/*
 * Copyright 2000-2014 Vaadin Ltd.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.vaadin.ui.declarative;

import java.beans.IntrospectionException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.Serializable;
import java.lang.annotation.Annotation;
import java.util.Collection;

import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Document.OutputSettings.Syntax;
import org.jsoup.nodes.DocumentType;
import org.jsoup.nodes.Element;
import org.jsoup.nodes.Node;
import org.jsoup.parser.Parser;
import org.jsoup.select.Elements;

import com.vaadin.annotations.DesignRoot;
import com.vaadin.ui.Component;
import com.vaadin.ui.declarative.DesignContext.ComponentCreatedEvent;
import com.vaadin.ui.declarative.DesignContext.ComponentCreationListener;

/**
 * Design is used for reading a component hierarchy from an html string or input
 * stream and, conversely, for writing an html representation corresponding to a
 * given component hierarchy.
 * 
 * <p>
 * In html form a valid nonempty component hierarchy contains a single root
 * element located under the &lt;body&gt; tag. A hierarchy of components is
 * achieved by nesting other elements under the root element. An empty component
 * hierarchy is represented as no elements under the &lt;body&gt; tag.
 * 
 * <p>
 * For writing a component hierarchy the root element is specified as a
 * Component parameter or as a DesignContext object containing the root
 * Component. An empty hierarchy can be written by giving a null root Component.
 * 
 * @since 7.4
 * @author Vaadin Ltd
 */
public class Design implements Serializable {
    /**
     * Parses the given input stream into a jsoup document
     * 
     * @param html
     *            the stream containing the design
     * @return the parsed jsoup document
     * @throws IOException
     */
    private static Document parse(InputStream html) {
        try {
            Document doc = Jsoup.parse(html, "UTF-8", "", Parser.htmlParser());
            return doc;
        } catch (IOException e) {
            throw new DesignException("The html document cannot be parsed.");
        }

    }

    /**
     * Constructs a component hierarchy from the design specified as an html
     * document. The hierarchy must contain at most one top-level component,
     * which should be located under &lt;body&gt;. Also invalid html containing
     * the hierarchy without &lt;html&gt;, &lt;head&gt; and &lt;body&gt; tags is
     * accepted. You can optionally pass an instance for the root component with
     * some uninitialized instance fields. The fields will be automatically
     * populated when parsing the design based on the component ids, local ids,
     * and captions of the components in the design.
     * 
     * @param html
     *            the html document describing the component design
     * @param rootInstance
     *            the root instance with fields to be mapped to components in
     *            the design
     * @return the DesignContext created while traversing the tree. The
     *         top-level component of the created component hierarchy can be
     *         accessed using result.getRootComponent(), where result is the
     *         object returned by this method.
     * @throws IOException
     */
    private static DesignContext parse(InputStream html, Component rootInstance) {
        Document doc = parse(html);
        return designToComponentTree(doc, rootInstance);
    }

    /**
     * Constructs a component hierarchy from the design specified as an html
     * document given as a string. The hierarchy must contain at most one
     * top-level component, which should be located under &lt;body&gt;. Also
     * invalid html containing the hierarchy without &lt;html&gt;, &lt;head&gt;
     * and &lt;body&gt; tags is accepted. You can optionally pass an instance
     * for the root component with some uninitialized instance fields. The
     * fields will be automatically populated when parsing the design based on
     * the component ids, local ids, and captions of the components in the
     * design.
     * 
     * @param html
     *            the html document describing the component design
     * @param rootInstance
     *            the root instance with fields to be mapped to components in
     *            the design
     * @return the DesignContext created while traversing the tree. The
     *         top-level component of the created component hierarchy can be
     *         accessed using result.getRootComponent(), where result is the
     *         object returned by this method.
     * @throws IOException
     */
    private static DesignContext parse(String html, Component rootInstance) {
        Document doc = Jsoup.parse(html);
        return designToComponentTree(doc, rootInstance);
    }

    /**
     * Constructs a component hierarchy from the design specified as an html
     * tree.
     * 
     * <p>
     * If a component root is given, the component instances created during
     * reading the design are assigned to its member fields based on their id,
     * local id, and caption
     * 
     * @param doc
     *            the html tree
     * @param componentRoot
     *            optional component root instance. The type must match the type
     *            of the root element in the design. Any member fields whose
     *            type is assignable from {@link Component} are bound to fields
     *            in the design based on id/local id/caption
     */
    private static DesignContext designToComponentTree(Document doc,
            Component componentRoot) {
        if (componentRoot == null) {
            return designToComponentTree(doc, null, null);
        } else {
            return designToComponentTree(doc, componentRoot,
                    componentRoot.getClass());
        }

