// Copyright 2018 PingCAP, Inc.
//
// 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,
// See the License for the specific language governing permissions and
// limitations under the License.

package statistics

import (
	"bytes"

	. "github.com/pingcap/check"
	"github.com/pingcap/parser/mysql"
	"github.com/pingcap/tidb/types"
	"github.com/pingcap/tidb/util/codec"
)

var _ = Suite(&testFeedbackSuite{})

type testFeedbackSuite struct {
}

func newFeedback(lower, upper, count int64) Feedback {
	low, upp := types.NewIntDatum(lower), types.NewIntDatum(upper)
	return Feedback{&low, &upp, count, 0}
}

func genFeedbacks(lower, upper int64) []Feedback {
	var feedbacks []Feedback
	for i := lower; i < upper; i++ {
		feedbacks = append(feedbacks, newFeedback(i, upper, upper-i+1))
	}
	return feedbacks
}

func appendBucket(h *Histogram, l, r int64) {
	lower, upper := types.NewIntDatum(l), types.NewIntDatum(r)
	h.AppendBucket(&lower, &upper, 0, 0)
}

func genHistogram() *Histogram {
	h := NewHistogram(0, 0, 0, 0, types.NewFieldType(mysql.TypeLong), 5, 0)
	appendBucket(h, 1, 1)
	appendBucket(h, 2, 3)
	appendBucket(h, 5, 7)
	appendBucket(h, 10, 20)
	appendBucket(h, 30, 50)
	return h
}

func (s *testFeedbackSuite) TestUpdateHistogram(c *C) {
	feedbacks := []Feedback{
		newFeedback(0, 1, 10000),
		newFeedback(1, 2, 1),
		newFeedback(2, 3, 3),
		newFeedback(4, 5, 2),
		newFeedback(5, 7, 4),
	}
	feedbacks = append(feedbacks, genFeedbacks(8, 20)...)
	feedbacks = append(feedbacks, genFeedbacks(21, 60)...)

	q := NewQueryFeedback(0, genHistogram(), 0, false)
	q.Feedback = feedbacks
	originBucketCount := defaultBucketCount
	defaultBucketCount = 7
	defer func() { defaultBucketCount = originBucketCount }()
	c.Assert(UpdateHistogram(q.Hist, q).ToString(0), Equals,
		"column:0 ndv:10058 totColSize:0\n"+
			"num: 10000 lower_bound: 0 upper_bound: 1 repeats: 0\n"+
			"num: 9 lower_bound: 2 upper_bound: 7 repeats: 0\n"+
			"num: 11 lower_bound: 8 upper_bound: 19 repeats: 0\n"+
			"num: 0 lower_bound: 20 upper_bound: 20 repeats: 0\n"+
			"num: 18 lower_bound: 21 upper_bound: 39 repeats: 0\n"+
			"num: 18 lower_bound: 40 upper_bound: 58 repeats: 0\n"+
			"num: 2 lower_bound: 59 upper_bound: 60 repeats: 0")
}

func (s *testFeedbackSuite) TestSplitBuckets(c *C) {
	// test bucket split
	feedbacks := []Feedback{newFeedback(0, 1, 1)}
	for i := 0; i < 100; i++ {
		feedbacks = append(feedbacks, newFeedback(10, 15, 5))
	}
	q := NewQueryFeedback(0, genHistogram(), 0, false)
	q.Feedback = feedbacks
	buckets, isNewBuckets, totalCount := splitBuckets(q.Hist, q)
	c.Assert(buildNewHistogram(q.Hist, buckets).ToString(0), Equals,
		"column:0 ndv:0 totColSize:0\n"+
			"num: 1 lower_bound: 0 upper_bound: 1 repeats: 0\n"+
			"num: 0 lower_bound: 2 upper_bound: 3 repeats: 0\n"+
			"num: 0 lower_bound: 5 upper_bound: 7 repeats: 0\n"+
			"num: 5 lower_bound: 10 upper_bound: 15 repeats: 0\n"+
			"num: 0 lower_bound: 16 upper_bound: 20 repeats: 0\n"+
			"num: 0 lower_bound: 30 upper_bound: 50 repeats: 0")
	c.Assert(isNewBuckets, DeepEquals, []bool{false, false, false, true, true, false})
	c.Assert(totalCount, Equals, int64(6))

