feat(Queue): implement write-read item stream

Author: sharpvik

queue.go

@@ -0,0 +1,37 @@
+package fungi
+
+import "io"
+
+// Q is a clever data structure that implements Stream and allows item enqueue
+// operation.
+type Q[T any] struct {
+	items []T
+}
+
+// Queue is a default constructor for Q.
+func Queue[T any]() *Q[T] {
+	return QueueOf[T]()
+}
+
+// QueueOf allows you to initialise a queue with some elements.
+func QueueOf[T any](items ...T) *Q[T] {
+	return &Q[T]{
+		items: items,
+	}
+}
+
+// Add some items to the queue.
+func (q *Q[T]) Add(items ...T) {
+	q.items = append(q.items, items...)
+}
+
+// Next item from the queue or error if it's empty.
+func (q *Q[T]) Next() (item T, err error) {
+	if len(q.items) == 0 {
+		err = io.EOF
+		return
+	}
+	item = q.items[0]
+	q.items = q.items[1:]
+	return
+}

queue_test.go

@@ -0,0 +1,20 @@
+package fungi
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestQueue(t *testing.T) {
+	slice := []int{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
+	queue := Queue[int]()
+	for _, i := range slice {
+		queue.Add(i)
+	}
+	odds := Filter(func(i int) bool { return i%2 != 0 })
+	sum := Reduce(func(i, j int) int { return i + j }, 0)
+	result, err := sum(odds(queue))
+	assert.NoError(t, err)
+	assert.Equal(t, 25, result)
+}