exercise: LinkedList
version: 2
plan: 6
modules:
  - use: JSON::Fast
methods: 'push-list pop-list shift-list unshift-list'
tests: |-
  my $cases = from-json $=pod.pop.contents;
  for $cases.values -> $case {
    subtest $case.<name>, sub {
      my $linkedlist = LinkedList.new;
      for  |$case.<set> -> %set {
        for %set {
          my $value = $_.value;
          given $_.key  {
            when 'push'    { $linkedlist.?push-list( $value ) }
            when 'unshift' { $linkedlist.?unshift-list( $value ) }
            when 'pop'     { is $linkedlist.?pop-list, $value, 'pop' }
            when 'shift'   { is $linkedlist.?shift-list, $value, 'shift' }
          }
        }
      }
    }
  }

  =head2 Test Data
  =begin code
  [
    {
      "set" : [
        { "push" : 10 },
        { "push" : 20 },
        { "pop"  : 20 },
        { "pop"  : 10 }
      ],
      "name" : "push_pop"
    },
    {
      "set" : [
        { "push" : 10  },
        { "push" : 20  },
        { "shift" : 10 },
        { "shift" : 20 }
      ],
      "name" : "push_shift"
    },
    {
      "set" : [
        { "unshift" : 10 },
        { "unshift" : 20 },
        { "shift"   : 20 },
        { "shift"   : 10 }
      ],
      "name" : "unshift_shift"
    },
    {
      "set" : [
        { "unshift" : 10 },
        { "unshift" : 20 },
        { "pop"     : 10 },
        { "pop"     : 20 }
      ],
      "name" : "unshift_pop"
    },
    {
      "set" : [
        { "push"    : 10 },
        { "push"    : 20 },
        { "pop"     : 20 },
        { "push"    : 30 },
        { "shift"   : 10 },
        { "unshift" : 40 },
        { "push"    : 50 },
        { "shift"   : 40 },
        { "pop"     : 50 },
        { "shift"   : 30 }
      ],
      "name" : "example"
    }
  ]
  =end code

unit: class
example: |-
  class ListNode {
      has $.next     is rw;
      has $.previous is rw;
      has $.value;
  }

  has $!first;
  has $!last;

  method push-list($value) {
      my $next = ListNode.new( value => $value, previous => $!last );
      if ( $!last ) {
          $!last = $!last.next= $next ;
      }
      else {
          $!first = $!last = $next;
      }
  }

  method unshift-list($value) {
      my $next = ListNode.new( value => $value, next => $!first );
      if ( $!first ) {
          $!first = $!first.previous = $next ;
      }
      else {
          $!first = $!last = $next;
      }
  }

  method shift-list() {
      my $f = $!first;

      $!first = $!first.next;

      unless $!first  { $!last = $!first }

      return $f.value;
  }

  method pop-list() {
      my $f = $!last;

      $!last = $!last.previous;

      unless $!.last  { $!first = $!last }

      return $f.value;
  }