package influxql

// FloatMeanReducer calculates the mean of the aggregated points.
type FloatMeanReducer struct {
	sum   float64
	count uint32
}

// NewFloatMeanReducer creates a new FloatMeanReducer.
func NewFloatMeanReducer() *FloatMeanReducer {
	return &FloatMeanReducer{}
}

// AggregateFloat aggregates a point into the reducer.
func (r *FloatMeanReducer) AggregateFloat(p *FloatPoint) {
	if p.Aggregated >= 2 {
		r.sum += p.Value * float64(p.Aggregated)
		r.count += p.Aggregated
	} else {
		r.sum += p.Value
		r.count++
	}
}

// Emit emits the mean of the aggregated points as a single point.
func (r *FloatMeanReducer) Emit() []FloatPoint {
	return []FloatPoint{{
		Time:       ZeroTime,
		Value:      r.sum / float64(r.count),
		Aggregated: r.count,
	}}
}

// IntegerMeanReducer calculates the mean of the aggregated points.
type IntegerMeanReducer struct {
	sum   int64
	count uint32
}

// NewIntegerMeanReducer creates a new IntegerMeanReducer.
func NewIntegerMeanReducer() *IntegerMeanReducer {
	return &IntegerMeanReducer{}
}

// AggregateInteger aggregates a point into the reducer.
func (r *IntegerMeanReducer) AggregateInteger(p *IntegerPoint) {
	if p.Aggregated >= 2 {
		r.sum += p.Value * int64(p.Aggregated)
		r.count += p.Aggregated
	} else {
		r.sum += p.Value
		r.count++
	}
}

// Emit emits the mean of the aggregated points as a single point.
func (r *IntegerMeanReducer) Emit() []FloatPoint {
	return []FloatPoint{{
		Time:       ZeroTime,
		Value:      float64(r.sum) / float64(r.count),
		Aggregated: r.count,
	}}
}

// FloatDerivativeReducer calculates the derivative of the aggregated points.
type FloatDerivativeReducer struct {
	interval      Interval
	prev          FloatPoint
	curr          FloatPoint
	isNonNegative bool
	ascending     bool
}

// NewFloatDerivativeReducer creates a new FloatDerivativeReducer.
func NewFloatDerivativeReducer(interval Interval, isNonNegative, ascending bool) *FloatDerivativeReducer {
	return &FloatDerivativeReducer{
		interval:      interval,
		isNonNegative: isNonNegative,
		ascending:     ascending,
		prev:          FloatPoint{Nil: true},
		curr:          FloatPoint{Nil: true},
	}
}

// AggregateFloat aggregates a point into the reducer and updates the current window.
func (r *FloatDerivativeReducer) AggregateFloat(p *FloatPoint) {
	r.prev = r.curr
	r.curr = *p
}

// Emit emits the derivative of the reducer at the current point.
func (r *FloatDerivativeReducer) Emit() []FloatPoint {
	if !r.prev.Nil {
		// Calculate the derivative of successive points by dividing the
		// difference of each value by the elapsed time normalized to the interval.
		diff := r.curr.Value - r.prev.Value
		elapsed := r.curr.Time - r.prev.Time
		if !r.ascending {
			elapsed = -elapsed
		}
		value := diff / (float64(elapsed) / float64(r.interval.Duration))

		// Drop negative values for non-negative derivatives.
		if r.isNonNegative && diff < 0 {
			return nil
		}
		return []FloatPoint{{Time: r.curr.Time, Value: value}}
	}
	return nil
}

// IntegerDerivativeReducer calculates the derivative of the aggregated points.
type IntegerDerivativeReducer struct {
	interval      Interval
	prev          IntegerPoint
	curr          IntegerPoint
	isNonNegative bool
	ascending     bool
}

// NewIntegerDerivativeReducer creates a new IntegerDerivativeReducer.
func NewIntegerDerivativeReducer(interval Interval, isNonNegative, ascending bool) *IntegerDerivativeReducer {
	return &IntegerDerivativeReducer{
		interval:      interval,
		isNonNegative: isNonNegative,
		ascending:     ascending,
		prev:          IntegerPoint{Nil: true},
		curr:          IntegerPoint{Nil: true},
	}
}

// AggregateInteger aggregates a point into the reducer and updates the current window.
func (r *IntegerDerivativeReducer) AggregateInteger(p *IntegerPoint) {
	r.prev = r.curr
	r.curr = *p
}

// Emit emits the derivative of the reducer at the current point.
func (r *IntegerDerivativeReducer) Emit() []FloatPoint {
	if !r.prev.Nil {
		// Calculate the derivative of successive points by dividing the
		// difference of each value by the elapsed time normalized to the interval.
		diff := float64(r.curr.Value - r.prev.Value)
		elapsed := r.curr.Time - r.prev.Time
		if !r.ascending {
			elapsed = -elapsed
		}
		value := diff / (float64(elapsed) / float64(r.interval.Duration))

		// Drop negative values for non-negative derivatives.
		if r.isNonNegative && diff < 0 {
			return nil
		}
		return []FloatPoint{{Time: r.curr.Time, Value: value}}
	}
	return nil
}

