package cooldns

import (
	"log"
	"net"
	"os"
	"path/filepath"

	"github.com/miekg/dns"
)

type zoneView struct {
	rr  rrMap
	acl []string
}

type zoneMap map[string][]zoneView

// Start starts cooldns
func Start(configPath string) {
	config, err := loadConfig(configPath)
	if err != nil {
		log.Fatalf("Failed to load config: %s\n", err.Error())
	}

	err = os.Chdir(filepath.Dir(configPath))
	if err != nil {
		log.Fatalf("Failed to goto config dir: %s", err.Error())
	}

	zones, err := loadZones(config.Zones)
	if err != nil {
		log.Fatalf("Failed to load zones: %s\n", err.Error())
	}

	aclList, err := createACLList(config.ACL)
	if err != nil {
		log.Fatalf("Failed to parse ACL rules: %s\n", err.Error())
	}

	blacklist := loadBlacklist(config.Blacklist)

	var acmeMap *legoMap
	if config.Lego.Enable {
		acmeMap = startLEGOWebSever(config.Lego)
	}

	server := createServer(zones, *config, aclList, blacklist, acmeMap)

	listenAndServer(server, config.Address)

	if config.TLS.Enable {
		listenAndServerTLS(server, config.TLS.Address, config.TLS.Cert, config.TLS.Key)

		log.Printf("Start listening on tcp %s for tls", config.TLS.Address)
	}

	log.Printf("Start listening on udp %s and tcp %s\n", config.Address, config.Address)
}

// createServer creates a new serve mux. Adds all the logic to handle the request
func createServer(zones zoneMap, config config, aclList map[string]*net.IPNet, blacklist map[string]bool, acmeList *legoMap) *dns.ServeMux {
	srv := dns.NewServeMux()
	c := new(dns.Client)

	// For all zones set from the config
	for zoneName, zones := range zones {
		srv.HandleFunc(zoneName, createHandler(zones, config, aclList, acmeList))
	}

	// Handle any other request for forwarding
	srv.HandleFunc(".", func(w dns.ResponseWriter, r *dns.Msg) {

		// Parse IP
		remoteIP, _, err := net.SplitHostPort(w.RemoteAddr().String())
		ip := net.ParseIP(remoteIP)

		if err != nil && ip != nil {
			log.Printf("Faild to parse remote IP WTF? :%s\n", err.Error())
			return
		}

		// Check if it is a ACME DNS-01 challange
		if config.Lego.Enable && handleACMERequest(w, r, acmeList) {
			return
		}

		// Check ACL rules
		if config.Forward.Enable && !checkACL(config.Forward.ACL, aclList, ip) {
			rcodeRequest(w, r, dns.RcodeRefused)
			return
		}

		// Check if the domain is bocked
		if _, ok := blacklist[r.Question[0].Name]; ok {
			handleBlockedDomain(w, r)
		} else {
			// Forward request
			in, _, err := c.Exchange(r, config.Forward.Server)

			if err != nil {
				rcodeRequest(w, r, dns.RcodeServerFailure)
				return
			}

			w.WriteMsg(in)
		}
	})

	return srv
}

func listenAndServer(server *dns.ServeMux, address string) {
	// Start UDP listner
	go func() {
		if err := dns.ListenAndServe(address, "udp", server); err != nil {
			log.Fatalf("Failed to set udp listener %s\n", err.Error())
		}
	}()

	// Start TCP listner
	go func() {
		if err := dns.ListenAndServe(address, "tcp", server); err != nil {
			log.Fatalf("Failed to set tcp listener %s\n", err.Error())
		}
	}()
}

func listenAndServerTLS(server *dns.ServeMux, address, cert, key string) {
	// Start TLS listner
	go func() {
		if err := dns.ListenAndServeTLS(address, cert, key, server); err != nil {
			log.Fatalf("Failed to set DoT listener %s", err.Error())
		}
	}()
}

func checkACL(alcRules []string, aclList map[string]*net.IPNet, ip net.IP) bool {
	if len(alcRules) != 0 {
		passed := false
		for _, rule := range alcRules {

			if aclList[rule].Contains(ip) {
				passed = true
			}
		}
		return passed
	}
	return true
}

// rcodeRequest respond to a request with a response code
func rcodeRequest(w dns.ResponseWriter, r *dns.Msg, rcode int) {
	m := new(dns.Msg)
	m.SetReply(r)
	m.SetRcode(r, rcode)
	w.WriteMsg(m)
}

func createHandler(zones []zoneView, config config, aclList map[string]*net.IPNet, acmeList *legoMap) func(w dns.ResponseWriter, r *dns.Msg) {
	return func(w dns.ResponseWriter, r *dns.Msg) {
		// Parse IP
		remoteIP, _, err := net.SplitHostPort(w.RemoteAddr().String())
		ip := net.ParseIP(remoteIP)
		if err != nil && ip != nil {
			log.Printf("Faild to parse remote IP WTF? :%s\n", err.Error())
			return
		}

		// Check if it is a ACME DNS-01 challange
		if config.Lego.Enable && handleACMERequest(w, r, acmeList) {
			return
		}

		// find out what view to handle the request
		zoneIndex := -1

		for i, zone := range zones {
			if (len(zone.acl) == 0 && zoneIndex == -1) || checkACL(zone.acl, aclList, ip) {
				zoneIndex = i
			}
		}

		// No view found that can handle the request
		if zoneIndex == -1 {
			rcodeRequest(w, r, dns.RcodeRefused)
			return
		}

		handleRequest(w, r, zones[zoneIndex])
	}
}