implement RecordQueue type

internal/record.go

@@ -1,18 +1,56 @@
 package internal
 
 import (
+	"container/list"
 	"math/big"
 	"time"
 )
 
 type Record interface {
 	Symbol() string
+	Side() Side
 	Price() *big.Float
 	Quantity() *big.Float
-	Side() Side
 	Timestamp() time.Time
 }
 
-type RecordReader interface {
-	ReadRecord() (Record, error)
+type RecordQueue struct {
+	l *list.List
+}
+
+func (rq *RecordQueue) Push(r Record) {
+	if rq.l == nil {
+		rq.l = list.New()
+	}
+
+	if r == nil {
+		return
+	}
+
+	rq.l.PushBack(r)
+}
+
+// Pop removes and returns the first element of the list as the first return value. If the list is
+// empty returns falso on the 2nd return value, true otherwise.
+func (rq *RecordQueue) Pop() (Record, bool) {
+	if rq.l == nil {
+		return nil, false
+	}
+
+	el := rq.l.Front()
+	if el == nil {
+		return nil, false
+	}
+
+	val := rq.l.Remove(el)
+
+	return val.(Record), true
+}
+
+func (rq *RecordQueue) Len() int {
+	if rq.l == nil {
+		return 0
+	}
+
+	return rq.l.Len()
 }