package math

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

func TestFastLog2Floor(t *testing.T) {
	tests := []struct {
		n              uint64
		expectedResult uint8
	}{
		{1, 0},
		{2, 1},
		{3, 1},
		{4, 2},
		{5, 2},
		{16, 4},
		{31, 4},
		{1684234, 20},
		{4294967295, 31}, // math.MaxUint32 (2^32 - 1)
		{4294967296, 32}, // 2^32
		{4294967297, 32}, // 2^32 + 1
		{4611686018427387904, 62},
		{9223372036854775808, 63},  // 2^63
		{18446744073709551615, 63}, // math.MaxUint64 (2^64 - 1).
	}

	for _, test := range tests {
		actualResult := FastLog2Floor(test.n)

		if test.expectedResult != actualResult {
			t.Errorf("TestFastLog2Floor: %d: expected result: %d but got: %d", test.n, test.expectedResult, actualResult)
		}
	}
}

// TestBigToCompact ensures BigToCompact converts big integers to the expected
// compact representation.
func TestBigToCompact(t *testing.T) {
	tests := []struct {
		in  string
		out uint32
	}{
		{"0000000000000000000000000000000000000000000000000000000000000000", 0},
		{"-1", 25231360},
		{"9223372036854775807", 142606335},
		{"922337203685477580712312312123487", 237861256},
		{"128", 0x02008000},
	}

	for x, test := range tests {
		n := new(big.Int)
		n.SetString(test.in, 10)
		r := BigToCompact(n)
		if r != test.out {
			t.Errorf("TestBigToCompact test #%d failed: got %d want %d\n",
				x, r, test.out)
			return
		}
	}
}

// TestCompactToBig ensures CompactToBig converts numbers using the compact
// representation to the expected big integers.
func TestCompactToBig(t *testing.T) {
	tests := []struct {
		before uint32
		intHex string
		after  uint32
	}{
		{math.MaxUint32, "-7fffff000000000000000000000000000000000000000000000000000000000000000000000000" +
			"000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
			"000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
			"000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
			"000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
			"000000000000000000000000", math.MaxUint32},
		{0x00000000, "0000000000000000000000000000000000000000000000000000000000000000", 0x00000000},
		{0x0989680, "0000000000000000000000000000000000000000000000000000000000000000", 0x00000000},
		{0x87fffff, "0000000000000000000000000000000000000000000000007fffff0000000000", 0x87fffff},
		{0x1810000, "-000000000000000000000000000000000000000000000000000000000000001", 0x1810000},
		{0xe2d7988, "0000000000000000000000000000000000002d79880000000000000000000000", 0xe2d7988},
		{0x00123456, "0000000000000000000000000000000000000000000000000000000000000000", 0x00000000},
		{0x01003456, "0000000000000000000000000000000000000000000000000000000000000000", 0x00000000},
		{0x02000056, "0000000000000000000000000000000000000000000000000000000000000000", 0x00000000},
		{0x03000000, "0000000000000000000000000000000000000000000000000000000000000000", 0x00000000},
		{0x04000000, "0000000000000000000000000000000000000000000000000000000000000000", 0x00000000},
		{0x00923456, "0000000000000000000000000000000000000000000000000000000000000000", 0x00000000},
		{0x01803456, "0000000000000000000000000000000000000000000000000000000000000000", 0x00000000},
		{0x02800056, "0000000000000000000000000000000000000000000000000000000000000000", 0x00000000},
		{0x03800000, "0000000000000000000000000000000000000000000000000000000000000000", 0x00000000},
		{0x04800000, "0000000000000000000000000000000000000000000000000000000000000000", 0x00000000},
		{0x01123456, "0000000000000000000000000000000000000000000000000000000000000012", 0x01120000},
		{0x02008000, "0000000000000000000000000000000000000000000000000000000000000080", 0x02008000},
		{0x01fedcba, "-00000000000000000000000000000000000000000000000000000000000007e", 0x01fe0000},
		{0x02123456, "0000000000000000000000000000000000000000000000000000000000001234", 0x02123400},
		{0x03123456, "0000000000000000000000000000000000000000000000000000000000123456", 0x03123456},
		{0x04123456, "0000000000000000000000000000000000000000000000000000000012345600", 0x04123456},
		{0x04923456, "-000000000000000000000000000000000000000000000000000000012345600", 0x04923456},
		{0x05009234, "0000000000000000000000000000000000000000000000000000000092340000", 0x05009234},
		{0x20123456, "1234560000000000000000000000000000000000000000000000000000000000", 0x20123456},
		{0xff123456, "123456000000000000000000000000000000000000000000000000000000000000000000000000000000" +
			"000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
			"000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
			"000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" +
			"000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000", 0xff123456},
	}

	for i, test := range tests {
		n := CompactToBig(test.before)
		convertBack := BigToCompact(n)
		got := fmt.Sprintf("%064x", n)
		if got != test.intHex {
			t.Errorf("TestCompactToBig test #%d failed: got %s want %s, input: 0x%08x",
				i, got, test.intHex, test.before)
		}
		if convertBack != test.after {
			t.Errorf("TestCompactToBig test #%d failed: got: 0x%08x want 0x%08x input: 0x%08x", i, convertBack, test.after, test.before)
		}
	}
}