// SPDX-License-Identifier: MIT

package checker

import (
	"encoding/json"
	"fmt"
	"sort"
	"strings"
)

// ParseGrokOutput decodes the JSON produced by `dnsviz grok` into a typed
// map of zone analyses. Order lists zones from most-specific to root.
func ParseGrokOutput(raw []byte) (map[string]ZoneAnalysis, []string, error) {
	var top map[string]json.RawMessage
	if err := json.Unmarshal(raw, &top); err != nil {
		return nil, nil, err
	}

	out := make(map[string]ZoneAnalysis, len(top))
	for k, v := range top {
		// Skip non-zone keys some dnsviz versions emit (e.g. "_meta").
		if k == "" || strings.HasPrefix(k, "_") {
			continue
		}
		out[k] = decodeZone(v)
	}

	keys := make([]string, 0, len(out))
	for k := range out {
		keys = append(keys, k)
	}
	sort.Slice(keys, func(i, j int) bool {
		return labelDepth(keys[i]) > labelDepth(keys[j])
	})
	return out, keys, nil
}

func decodeZone(raw json.RawMessage) ZoneAnalysis {
	var z ZoneAnalysis
	var node any
	if err := json.Unmarshal(raw, &node); err != nil {
		return z
	}
	m, ok := node.(map[string]any)
	if !ok {
		if s, ok := node.(string); ok {
			z.Status = s
		}
		return z
	}

	if s, ok := m["status"].(string); ok {
		z.DNSStatus = s
	}
	// DNSSEC chain status lives under delegation.status.
	if del, ok := m["delegation"].(map[string]any); ok {
		if s, ok := del["status"].(string); ok {
			z.Status = s
		}
	}
	// Root has no parent and therefore no delegation block. dnsviz signals
	// trust-anchor validation through the RRSIG covering the apex DNSKEY
	// rrset (queries.<zone>/IN/DNSKEY.answer[*].rrsig[*].status). With
	// `dnsviz grok -t …` and a matching anchor, that RRSIG becomes VALID
	// and we lift the zone to SECURE; an INVALID/EXPIRED RRSIG drags it
	// to BOGUS. Without a trust anchor, this leaves Status empty and we
	// fall back to the DNS rcode below.
	if z.Status == "" {
		z.Status = inferApexDNSKEYStatus(m["queries"])
	}
	if z.Status == "" {
		z.Status = z.DNSStatus
	}

	z.Errors, z.Warnings = collectFindings(m, "")
	return z
}

func collectFindings(node any, path string) (errs, warns []Finding) {
	switch v := node.(type) {
	case map[string]any:
		for k, val := range v {
			sub := joinPath(path, k)
			switch k {
			case "errors":
				errs = append(errs, asFindings(val, path)...)
				continue
			case "warnings":
				warns = append(warns, asFindings(val, path)...)
				continue
			}
			e, w := collectFindings(val, sub)
			errs = append(errs, e...)
			warns = append(warns, w...)
		}
	case []any:
		for i, item := range v {
			sub := fmt.Sprintf("%s[%d]", path, i)
			e, w := collectFindings(item, sub)
			errs = append(errs, e...)
			warns = append(warns, w...)
		}
	}
	return
}

func joinPath(parent, key string) string {
	if parent == "" {
		return key
	}
	return parent + "/" + key
}

// asFindings turns a value attached to an "errors"/"warnings" key into a
// slice of Finding. DNSViz uses a few shapes here across versions:
//   - []object{description, code, servers}
//   - []string (rare, very old grok)
//   - object keyed by code -> entry (newer grok flattens findings by code)
func asFindings(raw any, path string) []Finding {
	switch v := raw.(type) {
	case []any:
		out := make([]Finding, 0, len(v))
		for _, item := range v {
			out = append(out, makeFinding(item, "", path))
		}
		return out
	case map[string]any:
		out := make([]Finding, 0, len(v))
		keys := make([]string, 0, len(v))
		for k := range v {
			keys = append(keys, k)
		}
		sort.Strings(keys)
		for _, k := range keys {
			out = append(out, makeFinding(v[k], k, path))
		}
		return out
	case []string:
		out := make([]Finding, 0, len(v))
		for _, s := range v {
			out = append(out, Finding{Description: s, Path: path})
		}
		return out
	}
	return nil
}

func makeFinding(item any, codeHint, path string) Finding {
	f := Finding{Path: path, Code: codeHint}
	switch v := item.(type) {
	case string:
		f.Description = v
	case map[string]any:
		if s, ok := v["code"].(string); ok && s != "" {
			f.Code = s
		}
		if s, ok := v["description"].(string); ok && s != "" {
			f.Description = s
		} else if s, ok := v["message"].(string); ok && s != "" {
			f.Description = s
		}
		if servers, ok := v["servers"].([]any); ok {
			for _, s := range servers {
				if str, ok := s.(string); ok {
					f.Servers = append(f.Servers, str)
				}
			}
		}
		// If we couldn't extract a human description, keep the raw structure
		// in Extra rather than synthesising a JSON blob into the description
		// field (which would then be rendered as ugly text in the report).
		if f.Description == "" {
			f.Extra = v
		}
	default:
		// Unknown shape: stash the raw value so the report can still surface
		// it from a debug section, but don't pollute Description.
		f.Extra = map[string]any{"value": item}
	}
	return f
}

// 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 any) string {
	q, ok := queries.(map[string]any)
	if !ok {
		return ""
	}
	var dnskeyQ map[string]any
	for k, v := range q {
		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 labelDepth(zone string) int {
	z := strings.TrimSuffix(zone, ".")
	if z == "" {
		return 0
	}
	return strings.Count(z, ".") + 1
}