#!/usr/bin/env perl
use 5.024;
use warnings;
use experimental qw< postderef signatures >;
no warnings qw< experimental::postderef experimental::signatures >;
use Curses;

my $win = Curses->new;
curs_set(0);       # don't show the cursor
noecho();          # don't echo keypresses on screen
cbreak();          # get anything unbuffered
$win->keypad(1);

# ... now use $win for most things
# load a maze
my $maze = load_maze(@ARGV[0,1]);

# display it
maze_display($win, $maze);

# main loop
make_a_move($win, $maze) until hero_reached_exit($maze);

# salutations
goodbye_display($win, $maze);

END {
   endwin();
}

sub path_loop_erasure ($input_path) {
   my @output_path;
   my $i = -1;
   my $N = $input_path->@*;
   while (++$i < $N) {
      print "i<$i>\n";

      # find latest occurrence of $input_path->[$i]
      my $j = $i;
      while (++$j < $N) {
         # "advance" $i if the corresponding item is found
         # later in the array
         $i = $j if $input_path->[$i]{id} eq $input_path->[$j]{id};
      }

      # whatever, this item fits into the output
      print "  --> i<$i>\n";
      push @output_path, $input_path->[$i];
   }
   return \@output_path;
}

sub random_walk ($maze, $r, $c) {
   my @retval;
   my @moves = ([-2, 0], [0, 2], [2, 0], [0, -2]);
   my $Mr = $#$maze;
   my $Mc = $#{$maze->[0]};
   while ('necessary') {
      push @retval, {
         row => $r,
         col => $c,
         id  => "$r-$c",
      };
      last if $maze->[$r][$c] eq ' ';
      my $move = @moves[rand @moves];
      my ($cr, $cc) = ($r + $move->[0], $c + $move->[1]);
      next if $cr < 0 || $cr > $Mr || $cc < 0 || $cc > $Mc;
      ($r, $c) = ($cr, $cc);
   }
   return \@retval;
}

sub generate_maze ($rows, $cols) {
   $_ -= 2 for $rows, $cols; # will add boundary walls at the end
   my @maze = map { [('#') x $cols] } 1 .. $rows;
   $maze[0][0] = ' '; # starting position is in maze
   my $row = 0;
   my $col = 0;
   while ($row < $rows) {
      if ($maze[$row][$col] eq '#') { # not reached yet
         my $path = random_walk(\@maze, $row, $col);
         say $_->{id} for $path->@*; 
         $path = path_loop_erasure($path);

         # apply path to maze
         my ($pr, $pc);
         my $n = 0;
         for my $v ($path->@*) {
            my ($r, $c) = $v->@{qw< row col >};
            printf {*STDERR} "row<$r> col<$c>\n";
            $maze[$r][$c] = ' ';
            $maze[($r + $pr) / 2][($c + $pc)/2] = ' ' if defined $pr;
            ($pr, $pc) = ($r, $c);
         }
      }
      $col += 2;
      ($row, $col) = ($row + 2, 0) if $col > $cols;
   }
   my $hwall = '#' x ($cols + 2);
   join "\n", $hwall, (map { join '', '#', $_->@*, '#' } @maze), $hwall;
}

sub load_maze ($rows, $cols) {
   $rows //= 15;
   $cols //= 49;
   $rows-- unless $rows % 2;
   $cols-- unless $cols % 2;
   my $maze = generate_maze($rows, $cols);

   return {
      exit => [$rows - 1, $cols - 2], # lower-right corner
      hero => [1, 1],   # upper-left  corner
      maze => $maze,
      moves => 0,
   };
}

sub maze_display ($win, $maze) {
   my $n_row = 0;
   for my $row (split m{\n+}mxs, $maze->{maze}) {
      $win->addstr($n_row++, 0, $row);
   }
   $win->addch($maze->{exit}->@*, '.');
   $win->addch($maze->{hero}->@*, '@');
   $win->refresh;
}

sub make_a_move ($win, $maze) {
   my ($ch, $key) = $win->getchar;
   if (defined $key) {
      my $key_up = KEY_UP;
      try_move($win, $maze, -1,  0) if $key == KEY_UP;
      try_move($win, $maze,  0,  1) if $key == KEY_RIGHT;
      try_move($win, $maze,  1,  0) if $key == KEY_DOWN;
      try_move($win, $maze,  0, -1) if $key == KEY_LEFT;
   }
   elsif (defined $ch) {
      exit 0 if $ch eq 'q';
   }
   else {
      die 'getch failed?!?';
   }
   return;
}

sub try_move ($win, $maze, $row_delta, $col_delta) {
   my ($row, $col) = $maze->{hero}->@*;
   $row += $row_delta;
   $col += $col_delta;
   my $char = $win->inch($row, $col);
   if ($char ne '#') {
      $maze->{hero}->@* = ($row, $col);
      $maze->{moves}++;
      maze_display($win, $maze);
   }
   return;
}

sub hero_reached_exit ($maze) {
   return $maze->{hero}[0] == $maze->{exit}[0]
      &&  $maze->{hero}[1] == $maze->{exit}[1];
}

sub goodbye_display ($win, $maze) {
   $win->addstr(4, 17, '                  ');
   $win->addstr(5, 17, ' +--------------+ ');
   $win->addstr(6, 17, ' | YOU MADE IT! | ');
   $win->addstr(7, 17, ' +--------------+ ');
   $win->addstr(8, 17, '                  ');
   $win->refresh;
   $win->getchar;
}