    }

    /**
     * Constructs a component hierarchy from the design specified as an html
     * tree.
     * 
     * <p>
     * If a component root is given, the component instances created during
     * reading the design are assigned to its member fields based on their id,
     * local id, and caption
     * 
     * @param doc
     *            the html tree
     * @param componentRoot
     *            optional component root instance. The type must match the type
     *            of the root element in the design.
     * @param classWithFields
     *            a class (componentRoot class or a super class) with some
     *            member fields. The member fields whose type is assignable from
     *            {@link Component} are bound to fields in the design based on
     *            id/local id/caption
     */
    private static DesignContext designToComponentTree(Document doc,
            Component componentRoot, Class<?> classWithFields) {
        DesignContext designContext = new DesignContext(doc);
        designContext.readPackageMappings(doc);
        // No special handling for a document without a body element - should be
        // taken care of by jsoup.
        Element root = doc.body();
        Elements children = root.children();
        if (children.size() != 1) {
            throw new DesignException(
                    "The first level of a component hierarchy should contain exactly one root component, but found "
                            + children.size());
        }
        Element element = children.first();
        if (componentRoot != null) {
            // user has specified root instance that may have member fields that
            // should be bound
            final FieldBinder binder;
            try {
                binder = new FieldBinder(componentRoot, classWithFields);
            } catch (IntrospectionException e) {
                throw new DesignException(
                        "Could not bind fields of the root component", e);
            }
            // create listener for component creations that binds the created
            // components to the componentRoot instance fields
            ComponentCreationListener creationListener = new ComponentCreationListener() {
                @Override
                public void componentCreated(ComponentCreatedEvent event) {
                    binder.bindField(event.getComponent(), event.getLocalId());
                }
            };
            designContext.addComponentCreationListener(creationListener);
            // create subtree
            designContext.readDesign(element, componentRoot);
            // make sure that all the member fields are bound
            Collection<String> unboundFields = binder.getUnboundFields();
            if (!unboundFields.isEmpty()) {
                throw new DesignException(
                        "Found unbound fields from component root "
                                + unboundFields);
            }
            // no need to listen anymore
            designContext.removeComponentCreationListener(creationListener);
        } else {
            // createChild creates the entire component hierarchy
            componentRoot = designContext.readDesign(element);
        }
        designContext.setRootComponent(componentRoot);
        return designContext;
    }

    /**
     * Generates an html tree representation of the component hierarchy having
     * the root designContext.getRootComponent(). The hierarchy is stored under
     * &lt;body&gt; in the tree. The generated tree represents a valid html
     * document.
     * 
     * 
     * @param designContext
     *            a DesignContext object specifying the root component
     *            (designContext.getRootComponent()) of the hierarchy
     * @return an html tree representation of the component hierarchy
     */
    private static Document createHtml(DesignContext designContext) {
        // Create the html tree skeleton.
        Document doc = new Document("");
        DocumentType docType = new DocumentType("html", "", "", "");
        doc.appendChild(docType);
        Element html = doc.createElement("html");
        doc.appendChild(html);
        html.appendChild(doc.createElement("head"));
        Element body = doc.createElement("body");
        html.appendChild(body);

        // Append the design under <body> in the html tree. createNode
        // creates the entire component hierarchy rooted at the
        // given root node.
        Component root = designContext.getRootComponent();
        Node rootNode = designContext.createElement(root);
        body.appendChild(rootNode);
        designContext.writePackageMappings(doc);
        return doc;
    }

    /**
     * Loads a design for the given root component.
     * <p>
     * This methods assumes that the component class (or a super class) has been
     * marked with an {@link DesignRoot} annotation and will either use the
     * value from the annotation to locate the design file, or will fall back to
     * using a design with the same same as the annotated class file (with an
     * .html extension)
     * <p>
     * Any {@link Component} type fields in the root component which are not
     * assigned (i.e. are null) are mapped to corresponding components in the
     * design. Matching is done based on field name in the component class and
     * id/local id/caption in the design file.
     * <p>
     * The type of the root component must match the root element in the design
     * 
     * @param rootComponent
     *            The root component of the layout
     * @return The design context used in the load operation
     * @throws DesignException
     *             If the design could not be loaded
     */
    public static DesignContext read(Component rootComponent)
            throws DesignException {
        // Try to find an @DesignRoot annotation on the class or any parent
        // class
        Class<? extends Component> annotatedClass = findClassWithAnnotation(
                rootComponent.getClass(), DesignRoot.class);
        if (annotatedClass == null) {
            throw new IllegalArgumentException(
                    "The class "
                            + rootComponent.getClass().getName()
                            + " or any of its superclasses do not have an @DesignRoot annotation");
        }

        DesignRoot designAnnotation = annotatedClass
                .getAnnotation(DesignRoot.class);
        String filename = designAnnotation.value();
        if (filename.equals("")) {
            // No value, assume the html file is named as the class
            filename = annotatedClass.getSimpleName() + ".html";
        }

