// Package shape validates the candidate shape of D&D enemy-event artifacts.
package shape

import (
	"context"
	"fmt"
	"strings"

	"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"
)

const (
	Key        = "extract/dnd/enemy-events/shape"
	ReasonCode = "invalid_enemy_event_shape"
	policy     = "dnd.enemy_events.validator.shape.v2"
)

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) {
	issues, corrections := assess(req.Value)
	if len(issues) != 0 {
		return contracts.ValidationResult{
			Approved:           false,
			ReasonCode:         ReasonCode,
			Message:            diagnostics.Aggregate("invalid enemy event shape", issues),
			CorrectionGuidance: corrections.Guidance("Correct every rejected enemy event and return the complete replacement event list"),
		}, nil
	}
	return contracts.ValidationResult{Approved: true}, nil
}

func Validate(value dnd.EnemyEventList) error {
	issues, _ := assess(value)
	if len(issues) == 0 {
		return nil
	}
	return fmt.Errorf("%s", diagnostics.Aggregate("invalid enemy event shape", issues))
}

func assess(value dnd.EnemyEventList) ([]string, diagnostics.Corrections) {
	var corrections diagnostics.Corrections
	if value.Events == nil {
		corrections.Add("list", "Return an `events` array; use an empty array when the combat scene establishes no enemy events.", "")
		return []string{"events must be present"}, corrections
	}
	issues := make([]string, 0)
	for eventIndex, event := range value.Events {
		prefix := fmt.Sprintf("events[%d]", eventIndex)
		record := fmt.Sprintf("Affected %s event for enemy %s %s.", diagnostics.Quote(string(event.Kind)), diagnostics.Quote(strings.TrimSpace(event.Name)), diagnostics.SourceRange(event.SourceRefs))
		if strings.TrimSpace(event.Name) == "" {
			issues = append(issues, prefix+".name must not be empty: "+diagnostics.Quote(event.Name))
			corrections.Add("name", "Select a nonblank contextual enemy name from the supplied NPC registry for every event.", record)
		}
		if !enemyeventmodel.SupportedKind(event.Kind) {
			issues = append(issues, prefix+".kind is unsupported: "+diagnostics.Quote(string(event.Kind)))
			corrections.Add("kind", "Set `kind` to exactly one of `engaged`, `killed`, `fled`, `captured`, or `incapacitated`.", record)
		}
		if len(event.SourceRefs) == 0 {
			issues = append(issues, prefix+".source_refs must contain at least one reference")
			corrections.Add("source-refs", "Provide at least one transcript source range that directly supports every enemy event.", record)
		}
	}
	return issues, corrections
}

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 }
