// Licensed to the LF AI & Data foundation under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you 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 storage

import (
	"fmt"
	"io"
	"math"
	"testing"

	"github.com/apache/arrow/go/v17/arrow"
	"github.com/apache/arrow/go/v17/arrow/array"
	"github.com/apache/arrow/go/v17/arrow/memory"
	"github.com/bytedance/mockey"
	"github.com/stretchr/testify/assert"

	"github.com/milvus-io/milvus-proto/go-api/v3/schemapb"
	"github.com/milvus-io/milvus/pkg/v3/common"
)

type oneShotRecordReader struct {
	rec  Record
	done bool
}

func (r *oneShotRecordReader) Next() (Record, error) {
	if r.done {
		return nil, io.EOF
	}
	r.done = true
	return r.rec, nil
}

func (r *oneShotRecordReader) Close() error {
	return nil
}

func TestRadixSortByInt64(t *testing.T) {
	t.Run("edge values across records", func(t *testing.T) {
		// Keys laid out across 3 records, mixing negatives, zero, duplicates and
		// the int64 bounds to exercise the sign-bit flip and every byte position.
		keys := [][]int64{
			{5, math.MaxInt64, -1},
			{0, math.MinInt64, -1},
			{42, 5},
		}
		var indices []rowIndex
		for ri := range keys {
			for i := range keys[ri] {
				indices = append(indices, rowIndex{int32(ri), int32(i)})
			}
		}

		radixSortByInt64(indices, keys)

		got := make([]int64, len(indices))
		for k, idx := range indices {
			got[k] = keys[idx.ri][idx.i]
		}
		assert.Equal(t, []int64{math.MinInt64, -1, -1, 0, 5, 5, 42, math.MaxInt64}, got)
	})

	t.Run("stable for equal keys", func(t *testing.T) {
		// Three rows share key 7 ({0,0},{1,0},{1,1} in input order); a stable sort
		// must keep that relative order among the duplicates.
		keys := [][]int64{
			{7, 3},
			{7, 7, 1},
		}
		indices := []rowIndex{{0, 0}, {0, 1}, {1, 0}, {1, 1}, {1, 2}}

		radixSortByInt64(indices, keys)

		assert.Equal(t, []rowIndex{{1, 2}, {0, 1}, {0, 0}, {1, 0}, {1, 1}}, indices)
	})

	t.Run("small inputs are no-ops", func(t *testing.T) {
		single := []rowIndex{{0, 0}}
		radixSortByInt64(single, [][]int64{{99}})
		assert.Equal(t, []rowIndex{{0, 0}}, single)

		assert.NotPanics(t, func() { radixSortByInt64(nil, nil) })
	})
}

func TestSort(t *testing.T) {
	const batchSize = 64 * 1024 * 1024

	getReaders := func() []RecordReader {
		blobs, err := generateTestDataWithSeed(10, 3)
		assert.NoError(t, err)
		reader10 := newIterativeCompositeBinlogRecordReader(generateTestSchema(), nil, MakeBlobsReader(blobs))
		blobs, err = generateTestDataWithSeed(20, 3)
		assert.NoError(t, err)
		reader20 := newIterativeCompositeBinlogRecordReader(generateTestSchema(), nil, MakeBlobsReader(blobs))
		rr := []RecordReader{reader20, reader10}
		return rr
	}

	lastPK := int64(-1)
	rw := &MockRecordWriter{
		writefn: func(r Record) error {
			pk := r.Column(common.RowIDField).(*array.Int64).Value(0)
			assert.Greater(t, pk, lastPK)
			lastPK = pk
			return nil
		},

		closefn: func() error {
			lastPK = int64(-1)
			return nil
		},
	}

	t.Run("sort", func(t *testing.T) {
		gotNumRows, timings, err := Sort(batchSize, generateTestSchema(), getReaders(), rw, func(r Record, ri, i int) bool {
			return true
		}, []int64{common.RowIDField})
		assert.NoError(t, err)
		assert.Equal(t, 6, gotNumRows)
		assert.NotNil(t, timings)
		assert.Equal(t, 6, timings.NumRows)
		assert.Greater(t, timings.NumBatches, 0)
		assert.GreaterOrEqual(t, timings.ReadCost.Nanoseconds(), int64(0))
		assert.GreaterOrEqual(t, timings.SortCost.Nanoseconds(), int64(0))
		assert.GreaterOrEqual(t, timings.WriteCost.Nanoseconds(), int64(0))
		err = rw.Close()
		assert.NoError(t, err)
	})

