// Copyright 2017 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package math

import (
	"bytes"
	"encoding/hex"
	"math/big"
	"testing"
)

func TestHexOrDecimal256(t *testing.T) {
	tests := []struct {
		input string
		num   *big.Int
		ok    bool
	}{
		{"", big.NewInt(0), true},
		{"0", big.NewInt(0), true},
		{"0x0", big.NewInt(0), true},
		{"12345678", big.NewInt(12345678), true},
		{"0x12345678", big.NewInt(0x12345678), true},
		{"0X12345678", big.NewInt(0x12345678), true},
		// Tests for leading zero behaviour:
		{"0123456789", big.NewInt(123456789), true}, // note: not octal
		{"00", big.NewInt(0), true},
		{"0x00", big.NewInt(0), true},
		{"0x012345678abc", big.NewInt(0x12345678abc), true},
		// Invalid syntax:
		{"abcdef", nil, false},
		{"0xgg", nil, false},
		// Larger than 256 bits:
		{"115792089237316195423570985008687907853269984665640564039457584007913129639936", nil, false},
	}
	for _, test := range tests {
		var num HexOrDecimal256
		err := num.UnmarshalText([]byte(test.input))
		if (err == nil) != test.ok {
			t.Errorf("ParseBig(%q) -> (err == nil) == %t, want %t", test.input, err == nil, test.ok)
			continue
		}
		if test.num != nil && (*big.Int)(&num).Cmp(test.num) != 0 {
			t.Errorf("ParseBig(%q) -> %d, want %d", test.input, (*big.Int)(&num), test.num)
		}
	}
}

func TestMustParseBig256(t *testing.T) {
	defer func() {
		if recover() == nil {
			t.Error("MustParseBig should've panicked")
		}
	}()
	MustParseBig256("ggg")
}

func TestPaddedBigBytes(t *testing.T) {
	tests := []struct {
		num    *big.Int
		n      int
		result []byte
	}{
		{num: big.NewInt(0), n: 4, result: []byte{0, 0, 0, 0}},
		{num: big.NewInt(1), n: 4, result: []byte{0, 0, 0, 1}},
		{num: big.NewInt(512), n: 4, result: []byte{0, 0, 2, 0}},
		{num: BigPow(2, 32), n: 4, result: []byte{1, 0, 0, 0, 0}},
	}
	for _, test := range tests {
		if result := PaddedBigBytes(test.num, test.n); !bytes.Equal(result, test.result) {
			t.Errorf("PaddedBigBytes(%d, %d) = %v, want %v", test.num, test.n, result, test.result)
		}
	}
}

func BenchmarkPaddedBigBytesLargePadding(b *testing.B) {
	bigint := MustParseBig256("123456789123456789123456789123456789")
	for i := 0; i < b.N; i++ {
		PaddedBigBytes(bigint, 200)
	}
}

func BenchmarkPaddedBigBytesSmallPadding(b *testing.B) {
	bigint := MustParseBig256("0x18F8F8F1000111000110011100222004330052300000000000000000FEFCF3CC")
	for i := 0; i < b.N; i++ {
		PaddedBigBytes(bigint, 5)
	}
}

func BenchmarkPaddedBigBytesSmallOnePadding(b *testing.B) {
	bigint := MustParseBig256("0x18F8F8F1000111000110011100222004330052300000000000000000FEFCF3CC")
	for i := 0; i < b.N; i++ {
		PaddedBigBytes(bigint, 32)
	}
}

func BenchmarkByteAtOld(b *testing.B) {
	bigint := MustParseBig256("0x18F8F8F1000111000110011100222004330052300000000000000000FEFCF3CC")
	for i := 0; i < b.N; i++ {
		PaddedBigBytes(bigint, 32)
	}
}

func TestReadBits(t *testing.T) {
	check := func(input string) {
		want, _ := hex.DecodeString(input)
		n, _ := new(big.Int).SetString(input, 16)
		buf := make([]byte, len(want))
		ReadBits(n, buf)
		if !bytes.Equal(buf, want) {
			t.Errorf("have: %x\nwant: %x", buf, want)
		}
	}
	check("000000000000000000000000000000000000000000000000000000FEFCF3F8F0")
	check("0000000000012345000000000000000000000000000000000000FEFCF3F8F0")
	check("18F8F8F1000111000110011100222004330052300000000000000000FEFCF3F8F0")
}

func TestU256(t *testing.T) {
	tests := []struct{ x, y *big.Int }{
		{x: big.NewInt(0), y: big.NewInt(0)},
		{x: big.NewInt(1), y: big.NewInt(1)},
		{x: BigPow(2, 255), y: BigPow(2, 255)},
		{x: BigPow(2, 256), y: big.NewInt(0)},
		{x: new(big.Int).Add(BigPow(2, 256), big.NewInt(1)), y: big.NewInt(1)},
		// negative values
		{x: big.NewInt(-1), y: new(big.Int).Sub(BigPow(2, 256), big.NewInt(1))},
		{x: big.NewInt(-2), y: new(big.Int).Sub(BigPow(2, 256), big.NewInt(2))},
		{x: BigPow(2, -255), y: big.NewInt(1)},
	}
	for _, test := range tests {
		if y := U256(new(big.Int).Set(test.x)); y.Cmp(test.y) != 0 {
			t.Errorf("U256(%x) = %x, want %x", test.x, y, test.y)
		}
	}
}

func TestU256Bytes(t *testing.T) {
	ubytes := make([]byte, 32)
	ubytes[31] = 1

	unsigned := U256Bytes(big.NewInt(1))
	if !bytes.Equal(unsigned, ubytes) {
		t.Errorf("expected %x got %x", ubytes, unsigned)
	}
}

func TestHexOrDecimal256_MarshalText(t *testing.T) {
	tests := []struct {
		name    string
		input   *HexOrDecimal256
		want    []byte
		wantErr bool
	}{
		{
			name:  "nil input",
			input: nil,
			want:  []byte("0x0"),
		},
		{
			name:  "zero value",
			input: (*HexOrDecimal256)(big.NewInt(0)),
			want:  []byte("0x0"),
		},
		{
			name:  "positive value",
			input: (*HexOrDecimal256)(big.NewInt(0x123abc)),
			want:  []byte("0x123abc"),
		},
		{
			name:  "large positive value",
			input: (*HexOrDecimal256)(new(big.Int).SetBytes(bytes.Repeat([]byte{0xff}, 32))),
			want:  []byte("0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"),
		},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			got, err := tt.input.MarshalText()
			if (err != nil) != tt.wantErr {
				t.Errorf("HexOrDecimal256.MarshalText() error = %v, wantErr %v", err, tt.wantErr)
				return
			}
			if !bytes.Equal(got, tt.want) {
				t.Errorf("HexOrDecimal256.MarshalText() = %s, want %s", got, tt.want)
			}
		})
	}
}
