package server

import (
	"net/http"
	"net/netip"
	"slices"
	"strconv"
	"strings"

	"jarl/internal/auth"
	"jarl/internal/certs"
	"jarl/internal/encdns"
	"jarl/internal/model"
	"jarl/internal/nscheck"
)

// DNS over TLS and HTTPS (docs/encrypted-dns.md).

type encAddress struct {
	Address string `json:"address"`
	Private bool   `json:"private"`
}

type encView struct {
	Name    string `json:"name"`
	Public  bool   `json:"public"`
	HasZone bool   `json:"has_zone,omitempty"` // has a zone for the host name
}

type encCert struct {
	Name     string       `json:"name"`
	Names    []string     `json:"names"`
	Domains  []string     `json:"domains"`
	DNS      bool         `json:"dns"` // has the dns use
	Status   certs.Status `json:"status"`
	Obtained bool         `json:"obtained"`
}

type encStatus struct {
	encdns.Status
	// Hostname is the name clients connect to (the certificate's first).
	Hostname string `json:"hostname,omitempty"`
	// DoTHost and DoHURL are what to give clients.
	DoTHost string `json:"dot_host,omitempty"`
	DoHURL  string `json:"doh_url,omitempty"`
	// For the setup form.
	Addresses    []encAddress `json:"addresses"`
	Views        []encView    `json:"views"`
	Certificates []encCert    `json:"certificates"`
}

func (s *Server) encReady(p *auth.Principal, write bool) error {
	if err := require(p, auth.Action{Resource: auth.ResOptions, Write: write}); err != nil {
		return err
	}
	if s.cfg.Certs == nil {
		return &httpError{http.StatusNotFound, "disabled", "certificates aren't available in this jarld"}
	}
	return nil
}

// localAddrs returns this host's addresses (a test may replace it).
var localAddrs = nscheck.LocalAddrs

// encryptedDNS: GET /encrypted-dns.
func (s *Server) encryptedDNS(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := s.encReady(p, false); err != nil {
		return err
	}
	st, err := s.store.LoadState(r.Context())
	if err != nil {
		return err
	}
	m := s.cfg.Certs
	out := encStatus{Status: encdns.GetStatus(st, m.FilesDir("")), Addresses: []encAddress{}, Views: []encView{}, Certificates: []encCert{}}
	all, err := m.List(r.Context())
	if err != nil {
		return err
	}
	for _, c := range all {
		out.Certificates = append(out.Certificates, encCert{Name: c.Name, Names: c.Names, Domains: c.Domains, DNS: c.HasUse(model.CertUseDNS),
			Status: m.StatusOf(c), Obtained: c.NotAfter != nil})
		if c.Name == out.Certificate {
			for _, n := range append(c.Names, c.Domains...) {
				if !strings.HasPrefix(n, "*.") {
					out.Hostname = n
					break
				}
			}
		}
	}
	if out.Hostname != "" {
		if len(out.DoT) > 0 {
			out.DoTHost = out.Hostname
			if out.DoT[0].Port != encdns.DoTPort {
				out.DoTHost += ":" + strconv.Itoa(out.DoT[0].Port)
			}
		}
		if len(out.DoH) > 0 {
			out.DoHURL = "https://" + out.Hostname
			if out.DoH[0].Port != 443 {
				out.DoHURL += ":" + strconv.Itoa(out.DoH[0].Port)
			}
			out.DoHURL += "/dns-query"
		}
	}
	seen := map[netip.Addr]bool{}
	for _, a := range localAddrs() {
		a = a.Unmap()
		if seen[a] || a.IsLinkLocalUnicast() {
			continue
		}
		seen[a] = true
		out.Addresses = append(out.Addresses, encAddress{Address: a.String(), Private: encdns.Private(a)})
	}
	slices.SortFunc(out.Addresses, func(a, b encAddress) int { return strings.Compare(a.Address, b.Address) })
	host := strings.TrimSuffix(r.URL.Query().Get("hostname"), ".")
	if host == "" {
		host = out.Hostname
	}
	for _, x := range s.eng.Exposures(st) {
		if x.View == "" {
			continue
		}
		v := encView{Name: x.View, Public: x.Public}
		if host != "" {
			if vv := st.ViewByName(x.View); vv != nil {
				for _, z := range st.ZonesInView(vv.ID) {
					if z.Type == model.ZonePrimary && (host+"." == z.Name || strings.HasSuffix(host+".", "."+z.Name)) {
						v.HasZone = true
					}
				}
			}
		}
		out.Views = append(out.Views, v)
	}
	writeJSON(w, http.StatusOK, out)
	return nil
}

