => 1.0 } }
}

sub cmd_defobj {
    my ($id);
    $id= can(\&cva_idstr);
    die "nested defobj" if $defobj_save;
    die "repeated defobj" if exists $objs{$id};
    $defobj_save= $ctx;
    newctx();
    $ctx->{CmdLog}= [ ];
    $ctx->{InDefObj}= $id;
}

sub cmd_enddefobj {
    my ($bit,$id);
    $id= $ctx->{InDefObj};
    die "unmatched enddefobj" unless defined $id;
    foreach $bit (qw(CmdLog Loc)) {
	$objs{$id}{$bit}= $ctx->{$bit};
    }
    $ctx= $defobj_save;
    $defobj_save= undef;
}

sub cmd_obj { cmd__obj(1); }
sub cmd_objflip { cmd__obj(-1); }
sub cmd__obj ($) {
    my ($flipsignum)=@_;
    my ($obj_id, $ctx_save, $pfx);
    $obj_id= can(\&cva_idstr);
    $actual= can(\&cva_idex);
    $formal_id= can(\&cva_idstr);
    $obj= $objs{$obj_id};
    dv("cmd__obj ",'$obj',$obj);
    die "unknown obj $obj_id" unless $obj;
    $formal= $obj->{Loc}{$formal_id};
    die "unknown formal $formal_id" unless $formal;
    $ctx_save= $ctx;
    newctx();
    o("%  obj $obj_id\n");
    $ctx->{Trans}{AA}= $flipsignum;
    $ctx->{Trans}{A0}= $actual->{A} - $formal->{A}/$flipsignum;
    $ctx->{Trans}{XX}= cos($ctx->{Trans}{A0});
    $ctx->{Trans}{YY}= $flipsignum * cos($ctx->{Trans}{A0});
    $ctx->{Trans}{XY}= $flipsignum * sin($ctx->{Trans}{A0});
    $ctx->{Trans}{YX}= -$flipsignum * sin($ctx->{Trans}{A0});
    ($xformcv,$yformcv)= input_abscoords($formal->{X}, $formal->{Y});
print STDERR ">$xformcv|$yformcv<\n";
    $ctx->{Trans}{X0}= $actual->{X} - $xformcv;
    $ctx->{Trans}{Y0}= $actual->{Y} - $yformcv;
    {
	local (@al);
	foreach $c (@{ $obj->{CmdLog} }) {
	    @al= @$c;
	    next if $al[0] eq 'enddefobj';
	    cmd__one();
	}
    }
    $pfx= cano(\&cva_idstr,'');
    if (length $pfx) {
	foreach $id (keys %{ $ctx->{Loc} }) {
	    $newid= $pfx.$id;
	    next if exists $ctx_save->{Loc}{$newid};
	    $pt= $ctx->{Loc}{$id};
	    $newpt= { A => input_absang($pt->{A}) };
	    ($newpt->{X}, $newpt->{Y})= input_abscoords($pt->{X}, $pt->{Y});
	    $ctx_save->{Loc}{$newid}= $newpt;
	}
    }
    $ctx= $ctx_save;
}

$ptscale= 72/25.4 / 5.0;

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

newctx();
    
while (<>) {
    next if m/^\s*\#/;
    chomp; s/^\s+//; s/\s+$//;
    @al= split /\s+/, $_;
    next unless @al;
    print DEBUG "=== @al\n";
    push @{ $ctx->{CmdLog} }, [ @al ] if exists $ctx->{CmdLog};
    cmd__one();
}
o("  showpage\n");