package dns

import (
	"v2ray.com/core/common"
	"v2ray.com/core/common/net"
	"v2ray.com/core/common/strmatcher"
	"v2ray.com/core/features"
)

// StaticHosts represents static domain-ip mapping in DNS server.
type StaticHosts struct {
	ips      [][]net.IP
	matchers *strmatcher.MatcherGroup
}

var typeMap = map[DomainMatchingType]strmatcher.Type{
	DomainMatchingType_Full:      strmatcher.Full,
	DomainMatchingType_Subdomain: strmatcher.Domain,
	DomainMatchingType_Keyword:   strmatcher.Substr,
	DomainMatchingType_Regex:     strmatcher.Regex,
}

func toStrMatcher(t DomainMatchingType, domain string) (strmatcher.Matcher, error) {
	strMType, f := typeMap[t]
	if !f {
		return nil, newError("unknown mapping type", t).AtWarning()
	}
	matcher, err := strMType.New(domain)
	if err != nil {
		return nil, newError("failed to create str matcher").Base(err)
	}
	return matcher, nil
}

// NewStaticHosts creates a new StaticHosts instance.
func NewStaticHosts(hosts []*Config_HostMapping, legacy map[string]*net.IPOrDomain) (*StaticHosts, error) {
	g := new(strmatcher.MatcherGroup)
	sh := &StaticHosts{
		ips:      make([][]net.IP, len(hosts)+len(legacy)+16),
		matchers: g,
	}

	if legacy != nil {
		features.PrintDeprecatedFeatureWarning("simple host mapping")

		for domain, ip := range legacy {
			matcher, err := strmatcher.Full.New(domain)
			common.Must(err)
			id := g.Add(matcher)

			address := ip.AsAddress()
			if address.Family().IsDomain() {
				return nil, newError("ignoring domain address in static hosts: ", address.Domain()).AtWarning()
			}

			sh.ips[id] = []net.IP{address.IP()}
		}
	}

	for _, mapping := range hosts {
		matcher, err := toStrMatcher(mapping.Type, mapping.Domain)
		if err != nil {
			return nil, newError("failed to create domain matcher").Base(err)
		}
		id := g.Add(matcher)
		ips := make([]net.IP, len(mapping.Ip))
		for idx, ip := range mapping.Ip {
			ips[idx] = net.IP(ip)
		}
		sh.ips[id] = ips
	}

	return sh, nil
}

func filterIP(ips []net.IP, option IPOption) []net.IP {
	filtered := make([]net.IP, 0, len(ips))
	for _, ip := range ips {
		if (len(ip) == net.IPv4len && option.IPv4Enable) || (len(ip) == net.IPv6len && option.IPv6Enable) {
			filtered = append(filtered, ip)
		}
	}
	if len(filtered) == 0 {
		return nil
	}
	return filtered
}

// LookupIP returns IP address for the given domain, if exists in this StaticHosts.
func (h *StaticHosts) LookupIP(domain string, option IPOption) []net.IP {
	id := h.matchers.Match(domain)
	if id == 0 {
		return nil
	}
	return filterIP(h.ips[id], option)
}