// Package registry validates D&D NPC occurrence names against NPC grounding.
package registry

import (
	"context"
	"fmt"

	"gitea.maximumdirect.net/eric/notarius/internal/framework/contracts"
	"gitea.maximumdirect.net/eric/notarius/internal/framework/pipeline"
	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd"
	npcregistry "gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/npcs/registry"
	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/shared/diagnostics"
	occurrenceshape "gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/validate/npcoccurrences/shape"
)

const (
	Key        = "extract/dnd/npc-occurrences/registry"
	ReasonCode = "invalid_npc_occurrence_registry"
	policy     = "dnd.npc_occurrences.validator.registry.v2"
)

type Options struct{}

type Validator struct {
	npcResolver *npcregistry.Resolver
}

var _ contracts.TypedValidator[dnd.NPCOccurrenceList] = (*Validator)(nil)
var _ contracts.ManifestMetadataProvider = (*Validator)(nil)
var _ pipeline.CheckpointFingerprintProvider = (*Validator)(nil)

func New(_ Options, references ...contracts.ReferenceSet) (*Validator, error) {
	if len(references) > 1 {
		return nil, fmt.Errorf("NPC occurrence registry validator accepts at most one reference set")
	}
	var referenceSet contracts.ReferenceSet
	if len(references) == 1 {
		referenceSet = references[0]
	}
	resolver, err := npcregistry.NewResolver(referenceSet)
	if err != nil {
		return nil, fmt.Errorf("prepare NPC registry: %w", err)
	}
	return &Validator{npcResolver: resolver}, nil
}

func (v *Validator) Name() string { return Key }
func (v *Validator) ExecutionClass() contracts.ExecutionClass {
	return contracts.ExecutionClassDeterministic
}

func (v *Validator) ManifestMetadata() map[string]any {
	if v == nil || v.npcResolver == nil {
		return nil
	}
	metadata := map[string]any{"policy": policy}
	seeded := v.npcResolver.Seeded()
	if seeded.Bound() {
		metadata["npc_registry_digest"] = seeded.Digest()
		metadata["npc_count"] = seeded.Count()
	}
	return metadata
}

func (v *Validator) CheckpointFingerprints() []pipeline.CheckpointFingerprint {
	if v == nil || v.npcResolver == nil {
		return nil
	}
	return []pipeline.CheckpointFingerprint{
		{Name: "policy", Value: policy},
		{Name: "npc_registry", Value: v.npcResolver.Seeded().IdentityDigest()},
	}
}

func (v *Validator) Validate(_ context.Context, req contracts.TypedValidationRequest[dnd.NPCOccurrenceList]) (contracts.ValidationResult, error) {
	if occurrenceshape.Validate(req.Value) != nil {
		return contracts.ValidationResult{Approved: true}, nil
	}
	if v == nil || v.npcResolver == nil {
		return contracts.ValidationResult{}, fmt.Errorf("NPC occurrence registry validator must not be nil")
	}
	npcRegistry, err := v.npcResolver.Resolve(req.References)
	if err != nil {
		return contracts.ValidationResult{}, fmt.Errorf("resolve NPC registry: %w", err)
	}
	if !npcRegistry.Bound() {
		var corrections diagnostics.Corrections
		corrections.Add("registry", "Use only contextual NPC names from the supplied NPC registry; omit an occurrence that cannot be matched unambiguously.", "")
		return rejection([]string{"NPC registry reference is required"}, corrections), nil
	}
	issues := make([]string, 0)
	var corrections diagnostics.Corrections
	for index, occurrence := range req.Value.Occurrences {
		record := fmt.Sprintf("Affected %s occurrence for NPC %s %s.", diagnostics.Quote(string(occurrence.Kind)), diagnostics.Quote(occurrence.Name), diagnostics.SourceRange(occurrence.SourceRefs))
		canonical, ok := npcRegistry.LookupID(occurrence.NPCID)
		if !ok {
			issues = append(issues, fmt.Sprintf("occurrences[%d].npc_id is not in the NPC registry: %s", index, diagnostics.Quote(occurrence.NPCID)))
			corrections.Add("registry", "Use only contextual NPC names from the supplied NPC registry; omit an occurrence that cannot be matched unambiguously.", record)
			continue
		}
		if occurrence.Name != canonical.Name {
			issues = append(issues, fmt.Sprintf("occurrences[%d].name does not match npc_id: %s", index, diagnostics.Quote(occurrence.Name)))
			corrections.Add("canonical-name", "Use the exact contextual NPC name supplied by the registry.", record+" Use registry name "+diagnostics.Quote(canonical.Name)+".")
		}
	}
	if len(issues) == 0 {
		return contracts.ValidationResult{Approved: true}, nil
	}
	return rejection(issues, corrections), nil
}

func rejection(issues []string, corrections diagnostics.Corrections) contracts.ValidationResult {
	return contracts.ValidationResult{
		Approved:           false,
		ReasonCode:         ReasonCode,
		Message:            diagnostics.Aggregate("invalid NPC occurrence registry", issues),
		CorrectionGuidance: corrections.Guidance("Correct every rejected NPC occurrence and return the complete replacement occurrence list"),
	}
}

func Spec() pipeline.ValidatorSpec {
	return pipeline.ValidatorSpec{Key: Key, ExecutionClass: contracts.ExecutionClassDeterministic}
}

func Register(registry *pipeline.ValidatorRegistry) error {
	return pipeline.RegisterTypedValidatorBuilder(registry, dnd.NPCOccurrenceListKind, Spec(), validateOptions, func(request pipeline.BuildRequest) (contracts.TypedValidator[dnd.NPCOccurrenceList], error) {
		options, err := DecodeOptions(request.Options)
		if err != nil {
			return nil, err
		}
		return New(options, request.References)
	})
}

func DecodeOptions(options map[string]any) (Options, error) {
	if err := pipeline.RejectUnknownOptions(options); err != nil {
		return Options{}, err
	}
	return Options{}, nil
}

func validateOptions(options map[string]any) error { _, err := DecodeOptions(options); return err }