	// test do not split if the bucket count is too small
	feedbacks = []Feedback{newFeedback(0, 1, 100000)}
	for i := 0; i < 100; i++ {
		feedbacks = append(feedbacks, newFeedback(10, 15, 1))
	}
	q = NewQueryFeedback(0, genHistogram(), 0, false)
	q.Feedback = feedbacks
	buckets, isNewBuckets, totalCount = splitBuckets(q.Hist, q)
	c.Assert(buildNewHistogram(q.Hist, buckets).ToString(0), Equals,
		"column:0 ndv:0 totColSize:0\n"+
			"num: 100000 lower_bound: 0 upper_bound: 1 repeats: 0\n"+
			"num: 0 lower_bound: 2 upper_bound: 3 repeats: 0\n"+
			"num: 0 lower_bound: 5 upper_bound: 7 repeats: 0\n"+
			"num: 1 lower_bound: 10 upper_bound: 15 repeats: 0\n"+
			"num: 0 lower_bound: 16 upper_bound: 20 repeats: 0\n"+
			"num: 0 lower_bound: 30 upper_bound: 50 repeats: 0")
	c.Assert(isNewBuckets, DeepEquals, []bool{false, false, false, true, true, false})
	c.Assert(totalCount, Equals, int64(100001))

	// test do not split if the result bucket count is too small
	h := NewHistogram(0, 0, 0, 0, types.NewFieldType(mysql.TypeLong), 5, 0)
	appendBucket(h, 0, 1000000)
	h.Buckets[0].Count = 1000000
	feedbacks = feedbacks[:0]
	for i := 0; i < 100; i++ {
		feedbacks = append(feedbacks, newFeedback(0, 10, 1))
	}
	q = NewQueryFeedback(0, h, 0, false)
	q.Feedback = feedbacks
	buckets, isNewBuckets, totalCount = splitBuckets(q.Hist, q)
	c.Assert(buildNewHistogram(q.Hist, buckets).ToString(0), Equals,
		"column:0 ndv:0 totColSize:0\n"+
			"num: 1000000 lower_bound: 0 upper_bound: 1000000 repeats: 0")
	c.Assert(isNewBuckets, DeepEquals, []bool{false})
	c.Assert(totalCount, Equals, int64(1000000))

	// test split even if the feedback range is too small
	h = NewHistogram(0, 0, 0, 0, types.NewFieldType(mysql.TypeLong), 5, 0)
	appendBucket(h, 0, 1000000)
	feedbacks = feedbacks[:0]
	for i := 0; i < 100; i++ {
		feedbacks = append(feedbacks, newFeedback(0, 10, 1))
	}
	q = NewQueryFeedback(0, h, 0, false)
	q.Feedback = feedbacks
	buckets, isNewBuckets, totalCount = splitBuckets(q.Hist, q)
	c.Assert(buildNewHistogram(q.Hist, buckets).ToString(0), Equals,
		"column:0 ndv:0 totColSize:0\n"+
			"num: 1 lower_bound: 0 upper_bound: 10 repeats: 0\n"+
			"num: 0 lower_bound: 11 upper_bound: 1000000 repeats: 0")
	c.Assert(isNewBuckets, DeepEquals, []bool{true, true})
	c.Assert(totalCount, Equals, int64(1))

	// test merge the non-overlapped feedbacks.
	h = NewHistogram(0, 0, 0, 0, types.NewFieldType(mysql.TypeLong), 5, 0)
	appendBucket(h, 0, 10000)
	feedbacks = feedbacks[:0]
	feedbacks = append(feedbacks, newFeedback(0, 4000, 4000))
	feedbacks = append(feedbacks, newFeedback(4001, 9999, 1000))
	q = NewQueryFeedback(0, h, 0, false)
	q.Feedback = feedbacks
	buckets, isNewBuckets, totalCount = splitBuckets(q.Hist, q)
	c.Assert(buildNewHistogram(q.Hist, buckets).ToString(0), Equals,
		"column:0 ndv:0 totColSize:0\n"+
			"num: 5001 lower_bound: 0 upper_bound: 10000 repeats: 0")
	c.Assert(isNewBuckets, DeepEquals, []bool{false})
	c.Assert(totalCount, Equals, int64(5001))
}

