package dnssec

import (
	"fmt"
	"strings"
	"time"
)

// Phases of a zone, from unsigned to signed and back. Turning signing on:
// off -> starting -> signing -> ready (add the DS at the parent) ->
// ds_pending -> secure. Turning it off: secure -> removing_ds (remove the
// DS at the parent) -> ds_expiring -> removing_keys -> unsigned -> off.
const (
	PhaseOff          = "off"           // not signed, no keys
	PhaseLeftover     = "leftover_keys" // not signed, but old keys are still in the key directory
	PhaseStarting     = "starting"      // signing is on in Jarl; named hasn't made keys yet
	PhaseSigning      = "signing"       // keys made, zone signed; not yet safe to add the DS
	PhaseReady        = "ready"         // safe to add the DS at the parent
	PhaseDSPending    = "ds_pending"    // the DS is at the parent; named waits for its TTL
	PhaseSecure       = "secure"        // signed, and the parent's DS is in place
	PhaseRemovingDS   = "removing_ds"   // turning off: the DS must go from the parent first
	PhaseDSExpiring   = "ds_expiring"   // the DS is gone; named waits until caches forget it
	PhaseRemovingKeys = "removing_keys" // named removes the keys and signatures
	PhaseUnsigned     = "unsigned"      // turning off has finished; switch DNSSEC off
)

// Phase says where a zone is and what comes next.
type Phase struct {
	Code    string `json:"code"`
	Summary string `json:"summary"`
	Next    string `json:"next,omitempty"`
	// DSReadyAt is when the DS can safely be added at the parent (phase
	// signing).
	DSReadyAt *time.Time `json:"ds_ready_at,omitempty"`
	// CanPublishDS: the zone is ready for (or already has) a DS at the
	// parent.
	CanPublishDS bool `json:"can_publish_ds"`
	// CanFinish: the zone is being turned off and the parent has no DS
	// any more (as far as named knows), so DNSSEC can be switched off.
	CanFinish bool `json:"can_finish"`
	// NeedsDS lists the signing keys whose DS should be at the parent,
	// and StaleDS those whose DS should be removed from it.
	NeedsDS []uint16 `json:"needs_ds,omitempty"`
	StaleDS []uint16 `json:"stale_ds,omitempty"`
}

// Assess works out the phase of a zone signed with policy ("" when Jarl
// doesn't sign it, "insecure" while signing is being removed) that has
// keys.
func Assess(policy string, keys []*Key) Phase {
	var live []*Key // signing keys named keeps (or is introducing)
	for _, k := range keys {
		if k.SigningKey() && k.Goal == Omnipresent {
			live = append(live, k)
		}
	}
	switch {
	case policy == "":
		if len(keys) == 0 {
			return Phase{Code: PhaseOff, Summary: "DNSSEC is off."}
		}
		return Phase{Code: PhaseLeftover, Summary: "DNSSEC is off, but keys from when the zone was signed are still in its key directory.",
			Next: "Wipe them (jarl zone dnssec wipe) once you're sure the parent zone has no DS record for them, or turn signing on again to reuse them."}
	case policy == "insecure":
		return assessOff(keys)
	}
	if len(live) == 0 {
		return Phase{Code: PhaseStarting, Summary: "Signing is on; named hasn't created the zone's keys yet.",
			Next: "Wait a moment: named makes the keys when it loads the configuration."}
	}
	p := Phase{}
	var notReady []*Key
	for _, k := range live {
		if k.DNSKEYState != Omnipresent || k.KeyRRSIG != Omnipresent {
			notReady = append(notReady, k)
		}
	}
	for _, k := range keys {
		if k.SigningKey() && k.Goal == Hidden && k.DSState != Hidden && k.DSRemoved == nil {
			p.StaleDS = append(p.StaleDS, k.Tag)
		}
	}
	if len(notReady) > 0 {
		p.Code = PhaseSigning
		p.Summary = "named is signing the zone. Resolvers still treat it as unsigned, because the parent zone has no DS record for it."
		for _, k := range notReady {
			if k.PublishCDS != nil && (p.DSReadyAt == nil || k.PublishCDS.After(*p.DSReadyAt)) {
				t := *k.PublishCDS
				p.DSReadyAt = &t
			}
		}
		if p.DSReadyAt != nil {
			p.Next = fmt.Sprintf("Wait until %s before adding the DS at the parent: until then some resolvers may still have unsigned answers cached, and would reject them once the DS appears.", p.DSReadyAt.UTC().Format("Mon 2 Jan 15:04 MST"))
		} else {
			p.Next = "Wait until named has published the keys long enough for caches to pick them up before adding the DS."
		}
		return p
	}
	p.CanPublishDS = true
	var pending, secure int
	for _, k := range live {
		switch {
		case k.DSState == Omnipresent:
			secure++
		case k.DSPublished != nil:
			pending++
		default:
			p.NeedsDS = append(p.NeedsDS, k.Tag)
		}
	}
	switch {
	case len(p.NeedsDS) > 0:
		p.Code = PhaseReady
		p.Summary = "The zone is signed and ready: add the DS record at the parent zone (your registrar) to turn validation on."
		p.Next = "Add the DS record (" + tags(p.NeedsDS) + ") at your registrar, then run the DS check so named knows it's there."
	case pending > 0:
		p.Code = PhaseDSPending
		p.Summary = "The parent zone has the DS record. named waits for the parent's TTL before it treats it as in place."
	default:
		p.Code = PhaseSecure
		p.Summary = "The zone is signed and the parent zone's DS record points at its key: validating resolvers check its answers."
	}
	if len(p.StaleDS) > 0 && p.Next == "" {
		p.Next = "Remove the DS record of the retired key " + tags(p.StaleDS) + " at your registrar, then run the DS check."
	}
	return p
}

func assessOff(keys []*Key) Phase {
	var dsUp, dsGoing, keysLeft bool
	for _, k := range keys {
		if !k.SigningKey() {
			if !k.Gone() {
				keysLeft = true
			}
			continue
		}
		switch {
		case k.DSState == Hidden || k.DSState == "":
		case k.DSRemoved != nil:
			dsGoing = true
		default:
			dsUp = true
		}
		if !k.Gone() {
			keysLeft = true
		}
	}
	switch {
	case dsUp:
		return Phase{Code: PhaseRemovingDS, Summary: "Turning DNSSEC off: named keeps the zone signed until the parent zone's DS record is gone.",
			Next: "Remove the DS record at your registrar, then run the DS check so named knows. Don't switch DNSSEC off before that: the zone would fail to validate."}
	case dsGoing:
		return Phase{Code: PhaseDSExpiring, Summary: "Turning DNSSEC off: the parent's DS record is gone; named keeps signing until resolvers' cached copies of it expire (the parent's DS TTL, often a day).",
			Next: "Wait: switching DNSSEC off now would make the zone fail to validate for resolvers that still have the DS cached."}
	case keysLeft:
		return Phase{Code: PhaseRemovingKeys, Summary: "Turning DNSSEC off: the parent has no DS any more, and named is removing the keys and signatures.",
			Next: "Wait until named has finished, then switch DNSSEC off.", CanFinish: true}
	}
	return Phase{Code: PhaseUnsigned, Summary: "Turning DNSSEC off has finished: the zone is no longer signed.",
		Next: "Switch DNSSEC off for the zone to finish (jarl zone dnssec disable), and wipe the old keys if you like.", CanFinish: true}
}

func tags(ts []uint16) string {
	var s []string
	for _, t := range ts {
		s = append(s, fmt.Sprintf("key %d", t))
	}
	return strings.Join(s, ", ")
}