package tz

import (
	"encoding/hex"
	"fmt"
	"io"
	"math/rand"
	"testing"

	"github.com/stretchr/testify/require"
	"golang.org/x/sys/cpu"
)

const benchDataSize = 100000

type arch struct {
	HasAVX  bool
	HasAVX2 bool
}

var backends = []struct {
	Name string
	arch
}{
	{"AVX", arch{true, false}},
	{"AVX2", arch{true, true}},
	{"Generic", arch{false, false}},
}

var testCases = []struct {
	input []byte
	hash  string
}{
	{
		[]byte{},
		"00000000000000000000000000000001000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001",
	},
	{
		[]byte{0},
		"00000000000000000000000000000151000000000000000000000000000000800000000000000000000000000000008000000000000000000000000000000051",
	},
	{
		[]byte{1, 2},
		"000000000000000000000000000139800000000000000000000000000000c0010000000000000000000000000000b98100000000000000000000000000007981",
	},
	{
		[]byte{2, 0, 1},
		"00000000000000000000000001f980d10000000000000000000000000139805100000000000000000000000000c001d100000000000000000000000000b98080",
	},
	{
		[]byte{3, 2, 1, 0},
		"0000000000000000000000015540398000000000000000000000000082a1a88100000000000000000000000082a1d10100000000000000000000000050006881",
	},
	{
		[]byte{0xFF, 0xFF, 0xFF, 0xFF, 0xFF},
		"0000000000000000000001bb00ba00ba000000000000000000000101010101010000000000000000000000ff00ff00ff0000000000000000000000ba01bb01bb",
	},
	{
		[]byte{0xAA, 0xAA, 0xAA, 0xAA, 0xAA, 0xAA},
		"000000000000000000016ad06ad16bd100000000000000000000ff00ff00ff0000000000000000000000808080808080000000000000000000006bd16bd06ad1",
	},
	{
		[]byte{0x55, 0x55, 0x55, 0x55, 0x55, 0x55, 0x55},
		"0000000000000000018c8c118d9d009d00000000000000000169680169680168000000000000000000f0f000f0f000f00000000000000000009d9c109c8d018d",
	},
	{
		[]byte{0, 1, 2, 3, 4, 5, 6, 7, 8},
		"00000000000001e4a545e5b90fb6882b00000000000000c849cd88f79307f67100000000000000cd0c898cb68356e624000000000000007cbcdc7c5e89b16e4b",
	},
	{
		[]byte{4, 8, 15, 16, 23, 42, 255, 0, 127, 65, 32, 123, 42, 45, 201, 210, 213, 244},
		"4db8a8e253903c70ab0efb65fe6de05a36d1dc9f567a147152d0148a86817b2062908d9b026a506007c1118e86901b672a39317c55ee3c10ac8efafa79efe8ee",
	},
}

func TestHash(t *testing.T) {
	for i, b := range backends {
		t.Run(b.Name+" digest", func(t *testing.T) {
			prepareArch(t, backends[i].arch)

			fmt.Println("FEATURES:", cpu.X86.HasAVX, cpu.X86.HasAVX2)
			d := New()
			for _, tc := range testCases {
				d.Reset()
				_, _ = d.Write(tc.input)
				sum := d.Sum(nil)
				require.Equal(t, tc.hash, hex.EncodeToString(sum[:]))
			}
		})
	}
}

func prepareArch(t testing.TB, b arch) {
	realCPU := cpu.X86
	if !realCPU.HasAVX2 && b.HasAVX2 || !realCPU.HasAVX && b.HasAVX {
		t.Skip("Underlying CPU doesn't support necessary features")
	} else {
		t.Cleanup(func() {
			cpu.X86.HasAVX = realCPU.HasAVX
			cpu.X86.HasAVX2 = realCPU.HasAVX2
		})
		cpu.X86.HasAVX = b.HasAVX
		cpu.X86.HasAVX2 = b.HasAVX2
	}
}

func newBuffer() (data []byte) {
	data = make([]byte, benchDataSize)

	r := rand.New(rand.NewSource(0))
	_, err := io.ReadFull(r, data)
	if err != nil {
		panic("cant initialize buffer")
	}
	return
}

func BenchmarkSum(b *testing.B) {
	data := newBuffer()

	for i := range backends {
		b.Run(backends[i].Name+" digest", func(b *testing.B) {
			prepareArch(b, backends[i].arch)

			b.ResetTimer()
			b.ReportAllocs()
			d := New()
			for i := 0; i < b.N; i++ {
				d.Reset()
				_, _ = d.Write(data)
				d.Sum(nil)
			}
			b.SetBytes(int64(len(data)))
		})
	}
}

func TestHomomorphism(t *testing.T) {
	var (
		c1, c2    sl2
		n         int
		err       error
		h, h1, h2 [Size]byte
		b         []byte
	)

	b = make([]byte, 64)
	n, err = rand.Read(b)
	require.Equal(t, 64, n)
	require.NoError(t, err)

