// Copyright 2022 The Ip2Region Authors. All rights reserved.
// Use of this source code is governed by a Apache2.0-style
// license that can be found in the LICENSE file.

// ---
// @Author Lion <chenxin619315@gmail.com>
// @Date   2022/06/16

package xdb

import (
	"encoding/binary"
	"fmt"
	"testing"
	"time"
)

// bytesToInt64 converts a big-endian byte slice (variable length) to int64.
// This handles the carry byte produced by IPSub when the addition overflows 4 bytes.
func bytesToInt64(buf []byte) int64 {
	var v int64
	for _, b := range buf {
		v = (v << 8) | int64(b)
	}
	return v
}

func TestParseIP(t *testing.T) {
	var ips = []string{"29.34.191.255", "2c0f:fff0::", "2fff:ffff:ffff:ffff:ffff:ffff:ffff:ffff"}
	for _, ip := range ips {
		bytes, err := ParseIP(ip)
		if err != nil {
			t.Errorf("check ip `%s`: %s\n", IP2String(bytes), err)
		}

		nip := IP2String(bytes)
		fmt.Printf("checkip: (%s / %s), isEqual: %v\n", ip, nip, ip == nip)
	}
}

func TestIPCompare(t *testing.T) {
	var ipPairs = [][]string{
		{"1.2.3.4", "1.2.3.5"},
		{"58.250.36.41", "58.250.30.41"},
		{"2c10::", "2e00::"},
		{"fdff:ffff:ffff:ffff:ffff:ffff:ffff:ffff", "febf:ffff:ffff:ffff:ffff:ffff:ffff:ffff"},
		{"fe7f:ffff:ffff:ffff:ffff:ffff:ffff:ffff", "fe00::"},
	}

	for _, pairs := range ipPairs {
		fmt.Printf("IPCompare(%s, %s): %d\n", pairs[0], pairs[1], IPCompare([]byte(pairs[0]), []byte(pairs[1])))
	}
}

func TestIPSub(t *testing.T) {
	var strToSub = "1.2.3.4"
	bytesToSub, err := ParseIP(strToSub)
	if err != nil {
		t.Fatalf("failed to parse ip %s", strToSub)
	}
	var intToSub = int(binary.BigEndian.Uint32(bytesToSub))
	t.Logf("to sub ip: %d -> %s", intToSub, strToSub)

	// edge cases
	edgeValues := []uint32{0, 1, 2, 0x7FFFFFFF, 0x80000000, 0xFFFFFFFE, 0xFFFFFFFF}
	for _, v := range edgeValues {
		buf := make([]byte, 4)
		binary.BigEndian.PutUint32(buf, v)
		subVal, err := IPSub(buf, bytesToSub)
		if err != nil {
			t.Fatalf("failed to IPSub(%s,%s): %s", IP2String(buf), strToSub, err)
		}
		byteSub := bytesToInt64(subVal)
		intSub := int64(v) + int64(intToSub)
		if byteSub != intSub {
			t.Fatalf("IPSub(%d, %d): byte=%d, int=%d", v, intToSub, byteSub, intSub)
		}
	}

	// stride-based sampling across the full range
	counter := 0
	const stride = 0x100000
	buf := make([]byte, 4)
	for i := uint32(0); i < 0xFFFFFFFF-stride; i += stride {
		binary.BigEndian.PutUint32(buf, i)
		subVal, err := IPSub(buf, bytesToSub)
		if err != nil {
			t.Fatalf("failed to IPSub(%s,%s): %s", IP2String(buf), strToSub, err)
		}

		byteSub := bytesToInt64(subVal)
		intSub := int64(i) + int64(intToSub)
		if byteSub != intSub {
			t.Fatal("byte and int sub value are not the same")
		}

		counter++
	}
	// also test the final boundary value
	binary.BigEndian.PutUint32(buf, 0xFFFFFFFF)
	subVal, err := IPSub(buf, bytesToSub)
	if err != nil {
		t.Fatalf("failed to IPSub(%s,%s): %s", IP2String(buf), strToSub, err)
	}
	byteSub := bytesToInt64(subVal)
	intSub := int64(4294967295) + int64(intToSub)
	if byteSub != intSub {
		t.Fatalf("IPSub(0xFFFFFFFF, %d): byte=%d, int=%d", intToSub, byteSub, intSub)
	}
	counter++