func (s *testFeedbackSuite) TestMergeBuckets(c *C) {
	originBucketCount := defaultBucketCount
	defer func() { defaultBucketCount = originBucketCount }()
	tests := []struct {
		points       []int64
		counts       []int64
		isNewBuckets []bool
		bucketCount  int
		result       string
	}{
		{
			points:       []int64{1, 2},
			counts:       []int64{1},
			isNewBuckets: []bool{false},
			bucketCount:  1,
			result:       "column:0 ndv:0 totColSize:0\nnum: 1 lower_bound: 1 upper_bound: 2 repeats: 0",
		},
		{
			points:       []int64{1, 2, 2, 3, 3, 4},
			counts:       []int64{100000, 1, 1},
			isNewBuckets: []bool{false, false, false},
			bucketCount:  2,
			result: "column:0 ndv:0 totColSize:0\n" +
				"num: 100000 lower_bound: 1 upper_bound: 2 repeats: 0\n" +
				"num: 2 lower_bound: 2 upper_bound: 4 repeats: 0",
		},
		// test do not Merge if the result bucket count is too large
		{
			points:       []int64{1, 2, 2, 3, 3, 4, 4, 5},
			counts:       []int64{1, 1, 100000, 100000},
			isNewBuckets: []bool{false, false, false, false},
			bucketCount:  3,
			result: "column:0 ndv:0 totColSize:0\n" +
				"num: 2 lower_bound: 1 upper_bound: 3 repeats: 0\n" +
				"num: 100000 lower_bound: 3 upper_bound: 4 repeats: 0\n" +
				"num: 100000 lower_bound: 4 upper_bound: 5 repeats: 0",
		},
	}
	for _, t := range tests {
		bkts := make([]bucket, 0, len(t.counts))
		totalCount := int64(0)
		for i := 0; i < len(t.counts); i++ {
			lower, upper := types.NewIntDatum(t.points[2*i]), types.NewIntDatum(t.points[2*i+1])
			bkts = append(bkts, bucket{&lower, &upper, t.counts[i], 0})
			totalCount += t.counts[i]
		}
		defaultBucketCount = t.bucketCount
		bkts = mergeBuckets(bkts, t.isNewBuckets, float64(totalCount))
		result := buildNewHistogram(&Histogram{Tp: types.NewFieldType(mysql.TypeLong)}, bkts).ToString(0)
		c.Assert(result, Equals, t.result)
	}
}

func encodeInt(v int64) *types.Datum {
	val := codec.EncodeInt(nil, v)
	d := types.NewBytesDatum(val)
	return &d
}

func (s *testFeedbackSuite) TestFeedbackEncoding(c *C) {
	hist := NewHistogram(0, 0, 0, 0, types.NewFieldType(mysql.TypeLong), 0, 0)
	q := &QueryFeedback{Hist: hist, Tp: PkType}
	q.Feedback = append(q.Feedback, Feedback{encodeInt(0), encodeInt(3), 1, 0})
	q.Feedback = append(q.Feedback, Feedback{encodeInt(0), encodeInt(5), 1, 0})
	val, err := EncodeFeedback(q)
	c.Assert(err, IsNil)
	rq := &QueryFeedback{}
	c.Assert(DecodeFeedback(val, rq, nil, hist.Tp), IsNil)
	for _, fb := range rq.Feedback {
		fb.Lower.SetBytes(codec.EncodeInt(nil, fb.Lower.GetInt64()))
		fb.Upper.SetBytes(codec.EncodeInt(nil, fb.Upper.GetInt64()))
	}
	c.Assert(q.Equal(rq), IsTrue)

	hist.Tp = types.NewFieldType(mysql.TypeBlob)
	q = &QueryFeedback{Hist: hist}
	q.Feedback = append(q.Feedback, Feedback{encodeInt(0), encodeInt(3), 1, 0})
	q.Feedback = append(q.Feedback, Feedback{encodeInt(0), encodeInt(1), 1, 0})
	val, err = EncodeFeedback(q)
	c.Assert(err, IsNil)
	rq = &QueryFeedback{}
	cms := NewCMSketch(4, 4)
	c.Assert(DecodeFeedback(val, rq, cms, hist.Tp), IsNil)
	c.Assert(cms.QueryBytes(codec.EncodeInt(nil, 0)), Equals, uint64(1))
	q.Feedback = q.Feedback[:1]
	c.Assert(q.Equal(rq), IsTrue)
}

// Equal tests if two query feedback equal, it is only used in test.
func (q *QueryFeedback) Equal(rq *QueryFeedback) bool {
	if len(q.Feedback) != len(rq.Feedback) {
		return false
	}
	for i, fb := range q.Feedback {
		rfb := rq.Feedback[i]
		if fb.Count != rfb.Count {
			return false
		}
		if fb.Lower.Kind() == types.KindInt64 {
			if fb.Lower.GetInt64() != rfb.Lower.GetInt64() {
				return false
			}
			if fb.Upper.GetInt64() != rfb.Upper.GetInt64() {
				return false
			}
		} else {
			if !bytes.Equal(fb.Lower.GetBytes(), rfb.Lower.GetBytes()) {
				return false
			}
			if !bytes.Equal(fb.Upper.GetBytes(), rfb.Upper.GetBytes()) {
				return false
			}
		}
	}
	return true
}
