package policy

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"regexp"
	"sort"
	"strings"

	"gopkg.in/yaml.v3"
)

// POLICY-ATTRIBUTE-UNDECLARED is reported when a package reads
// input.{resource,subject}.attributes.<key> that no sibling registry or
// manifest supplies. The key then resolves only from caller input
// (FLEX-WP-0025-T03 / FLEX-DEC-2026-012).
const undeclaredAttributeCode = "POLICY-ATTRIBUTE-UNDECLARED"

var (
	attrDot = regexp.MustCompile(`input\.(resource|subject)\.attributes\.([A-Za-z_][A-Za-z0-9_]*)`)
	attrGet = regexp.MustCompile(`object\.get\(\s*input\.(resource|subject)\.attributes\s*,\s*"([A-Za-z_][A-Za-z0-9_]*)"`)
	attrNestedGet = regexp.MustCompile(`object\.get\(\s*object\.get\(\s*input\.(resource|subject)\s*,\s*"attributes"\s*,\s*\{\}\s*\)\s*,\s*"([A-Za-z_][A-Za-z0-9_]*)"`)
)

type attributeRead struct {
	Kind string
	Key  string
}

func (p *Package) undeclaredAttributeDiagnostics() []Diagnostic {
	reads := attributeReads(p.RegoModule)
	if len(reads) == 0 {
		return nil
	}
	dir := filepath.Dir(p.Source)
	if dir == "." || dir == "" || !filepath.IsAbs(p.Source) && !fileExists(p.Source) {
		// Inline documents have no sibling registry. Skip unless the source
		// path points at a real file (LoadAndValidateFile).
		if _, err := os.Stat(p.Source); err != nil {
			return nil
		}
	}
	supplied := siblingSuppliedAttributes(filepath.Dir(p.Source))
	var diagnostics []Diagnostic
	seen := map[string]bool{}
	for _, read := range reads {
		id := read.Kind + "." + read.Key
		if seen[id] {
			continue
		}
		seen[id] = true
		if supplied[read.Kind][read.Key] {
			continue
		}
		diagnostics = append(diagnostics, Diagnostic{
			Code:     undeclaredAttributeCode,
			Severity: "error",
			Message:  fmt.Sprintf("package reads input.%s.attributes.%s, which no sibling registry or manifest supplies; the value can only come from the caller", read.Kind, read.Key),
			Fields:   []string{"input." + read.Kind + ".attributes." + read.Key},
			Metadata: map[string]any{
				"kind": read.Kind,
				"key":  read.Key,
			},
		})
	}
	sort.Slice(diagnostics, func(i, j int) bool {
		return diagnostics[i].Message < diagnostics[j].Message
	})
	return diagnostics
}

func attributeReads(regoModule string) []attributeRead {
	var reads []attributeRead
	add := func(kind, key string) {
		reads = append(reads, attributeRead{Kind: kind, Key: key})
	}
	for _, re := range []*regexp.Regexp{attrDot, attrGet, attrNestedGet} {
		for _, match := range re.FindAllStringSubmatch(regoModule, -1) {
			add(match[1], match[2])
		}
	}
	return reads
}

func siblingSuppliedAttributes(dir string) map[string]map[string]bool {
	out := map[string]map[string]bool{
		"resource": {},
		"subject":  {},
	}
	names := []string{
		"registry_snapshot.json",
		"production_registry_snapshot.json",
		"registry.json",
		"resource_manifest.yaml",
		"subject_manifest.yaml",
	}
	for _, name := range names {
		path := filepath.Join(dir, name)
		data, err := os.ReadFile(path)
		if err != nil {
			continue
		}
		var doc any
		if strings.HasSuffix(name, ".json") {
			if err := json.Unmarshal(data, &doc); err != nil {
				continue
			}
		} else if err := yaml.Unmarshal(data, &doc); err != nil {
			continue
		}
		collectSuppliedAttributes(doc, out)
	}
	return out
}

func collectSuppliedAttributes(doc any, out map[string]map[string]bool) {
	obj, ok := asMap(doc)
	if !ok {
		return
	}
	if resources, ok := asList(obj["resources"]); ok {
		for _, item := range resources {
			collectResourceKeys(item, out["resource"])
		}
	}
	if manifests, ok := asList(obj["resource_manifests"]); ok {
		for _, item := range manifests {
			collectSuppliedAttributes(item, out)
		}
	}
	if subjects, ok := asList(obj["subjects"]); ok {
		for _, item := range subjects {
			collectSubjectKeys(item, out["subject"])
		}
	}
}

func asList(value any) ([]any, bool) {
	switch typed := value.(type) {
	case []any:
		return typed, true
	default:
		return nil, false
	}
}

func collectResourceKeys(item any, keys map[string]bool) {
	obj, ok := asMap(item)
	if !ok {
		return
	}
	// First-class fields enrichment copies into attributes.
	for _, key := range []string{"path", "parent", "labels", "trust_zone", "owner"} {
		keys[key] = true
	}
	addMapKeys(obj["attributes"], keys)
}

func collectSubjectKeys(item any, keys map[string]bool) {
	obj, ok := asMap(item)
	if !ok {
		return
	}
	for _, key := range []string{"display_name", "organization_relation", "roles", "groups"} {
		keys[key] = true
	}
	addMapKeys(obj["attributes"], keys)
	addMapKeys(obj["claims"], keys)
	addMapKeys(obj["metadata"], keys)
}

func addMapKeys(value any, keys map[string]bool) {
	obj, ok := asMap(value)
	if !ok {
		return
	}
	for key := range obj {
		keys[key] = true
	}
}

func asMap(value any) (map[string]any, bool) {
	switch typed := value.(type) {
	case map[string]any:
		return typed, true
	case map[any]any:
		return stringifyKeys(typed), true
	default:
		return nil, false
	}
}

func stringifyKeys(in map[any]any) map[string]any {
	out := make(map[string]any, len(in))
	for key, value := range in {
		out[fmt.Sprint(key)] = value
	}
	return out
}

func fileExists(path string) bool {
	_, err := os.Stat(path)
	return err == nil
}