	t.Run("sort with predicate", func(t *testing.T) {
		gotNumRows, timings, err := Sort(batchSize, generateTestSchema(), getReaders(), rw, func(r Record, ri, i int) bool {
			pk := r.Column(common.RowIDField).(*array.Int64).Value(i)
			return pk >= 20
		}, []int64{common.RowIDField})
		assert.NoError(t, err)
		assert.Equal(t, 3, gotNumRows)
		assert.NotNil(t, timings)
		assert.Equal(t, 3, timings.NumRows)
		err = rw.Close()
		assert.NoError(t, err)
	})

	t.Run("sort empty readers", func(t *testing.T) {
		gotNumRows, timings, err := Sort(batchSize, generateTestSchema(), []RecordReader{}, rw, func(r Record, ri, i int) bool {
			return true
		}, []int64{common.RowIDField})
		assert.NoError(t, err)
		assert.Equal(t, 0, gotNumRows)
		assert.NotNil(t, timings)
		assert.GreaterOrEqual(t, timings.ReadCost.Nanoseconds(), int64(0))
	})

	t.Run("sort with reader error", func(t *testing.T) {
		mockNext := mockey.Mock((*IterativeRecordReader).Next).Return(nil, fmt.Errorf("read error")).Build()
		defer mockNext.UnPatch()
		errReader := &IterativeRecordReader{}
		gotNumRows, timings, err := Sort(batchSize, generateTestSchema(), []RecordReader{errReader}, rw, func(r Record, ri, i int) bool {
			return true
		}, []int64{common.RowIDField})
		assert.Error(t, err)
		assert.Equal(t, 0, gotNumRows)
		assert.Nil(t, timings)
	})

	t.Run("sort with batch write error", func(t *testing.T) {
		errWriter := &MockRecordWriter{
			writefn: func(r Record) error {
				return fmt.Errorf("write error")
			},
			closefn: func() error {
				return nil
			},
		}
		// Use small batchSize to trigger mid-loop batch write error (line 157)
		gotNumRows, timings, err := Sort(1, generateTestSchema(), getReaders(), errWriter, func(r Record, ri, i int) bool {
			return true
		}, []int64{common.RowIDField})
		assert.Error(t, err)
		assert.Equal(t, 0, gotNumRows)
		assert.Nil(t, timings)
	})

	t.Run("sort with final write error", func(t *testing.T) {
		errWriter := &MockRecordWriter{
			writefn: func(r Record) error {
				// Fail on the first write (which is the final batch write when batchSize is large)
				return fmt.Errorf("write error")
			},
			closefn: func() error {
				return nil
			},
		}
		// Use large batchSize so data doesn't trigger mid-loop write, only the final batch write (line 164)
		gotNumRows, timings, err := Sort(batchSize, generateTestSchema(), getReaders(), errWriter, func(r Record, ri, i int) bool {
			return true
		}, []int64{common.RowIDField})
		assert.Error(t, err)
		assert.Equal(t, 0, gotNumRows)
		assert.Nil(t, timings)
	})
}

func TestMergeSort(t *testing.T) {
	getReaders := func() []RecordReader {
		blobs, err := generateTestDataWithSeed(1000, 5000)
		assert.NoError(t, err)
		reader10 := newIterativeCompositeBinlogRecordReader(generateTestSchema(), nil, MakeBlobsReader(blobs))
		blobs, err = generateTestDataWithSeed(4000, 5000)
		assert.NoError(t, err)
		reader20 := newIterativeCompositeBinlogRecordReader(generateTestSchema(), nil, MakeBlobsReader(blobs))
		rr := []RecordReader{reader20, reader10}
		return rr
	}

	lastPK := int64(-1)
	rw := &MockRecordWriter{
		writefn: func(r Record) error {
			pk := r.Column(common.RowIDField).(*array.Int64).Value(0)
			assert.Greater(t, pk, lastPK)
			lastPK = pk
			return nil
		},

		closefn: func() error {
			lastPK = int64(-1)
			return nil
		},
	}

	const batchSize = 64 * 1024 * 1024

	t.Run("merge sort", func(t *testing.T) {
		gotNumRows, err := MergeSort(batchSize, generateTestSchema(), getReaders(), rw, func(r Record, ri, i int) bool {
			return true
		}, []int64{common.RowIDField})
		assert.NoError(t, err)
		assert.Equal(t, 10000, gotNumRows)
		err = rw.Close()
		assert.NoError(t, err)
	})

	t.Run("merge sort with predicate", func(t *testing.T) {
		gotNumRows, err := MergeSort(batchSize, generateTestSchema(), getReaders(), rw, func(r Record, ri, i int) bool {
			pk := r.Column(common.RowIDField).(*array.Int64).Value(i)
			// cover a single record (1024 rows) that is deleted, or the last data in the record is deleted
			// index 1023 is deleted. records (1024-2048) and (5000-6023) are all deleted
			return pk < 2000 || (pk >= 3050 && pk < 5000) || pk >= 7000
		}, []int64{common.RowIDField})
		assert.NoError(t, err)
		assert.Equal(t, 5950, gotNumRows)
		err = rw.Close()
		assert.NoError(t, err)
	})
}

