private void checkStructure(PsiElement document, @NotNull AnnotationHolder annotationHolder) {
    PsiElement[] children = document.getChildren();
    List<String> acceptedTag = Arrays.asList("template","element","script", "style");
    for (PsiElement element : children) {
        if (element instanceof HtmlTag) {
            if (!acceptedTag.contains(((HtmlTag) element).getName().toLowerCase())) {
                annotationHolder.createErrorAnnotation(element, "Invalid tag '"
                        + ((HtmlTag) element).getName() + "', only the [template, element, script, style] tags are allowed here.");
            }
            checkAttributes((XmlTag) element, annotationHolder);
        } else {
            if (!(element instanceof PsiWhiteSpace)
                    && !(element instanceof XmlProlog)
                    && !(element instanceof XmlText)
                    && !(element instanceof XmlComment)) {
                String s = element.getText();
                if (s.length() > 20) {
                    s = s.substring(0, 20);
                }
                annotationHolder.createErrorAnnotation(element, "Invalid content '" + s +
                        "', only the [template, script, style] tags are allowed here.");
            }
        }
    }
}
 

public static List<String> loadImportedTags(@NotNull XmlFile file, @NotNull XmlTag context) {
//        PsiElement[] arr = file.getRootTag().getChildren();
//        Collection<HtmlTag> tags = PsiTreeUtil.findChildrenOfType(file, HtmlTag.class);
        PsiElement[] reqTags = PsiTreeUtil.collectElements(file, new PsiElementFilter() {
            @Override
            public boolean isAccepted(PsiElement element) {
                return element instanceof HtmlTag && (((HtmlTag) element).getName().equals(RTTagDescriptorsProvider.RT_REQUIRE) || ((HtmlTag) element).getName().equals(RTTagDescriptorsProvider.RT_IMPORT));
            }
        });

        List<String> importedTags = new ArrayList<String>();
        for (PsiElement elem : reqTags) {
            String as = ((HtmlTag) elem).getAttributeValue("as");
            if (!Strings.isNullOrEmpty(as)) {
                importedTags.add(as);
            }
        }
        return importedTags;
    }
 

public static List<String> loadImportedTags(@NotNull XmlFile file, @NotNull XmlTag context) {
//        PsiElement[] arr = file.getRootTag().getChildren();
//        Collection<HtmlTag> tags = PsiTreeUtil.findChildrenOfType(file, HtmlTag.class);
        PsiElement[] reqTags = PsiTreeUtil.collectElements(file, new PsiElementFilter() {
            @Override
            public boolean isAccepted(PsiElement element) {
                return element instanceof HtmlTag && (((HtmlTag) element).getName().equals(RTTagDescriptorsProvider.RT_REQUIRE) || ((HtmlTag) element).getName().equals(RTTagDescriptorsProvider.RT_IMPORT));
            }
        });

        List<String> importedTags = new ArrayList<String>();
        for (PsiElement elem : reqTags) {
            String as = ((HtmlTag) elem).getAttributeValue("as");
            if (!Strings.isNullOrEmpty(as)) {
                importedTags.add(as);
            }
        }
        return importedTags;
    }
 

@Nullable
    @Override
    public XmlElementDescriptor getDescriptor(XmlTag xmlTag) {
//        System.out.println("getDescriptor " + xmlTag);
        if (!(xmlTag instanceof HtmlTag && RTProjectComponent.isEnabled(xmlTag.getProject()))) {
            return null;
        }
        final String directiveName = DirectiveUtil.normalizeAttributeName(xmlTag.getName());
        if (directiveName.equals(RT_REQUIRE)) {
            return new RTRequireTagDescriptor(RT_REQUIRE, xmlTag);
        }
        if (directiveName.equals(RT_IMPORT)) {
            return new RTImportTagDescriptor(RT_IMPORT, xmlTag);
        }

        if (xmlTag.getContainingFile() instanceof XmlFile) {
            List<String> tags = RTHtmlExtension.loadImportedTags((XmlFile) xmlTag.getContainingFile(), xmlTag);
            for (String tag : tags) {
                if (Strings.areEqual(tag, directiveName)) {
                    return new RTClassTagDescriptor(directiveName, xmlTag);
                }
            }
        }
        // TODO: support required tags
        //return new AnyXmlElementDescriptor()
        return null;
    }
 

@Override
    public XmlAttributeDescriptor[] getAttributeDescriptors(XmlTag xmlTag) {
        if (xmlTag instanceof HtmlTag /*&& RTFileUtil.hasRTExt(xmlTag.getContainingFile())*/) {
            final Project project = xmlTag.getProject();
            if (RTActionUtil.isRTEnabled(project)) {
                final Map<String, XmlAttributeDescriptor> result = new LinkedHashMap<String, XmlAttributeDescriptor>();
                for (String attr : RTAttributes.ALL_ATTRIBUTES) {
                    result.put(attr, new RTXmlAttributeDescriptor(attr));
                }
//                result.put("rt-repeat", new RTXmlAttributeDescriptor("rt-repeat")); // x in [javascript]
//                result.put("rt-if", new RTXmlAttributeDescriptor("rt-if")); //[javascript]
//                result.put("rt-scope", new RTXmlAttributeDescriptor("rt-scope")); //a as b;c as d
//                result.put("rt-class", new RTXmlAttributeDescriptor("rt-class")); // [javascript]
//                result.put("rt-props", new RTXmlAttributeDescriptor("rt-props")); // [javascript]
                return result.values().toArray(new XmlAttributeDescriptor[result.size()]);

