// Package sourcerefs validates D&D NPC interaction transcript evidence.
package sourcerefs

import (
	"context"
	"fmt"

	"gitea.maximumdirect.net/eric/notarius/internal/core/source"
	"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"
	interactionshape "gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/validate/npcinteractions/shape"
)

const (
	Key        = "extract/dnd/npc-interactions/source_refs"
	ReasonCode = "invalid_npc_interaction_source_refs"
	policy     = "dnd.npc_interactions.validator.source_refs.v2"
)

type Options struct{}
type Validator struct{}

var _ contracts.TypedValidator[dnd.NPCInteractionList] = (*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.NPCInteractionList]) (contracts.ValidationResult, error) {
	if req.Stage == string(pipeline.StageExtract) && req.Chunk == nil {
		return contracts.ValidationResult{}, fmt.Errorf("NPC interaction source-reference validator requires the current extraction chunk")
	}
	if interactionshape.Validate(req.Value) != nil {
		return contracts.ValidationResult{Approved: true}, nil
	}
	index := source.NewDocumentIndex(req.Source)
	issues := make([]string, 0)
	for interactionIndex, interaction := range req.Value.Interactions {
		for refIndex, ref := range interaction.SourceRefs {
			if err := index.ValidateRef(ref); err != nil {
				issues = append(issues, fmt.Sprintf("interactions[%d].source_refs[%d]: %s", interactionIndex, refIndex, diagnostics.Truncate(err.Error())))
				continue
			}
			if req.Stage == string(pipeline.StageExtract) && !chunkContainsRef(req.Chunk, ref) {
				issues = append(issues, fmt.Sprintf(
					"interactions[%d].source_refs[%d]: source reference is outside the current extraction chunk",
					interactionIndex, refIndex,
				))
			}
		}
	}
	if len(issues) == 0 {
		return contracts.ValidationResult{Approved: true}, nil
	}
	return contracts.ValidationResult{
		Approved:   false,
		ReasonCode: ReasonCode,
		Message:    diagnostics.Aggregate("invalid NPC interaction source references", issues),
	}, nil
}

func chunkContainsRef(chunk *source.Chunk, ref source.SourceRef) bool {
	if chunk == nil || ref.SourceID != chunk.SourceID {
		return false
	}
	startFound := false
	endFound := false
	for _, unit := range chunk.Units {
		startFound = startFound || unit.ID == ref.StartUnitID
		endFound = endFound || unit.ID == ref.EndUnitID
	}
	return startFound && endFound
}

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

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