github.com/songzhibin97/go-baseutils@v0.0.2-0.20240302024150-487d8ce9c082/structure/queues/arrayqueue/iterator.go (about)

     1  package arrayqueue
     2  
     3  import "github.com/songzhibin97/go-baseutils/structure/containers"
     4  
     5  // Assert Iterator implementation
     6  var _ containers.ReverseIteratorWithIndex[any] = (*Iterator[any])(nil)
     7  
     8  // Iterator returns a stateful iterator whose values can be fetched by an index.
     9  type Iterator[E any] struct {
    10  	queue *Queue[E]
    11  	index int
    12  }
    13  
    14  // Iterator returns a stateful iterator whose values can be fetched by an index.
    15  func (queue *Queue[E]) Iterator() Iterator[E] {
    16  	return Iterator[E]{queue: queue, index: -1}
    17  }
    18  
    19  // Next moves the iterator to the next element and returns true if there was a next element in the container.
    20  // If Next() returns true, then next element's index and value can be retrieved by Index() and Value().
    21  // If Next() was called for the first time, then it will point the iterator to the first element if it exists.
    22  // Modifies the state of the iterator.
    23  func (iterator *Iterator[E]) Next() bool {
    24  	if iterator.index < iterator.queue.Size() {
    25  		iterator.index++
    26  	}
    27  	return iterator.queue.withinRange(iterator.index)
    28  }
    29  
    30  // Prev moves the iterator to the previous element and returns true if there was a previous element in the container.
    31  // If Prev() returns true, then previous element's index and value can be retrieved by Index() and Value().
    32  // Modifies the state of the iterator.
    33  func (iterator *Iterator[E]) Prev() bool {
    34  	if iterator.index >= 0 {
    35  		iterator.index--
    36  	}
    37  	return iterator.queue.withinRange(iterator.index)
    38  }
    39  
    40  // Value returns the current element's value.
    41  // Does not modify the state of the iterator.
    42  func (iterator *Iterator[E]) Value() E {
    43  	value, _ := iterator.queue.list.Get(iterator.index)
    44  	return value
    45  }
    46  
    47  // Index returns the current element's index.
    48  // Does not modify the state of the iterator.
    49  func (iterator *Iterator[E]) Index() int {
    50  	return iterator.index
    51  }
    52  
    53  // Begin resets the iterator to its initial state (one-before-first)
    54  // Call Next() to fetch the first element if any.
    55  func (iterator *Iterator[E]) Begin() {
    56  	iterator.index = -1
    57  }
    58  
    59  // End moves the iterator past the last element (one-past-the-end).
    60  // Call Prev() to fetch the last element if any.
    61  func (iterator *Iterator[E]) End() {
    62  	iterator.index = iterator.queue.Size()
    63  }
    64  
    65  // First moves the iterator to the first element and returns true if there was a first element in the container.
    66  // If First() returns true, then first element's index and value can be retrieved by Index() and Value().
    67  // Modifies the state of the iterator.
    68  func (iterator *Iterator[E]) First() bool {
    69  	iterator.Begin()
    70  	return iterator.Next()
    71  }
    72  
    73  // Last moves the iterator to the last element and returns true if there was a last element in the container.
    74  // If Last() returns true, then last element's index and value can be retrieved by Index() and Value().
    75  // Modifies the state of the iterator.
    76  func (iterator *Iterator[E]) Last() bool {
    77  	iterator.End()
    78  	return iterator.Prev()
    79  }
    80  
    81  // NextTo moves the iterator to the next element from current position that satisfies the condition given by the
    82  // passed function, and returns true if there was a next element in the container.
    83  // If NextTo() returns true, then next element's index and value can be retrieved by Index() and Value().
    84  // Modifies the state of the iterator.
    85  func (iterator *Iterator[E]) NextTo(f func(index int, value E) bool) bool {
    86  	for iterator.Next() {
    87  		index, value := iterator.Index(), iterator.Value()
    88  		if f(index, value) {
    89  			return true
    90  		}
    91  	}
    92  	return false
    93  }
    94  
    95  // PrevTo moves the iterator to the previous element from current position that satisfies the condition given by the
    96  // passed function, and returns true if there was a next element in the container.
    97  // If PrevTo() returns true, then next element's index and value can be retrieved by Index() and Value().
    98  // Modifies the state of the iterator.
    99  func (iterator *Iterator[E]) PrevTo(f func(index int, value E) bool) bool {
   100  	for iterator.Prev() {
   101  		index, value := iterator.Index(), iterator.Value()
   102  		if f(index, value) {
   103  			return true
   104  		}
   105  	}
   106  	return false
   107  }