closes #9: fix tier interface implementations

Author: vocatart

textgrid/textgrid.go

@@ -54,6 +54,36 @@ func (tg TextGrid) GetTiers() []Tier {
 	return tg.tiers
 }
 
+// Returns true if TextGrid has IntervalTier
+func (tg TextGrid) HasIntervalTier() bool {
+	for _, tier := range tg.tiers {
+		if tier.TierType() == "IntervalTier" {
+			return true
+		}
+	}
+	return false
+}
+
+// Returns true if TextGrid has PointTier
+func (tg TextGrid) HasPointTier() bool {
+	for _, tier := range tg.tiers {
+		if tier.TierType() == "PointTier" {
+			return true
+		}
+	}
+	return false
+}
+
+// Returns tier with given name, if it exists
+func (tg TextGrid) GetTier(name string) Tier {
+	for _, tier := range tg.tiers {
+		if tier.TierName() == name {
+			return tier
+		}
+	}
+	return nil
+}
+
 // Takes a path to a .TextGrid file and reads its contents into a TextGrid.
 func ReadTextgrid(path string) TextGrid {
 	tg := TextGrid{}

textgrid/tiers.go

@@ -16,7 +16,12 @@ type Tier interface {
 	SetName(string)
 	SetXmin(float64, ...bool) error
 	SetXmax(float64, ...bool) error
-	GetSize() int
+	GetIntervals() []Interval
+	GetPoints() []Point
+	PushInterval(Interval, ...bool) error
+	PushIntervals([]Interval, ...bool) error
+	PushPoint(Point, ...bool) error
+	PushPoints([]Point, ...bool) error
 	sort()
 }
 
@@ -206,11 +211,41 @@ func (iTier IntervalTier) GetIntervals() []Interval {
 	return iTier.intervals
 }
 
+// GetPoints implements Tier.
+func (iTier *IntervalTier) GetPoints() []Point {
+	panic("not point tier")
+}
+
+// PushPoint implements Tier.
+func (iTier *IntervalTier) PushPoint(Point, ...bool) error {
+	panic("not point tier")
+}
+
+// PushPoints implements Tier.
+func (iTier *IntervalTier) PushPoints([]Point, ...bool) error {
+	panic("not point tier")
+}
+
 // Returns slice of points from a `PointTier`
 func (pTier PointTier) GetPoints() []Point {
 	return pTier.points
 }
 
+// GetIntervals implements Tier.
+func (pTier *PointTier) GetIntervals() []Interval {
+	panic("not interval tier")
+}
+
+// PushInterval implements Tier.
+func (pTier *PointTier) PushInterval(Interval, ...bool) error {
+	panic("not interval tier")
+}
+
+// PushIntervals implements Tier.
+func (pTier *PointTier) PushIntervals([]Interval, ...bool) error {
+	panic("not interval tier")
+}
+
 // Pushes an interval to the interval tier. Sorts intervals by minimum x value after pushing the interval.
 func (iTier *IntervalTier) PushInterval(intervalPush Interval, warn ...bool) error {