// SPDX-License-Identifier: MIT

package checker

import (
	"context"
	"fmt"
	"sort"
	"strings"

	sdk "git.happydns.org/checker-sdk-go/checker"
)

// Rules returns the full rule set evaluated against a DNSVizData observation.
// Subject is the zone FQDN so a fault at the TLD is never silently merged with a leaf fault.
func Rules() []sdk.CheckRule {
	return []sdk.CheckRule{
		&overallStatusRule{},
		&perZoneStatusRule{},
		&zoneErrorsRule{},
		&zoneWarningsRule{},
		&commonFailuresRule{},
	}
}

func loadData(ctx context.Context, obs sdk.ObservationGetter, code string) (*DNSVizData, []sdk.CheckState) {
	var data DNSVizData
	if err := obs.Get(ctx, ObservationKeyDNSViz, &data); err != nil {
		return nil, []sdk.CheckState{{
			Status:  sdk.StatusError,
			Code:    code,
			Message: fmt.Sprintf("Failed to load DNSViz observation: %v", err),
		}}
	}
	return &data, nil
}

func orderedZones(data *DNSVizData) []string {
	if len(data.Order) > 0 {
		return data.Order
	}
	keys := make([]string, 0, len(data.Zones))
	for k := range data.Zones {
		keys = append(keys, k)
	}
	sort.Slice(keys, func(i, j int) bool {
		return labelDepth(keys[i]) > labelDepth(keys[j])
	})
	return keys
}

// effectiveStatus returns the DNSSEC status for a zone, applying the
// inference chain that the observation layer deliberately leaves to rules:
//  1. delegation.status (z.Status) — the authoritative answer when present.
//  2. RRSIG-based inference — for zones without a delegation block (root),
//     dnsviz surfaces trust-anchor validation only through per-RRSIG statuses.
//  3. DNS rcode fallback (z.DNSStatus) — when the zone is unsigned or grok
//     did not classify it at all.
func effectiveStatus(z ZoneAnalysis) string {
	if z.Status != "" {
		return z.Status
	}
	if s := inferApexDNSKEYStatus(z.Queries); s != "" {
		return s
	}
	return z.DNSStatus
}

// inferApexDNSKEYStatus returns "SECURE", "BOGUS", or "" based on the
// status of RRSIGs covering the zone's apex DNSKEY rrset. dnsviz attaches
// a per-RRSIG status whenever a key reaches it (either through DS from
// the parent or through a configured trust anchor at this zone). For
// the root, this is the only place where trust-anchor validation
// surfaces in the grok output.
//
// queries is the value at zone["queries"], a map keyed by
// "<zone>/IN/<RRTYPE>". We pick the DNSKEY query and look at every
// RRSIG inside its answer.
func inferApexDNSKEYStatus(queries map[string]any) string {
	var dnskeyQ map[string]any
	for k, v := range queries {
		if !strings.HasSuffix(k, "/IN/DNSKEY") {
			continue
		}
		if m, ok := v.(map[string]any); ok {
			dnskeyQ = m
			break
		}
	}
	if dnskeyQ == nil {
		return ""
	}
	answers, _ := dnskeyQ["answer"].([]any)
	sawValid := false
	for _, a := range answers {
		am, _ := a.(map[string]any)
		if am == nil {
			continue
		}
		rrsigs, _ := am["rrsig"].([]any)
		for _, rs := range rrsigs {
			rm, _ := rs.(map[string]any)
			if rm == nil {
				continue
			}
			s, _ := rm["status"].(string)
			switch strings.ToUpper(s) {
			case "INVALID", "BOGUS", "EXPIRED", "PREMATURE":
				return "BOGUS"
			case "VALID", "SECURE":
				sawValid = true
			}
		}
	}
	if sawValid {
		return "SECURE"
	}
	return ""
}

func statusFromGrok(s string) sdk.Status {
	switch strings.ToUpper(strings.TrimSpace(s)) {
	case "SECURE":
		return sdk.StatusOK
	case "INSECURE":
		// "INSECURE" means "no DNSSEC and no parent DS": informational, not
		// a failure. Rules elsewhere can still flag a missing chain.
		return sdk.StatusInfo
	case "BOGUS":
		return sdk.StatusCrit
	case "INDETERMINATE":
		return sdk.StatusWarn
	case "NON_EXISTENT":
		return sdk.StatusInfo
	case "NOERROR":
		// DNS-level OK with no DNSSEC chain status reported. The zone
		// resolves but isn't signed (or grok didn't classify it).
		return sdk.StatusInfo
	case "":
		return sdk.StatusUnknown
	default:
		return sdk.StatusUnknown
	}
}