// encryptedDNSCheck: POST /encrypted-dns/check {"addresses", "dot", "doh",
// "doh_port"} says what already listens where the listeners would go.
func (s *Server) encryptedDNSCheck(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := s.encReady(p, false); err != nil {
		return err
	}
	var in encdns.Setup
	if err := decodeJSON(r, &in); err != nil {
		return err
	}
	st, err := s.store.LoadState(r.Context())
	if err != nil {
		return err
	}
	if in.DoHPort == 0 {
		in.DoHPort = 443
	}
	if in.DoTPort == 0 {
		in.DoTPort = encdns.DoTPort
	}
	var ports []int
	if in.DoT {
		ports = append(ports, in.DoTPort)
	}
	if in.DoH {
		ports = append(ports, in.DoHPort)
	}
	conflicts, err := encdns.PortCheck(st, in.Addresses, ports, s.cfg.Listen)
	out := map[string]any{"conflicts": conflicts}
	if err != nil {
		out["error"] = "can't see which ports are in use: " + err.Error()
	}
	if conflicts == nil {
		out["conflicts"] = []encdns.Conflict{}
	}
	if in.DoH {
		out["free_doh_port"] = encdns.FreeDoHPort(st, in.Addresses, s.cfg.Listen)
	}
	writeJSON(w, http.StatusOK, out)
	return nil
}

// encryptedDNSSetup: POST /encrypted-dns stages (or applies) the setup.
func (s *Server) encryptedDNSSetup(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := s.encReady(p, true); err != nil {
		return err
	}
	var in encdns.Setup
	if err := decodeJSON(r, &in); err != nil {
		return err
	}
	c, err := s.cfg.Certs.Get(r.Context(), in.Certificate)
	if err != nil {
		return certErr(err)
	}
	switch {
	case !c.HasUse(model.CertUseDNS):
		return badRequest("certificate %s doesn't have the dns use, so named can't read it: jarl cert update %s --use dns (and keep its other uses)", c.Name, c.Name)
	case c.NotAfter == nil:
		return conflict("certificate %s hasn't been obtained yet (%s); set up encrypted DNS once it has", c.Name, s.cfg.Certs.StatusOf(c).Message)
	case in.Hostname != "" && !certs.Covers(c.Names, []string{in.Hostname}):
		return badRequest("certificate %s is for %s, not %s: clients would reject it", c.Name, strings.Join(c.Names, ", "), in.Hostname)
	}
	st, err := s.store.LoadState(r.Context())
	if err != nil {
		return err
	}
	reqs, notes, err := encdns.Plan(st, in, s.cfg.Certs.FilesDir(""))
	if err != nil {
		return badRequest("%v", err)
	}
	what := []string{}
	if in.DoT {
		what = append(what, "DNS over TLS")
	}
	if in.DoH {
		what = append(what, "DNS over HTTPS")
	}
	return s.mutateNotes(w, r, p, "set up "+strings.Join(what, " and ")+" for "+in.Hostname, reqs, nil, notes)
}

// encryptedDNSDisable: DELETE /encrypted-dns.
func (s *Server) encryptedDNSDisable(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := s.encReady(p, true); err != nil {
		return err
	}
	st, err := s.store.LoadState(r.Context())
	if err != nil {
		return err
	}
	reqs := encdns.Disable(st)
	if len(reqs) == 0 {
		return conflict("encrypted DNS isn't set up")
	}
	return s.mutate(w, r, p, "turn DNS over TLS and HTTPS off", reqs, nil)
}