package server

import (
	"context"
	"net/http"
	"time"

	"jarl/internal/auth"
	"jarl/internal/mailcheck"
)

// mailCheckEvery is how often jarld checks the reverse DNS of the
// addresses that send and receive mail (docs/exposure.md#mail).
const mailCheckEvery = 6 * time.Hour

// checkMail checks the reverse DNS of the public zones' mail addresses and
// keeps the report; it logs addresses that became wrong.
func (s *Server) checkMail(ctx context.Context) *mailcheck.Report {
	st, err := s.store.LoadState(ctx)
	if err != nil {
		s.log.Warn("mail reverse DNS check: loading state", "err", err)
		return nil
	}
	public := map[int64]bool{}
	for _, x := range s.eng.Exposures(st) {
		public[x.ViewID] = x.Public
	}
	if len(st.Views) == 0 {
		public[0] = true
	}
	ctx, cancel := context.WithTimeout(ctx, 2*time.Minute)
	defer cancel()
	rep := mailcheck.Check(ctx, st, func(id int64) bool { return public[id] }, mailcheck.Resolver{Servers: s.cfg.Resolvers})
	s.mail.Lock()
	prev := s.mail.r
	s.mail.r = rep
	s.mail.Unlock()
	was := map[string]bool{}
	if prev != nil {
		for _, r := range prev.Results {
			was[r.Zone+"|"+r.Address] = r.OK
		}
	}
	for _, r := range rep.Results {
		if ok, seen := was[r.Zone+"|"+r.Address]; !r.OK && (ok || !seen) {
			s.log.Warn("mail reverse DNS", "zone", r.Zone, "address", r.Address, "problem", r.Message)
		}
	}
	return rep
}

func (s *Server) mailReport() *mailcheck.Report {
	s.mail.Lock()
	defer s.mail.Unlock()
	return s.mail.r
}

// mailCheckNow: POST /exposure/mail checks now and returns the report.
func (s *Server) mailCheckNow(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
	if err := require(p, auth.Action{Resource: auth.ResOptions}); err != nil {
		return err
	}
	rep := s.checkMail(r.Context())
	if rep == nil {
		rep = &mailcheck.Report{Checked: time.Now(), Results: []mailcheck.Result{}}
	}
	writeJSON(w, http.StatusOK, rep)
	return nil
}

// mailLoop checks a minute after the start, then every mailCheckEvery.
func (s *Server) mailLoop(ctx context.Context) {
	wait := time.Minute
	for {
		select {
		case <-ctx.Done():
			return
		case <-time.After(wait):
			s.checkMail(ctx)
			wait = mailCheckEvery
		}
	}
}