	t.Logf("test done with %d ips (sampled)", counter)
}

func TestIPHalf(t *testing.T) {
	// edge cases
	edgeValues := []uint32{0, 1, 2, 0x7FFFFFFF, 0x80000000, 0xFFFFFFFE, 0xFFFFFFFF}
	for _, v := range edgeValues {
		buf := make([]byte, 4)
		binary.BigEndian.PutUint32(buf, v)
		half := IPHalf(buf)

		byteMiddle := binary.BigEndian.Uint32(half)
		intMidle := v >> 1
		if byteMiddle != intMidle {
			t.Fatalf("IPHalf(0x%08x): byte=0x%08x, int=0x%08x", v, byteMiddle, intMidle)
		}
	}

	// stride-based sampling across the full range
	const stride = 0x100000
	buf := make([]byte, 4)
	for i := uint32(0); i < 0xFFFFFFFF-stride; i += stride {
		binary.BigEndian.PutUint32(buf, i)
		half := IPHalf(buf)

		byteMiddle := binary.BigEndian.Uint32(half)
		intMidle := i >> 1
		if byteMiddle != intMidle {
			t.Fatalf("IPHalf(0x%08x): byte=0x%08x, int=0x%08x", i, byteMiddle, intMidle)
		}
	}
}

func TestSubOverflow(t *testing.T) {
	var ip1Str = "255.255.255.250"
	ip1Bytes, err := ParseIP(ip1Str)
	if err != nil {
		t.Fatalf("failed to ParseIP(%s): %s", ip1Str, err)
	}

	var buff = make([]byte, 4)
	for i := 0; i < 10; i++ {
		binary.BigEndian.PutUint32(buff, uint32(i))
		ipSub, err := IPSub(ip1Bytes, buff)
		if err != nil {
			t.Fatalf("failed to IPSub(%s, %s): %s", ip1Str, IP2String(buff), err)
		}

		t.Logf("IPSub(%s, %s) = %+v", ip1Str, IP2String(buff), ipSub)
	}
}

func TestIPMiddle(t *testing.T) {
	var sIPStr = "0.0.0.0"
	sBytes, err := ParseIP(sIPStr)
	if err != nil {
		t.Fatalf("failed to parse ip %s", sIPStr)
	}
	var sInt = int(binary.BigEndian.Uint32(sBytes))
	t.Logf("start ip: %d -> %s", sInt, sIPStr)

	// edge cases
	edgeValues := []uint32{0, 1, 2, 0x7FFFFFFF, 0x80000000, 0xFFFFFFFE, 0xFFFFFFFF}
	for _, v := range edgeValues {
		buf := make([]byte, 4)
		binary.BigEndian.PutUint32(buf, v)
		midVal, err := IPMiddle(sBytes, buf)
		if err != nil {
			t.Fatalf("failed to IPMiddle(%s,%s): %s", sIPStr, IP2String(buf), err)
		}
		byteMid := int(binary.BigEndian.Uint32(midVal))
		intMid := (sInt + int(v)) >> 1
		if byteMid != intMid {
			t.Fatalf("IPMiddle(%d, %d): byte=%d, int=%d", sInt, v, byteMid, intMid)
		}
	}

	// stride-based sampling across the full range
	counter := 0
	const stride = 0x100000
	buf := make([]byte, 4)
	for i := uint32(0); i < 0xFFFFFFFF-stride; i += stride {
		binary.BigEndian.PutUint32(buf, i)
		midVal, err := IPMiddle(sBytes, buf)
		if err != nil {
			t.Fatalf("failed to IPMiddle(%s,%s): %s", sIPStr, IP2String(buf), err)
		}

		byteMid := int(binary.BigEndian.Uint32(midVal))
		intMid := (sInt + int(i)) >> 1
		if byteMid != intMid {
			t.Fatal("byte and int middle value are not the same")
		}

		counter++
	}

	t.Logf("test done with %d ips (sampled)", counter)
}

func TestLoadVectorIndex(t *testing.T) {
	vIndex, err := LoadVectorIndexFromFile("../../../data/ip2region_v4.xdb")
	if err != nil {
		fmt.Printf("failed to load vector index: %s\n", err)
		return
	}

	fmt.Printf("vIndex length: %d\n", len(vIndex))
}

func TestLoadContent(t *testing.T) {
	buff, err := LoadContentFromFile("../../../data/ip2region_v4.xdb")
	if err != nil {
		fmt.Printf("failed to load xdb content: %s\n", err)
		return
	}