func TestMergeSortReturnsRecordBuilderAppendError(t *testing.T) {
	textBuilder := array.NewStringBuilder(memory.DefaultAllocator)
	textBuilder.Append("not-a-lob-ref")
	textColumn := textBuilder.NewArray()
	defer textColumn.Release()
	textBuilder.Release()

	pkBuilder := array.NewInt64Builder(memory.DefaultAllocator)
	pkBuilder.Append(1)
	pkColumn := pkBuilder.NewArray()
	defer pkColumn.Release()
	pkBuilder.Release()

	rec := NewSimpleArrowRecord(array.NewRecord(
		arrow.NewSchema([]arrow.Field{
			{Name: "pk", Type: arrow.PrimitiveTypes.Int64},
			{Name: "text", Type: arrow.BinaryTypes.String},
		}, nil),
		[]arrow.Array{pkColumn, textColumn},
		1,
	), map[FieldID]int{100: 0, 101: 1})
	defer rec.Release()

	reader := &oneShotRecordReader{rec: rec}
	writer := &MockRecordWriter{
		writefn: func(r Record) error {
			return nil
		},
		closefn: func() error {
			return nil
		},
	}
	schema := &schemapb.CollectionSchema{Fields: []*schemapb.FieldSchema{
		{FieldID: 100, Name: "pk", DataType: schemapb.DataType_Int64, IsPrimaryKey: true},
		{FieldID: 101, Name: "text", DataType: schemapb.DataType_Text},
	}}

	_, err := MergeSort(1024, schema, []RecordReader{reader}, writer, func(r Record, ri, i int) bool {
		return true
	}, []int64{100})
	assert.ErrorContains(t, err, "failed to append value")
}

// Benchmark sort
func BenchmarkSort(b *testing.B) {
	batch := 500000
	blobs, err := generateTestDataWithSeed(batch, batch)
	assert.NoError(b, err)
	reader10 := newIterativeCompositeBinlogRecordReader(generateTestSchema(), nil, MakeBlobsReader(blobs))
	blobs, err = generateTestDataWithSeed(batch*2+1, batch)
	assert.NoError(b, err)
	reader20 := newIterativeCompositeBinlogRecordReader(generateTestSchema(), nil, MakeBlobsReader(blobs))
	rr := []RecordReader{reader20, reader10}

	rw := &MockRecordWriter{
		writefn: func(r Record) error {
			return nil
		},

		closefn: func() error {
			return nil
		},
	}

	const batchSize = 64 * 1024 * 1024
	b.ResetTimer()

	b.Run("sort", func(b *testing.B) {
		for i := 0; i < b.N; i++ {
			Sort(batchSize, generateTestSchema(), rr, rw, func(r Record, ri, i int) bool {
				return true
			}, []int64{common.RowIDField})
		}
	})
}

func TestSortByMoreThanOneField(t *testing.T) {
	const batchSize = 10000
	sortByFieldIDs := []int64{common.RowIDField, common.TimeStampField}

	blobs, err := generateTestDataWithSeed(10, batchSize)
	assert.NoError(t, err)
	reader10 := newIterativeCompositeBinlogRecordReader(generateTestSchema(), nil, MakeBlobsReader(blobs))
	blobs, err = generateTestDataWithSeed(20, batchSize)
	assert.NoError(t, err)
	reader20 := newIterativeCompositeBinlogRecordReader(generateTestSchema(), nil, MakeBlobsReader(blobs))
	rr := []RecordReader{reader20, reader10}

	lastPK := int64(-1)
	lastTS := int64(-1)
	rw := &MockRecordWriter{
		writefn: func(r Record) error {
			pk := r.Column(common.RowIDField).(*array.Int64).Value(0)
			ts := r.Column(common.TimeStampField).(*array.Int64).Value(0)
			assert.True(t, pk > lastPK || (pk == lastPK && ts > lastTS))
			lastPK = pk
			return nil
		},

		closefn: func() error {
			lastPK = int64(-1)
			return nil
		},
	}
	gotNumRows, _, err := Sort(batchSize, generateTestSchema(), rr, rw, func(r Record, ri, i int) bool {
		return true
	}, sortByFieldIDs)
	assert.NoError(t, err)
	assert.Equal(t, batchSize*2, gotNumRows)
	assert.NoError(t, rw.Close())
}