	// Test if our hashing is really homomorphic
	h = Sum(b)
	require.NotEqual(t, [64]byte{}, h)
	h1 = Sum(b[:32])
	h2 = Sum(b[32:])

	err = c1.UnmarshalBinary(h1[:])
	require.NoError(t, err)
	err = c2.UnmarshalBinary(h2[:])
	require.NoError(t, err)

	c1.Mul(&c1, &c2)
	require.Equal(t, h, c1.Bytes())
}

var testCasesConcat = []struct {
	Hash  string
	Parts []string
}{{
	Hash: "7f5c9280352a8debea738a74abd4ec787f2c5e556800525692f651087442f9883bb97a2c1bc72d12ba26e3df8dc0f670564292ebc984976a8e353ff69a5fb3cb",
	Parts: []string{
		"4275945919296224acd268456be23b8b2df931787a46716477e32cd991e98074029d4f03a0fedc09125ee4640d228d7d40d430659a0b2b70e9cd4d4c5361865a",
		"2828661d1b1e77f21788d3b365f140a2395d57dc2083c33e60d9a80e69017d5016a249c7adfe1718a10ba887dedbdaec5c4c1fbecdb1f98776b43f1142c26a88",
		"02310598b45dfa77db9f00eed6ab60773dd8bed7bdac431b42e441fae463f64c6e2688402cfdcec5def47a299b0651fb20878cf4410991bd57056d7b4b31635a",
		"1ed7e0b065c060d915e7355cdcb4edc752c06d2a4b39d90c8985aeb58e08cb9e5bbe4b2b45524efbd68cd7e4081a1b8362941200a4c9f76a0a9f9ac9b7868c03",
		"6f11e3dc4fff99ffa45e36e4655cfc657c29e950e598a90f426bf5710de9171323523db7636643b23892783f4fb3cf8e583d584c82d29558a105a615a668fc9e",
		"1865dbdb4c849620fb2c4809d75d62490f83c11f2145abaabbdc9a66ae58ce1f2e42c34d3b380e5dea1b45217750b42d130f995b162afbd2e412b0d41ec8871b",
		"5102dd1bd1f08f44dbf3f27ac895020d63f96044ce3b491aed3efbc7bbe363bc5d800101d63890f89a532427812c30c9674f37476ba44daf758afa88d4f91063",
		"70cab735dad90164cc61f7411396221c4e549f12392c0d77728c89a9754f606c7d961169d4fa88133a1ba954bad616656c86f8fd1335a2f3428fd4dca3a3f5a5",
		"430f3e92536ff9a50cbcdf08d8810a59786ca37e31d54293646117a93469f61c6cdd67933128407d77f3235293293ee86dbc759d12dfe470969eba1b4a373bd0",
		"46e1d97912ca2cf92e6a9a63667676835d900cdb2fff062136a64d8d60a8e5aa644ccee3558900af8e77d56b013ed5da12d9d0b7de0f56976e040b3d01345c0d",
	},
}}

func TestConcat(t *testing.T) {
	var (
		actual, expect []byte
		ps             [][]byte
		err            error
	)

	for _, tc := range testCasesConcat {
		expect, err = hex.DecodeString(tc.Hash)
		require.NoError(t, err)

		ps = make([][]byte, len(tc.Parts))
		for j := 0; j < len(tc.Parts); j++ {
			ps[j], err = hex.DecodeString(tc.Parts[j])
			require.NoError(t, err)
		}

		actual, err = Concat(ps)
		require.NoError(t, err)
		require.Equal(t, expect, actual)
	}
}

func TestValidate(t *testing.T) {
	var (
		h   []byte
		ps  [][]byte
		got bool
		err error
	)

	for _, tc := range testCasesConcat {
		h, _ = hex.DecodeString(tc.Hash)
		require.NoError(t, err)

		ps = make([][]byte, len(tc.Parts))
		for j := 0; j < len(tc.Parts); j++ {
			ps[j], _ = hex.DecodeString(tc.Parts[j])
			require.NoError(t, err)
		}

		got, err = Validate(h, ps)
		require.NoError(t, err)
		require.True(t, got)
	}
}

var testCasesSubtract = []struct {
	first, second, result string
}{
	{
		first:  "4275945919296224acd268456be23b8b2df931787a46716477e32cd991e98074029d4f03a0fedc09125ee4640d228d7d40d430659a0b2b70e9cd4d4c5361865a",
		second: "277c10e0d7c52fcc0b23ba7dbf2c3dde7dcfc1f7c0cc0d998b2de504b8c1e17c6f65ab1294aea676d4060ed2ca18c1c26fd7cec5012ab69a4ddb5e6555ac8a59",
		result: "7f5c9280352a8debea738a74abd4ec787f2c5e556800525692f651087442f9883bb97a2c1bc72d12ba26e3df8dc0f670564292ebc984976a8e353ff69a5fb3cb",
	},
	{
		first:  "18e2ce290cc74998ebd0bef76454b52a40428f13bb612e40b5b96187e9cc813248a0ed5f7ec9fb205d55d3f243e2211363f171b19eb8acc7931cf33853a79069",
		second: "73a0582fa7d00d62fd09c1cd18589cdb2b126cb58b3a022ae47a8a787dabe35c4388aaf0d8bb343b1e58ee8d267812d115f40a0da611f42458f452e102f60700",
		result: "54ccaad1bb15b2989fa31109713bca955ea5d87bbd3113b3008cea167c00052266e9c9fcb73ece98c6c08cccb074ba3d39b5d8685f022fc388e2bf1997c5bd1d",
	},
}

func TestSubtract(t *testing.T) {
	var (
		a, b, c, r []byte
		err        error
	)

	for _, tc := range testCasesSubtract {
		a, err = hex.DecodeString(tc.first)
		require.NoError(t, err)

		b, err = hex.DecodeString(tc.second)
		require.NoError(t, err)

		c, err = hex.DecodeString(tc.result)
		require.NoError(t, err)

		r, err = SubtractR(c, b)
		require.NoError(t, err)
		require.Equal(t, a, r)

		r, err = SubtractL(c, a)
		require.NoError(t, err)
		require.Equal(t, b, r)
	}
}