// Copyright 2018 TiKV Project Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package movingaverage

import (
	"math"
	"math/rand"
	"testing"
	"time"

	"github.com/stretchr/testify/require"
)

func addRandData(ma MovingAvg, n int, mx float64) {
	r := rand.New(rand.NewSource(time.Now().UnixNano()))
	for range n {
		ma.Add(r.Float64() * mx)
	}
}

// checkReset checks the Reset works properly.
// emptyValue is the moving average of empty data set.
func checkReset(re *require.Assertions, ma MovingAvg, emptyValue float64) {
	addRandData(ma, 100, 1000)
	ma.Reset()
	re.Equal(emptyValue, ma.Get())
}

// checkAddGet checks Add works properly.
func checkAdd(re *require.Assertions, ma MovingAvg, data []float64, expected []float64) {
	re.Len(data, len(expected))
	for i, x := range data {
		ma.Add(x)
		re.Equal(x, ma.GetInstantaneous())
		re.LessOrEqual(math.Abs(ma.Get()-expected[i]), 1e-7)
	}
}

// checkSet checks Set = Reset + Add
func checkSet(re *require.Assertions, ma MovingAvg, data []float64, expected []float64) {
	re.Len(data, len(expected))

	// Reset + Add
	addRandData(ma, 100, 1000)
	ma.Reset()
	checkAdd(re, ma, data, expected)

	// Set
	addRandData(ma, 100, 1000)
	ma.Set(data[0])
	re.Equal(expected[0], ma.Get())
	checkAdd(re, ma, data[1:], expected[1:])
}

// checkInstantaneous checks GetInstantaneous
func checkInstantaneous(re *require.Assertions, ma MovingAvg) {
	value := 100.000000
	ma.Add(value)
	re.Equal(value, ma.GetInstantaneous())
}

func TestMedianFilter(t *testing.T) {
	re := require.New(t)
	var empty float64 = 0
	data := []float64{2, 4, 2, 800, 600, 6, 3}
	expected := []float64{2, 3, 2, 3, 4, 6, 6}

	mf := NewMedianFilter(5)
	re.Equal(empty, mf.Get())

	checkReset(re, mf, empty)
	checkAdd(re, mf, data, expected)
	checkSet(re, mf, data, expected)
}

type testCase struct {
	ma       MovingAvg
	expected []float64
}

func TestMovingAvg(t *testing.T) {
	re := require.New(t)
	var empty float64 = 0
	data := []float64{1, 1, 1, 1, 5, 1, 1, 1}
	testCases := []testCase{{
		ma:       NewEMA(0.9),
		expected: []float64{1.000000, 1.000000, 1.000000, 1.000000, 4.600000, 1.360000, 1.036000, 1.003600},
	}, {
		ma:       NewWMA(5),
		expected: []float64{1.00000000, 1.00000000, 1.00000000, 1.00000000, 2.33333333, 2.06666667, 1.80000000, 1.533333333},
	}, {
		ma:       NewHMA(5),
		expected: []float64{1.0000000, 1.0000000, 1.0000000, 1.0000000, 3.6666667, 3.4000000, 1.0000000, 0.3777778},
	}, {
		ma:       NewMedianFilter(5),
		expected: []float64{1.000000, 1.000000, 1.000000, 1.000000, 1.000000, 1.000000, 1.000000, 1.000000},
	}, {
		ma:       NewMaxFilter(5),
		expected: []float64{1.000000, 1.000000, 1.000000, 1.000000, 5.000000, 5.000000, 5.000000, 5.000000},
	},
	}
	for _, testCase := range testCases {
		re.Equal(empty, testCase.ma.Get())
		checkReset(re, testCase.ma, empty)
		checkAdd(re, testCase.ma, data, testCase.expected)
		checkSet(re, testCase.ma, data, testCase.expected)
		checkInstantaneous(re, testCase.ma)
	}
}