	fmt.Printf("buff length: %d\n", len(buff))
}

func TestIPv4CompareCorrectness(t *testing.T) {
	tests := []struct {
		name string
		ip1  []byte // big-endian (from ParseIP)
		ip2  []byte // little-endian (from xdb index)
		want int
	}{
		// equal
		{"equal", []byte{1, 2, 3, 4}, []byte{4, 3, 2, 1}, 0},
		{"equal_zero", []byte{0, 0, 0, 0}, []byte{0, 0, 0, 0}, 0},
		{"equal_max", []byte{255, 255, 255, 255}, []byte{255, 255, 255, 255}, 0},

		// less at each byte position
		{"less_b0", []byte{0, 2, 3, 4}, []byte{4, 3, 2, 1}, -1},
		{"less_b1", []byte{1, 1, 3, 4}, []byte{4, 3, 2, 1}, -1},
		{"less_b2", []byte{1, 2, 2, 4}, []byte{4, 3, 2, 1}, -1},
		{"less_b3", []byte{1, 2, 3, 3}, []byte{4, 3, 2, 1}, -1},

		// greater at each byte position
		{"greater_b0", []byte{2, 2, 3, 4}, []byte{4, 3, 2, 1}, 1},
		{"greater_b1", []byte{1, 3, 3, 4}, []byte{4, 3, 2, 1}, 1},
		{"greater_b2", []byte{1, 2, 4, 4}, []byte{4, 3, 2, 1}, 1},
		{"greater_b3", []byte{1, 2, 3, 5}, []byte{4, 3, 2, 1}, 1},

		// edge: LE ip2 with byte0=0x00 (common for small IPs)
		{"le_zero_leading", []byte{1, 0, 0, 1}, []byte{1, 0, 0, 1}, 0},
	}

	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			ip2Copy := make([]byte, 4)
			copy(ip2Copy, tc.ip2)
			got := IPv4.IPCompare(tc.ip1, tc.ip2)
			if got != tc.want {
				t.Errorf("IPv4.IPCompare(%v, %v) = %d, want %d", tc.ip1, tc.ip2, got, tc.want)
			}
			// verify ip2 is not mutated
			for i := 0; i < 4; i++ {
				if tc.ip2[i] != ip2Copy[i] {
					t.Errorf("IPv4.IPCompare mutated ip2 at byte %d: was 0x%02x, now 0x%02x", i, ip2Copy[i], tc.ip2[i])
				}
			}
		})
	}
}

func TestIPCompareNoMutation(t *testing.T) {
	// verify that IPv4.IPCompare does NOT mutate the input ip2 slice
	ip1, _ := ParseIP("1.2.3.4")
	ip2Orig := []byte{0x04, 0x03, 0x02, 0x01} // LE representation of 1.2.3.4
	ip2Copy := make([]byte, 4)
	copy(ip2Copy, ip2Orig)

	result := IPv4.IPCompare(ip1, ip2Orig)
	if result != 0 {
		t.Fatalf("IPv4.IPCompare(1.2.3.4, LE[1.2.3.4]) = %d, want 0", result)
	}

	// verify ip2 is unchanged
	for i := 0; i < 4; i++ {
		if ip2Orig[i] != ip2Copy[i] {
			t.Fatalf("IPv4.IPCompare mutated ip2 at byte %d: was 0x%02x, now 0x%02x", i, ip2Copy[i], ip2Orig[i])
		}
	}
	_ = ip2Copy
}

func TestLoadHeader(t *testing.T) {
	header, err := LoadHeaderFromFile("../../../data/ip2region_v4.xdb")
	if err != nil {
		fmt.Printf("failed to load xdb header info: %s\n", err)
		return
	}

	fmt.Printf("Version         : %d\n", header.Version)
	fmt.Printf("IndexPolicy     : %s\n", header.IndexPolicy.String())
	fmt.Printf("CreatedAt       : %d(%s)\n", header.CreatedAt, time.Unix(int64(header.CreatedAt), 0).Format(time.RFC3339))
	fmt.Printf("StartIndexPtr   : %d\n", header.StartIndexPtr)
	fmt.Printf("EndIndexPtr     : %d\n", header.EndIndexPtr)
	fmt.Printf("IPVersion       : %d\n", header.IPVersion)
	fmt.Printf("RuntimePtrBytes : %d\n", header.RuntimePtrBytes)
}