    //            return new XmlAttributeDescriptor[]{
    //                    new AnyXmlAttributeDescriptor("rt-if"),
    //                    new AnyXmlAttributeDescriptor("rt-repeat"),
    //                    new AnyXmlAttributeDescriptor("rt-scope"),
    //                    new AnyXmlAttributeDescriptor("rt-props"),
    //                    new AnyXmlAttributeDescriptor("rt-class"),
    //                    new AnyXmlAttributeDescriptor("rt-require")
    //            };
            }
        }
        return XmlAttributeDescriptor.EMPTY;
    }
 

@Nullable
@Override
public XmlElementDescriptor getDescriptor(XmlTag tag) {
    if (!(tag instanceof HtmlTag)) {
        return null;
    }

    final XmlNSDescriptor nsDescriptor = tag.getNSDescriptor(tag.getNamespace(), false);
    final XmlElementDescriptor descriptor = nsDescriptor != null ? nsDescriptor.getElementDescriptor(tag) : null;
    if (descriptor != null && !(descriptor instanceof AnyXmlElementDescriptor)) {
        return null;
    }

    return new ISMLTagDescriptor(tag.getName(), tag);
}
 

@Override
public void addTagNameVariants(List<LookupElement> elements, XmlTag tag, String prefix) {
    if (!(tag instanceof HtmlTag)) return;
    for (String tagName : ismlTagNames) {
        elements.add(LookupElementBuilder.create(tagName));
    }
}
 

@Nullable
    @Override
    public XmlElementDescriptor getDescriptor(XmlTag xmlTag) {
//        System.out.println("getDescriptor " + xmlTag);
        if (!(xmlTag instanceof HtmlTag && RTProjectComponent.isEnabled(xmlTag.getProject()))) {
            return null;
        }
        final String directiveName = DirectiveUtil.normalizeAttributeName(xmlTag.getName());
        if (directiveName.equals(RT_REQUIRE)) {
            return new RTRequireTagDescriptor(RT_REQUIRE, xmlTag);
        }
        if (directiveName.equals(RT_IMPORT)) {
            return new RTImportTagDescriptor(RT_IMPORT, xmlTag);
        }

        if (xmlTag.getContainingFile() instanceof XmlFile) {
            List<String> tags = RTHtmlExtension.loadImportedTags((XmlFile) xmlTag.getContainingFile(), xmlTag);
            for (String tag : tags) {
                if (Strings.areEqual(tag, directiveName)) {
                    return new RTClassTagDescriptor(directiveName, xmlTag);
                }
            }
        }
        // TODO: support required tags
        //return new AnyXmlElementDescriptor()
        return null;
    }
 

@Override
    public XmlAttributeDescriptor[] getAttributeDescriptors(XmlTag xmlTag) {
        if (xmlTag instanceof HtmlTag /*&& RTFileUtil.hasRTExt(xmlTag.getContainingFile())*/) {
            final Project project = xmlTag.getProject();
            if (RTActionUtil.isRTEnabled(project)) {
                final Map<String, XmlAttributeDescriptor> result = new LinkedHashMap<String, XmlAttributeDescriptor>();
                for (String attr : RTAttributes.ALL_ATTRIBUTES) {
                    result.put(attr, new RTXmlAttributeDescriptor(attr));
                }
//                result.put("rt-repeat", new RTXmlAttributeDescriptor("rt-repeat")); // x in [javascript]
//                result.put("rt-if", new RTXmlAttributeDescriptor("rt-if")); //[javascript]
//                result.put("rt-scope", new RTXmlAttributeDescriptor("rt-scope")); //a as b;c as d
//                result.put("rt-class", new RTXmlAttributeDescriptor("rt-class")); // [javascript]
//                result.put("rt-props", new RTXmlAttributeDescriptor("rt-props")); // [javascript]
                return result.values().toArray(new XmlAttributeDescriptor[result.size()]);

    //            return new XmlAttributeDescriptor[]{
    //                    new AnyXmlAttributeDescriptor("rt-if"),
    //                    new AnyXmlAttributeDescriptor("rt-repeat"),
    //                    new AnyXmlAttributeDescriptor("rt-scope"),
    //                    new AnyXmlAttributeDescriptor("rt-props"),
    //                    new AnyXmlAttributeDescriptor("rt-class"),
    //                    new AnyXmlAttributeDescriptor("rt-require")
    //            };
            }
        }
        return XmlAttributeDescriptor.EMPTY;
    }
 

/**
 * <foo>bar</foo>
 */
public static PsiElementPattern.Capture<PsiElement> getTagTextPattern(@NotNull String... tag) {
    return XmlPatterns
        .psiElement().withParent(
            PlatformPatterns.psiElement(XmlText.class).withParent(
                PlatformPatterns.psiElement(HtmlTag.class).withName(tag)
            )
        )
        .inFile(XmlPatterns.psiFile()
            .withName(XmlPatterns
                .string().endsWith(".twig")
            )
        );
}