package ip2region

import (
	"os"
	"strings"
	"strconv"
	"io/ioutil"
	"errors"
)

const (
	INDEX_BLOCK_LENGTH  = 12
	TOTAL_HEADER_LENGTH = 8192
)

var err error
var ipInfo IpInfo

type Ip2Region struct {
	// db file handler
	dbFileHandler *os.File


	//header block info

	headerSip     []int64
	headerPtr     []int64
	headerLen     int64

	// super block index info
	firstIndexPtr int64
	lastIndexPtr  int64
	totalBlocks   int64

	// for memory mode only
	// the original db binary string

	dbBinStr      []byte
	dbFile        string
}

type IpInfo struct {
	CityId   int64
	Country  string
	Region   string
	Province string
	City     string
	ISP      string
}

func (ip IpInfo)String() string {
	return strconv.FormatInt(ip.CityId, 10) + "|" + ip.Country + "|" + ip.Region + "|" + ip.Province + "|" + ip.City + "|" + ip.ISP
}

func getIpInfo(cityId int64, line []byte) IpInfo {

	lineSlice := strings.Split(string(line), "|")
	ipInfo := IpInfo{}
	length := len(lineSlice)
	ipInfo.CityId = cityId
	if length < 5 {
		for i := 0; i <= 5 - length; i++ {
			lineSlice = append(lineSlice, "")
		}
	}

	ipInfo.Country = lineSlice[0]
	ipInfo.Region = lineSlice[1]
	ipInfo.Province = lineSlice[2]
	ipInfo.City = lineSlice[3]
	ipInfo.ISP = lineSlice[4]
	return ipInfo
}

func New(path string) (*Ip2Region, error) {

	file, err := os.Open(path)
	if err != nil {
		return nil, err
	}

	return &Ip2Region{
		dbFile:path,
		dbFileHandler:file,
	}, nil
}

func (this *Ip2Region) Close() {
	this.dbFileHandler.Close()
}

func (this *Ip2Region) MemorySearch(ipStr string) (ipInfo IpInfo, err error) {
	ipInfo = IpInfo{}

	if this.totalBlocks == 0 {
		this.dbBinStr, err = ioutil.ReadFile(this.dbFile)

		if err != nil {

			return ipInfo, err
		}

		this.firstIndexPtr = getLong(this.dbBinStr, 0)
		this.lastIndexPtr = getLong(this.dbBinStr, 4)
		this.totalBlocks = (this.lastIndexPtr - this.firstIndexPtr) / INDEX_BLOCK_LENGTH + 1
	}

	ip, err := ip2long(ipStr)
	if err != nil {
		return ipInfo, err
	}

	h := this.totalBlocks
	var dataPtr, l int64;
	for (l <= h) {

		m := (l + h) >> 1
		p := this.firstIndexPtr + m * INDEX_BLOCK_LENGTH
		sip := getLong(this.dbBinStr, p)
		if ip < sip {
			h = m - 1
		} else {
			eip := getLong(this.dbBinStr, p + 4)
			if ip > eip {
				l = m + 1
			} else {
				dataPtr = getLong(this.dbBinStr, p + 8)
				break;
			}
		}
	}
	if dataPtr == 0 {
		return ipInfo, errors.New("not found")
	}

	dataLen := ((dataPtr >> 24) & 0xFF)
	dataPtr = (dataPtr & 0x00FFFFFF);
	ipInfo = getIpInfo(getLong(this.dbBinStr, dataPtr), this.dbBinStr[(dataPtr) + 4:dataPtr + dataLen])
	return ipInfo, nil

}

func (this *Ip2Region)BinarySearch(ipStr string) (ipInfo IpInfo, err error) {
	ipInfo = IpInfo{}
	if this.totalBlocks == 0 {
		this.dbFileHandler.Seek(0, 0)
		superBlock := make([]byte, 8)
		this.dbFileHandler.Read(superBlock)
		this.firstIndexPtr = getLong(superBlock, 0)
		this.lastIndexPtr = getLong(superBlock, 4)
		this.totalBlocks = (this.lastIndexPtr - this.firstIndexPtr) / INDEX_BLOCK_LENGTH + 1
	}

	var l, dataPtr, p int64

	h := this.totalBlocks

	ip, err := ip2long(ipStr)

	if err != nil {
		return
	}

	for (l <= h) {
		m := (l + h) >> 1

		p = m * INDEX_BLOCK_LENGTH

		_, err = this.dbFileHandler.Seek(this.firstIndexPtr + p, 0)
		if err != nil {
			return
		}

		buffer := make([]byte, INDEX_BLOCK_LENGTH)
		_, err = this.dbFileHandler.Read(buffer)

		if err != nil {

		}
		sip := getLong(buffer, 0)
		if ip < sip {
			h = m - 1
		} else {
			eip := getLong(buffer, 4)
			if ip > eip {
				l = m + 1
			} else {
				dataPtr = getLong(buffer, 8)
				break;
			}
		}

