Add methods for Bucket structs

lib/bucket/bucket.go

@@ -7,3 +7,25 @@ type Bucket struct {
 	// Volume is the current volume of the bucket
 	Volume uint64
 }
+
+// Fill sets the volume to the capacity to fill bucket
+func (b *Bucket) Fill() {
+	b.Volume = b.Capacity
+}
+
+// Empty sets the volume to 0
+func (b *Bucket) Empty() {
+	b.Volume = 0
+}
+
+// Pour fills the target bucket to the top
+func (b *Bucket) Pour(target *Bucket) {
+	availableVolume := target.Capacity - target.Volume
+	if availableVolume > b.Volume {
+		target.Volume += b.Volume
+		b.Volume = 0
+	} else {
+		b.Volume -= availableVolume
+		target.Volume += availableVolume
+	}
+}

lib/bucket/bucket_test.go

@@ -0,0 +1,28 @@
+package bucket
+
+import "testing"
+
+func TestPour(t *testing.T) {
+	var testcases = []struct {
+		source            *Bucket
+		target            *Bucket
+		expectedSrcVol    uint64
+		expectedTargetVol uint64
+	}{
+		{&Bucket{Capacity: 5, Volume: 2}, &Bucket{Capacity: 3, Volume: 2}, 1, 3},
+		{&Bucket{Capacity: 5, Volume: 1}, &Bucket{Capacity: 3, Volume: 1}, 0, 2},
+		{&Bucket{Capacity: 5, Volume: 0}, &Bucket{Capacity: 3, Volume: 0}, 0, 0},
+		{&Bucket{Capacity: 5, Volume: 5}, &Bucket{Capacity: 3, Volume: 3}, 5, 3},
+		{&Bucket{Capacity: 5, Volume: 4}, &Bucket{Capacity: 3, Volume: 2}, 3, 3},
+	}
+
+	for _, tc := range testcases {
+		tc.source.Pour(tc.target)
+		if tc.source.Volume != tc.expectedSrcVol {
+			t.Errorf("expected source volume %d, got = %d", tc.expectedSrcVol, tc.source.Volume)
+		}
+		if tc.target.Volume != tc.expectedTargetVol {
+			t.Errorf("expected target volume %d, got = %d", tc.expectedTargetVol, tc.target.Volume)
+		}
+	}
+}