/**
 * Unit tests for ReedSolomon
 *
 * Copyright 2015, Klaus Post
 * Copyright 2015, Backblaze, Inc.  All rights reserved.
 */

package reedsolomon

import (
	"fmt"
	"math/rand"
	"testing"
)

func TestEncoding(t *testing.T) {
	perShard := 50000
	r, err := New(10, 3)
	if err != nil {
		t.Fatal(err)
	}
	shards := make([][]byte, 13)
	for s := range shards {
		shards[s] = make([]byte, perShard)
	}

	rand.Seed(0)
	for s := 0; s < 13; s++ {
		fillRandom(shards[s])
	}

	err = r.Encode(shards)
	if err != nil {
		t.Fatal(err)
	}
	ok, err := r.Verify(shards)
	if err != nil {
		t.Fatal(err)
	}
	if !ok {
		t.Fatal("Verification failed")
	}
}

func TestReconstruct(t *testing.T) {
	perShard := 50000
	r, err := New(10, 3)
	if err != nil {
		t.Fatal(err)
	}
	shards := make([][]byte, 13)
	for s := range shards {
		shards[s] = make([]byte, perShard)
	}

	rand.Seed(0)
	for s := 0; s < 13; s++ {
		fillRandom(shards[s])
	}

	err = r.Encode(shards)
	if err != nil {
		t.Fatal(err)
	}

	shards[0] = nil
	shards[7] = nil
	shards[11] = nil

	err = r.Reconstruct(shards)
	if err != nil {
		t.Fatal(err)
	}

	ok, err := r.Verify(shards)
	if err != nil {
		t.Fatal(err)
	}
	if !ok {
		t.Fatal("Verification failed")
	}
}

func TestVerify(t *testing.T) {
	perShard := 33333
	r, err := New(10, 4)
	if err != nil {
		t.Fatal(err)
	}
	shards := make([][]byte, 14)
	for s := range shards {
		shards[s] = make([]byte, perShard)
	}

	rand.Seed(0)
	for s := 0; s < 10; s++ {
		fillRandom(shards[s])
	}

	err = r.Encode(shards)
	if err != nil {
		t.Fatal(err)
	}
	ok, err := r.Verify(shards)
	if err != nil {
		t.Fatal(err)
	}
	if !ok {
		t.Fatal("Verification failed")
	}
	// Put in random data. Verification should fail
	fillRandom(shards[10])
	ok, err = r.Verify(shards)
	if err != nil {
		t.Fatal(err)
	}
	if ok {
		t.Fatal("Verification did not fail")
	}
	// Re-encode
	err = r.Encode(shards)
	if err != nil {
		t.Fatal(err)
	}
	// Fill a data segment with random data
	fillRandom(shards[0])
	ok, err = r.Verify(shards)
	if err != nil {
		t.Fatal(err)
	}
	if ok {
		t.Fatal("Verification did not fail")
	}
}

func TestOneEncode(t *testing.T) {
	codec, err := New(5, 5)
	if err != nil {
		t.Fatal(err)
	}
	shards := make([][]byte, 10)
	shards[0] = []byte{0, 1}
	shards[1] = []byte{4, 5}
	shards[2] = []byte{2, 3}
	shards[3] = []byte{6, 7}
	shards[4] = []byte{8, 9}
	shards[5] = []byte{0, 0}
	shards[6] = []byte{0, 0}
	shards[7] = []byte{0, 0}
	shards[8] = []byte{0, 0}
	shards[9] = []byte{0, 0}
	codec.Encode(shards)
	if shards[5][0] != 12 || shards[5][1] != 13 {
		t.Fatal("shard 5 mismatch")
	}
	if shards[6][0] != 10 || shards[6][1] != 11 {
		t.Fatal("shard 6 mismatch")
	}
	if shards[7][0] != 14 || shards[7][1] != 15 {
		t.Fatal("shard 7 mismatch")
	}
	if shards[8][0] != 90 || shards[8][1] != 91 {
		t.Fatal("shard 8 mismatch")
	}
	if shards[9][0] != 94 || shards[9][1] != 95 {
		t.Fatal("shard 9 mismatch")
	}

	ok, err := codec.Verify(shards)
	if err != nil {
		t.Fatal(err)
	}
	if !ok {
		t.Fatal("did not verify")
	}
	shards[8][0]++
	ok, err = codec.Verify(shards)
	if err != nil {
		t.Fatal(err)
	}
	if ok {
		t.Fatal("verify did not fail as expected")
	}