// FloatDifferenceReducer calculates the derivative of the aggregated points.
type FloatDifferenceReducer struct {
	prev FloatPoint
	curr FloatPoint
}

// NewFloatDifferenceReducer creates a new FloatDifferenceReducer.
func NewFloatDifferenceReducer() *FloatDifferenceReducer {
	return &FloatDifferenceReducer{
		prev: FloatPoint{Nil: true},
		curr: FloatPoint{Nil: true},
	}
}

// AggregateFloat aggregates a point into the reducer and updates the current window.
func (r *FloatDifferenceReducer) AggregateFloat(p *FloatPoint) {
	r.prev = r.curr
	r.curr = *p
}

// Emit emits the difference of the reducer at the current point.
func (r *FloatDifferenceReducer) Emit() []FloatPoint {
	if !r.prev.Nil {
		// Calculate the difference of successive points.
		value := r.curr.Value - r.prev.Value
		return []FloatPoint{{Time: r.curr.Time, Value: value}}
	}
	return nil
}

// IntegerDifferenceReducer calculates the derivative of the aggregated points.
type IntegerDifferenceReducer struct {
	prev IntegerPoint
	curr IntegerPoint
}

// NewIntegerDifferenceReducer creates a new IntegerDifferenceReducer.
func NewIntegerDifferenceReducer() *IntegerDifferenceReducer {
	return &IntegerDifferenceReducer{
		prev: IntegerPoint{Nil: true},
		curr: IntegerPoint{Nil: true},
	}
}

// AggregateInteger aggregates a point into the reducer and updates the current window.
func (r *IntegerDifferenceReducer) AggregateInteger(p *IntegerPoint) {
	r.prev = r.curr
	r.curr = *p
}

// Emit emits the difference of the reducer at the current point.
func (r *IntegerDifferenceReducer) Emit() []IntegerPoint {
	if !r.prev.Nil {
		// Calculate the difference of successive points.
		value := r.curr.Value - r.prev.Value
		return []IntegerPoint{{Time: r.curr.Time, Value: value}}
	}
	return nil
}

// FloatMovingAverageReducer calculates the moving average of the aggregated points.
type FloatMovingAverageReducer struct {
	pos  int
	sum  float64
	time int64
	buf  []float64
}

// NewFloatMovingAverageReducer creates a new FloatMovingAverageReducer.
func NewFloatMovingAverageReducer(n int) *FloatMovingAverageReducer {
	return &FloatMovingAverageReducer{
		buf: make([]float64, 0, n),
	}
}

// AggregateFloat aggregates a point into the reducer and updates the current window.
func (r *FloatMovingAverageReducer) AggregateFloat(p *FloatPoint) {
	if len(r.buf) != cap(r.buf) {
		r.buf = append(r.buf, p.Value)
	} else {
		r.sum -= r.buf[r.pos]
		r.buf[r.pos] = p.Value
	}
	r.sum += p.Value
	r.time = p.Time
	r.pos++
	if r.pos >= cap(r.buf) {
		r.pos = 0
	}
}

// Emit emits the moving average of the current window. Emit should be called
// after every call to AggregateFloat and it will produce one point if there
// is enough data to fill a window, otherwise it will produce zero points.
func (r *FloatMovingAverageReducer) Emit() []FloatPoint {
	if len(r.buf) != cap(r.buf) {
		return []FloatPoint{}
	}
	return []FloatPoint{
		{
			Value:      r.sum / float64(len(r.buf)),
			Time:       r.time,
			Aggregated: uint32(len(r.buf)),
		},
	}
}

// IntegerMovingAverageReducer calculates the moving average of the aggregated points.
type IntegerMovingAverageReducer struct {
	pos  int
	sum  int64
	time int64
	buf  []int64
}

// NewIntegerMovingAverageReducer creates a new IntegerMovingAverageReducer.
func NewIntegerMovingAverageReducer(n int) *IntegerMovingAverageReducer {
	return &IntegerMovingAverageReducer{
		buf: make([]int64, 0, n),
	}
}

// AggregateInteger aggregates a point into the reducer and updates the current window.
func (r *IntegerMovingAverageReducer) AggregateInteger(p *IntegerPoint) {
	if len(r.buf) != cap(r.buf) {
		r.buf = append(r.buf, p.Value)
	} else {
		r.sum -= r.buf[r.pos]
		r.buf[r.pos] = p.Value
	}
	r.sum += p.Value
	r.time = p.Time
	r.pos++
	if r.pos >= cap(r.buf) {
		r.pos = 0
	}
}

// Emit emits the moving average of the current window. Emit should be called
// after every call to AggregateInteger and it will produce one point if there
// is enough data to fill a window, otherwise it will produce zero points.
func (r *IntegerMovingAverageReducer) Emit() []FloatPoint {
	if len(r.buf) != cap(r.buf) {
		return []FloatPoint{}
	}
	return []FloatPoint{
		{
			Value:      float64(r.sum) / float64(len(r.buf)),
			Time:       r.time,
			Aggregated: uint32(len(r.buf)),
		},
	}
}