core/templates/bn/validation.go

package bn

import (
	"context"
	"io"

	"github.com/a-h/templ"
)

// validationContextKey is the key used to store validation tracking in context.
type validationContextKey struct{}

// ValidationTracker tracks which bn functions are called during template rendering.
// Used during template registration to validate templates include required calls.
type ValidationTracker struct {
	HeadCalled    bool
	BodyEndCalled bool
}

// NewValidationContext creates a context with validation tracking enabled.
// Use GetValidationTracker after rendering to check which functions were called.
func NewValidationContext(ctx context.Context) (context.Context, *ValidationTracker) {
	tracker := &ValidationTracker{}
	return context.WithValue(ctx, validationContextKey{}, tracker), tracker
}

// GetValidationTracker retrieves the validation tracker from context, if any.
func GetValidationTracker(ctx context.Context) *ValidationTracker {
	if tracker, ok := ctx.Value(validationContextKey{}).(*ValidationTracker); ok {
		return tracker
	}
	return nil
}

// recordValidationCall records that a bn function was called during rendering.
// Returns an empty component (renders nothing) but has the side effect of tracking the call.
func recordValidationCall(ctx context.Context, fnName string) templ.Component {
	if tracker := GetValidationTracker(ctx); tracker != nil {
		switch fnName {
		case "Head":
			tracker.HeadCalled = true
		case "BodyEnd":
			tracker.BodyEndCalled = true
		}
	}
	// Return empty component - renders nothing
	return templ.ComponentFunc(func(ctx context.Context, w io.Writer) error {
		return nil
	})
}