}

func fillRandom(b []byte) {
	for i := range b {
		b[i] = byte(rand.Int() & 0xff)
	}
}

func benchmarkEncode(b *testing.B, dataShards, parityShards, shardSize int) {
	r, err := New(dataShards, parityShards)
	if err != nil {
		b.Fatal(err)
	}
	shards := make([][]byte, dataShards+parityShards)
	for s := range shards {
		shards[s] = make([]byte, shardSize)
	}

	rand.Seed(0)
	for s := 0; s < dataShards; s++ {
		fillRandom(shards[s])
	}

	b.SetBytes(int64(shardSize * dataShards))
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		err = r.Encode(shards)
		if err != nil {
			b.Fatal(err)
		}
	}
}

func BenchmarkEncode10x2x10000(b *testing.B) {
	benchmarkEncode(b, 10, 2, 10000)
}

func BenchmarkEncode100x20x10000(b *testing.B) {
	benchmarkEncode(b, 100, 20, 10000)
}

func BenchmarkEncode17x3x1M(b *testing.B) {
	benchmarkEncode(b, 17, 3, 1024*1024)
}

// Benchmark 10 data shards and 4 parity shards with 16MB each.
func BenchmarkEncode10x4x16M(b *testing.B) {
	benchmarkEncode(b, 10, 4, 16*1024*1024)
}

// Benchmark 5 data shards and 2 parity shards with 1MB each.
func BenchmarkEncode5x2x1M(b *testing.B) {
	benchmarkEncode(b, 5, 2, 1024*1024)
}

// Benchmark 1 data shards and 2 parity shards with 1MB each.
func BenchmarkEncode10x2x1M(b *testing.B) {
	benchmarkEncode(b, 10, 2, 1024*1024)
}

// Benchmark 10 data shards and 4 parity shards with 1MB each.
func BenchmarkEncode10x4x1M(b *testing.B) {
	benchmarkEncode(b, 10, 4, 1024*1024)
}

// Benchmark 50 data shards and 20 parity shards with 1MB each.
func BenchmarkEncode50x20x1M(b *testing.B) {
	benchmarkEncode(b, 50, 20, 1024*1024)
}

// Benchmark 17 data shards and 3 parity shards with 16MB each.
func BenchmarkEncode17x3x16M(b *testing.B) {
	benchmarkEncode(b, 17, 3, 16*1024*1024)
}

func benchmarkVerify(b *testing.B, dataShards, parityShards, shardSize int) {
	r, err := New(dataShards, parityShards)
	if err != nil {
		b.Fatal(err)
	}
	shards := make([][]byte, parityShards+dataShards)
	for s := range shards {
		shards[s] = make([]byte, shardSize)
	}

	rand.Seed(0)
	for s := 0; s < dataShards; s++ {
		fillRandom(shards[s])
	}
	err = r.Encode(shards)
	if err != nil {
		b.Fatal(err)
	}

	b.SetBytes(int64(shardSize * dataShards))
	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		_, err = r.Verify(shards)
		if err != nil {
			b.Fatal(err)
		}
	}
}

// Benchmark 10 data slices with 2 parity slices holding 10000 bytes each
func BenchmarkVerify10x2x10000(b *testing.B) {
	benchmarkVerify(b, 10, 2, 10000)
}

// Benchmark 50 data slices with 5 parity slices holding 100000 bytes each
func BenchmarkVerify50x5x50000(b *testing.B) {
	benchmarkVerify(b, 50, 5, 100000)
}

// Benchmark 10 data slices with 2 parity slices holding 1MB bytes each
func BenchmarkVerify10x2x1M(b *testing.B) {
	benchmarkVerify(b, 10, 2, 1024*1024)
}

// Benchmark 5 data slices with 2 parity slices holding 1MB bytes each
func BenchmarkVerify5x2x1M(b *testing.B) {
	benchmarkVerify(b, 5, 2, 1024*1024)
}

// Benchmark 10 data slices with 4 parity slices holding 1MB bytes each
func BenchmarkVerify10x4x1M(b *testing.B) {
	benchmarkVerify(b, 10, 4, 1024*1024)
}

// Benchmark 5 data slices with 2 parity slices holding 1MB bytes each
func BenchmarkVerify50x20x1M(b *testing.B) {
	benchmarkVerify(b, 50, 20, 1024*1024)
}

// Benchmark 10 data slices with 4 parity slices holding 16MB bytes each
func BenchmarkVerify10x4x16M(b *testing.B) {
	benchmarkVerify(b, 10, 4, 16*1024*1024)
}

// Simple example of how to use all functions of the Encoder.
// Note that all error checks have been removed to keep it short.
func ExampleEncoder() {
	// Create some sample data
	var data = make([]byte, 250000)
	fillRandom(data)

	// Create an encoder with 17 data and 3 parity slices.
	enc, _ := New(17, 3)

	// Split the data into shards
	shards, _ := enc.Split(data)

	// Encode the parity set
	_ = enc.Encode(shards)

	// Verify the parity set
	ok, _ := enc.Verify(shards)
	if ok {
		fmt.Println("ok")
	}

	// Delete two shards
	shards[10], shards[11] = nil, nil

	// Reconstruct the shards
	_ = enc.Reconstruct(shards)

	// Verify the data set
	ok, _ = enc.Verify(shards)
	if ok {
		fmt.Println("ok")
	}
	// Output: ok
	// ok
}