// Package shape validates required D&D item-event candidate 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/itemevents"
	"gitea.maximumdirect.net/eric/notarius/internal/modules/dnd/shared/diagnostics"
)

const (
	Key        = "extract/dnd/item-events/shape"
	ReasonCode = "invalid_item_event_shape"
	policy     = "dnd.item_events.shape.v1"
)

type Options struct{}
type Validator struct{}

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

// Validate returns one bounded error for every owned item-event shape issue.
func Validate(value dnd.ItemEventList) error {
	issues := issuesFor(value)
	if len(issues) == 0 {
		return nil
	}
	return fmt.Errorf("%s", diagnostics.Aggregate("invalid item event shape", issues))
}

func issuesFor(value dnd.ItemEventList) []string {
	if value.Events == nil {
		return []string{"events must be present"}
	}
	issues := make([]string, 0)
	for index, event := range value.Events {
		prefix := fmt.Sprintf("events[%d]", index)
		if strings.TrimSpace(event.Name) == "" {
			issues = append(issues, prefix+".name must not be empty: "+diagnostics.Quote(event.Name))
		}
		if !itemevents.SupportedKind(event.Kind) {
			issues = append(issues, prefix+".kind is unsupported: "+diagnostics.Quote(string(event.Kind)))
		} else if !itemevents.ValidHolderCombination(event.Kind, event.From, event.To) {
			issues = append(issues, prefix+".from and .to are incompatible with "+diagnostics.Quote(string(event.Kind)))
		}
		if event.Quantity != nil && *event.Quantity < 1 {
			issues = append(issues, prefix+".quantity must be positive when present")
		}
		if len(event.SourceRefs) == 0 {
			issues = append(issues, prefix+".source_refs must contain at least one reference")
		}
	}
	return issues
}

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

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