package main

import (
	"context"
	"errors"
	"fmt"
	"log"
	"net"
	"net/http"
	"net/url"
	"strings"
	"sync"
	"time"
)

// PowerDNS defines the client to which queries are passed
type (
	PowerDNS struct {
		Scheme     string
		Hostname   string
		Port       string
		apiURL     string
		debug      bool
		Client     *http.Client
		m          sync.RWMutex
		listCache  map[string]*listCache
		DefaultTTL int
	}
)

// NewClient initializes a new PowerDNS client configuration
func NewClient(baseURL, apiKey string, timeout, ttl int) (*PowerDNS, error) {
	scheme, hostname, port, path, err := parseBaseURL(baseURL)
	if err != nil {
		log.Fatalf("%s is not a valid URL: %v", baseURL, err)
	}
	transport := http.DefaultTransport
	apiKeyTransport := &APIKeyTransport{
		Transport: transport,
		APIKey:    apiKey,
	}
	errorTransport := &ErrorTransport{
		Transport: apiKeyTransport,
	}
	powerDNS := &PowerDNS{
		Scheme:   scheme,
		Hostname: hostname,
		Port:     port,
		Client: &http.Client{
			Transport: errorTransport,
			Timeout:   time.Duration(timeout) * time.Second,
		},
		apiURL:     path,
		listCache:  map[string]*listCache{},
		DefaultTTL: ttl,
	}
	return powerDNS, nil
}

// Debug toggle the debug mode
func (p *PowerDNS) Debug() {
	p.debug = true
}

// LogDebug facility
func (p *PowerDNS) LogDebug(v ...interface{}) {
	if p.debug {
		log.Println(v...)
	}
}

// Lock the structure
func (p *PowerDNS) lock() {
	p.m.Lock()
}

// ...or unlock it
func (p *PowerDNS) unlock() {
	p.m.Unlock()
}

// Ping tries to contact a powerDNS URL API to make sure its up and accessible
func (p *PowerDNS) Ping(ctx context.Context) error {
	u := url.URL{}
	u.Host = p.Hostname + ":" + p.Port
	u.Scheme = p.Scheme
	u.Path = "/api"
	req, err := http.NewRequest("GET", u.String(), nil)
	if err != nil {
		return err
	}
	resp, err := p.Client.Do(req.WithContext(ctx))
	if resp != nil {
		defer resp.Body.Close()
	}
	return err
}

// Execute send the DNSQuery structure to the PDNS api
func (p *PowerDNS) Execute(d *DNSQuery) (int, http.Header, error) {
	uri := fmt.Sprintf("%s/%s/%s", p.apiURL, "zones", trimPoint(d.Domain))
	return p.sendQuery(context.Background(), uri, "PATCH", printJSON(d), nil)
}

// ExecuteZone send the DNSZone structure to the PDNS api
func (p *PowerDNS) ExecuteZone(d *DNSZone, resp *DNSQuery) (int, http.Header, error) {
	uri := fmt.Sprintf("%s/%s", p.apiURL, "zones")
	// purge the zone cache
	p.listCache = map[string]*listCache{}
	return p.sendQuery(context.Background(), uri, "POST", printJSON(d), resp)
}

// Zone return the whole zone if it exist
func (p *PowerDNS) Zone(name string) (*DNSQuery, error) {
	var result DNSQuery

	parentName, err := p.GetDomain(name)
	if err != nil {
		return nil, errors.New("Unknown domain")
	}
	code, _, err := p.sendQuery(context.Background(),
		fmt.Sprintf("%s/%s/%s", p.apiURL, "zones", parentName), "GET", nil, &result)
	if code != 200 {
		return nil, errors.New("Unknown zone, but it shouldn't")
	}
	// if this is a subzone, filter the result
	if strings.HasSuffix(name, "."+addPoint(parentName)) {
		good := []int{}
		filter := []*DNSRRSet{}
		sub := "." + name
		for i := range result.RRSets {
			if result.RRSets[i].Name == name || strings.HasSuffix(result.RRSets[i].Name, sub) {
				good = append(good, i)
			}
		}
		for _, i := range good {
			filter = append(filter, result.RRSets[i])
		}
		result.RRSets = filter
	}
	if err == nil {
		result.Domain = name
	}
	return &result, err
}

// Search perform a search in the pdns API
func (p *PowerDNS) Search(r string) (DNSSearch, error) {
	var records DNSSearch
	// remove any final point to the record if necessary
	url := fmt.Sprintf("%s/%s?max=5000&q=%s", p.apiURL, "search-data", trimPoint(r))

	if _, _, err := p.sendQuery(context.Background(), url, "GET", nil, &records); err != nil {
		return nil, err
	}
	return records, nil
}

// IsUsed search the DB to check if anyting is pointing to name
func (p *PowerDNS) IsUsed(name, exception string, rtype []string) bool {
	exception = strings.ToLower(exception)
	search, err := p.Search(name)
	if err != nil {
		return false
	}
	for _, rec := range search {
		if !rec.IsRecord() || rec.Name == exception {
			continue
		}
		for _, t := range rtype {
			if t == rec.Type {
				return true
			}
		}
	}
	return false
}

