// Copyright (c) 2023 Klaus Post. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package s2

import (
	"bytes"
	"encoding/binary"
	"path/filepath"
	"testing"

	"github.com/klauspost/compress/internal/lz4ref"
	"github.com/klauspost/compress/internal/snapref"
)

func TestLZ4sConverter_ConvertBlock(t *testing.T) {
	for _, tf := range testFiles {
		t.Run(tf.label, func(t *testing.T) {
			if err := downloadBenchmarkFiles(t, tf.filename); err != nil {
				t.Fatalf("failed to download testdata: %s", err)
			}

			bDir := filepath.FromSlash(*benchdataDir)
			data := readFile(t, filepath.Join(bDir, tf.filename))
			if n := tf.sizeLimit; 0 < n && n < len(data) {
				data = data[:n]
			}

			lz4Data := make([]byte, lz4ref.CompressBlockBound(len(data)))
			n, err := lz4ref.CompressBlockLZ4s(data, lz4Data)
			if err != nil {
				t.Fatal(err)
			}
			if n == 0 {
				t.Skip("incompressible")
				return
			}
			t.Log("input size:", len(data))
			t.Log("lz4 size:", n)
			lz4Data = lz4Data[:n]
			s2Dst := make([]byte, binary.MaxVarintLen32, MaxEncodedLen(len(data)))
			s2Dst = s2Dst[:binary.PutUvarint(s2Dst, uint64(len(data)))]
			hdr := len(s2Dst)

			conv := LZ4sConverter{}

			szS := 0
			out, n, err := conv.ConvertBlockSnappy(s2Dst, lz4Data)
			if err != nil {
				t.Fatal(err)
			}
			if n != len(data) {
				t.Fatalf("length mismatch: want %d, got %d", len(data), n)
			}
			szS = len(out) - hdr
			t.Log("lz4->snappy size:", szS)

			decom, err := snapref.Decode(nil, out)
			if err != nil {
				t.Fatal(err)
			}
			if !bytes.Equal(decom, data) {
				t.Errorf("output mismatch")
			}

			sz := 0
			out, n, err = conv.ConvertBlock(s2Dst, lz4Data)
			if err != nil {
				t.Fatal(err)
			}
			if n != len(data) {
				t.Fatalf("length mismatch: want %d, got %d", len(data), n)
			}
			sz = len(out) - hdr
			t.Log("lz4->s2 size:", sz)

			decom, err = Decode(nil, out)
			if err != nil {
				t.Fatal(err)
			}
			if !bytes.Equal(decom, data) {
				t.Errorf("output mismatch")
			}

			out2 := Encode(s2Dst[:0], data)
			sz2 := len(out2) - hdr
			t.Log("s2 (default) size:", sz2)

			out2 = EncodeBetter(s2Dst[:0], data)
			sz3 := len(out2) - hdr
			t.Log("s2 (better) size:", sz3)

			t.Log("lz4 -> s2 bytes saved:", len(lz4Data)-sz)
			t.Log("lz4 -> snappy bytes saved:", len(lz4Data)-szS)
			t.Log("data -> s2 (default) bytes saved:", len(lz4Data)-sz2)
			t.Log("data -> s2 (better) bytes saved:", len(lz4Data)-sz3)
			t.Log("direct data -> s2 (default) compared to converted from lz4:", sz-sz2)
			t.Log("direct data -> s2 (better) compared to converted from lz4:", sz-sz3)
		})
	}
}