package main

import (
	"errors"
	"net"
	"strconv"
	"strings"
)

// Safety feature, to avoid expanding subnets into a huge amount of IPs.
const maxNetmaskSize = 22 // expands into /10 for IPv4

// RegisterEndpoint builds an Endpoint and puts it to a global list of endpoints.
func RegisterEndpoint(ip string, ports []int, isIPv6 bool) int {
	for _, port := range ports {
		ep := Endpoint{addr: Address{ip: ip, port: port, v6: isIPv6}}
		ep.loginPos.Reset()
		ep.passwordPos.Reset()

		ep.listElement = endpoints.PushBack(&ep)
		log("ep", 3, "registered endpoint: %v", &ep)
	}

	return len(ports)
}

func incIP(ip net.IP) {
	for j := len(ip) - 1; j >= 0; j-- {
		ip[j]++
		if ip[j] > 0 {
			break
		}
	}
}

// parseCIDR registers multiple endpoints from a CIDR netmask.
func parseCIDR(ip string, ports []int, isIPv6 bool) int {
	na, nm, err := net.ParseCIDR(ip)
	if err != nil {
		log("ep", 0, "failed to parse CIDR notation for \"%v\": %v", ip, err.Error())
		return 0
	}

	mask, maskBits := nm.Mask.Size()
	if mask < maskBits-maxNetmaskSize {
		log("ep", 0, "ignoring out of safe bounds CIDR netmask for \"%v\": %v (max: %v, allowed: %v)", ip, mask, maskBits, maxNetmaskSize)
		return 0
	}

	curHost := 0
	maxHost := 1<<(maskBits-mask) - 1
	numParsed := 0
	strict := getParamSwitch("strict-subnets")

	log("ep", 2, "expanding CIDR: \"%v\" to %v hosts", ip, maxHost+1)

	for expIP := na.Mask(nm.Mask); nm.Contains(expIP); incIP(expIP) {
		if strict && (curHost == 0 || curHost == maxHost) && maskBits-mask >= 2 {
			log("ep", 1, "ignoring network/broadcast address due to strict-subnets: \"%v\"", expIP.String())
		} else {
			numParsed += RegisterEndpoint(expIP.String(), ports, isIPv6)
		}
		curHost++
	}

	return numParsed
}

// parseIPOrCIDR expands plain IP or CIDR to multiple endpoints.
func parseIPOrCIDR(ip string, ports []int, isIPv6 bool) int {
	// ip may be a domain name, a CIDR subnet or an IP address
	// CIDR subnets must be expanded to plain IPs

	if strings.LastIndex(ip, "/") >= 0 { // this is a CIDR subnet
		return parseCIDR(ip, ports, isIPv6)
	} else if strings.Count(ip, "/") > 1 { // invalid CIDR notation
		log("ep", 0, "invalid CIDR subnet format: \"%v\", ignoring", ip)
		return 0
	} else { // otherwise, just register
		return RegisterEndpoint(ip, ports, isIPv6)
	}
}

// extractIPAndPort extracts all endpoint components.
func extractIPAndPort(str string) (ip string, port int, err error) {
	var portString string
	ip, portString, err = net.SplitHostPort(str)
	if err != nil {
		return "", 0, err
	}

	port, err = strconv.Atoi(portString)
	if err != nil {
		return "", 0, err
	}

	if port <= 0 || port > 65535 {
		return "", 0, errors.New("invalid port: " + strconv.Itoa(port))
	}

	return ip, port, nil
}

// ParseEndpoints takes a string slice of IPs/CIDR subnets and converts it to a list of endpoints.
func ParseEndpoints(source []string) {
	log("ep", 1, "parsing endpoints")

	totalIPv6Skipped := 0
	numParsed := 0

	for _, str := range source {
		if !strings.Contains(str, ":") {
			// no ":": this is an ipv4/dn without port,
			// parse it with all known ports

			numParsed += parseIPOrCIDR(str, getParamIntSlice("port"), false)
		} else {
			// either ipv4/dn with port, or ipv6 with/without port

			isIPv6 := strings.Count(str, ":") > 1
			if isIPv6 && getParamSwitch("no-ipv6") {
				totalIPv6Skipped++
				continue
			}

			if !strings.Contains(str, "]:") && strings.Contains(str, "::") {
				// ipv6 without port
				numParsed += parseIPOrCIDR(str, getParamIntSlice("port"), true)
				continue
			}

			ip, port, err := extractIPAndPort(str)
			if err != nil {
				log("ep", 0, "failed to extract ip/port for \"%v\": %v, ignoring endpoint", str, err.Error())
				continue
			}

			ports := []int{port}
			// append all default ports
			if getParamSwitch("append-default-ports") {
				for _, port2 := range getParamIntSlice("port") {
					if port != port2 {
						ports = append(ports, port2)
					}
				}
			}

			numParsed += parseIPOrCIDR(ip, ports, isIPv6)
		}
	}

	logIf(totalIPv6Skipped > 0, "ep", 0, "skipped %v IPv6 targets due to no-ipv6 flag", totalIPv6Skipped)
	log("ep", 1, "finished parsing endpoints: parsed %v out of total %v", numParsed, endpoints.Len())
}