// Package engagements prevents duplicate enemy engagements within one scene.
package engagements

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"
	enemyeventmodel "gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/enemyevents"
	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/shared/diagnostics"
	enemyeventshape "gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/validate/enemyevents/shape"
)

const (
	Key        = "extract/dnd/enemy-events/engagements"
	ReasonCode = "duplicate_enemy_engagement"
	policy     = "dnd.enemy_events.validator.engagements.v1"
)

type Options struct{}
type Validator struct{}

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

func New(Options) *Validator      { return &Validator{} }
func (v *Validator) Name() string { return Key }
func (v *Validator) ExecutionClass() contracts.ExecutionClass {
	return contracts.ExecutionClassDeterministic
}
func (v *Validator) CheckpointFingerprints() []pipeline.CheckpointFingerprint {
	return []pipeline.CheckpointFingerprint{{Name: "policy", Value: policy}}
}

func (v *Validator) Validate(_ context.Context, req contracts.TypedValidationRequest[dnd.EnemyEventList]) (contracts.ValidationResult, error) {
	if enemyeventshape.Validate(req.Value) != nil {
		return contracts.ValidationResult{Approved: true}, nil
	}
	seen := make(map[string]struct{})
	for _, event := range req.Value.Events {
		if event.Kind != dnd.EnemyEventKindEngaged {
			continue
		}
		identity := enemyeventmodel.ComparisonKey(event.Name)
		if identity == "" {
			continue
		}
		if _, found := seen[identity]; found {
			return contracts.ValidationResult{
				Approved:   false,
				ReasonCode: ReasonCode,
				Message: diagnostics.Aggregate("duplicate enemy engagement", []string{
					fmt.Sprintf("subject %s has more than one engagement in one combat scene", diagnostics.Quote(event.Name)),
				}),
			}, nil
		}
		seen[identity] = struct{}{}
	}
	return contracts.ValidationResult{Approved: true}, nil
}

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

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

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 }