// ReverseChanges returns the list of changes needed if we move the value of
// the record d which pointed to excludeIP
func (p *PowerDNS) ReverseChanges(d *DNSQuery, excludeIP string) ([]*DNSQuery, error) {
	actions := []*DNSQuery{}
	for _, entry := range d.RRSets {
		for _, record := range entry.Records {
			ip := record.Content
			// ignore the record pointing to excludeIP
			if ip == excludeIP {
				continue
			}
			reverse, _ := p.GetReverse(ip, entry.Type == "A")
			// no reverse (inconstancy or external IP): no problem here
			if reverse == nil || reverse.Len() == 0 {
				continue
			}
			// this reverse doesn't point back to entry.Name, no action needed
			if !reverse.RemoveValue(entry.Name) {
				continue
			}
			// if we don't remove the reverse, no problem
			if !reverse.RRSets[0].IsDeletion() {
				continue
			}
			// there was only one PTR, and it's pointing back to j.Params.Name, we
			// need to remove it
			if p.IsUsed(ip, entry.Name, []string{entry.Type}) {
				message := "Reverse issue : %s is the reverse for %s and will be changed\n"
				message += "But other records are pointing to %s as well. Please cleanup first\n"
				return actions, fmt.Errorf(message, entry.Name, ip, ip)
			}
			actions = append(actions, reverse)
		}
	}
	return actions, nil
}

// getRecord get the PDNS record
func (p *PowerDNS) getRecord(r string, wanted, notWanted []string, ignoreBadDomain bool) (*DNSQuery, error) {
	// Get the domain
	d, err := p.GetDomain(r)

	// we don't manage the domain, no need to continue (ignoreBadDomain is used
	// for newly created domains only)
	if err != nil && !ignoreBadDomain {
		return nil, err
	}
	// get the records, in search format
	records, err := p.Search(r)
	if err != nil {
		return nil, err
	}
	// Now we convert the search format to the DNSQuery format
	query := records.DNSQuery()
	query.Domain = d

	// and we do some cleanup
	err = query.RecordFilter(r, wanted, notWanted)

	return query, err
}

// CanCreate return an error if t can be created on the local DNS and doesn't
// exist. An external record, existing or not, is fine
func (p *PowerDNS) CanCreate(r string, directOnly bool, target *DNSQuery) error {
	search, err := p.getRecord(r, []string{"*"}, []string{}, false)
	// copy the actual structure
	if target != nil && search != nil {
		*target = *search
	}
	switch {
	case err == nil:
		break
	case err.Error() == "Unknown domain":
		return nil
	case strings.HasSuffix(err.Error(), "delegated to another server"):
		return nil
	case err != nil:
		return err
	}
	if directOnly {
		if err := search.RecordFilter(r,
			[]string{"A", "AAAA"},
			[]string{"CNAME", "DNAME"}); err != nil {
			return fmt.Errorf("%s cannot be a CNAME", r)
		}
	}
	if search.Len() == 0 {
		return fmt.Errorf("%s doesn't exist, create it first", r)
	}
	return nil
}

// GetRecord get the PDNS record of type t
func (p *PowerDNS) GetRecord(r, t string, ignoreBadDomain bool) (*DNSQuery, error) {
	notWanted := []string{}
	wanted := []string{strings.ToUpper(t)}
	switch t {
	case "ttl":
		wanted = []string{"*"}
		notWanted = []string{}
	case "delete":
		wanted = []string{"*", "indirect"}
	case "cname":
		notWanted = []string{"*"}
	case "dname":
		notWanted = []string{"*"}
	case "ns":
		wanted = []string{"NS"}
		notWanted = []string{"*"}
	default:
		notWanted = []string{"CNAME", "DNAME"}
	}
	return p.getRecord(r, wanted, notWanted, ignoreBadDomain)
}

// GetReverse get the reverse DNS record of the IP
func (p *PowerDNS) GetReverse(ipString string, v4 bool) (*DNSQuery, error) {
	ip := net.ParseIP(ipString)
	if ip == nil || (v4 != (ip.To4() != nil)) {
		return nil, errors.New("not a valid IP address")
	}
	// we ignore the error on the actual query, which most certainly means
	// there is no reverse or that we don't manage it
	ret, _ := p.getRecord(iPtoReverse(ip), []string{"PTR"}, nil, false)

	return ret, nil
}

// SetNameServers returns a *DNSQuery to create a set of nameservers in a zone
// or its parent
func (p *PowerDNS) SetNameServers(zone, where string, servers []string) (*DNSQuery, error) {
	ns, err := p.GetRecord(zone, "NS", true)
	if err != nil {
		return nil, err
	}
	for _, nameServer := range servers {
		ns.ChangeValue(zone, nameServer, "NS", false, false)
	}
	ns.ChangeDomain(where)
	return ns, nil
}