	}

	if dataPtr == 0 {
		err = errors.New("not found")
		return
	}

	dataLen := ((dataPtr >> 24) & 0xFF)
	dataPtr = (dataPtr & 0x00FFFFFF);

	this.dbFileHandler.Seek(dataPtr, 0)
	data := make([]byte, dataLen)
	this.dbFileHandler.Read(data)
	ipInfo = getIpInfo(getLong(data, 0), data[4:dataLen])
	err = nil
	return
}

func (this *Ip2Region) BtreeSearch(ipStr string) (ipInfo IpInfo, err error) {
	ipInfo = IpInfo{}
	ip, err := ip2long(ipStr)

	if this.headerLen == 0 {
		this.dbFileHandler.Seek(8, 0)

		buffer := make([]byte, TOTAL_HEADER_LENGTH)
		this.dbFileHandler.Read(buffer)
		var idx int64;
		for i := 0; i < TOTAL_HEADER_LENGTH; i += 8 {
			startIp := getLong(buffer, int64(i))
			dataPar := getLong(buffer, int64(i + 4))
			if dataPar == 0 {
				break
			}

			this.headerSip = append(this.headerSip, startIp)
			this.headerPtr = append(this.headerPtr, dataPar)
			idx ++;
		}

		this.headerLen = idx
	}

	var l, sptr, eptr int64
	h := this.headerLen

	for l <= h {
		m := int64(l + h) >> 1
		if m < this.headerLen {
			if ip == this.headerSip[m] {
				if m > 0 {
					sptr = this.headerPtr[m - 1]
					eptr = this.headerPtr[m]
				} else {
					sptr = this.headerPtr[m]
					eptr = this.headerPtr[m + 1]
				}
				break
			}
			if ip < this.headerSip[m] {
				if m == 0 {
					sptr = this.headerPtr[m]
					eptr = this.headerPtr[m + 1]
					break
				} else if ip > this.headerSip[m - 1] {
					sptr = this.headerPtr[m - 1]
					eptr = this.headerPtr[m]
					break
				}
				h = m - 1
			} else {
				if m == this.headerLen - 1 {
					sptr = this.headerPtr[m - 1]
					eptr = this.headerPtr[m]
					break
				} else if ip <= this.headerSip[m + 1] {
					sptr = this.headerPtr[m ]
					eptr = this.headerPtr[m + 1]
					break
				}
				l = m + 1
			}
		}

	}

	if sptr == 0 {
		err = errors.New("not found")
		return
	}

	blockLen := eptr - sptr
	this.dbFileHandler.Seek(sptr, 0)
	index := make([]byte, blockLen + INDEX_BLOCK_LENGTH)
	this.dbFileHandler.Read(index)
	var dataptr int64
	h = blockLen / INDEX_BLOCK_LENGTH
	l = 0

	for l <= h {
		m := int64(l + h) >> 1
		p := m * INDEX_BLOCK_LENGTH
		sip := getLong(index, p)
		if ip < sip {
			h = m - 1;
		} else {
			eip := getLong(index, p + 4)
			if ip > eip {
				l = m + 1
			} else {
				dataptr = getLong(index, p + 8)
				break
			}
		}
	}

	if dataptr == 0 {
		err = errors.New("not found")
		return
	}

	dataLen := (dataptr >> 24) & 0xFF
	dataPtr := dataptr & 0x00FFFFFF

	this.dbFileHandler.Seek(dataPtr, 0)
	data := make([]byte, dataLen)
	this.dbFileHandler.Read(data)
	ipInfo = getIpInfo(getLong(data, 0), data[4:])
	return
}

func getLong(b []byte, offset int64) int64 {

	val := (int64(b[offset ]) |
		int64(b[offset + 1]) << 8 |
		int64(b[offset + 2]) << 16 |
		int64(b[offset + 3]) << 24)

	return val

}

func ip2long(IpStr string) (int64, error) {
	bits := strings.Split(IpStr, ".")
	if len(bits) != 4 {
		return 0, errors.New("ip format error")
	}

	var sum int64
	for i, n := range bits {
		bit, _ := strconv.ParseInt(n, 10, 64)
		sum += bit << uint(24 - 8 * i)
	}

	return sum, nil
}