use shopspring/decimal library everywhere

internal/filler.go

@@ -0,0 +1,96 @@
+package internal
+
+import (
+	"container/list"
+
+	"github.com/shopspring/decimal"
+)
+
+type Filler struct {
+	Record
+
+	filled decimal.Decimal
+}
+
+func NewFiller(r Record) *Filler {
+	return &Filler{
+		Record: r,
+	}
+}
+
+// Fill accrues some quantity. Returns how mutch was accrued in the 1st return value and whether
+// it was filled or not on the 2nd return value.
+func (f *Filler) Fill(quantity decimal.Decimal) (decimal.Decimal, bool) {
+	unfilled := f.Record.Quantity().Sub(f.filled)
+	delta := decimal.Min(unfilled, quantity)
+	f.filled = f.filled.Add(delta)
+	return delta, f.IsFilled()
+}
+
+// IsFilled returns true if the fill is equal to the record quantity.
+func (f *Filler) IsFilled() bool {
+	return f.filled.Equal(f.Quantity())
+}
+
+type FillerQueue struct {
+	l *list.List
+}
+
+// Push inserts the Filler at the back of the queue.
+func (fq *FillerQueue) Push(f *Filler) {
+	if f == nil {
+		return
+	}
+
+	if fq == nil {
+		// This would cause a panic anyway so, we panic with a more meaningful message
+		panic("Push to nil FillerQueue")
+	}
+
+	if fq.l == nil {
+		fq.l = list.New()
+	}
+
+	fq.l.PushBack(f)
+}
+
+// Pop removes and returns the first Filler of the queue in the 1st return value. If the list is
+// empty returns false on the 2nd return value, true otherwise.
+func (fq *FillerQueue) Pop() (*Filler, bool) {
+	el := fq.frontElement()
+	if el == nil {
+		return nil, false
+	}
+
+	val := fq.l.Remove(el)
+
+	return val.(*Filler), true
+}
+
+// Peek returns the front Filler of the queue in the 1st return value. If the list is empty returns
+// false on the 2nd return value, true otherwise.
+func (fq *FillerQueue) Peek() (*Filler, bool) {
+	el := fq.frontElement()
+	if el == nil {
+		return nil, false
+	}
+
+	return el.Value.(*Filler), true
+}
+
+func (fq *FillerQueue) frontElement() *list.Element {
+	if fq == nil || fq.l == nil {
+		return nil
+	}
+
+	return fq.l.Front()
+}
+
+// Len returns how many elements are currently on the queue
+func (fq *FillerQueue) Len() int {
+	if fq == nil || fq.l == nil {
+		return 0
+	}
+
+	return fq.l.Len()
+}