        InputStream stream = annotatedClass.getResourceAsStream(filename);
        if (stream == null) {
            throw new DesignException("Unable to find design file " + filename
                    + " in " + annotatedClass.getPackage().getName());
        }

        Document doc = parse(stream);
        DesignContext context = designToComponentTree(doc, rootComponent,
                annotatedClass);

        return context;

    }

    /**
     * Find the first class with the given annotation, starting the search from
     * the given class and moving upwards in the class hierarchy.
     * 
     * @param componentClass
     *            the class to check
     * @param annotationClass
     *            the annotation to look for
     * @return the first class with the given annotation or null if no class
     *         with the annotation was found
     */
    private static Class<? extends Component> findClassWithAnnotation(
            Class<? extends Component> componentClass,
            Class<? extends Annotation> annotationClass) {
        if (componentClass == null) {
            return null;
        }

        if (componentClass.isAnnotationPresent(annotationClass)) {
            return componentClass;
        }

        Class<?> superClass = componentClass.getSuperclass();
        if (!Component.class.isAssignableFrom(superClass)) {
            return null;
        }

        return findClassWithAnnotation((Class<? extends Component>) superClass,
                annotationClass);
    }

    /**
     * Loads a design from the given file name using the given root component.
     * <p>
     * Any {@link Component} type fields in the root component which are not
     * assigned (i.e. are null) are mapped to corresponding components in the
     * design. Matching is done based on field name in the component class and
     * id/local id/caption in the design file.
     * <p>
     * The type of the root component must match the root element in the design.
     * 
     * @param filename
     *            The file name to load. Loaded from the same package as the
     *            root component
     * @param rootComponent
     *            The root component of the layout
     * @return The design context used in the load operation
     * @throws DesignException
     *             If the design could not be loaded
     */
    public static DesignContext read(String filename, Component rootComponent)
            throws DesignException {
        InputStream stream = rootComponent.getClass().getResourceAsStream(
                filename);
        if (stream == null) {
            throw new DesignException("File " + filename
                    + " was not found in the package "
                    + rootComponent.getClass().getPackage().getName());
        }
        return read(stream, rootComponent);
    }

    /**
     * Loads a design from the given stream using the given root component. If
     * rootComponent is null, the type of the root node is read from the design.
     * <p>
     * Any {@link Component} type fields in the root component which are not
     * assigned (i.e. are null) are mapped to corresponding components in the
     * design. Matching is done based on field name in the component class and
     * id/local id/caption in the design file.
     * <p>
     * If rootComponent is not null, its type must match the type of the root
     * element in the design
     * 
     * @param stream
     *            The stream to read the design from
     * @param rootComponent
     *            The root component of the layout
     * @return The design context used in the load operation
     * @throws DesignException
     *             If the design could not be loaded
     */
    public static DesignContext read(InputStream design, Component rootComponent) {
        if (design == null) {
            throw new DesignException("Stream cannot be null");
        }
        Document doc = parse(design);
        DesignContext context = designToComponentTree(doc, rootComponent);

        return context;
    }

    /**
     * Loads a design from the given input stream
     * 
     * @param design
     *            The stream to read the design from
     * @return The root component of the design
     */
    public static Component read(InputStream design) {
        DesignContext context = read(design, null);
        return context.getRootComponent();
    }

    /**
     * Writes the given component tree in design format to the given output
     * stream
     * 
     * @param component
     *            the root component of the component tree
     * @param outputStream
     *            the output stream to write the design to. The design is always
     *            written as UTF-8
     * @throws IOException
     */
    public static void write(Component component, OutputStream outputStream)
            throws IOException {
        DesignContext dc = new DesignContext();
        dc.setRootComponent(component);
        write(dc, outputStream);
    }

    /**
     * Writes the component, given in the design context, in design format to
     * the given output stream. The design context is used for writing local ids
     * and other information not available in the component tree.
     * 
     * @param designContext
     *            the DesignContext object specifying the component hierarchy
     *            and the local id values of the objects
     * @param outputStream
     *            the output stream to write the design to. The design is always
     *            written as UTF-8
     * @throws IOException
     *             if writing fails
     */
    public static void write(DesignContext designContext,
            OutputStream outputStream) throws IOException {
        Document doc = createHtml(designContext);
        write(doc, outputStream);
    }

    /**
     * Writes the given jsoup document to the output stream (in UTF-8)
     * 
     * @param doc
     *            the document to write
     * @param outputStream
     *            the stream to write to
     * @throws IOException
     *             if writing fails
     */
    private static void write(Document doc, OutputStream outputStream)
            throws IOException {
        doc.outputSettings().indentAmount(4);
        doc.outputSettings().syntax(Syntax.html);
        doc.outputSettings().prettyPrint(true);
        outputStream.write(doc.html().getBytes());
    }

}