// Package sourcerelatedness warns when scene prose has no lexical grounding.
package sourcerelatedness

import (
	"context"
	"fmt"
	"unicode/utf8"

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

const (
	Key               = "extract/dnd/scene-descriptions/source_relatedness"
	WarningReasonCode = "scene_description_not_near_source"
	OmittedReasonCode = "scene_description_relatedness_warnings_omitted"
	policy            = "dnd.scene_descriptions.validator.source_relatedness.v1"
)

var stopwords = map[string]struct{}{
	"a": {}, "an": {}, "and": {}, "are": {}, "as": {}, "at": {}, "be": {}, "but": {}, "by": {}, "for": {}, "from": {},
	"had": {}, "has": {}, "have": {}, "he": {}, "her": {}, "him": {}, "his": {}, "in": {}, "into": {}, "is": {}, "it": {}, "its": {},
	"of": {}, "on": {}, "or": {}, "she": {}, "that": {}, "the": {}, "their": {}, "them": {}, "they": {}, "this": {}, "to": {},
	"was": {}, "were": {}, "with": {},
}

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 shape.Validate(req.Value) != nil || !sourceRefsValid(req.Source, req.Value) {
		return contracts.ValidationResult{Approved: true}, nil
	}
	warnings := make([]contracts.Warning, 0)
	for index, scene := range req.Value.Scenes {
		citedText, err := shared.CitedText(req.Source, []source.SourceRef{scene.SourceRef})
		if err != nil {
			return contracts.ValidationResult{Approved: true}, nil
		}
		citedTokens := tokenSet(citedText)
		if !hasGroundedToken(citedTokens, scene.Title) {
			warnings = append(warnings, warning(index, "title"))
		}
		if !hasGroundedToken(citedTokens, scene.Summary) {
			warnings = append(warnings, warning(index, "summary"))
		}
	}
	return contracts.ValidationResult{
		Approved: true,
		Warnings: diagnostics.LimitWarnings(warnings, "scenes", OmittedReasonCode),
	}, nil
}

func sourceRefsValid(doc *source.SourceDocument, value dnd.SceneDescriptionList) bool {
	for _, scene := range value.Scenes {
		if source.ValidateRef(doc, scene.SourceRef) != nil {
			return false
		}
	}
	return true
}

func tokenSet(value string) map[string]struct{} {
	tokens := make(map[string]struct{})
	for _, token := range shared.NormalizedTokens(value) {
		if significant(token) {
			tokens[token] = struct{}{}
		}
	}
	return tokens
}

func hasGroundedToken(cited map[string]struct{}, value string) bool {
	for _, token := range shared.NormalizedTokens(value) {
		if !significant(token) {
			continue
		}
		if _, ok := cited[token]; ok {
			return true
		}
	}
	return false
}

func significant(token string) bool {
	if utf8.RuneCountInString(token) < 3 {
		return false
	}
	_, ignored := stopwords[token]
	return !ignored
}

func warning(index int, field string) contracts.Warning {
	return contracts.Warning{
		Scope:      fmt.Sprintf("scenes[%d].%s", index, field),
		ReasonCode: WarningReasonCode,
		Message:    "scene description " + field + " has no significant token in cited source text",
	}
}

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 }