// Package shape validates required D&D scene description fields.
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"
	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/shared/diagnostics"
)

const (
	Key        = "extract/dnd/scene-descriptions/shape"
	ReasonCode = "invalid_scene_description_shape"
	policy     = "dnd.scene_descriptions.validator.shape.v1"
)

type Options struct{}
type Validator struct{}

var _ contracts.TypedValidator[dnd.SceneDescriptionList] = (*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.SceneDescriptionList]) (contracts.ValidationResult, error) {
	if err := ValidateForStage(req.Value, req.Stage); err != nil {
		return contracts.ValidationResult{Approved: false, ReasonCode: ReasonCode, Message: err.Error()}, nil
	}
	return contracts.ValidationResult{Approved: true}, nil
}

func Validate(value dnd.SceneDescriptionList) error { return validate(value, false) }

func ValidateForStage(value dnd.SceneDescriptionList, stage string) error {
	return validate(value, stage == string(pipeline.StageExtract))
}

func validate(value dnd.SceneDescriptionList, exactlyOne bool) error {
	issues := make([]string, 0)
	if value.Scenes == nil {
		issues = append(issues, "scenes must be present")
	} else if len(value.Scenes) == 0 {
		issues = append(issues, "scenes must not be empty")
	} else if exactlyOne && len(value.Scenes) != 1 {
		issues = append(issues, "extraction must contain exactly one scene")
	}
	for index, scene := range value.Scenes {
		prefix := fmt.Sprintf("scenes[%d]", index)
		if strings.TrimSpace(scene.ID) == "" || scene.ID != strings.TrimSpace(scene.ID) {
			issues = append(issues, prefix+".id must be non-empty and trimmed")
		}
		if !ValidKind(scene.Kind) {
			issues = append(issues, prefix+".kind is unsupported: "+diagnostics.Quote(string(scene.Kind)))
		}
		if strings.TrimSpace(scene.Title) == "" || scene.Title != strings.TrimSpace(scene.Title) {
			issues = append(issues, prefix+".title must be non-empty and trimmed")
		}
		if strings.TrimSpace(scene.Summary) == "" || scene.Summary != strings.TrimSpace(scene.Summary) {
			issues = append(issues, prefix+".summary must be non-empty and trimmed")
		}
		if strings.TrimSpace(scene.SourceRef.SourceID) == "" || scene.SourceRef.SourceID != strings.TrimSpace(scene.SourceRef.SourceID) || scene.SourceRef.StartUnitID <= 0 || scene.SourceRef.EndUnitID <= 0 {
			issues = append(issues, prefix+".source_ref must have a trimmed source ID and positive unit IDs")
		}
	}
	if len(issues) == 0 {
		return nil
	}
	return fmt.Errorf("%s", diagnostics.Aggregate("invalid scene description shape", issues))
}

func ValidKind(value dnd.SceneKind) bool {
	switch value {
	case dnd.SceneKindCombat, dnd.SceneKindNarrative, dnd.SceneKindRecap, dnd.SceneKindMeta:
		return true
	default:
		return false
	}
}

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

func Register(registry *pipeline.ValidatorRegistry) error {
	return pipeline.RegisterTypedValidatorBuilder(registry, dnd.SceneDescriptionListKind, Spec(), validateOptions, func(request pipeline.BuildRequest) (contracts.TypedValidator[dnd.SceneDescriptionList], 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 }