package org.jsoup.select;

import org.jsoup.helper.Validate;
import org.jsoup.internal.StringUtil;
import org.jsoup.nodes.Comment;
import org.jsoup.nodes.DataNode;
import org.jsoup.nodes.Element;
import org.jsoup.nodes.FormElement;
import org.jsoup.nodes.Node;
import org.jsoup.nodes.TextNode;
import org.jspecify.annotations.Nullable;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.function.Predicate;
import java.util.function.UnaryOperator;

/**
 A list of {@link Element}s, with methods that act on every element in the list.
 <p>To get an {@code Elements} object, use the {@link Element#select(String)} method.</p>
 <p>Methods that {@link #set(int, Element) set}, {@link #remove(int) remove}, or {@link #replaceAll(UnaryOperator)
 replace} Elements in the list will also act on the underlying {@link org.jsoup.nodes.Document DOM}.</p>

 @author Jonathan Hedley, jonathan@hedley.net */
public class Elements extends ArrayList<Element> {
    public Elements() {
    }

    public Elements(int initialCapacity) {
        super(initialCapacity);
    }

    public Elements(Collection<Element> elements) {
        super(elements);
    }
    
    public Elements(List<Element> elements) {
        super(elements);
    }
    
    public Elements(Element... elements) {
        super(Arrays.asList(elements));
    }

    /**
     * Creates a deep copy of these elements.
     * @return a deep copy
     */
    @Override
    public Elements clone() {
        Elements clone = new Elements(size());
        for (Element e : this)
            clone.add(e.clone());
        return clone;
    }

    /**
     Convenience method to get the Elements as a plain ArrayList. This allows modification to the list of elements
     without modifying the source Document. I.e. whereas calling {@code elements.remove(0)} will remove the element from
     both the Elements and the DOM, {@code elements.asList().remove(0)} will remove the element from the list only.
     <p>Each Element is still the same DOM connected Element.</p>

     @return a new ArrayList containing the elements in this list
     @since 1.19.2
     @see #Elements(List)
     */
    public ArrayList<Element> asList() {
        return new ArrayList<>(this);
    }

    // attribute methods
    /**
     Get an attribute value from the first matched element that has the attribute.
     @param attributeKey The attribute key.
     @return The attribute value from the first matched element that has the attribute. If no elements were matched (isEmpty() == true),
     or if the no elements have the attribute, returns empty string.
     @see #hasAttr(String)
     */
    public String attr(String attributeKey) {
        for (Element element : this) {
            if (element.hasAttr(attributeKey))
                return element.attr(attributeKey);
        }
        return "";
    }

    /**
     Checks if any of the matched elements have this attribute defined.
     @param attributeKey attribute key
     @return true if any of the elements have the attribute; false if none do.
     */
    public boolean hasAttr(String attributeKey) {
        for (Element element : this) {
            if (element.hasAttr(attributeKey))
                return true;
        }
        return false;
    }

    /**
     * Get the attribute value for each of the matched elements. If an element does not have this attribute, no value is
     * included in the result set for that element.
     * @param attributeKey the attribute name to return values for. You can add the {@code abs:} prefix to the key to
     * get absolute URLs from relative URLs, e.g.: {@code doc.select("a").eachAttr("abs:href")} .
     * @return a list of each element's attribute value for the attribute
     */
    public List<String> eachAttr(String attributeKey) {
        List<String> attrs = new ArrayList<>(size());
        for (Element element : this) {
            if (element.hasAttr(attributeKey))
                attrs.add(element.attr(attributeKey));
        }
        return attrs;
    }

    /**
     * Set an attribute on all matched elements.
     * @param attributeKey attribute key
     * @param attributeValue attribute value
     * @return this
     */
    public Elements attr(String attributeKey, String attributeValue) {
        for (Element element : this) {
            element.attr(attributeKey, attributeValue);
        }
        return this;
    }

    /**
     * Remove an attribute from every matched element.
     * @param attributeKey The attribute to remove.
     * @return this (for chaining)
     */
    public Elements removeAttr(String attributeKey) {
        for (Element element : this) {
            element.removeAttr(attributeKey);
        }
        return this;
    }

    /**
     Add the class name to every matched element's {@code class} attribute.
     @param className class name to add
     @return this
     */
    public Elements addClass(String className) {
        for (Element element : this) {
            element.addClass(className);
        }
        return this;
    }

    /**
     Remove the class name from every matched element's {@code class} attribute, if present.
     @param className class name to remove
     @return this
     */
    public Elements removeClass(String className) {
        for (Element element : this) {
            element.removeClass(className);
        }
        return this;
    }

    /**
     Toggle the class name on every matched element's {@code class} attribute.
     @param className class name to add if missing, or remove if present, from every element.
     @return this
     */
    public Elements toggleClass(String className) {
        for (Element element : this) {
            element.toggleClass(className);
        }
        return this;
    }

    /**
     Determine if any of the matched elements have this class name set in their {@code class} attribute.
     @param className class name to check for
     @return true if any do, false if none do
     */
    public boolean hasClass(String className) {
        for (Element element : this) {
            if (element.hasClass(className))
                return true;
        }
        return false;
    }
    
    /**
     * Get the form element's value of the first matched element.
     * @return The form element's value, or empty if not set.
     * @see Element#val()
     */
    public String val() {
        if (size() > 0)
            //noinspection ConstantConditions
            return first().val(); // first() != null as size() > 0
        else
            return "";
    }
    
    /**
     * Set the form element's value in each of the matched elements.
     * @param value The value to set into each matched element
     * @return this (for chaining)
     */
    public Elements val(String value) {
        for (Element element : this)
            element.val(value);
        return this;
    }
    
    /**
     * Get the combined text of all the matched elements.
     * <p>
     * Note that it is possible to get repeats if the matched elements contain both parent elements and their own
     * children, as the Element.text() method returns the combined text of a parent and all its children.
     * @return string of all text: unescaped and no HTML.
     * @see Element#text()
     * @see #eachText()
     */
    public String text() {
        return stream()
            .map(Element::text)
            .collect(StringUtil.joining(" "));
    }

    /**
     Test if any matched Element has any text content, that is not just whitespace.
     @return true if any element has non-blank text content.
     @see Element#hasText()
     */
    public boolean hasText() {
        for (Element element: this) {
            if (element.hasText())
                return true;
        }
        return false;
    }

    /**
     * Get the text content of each of the matched elements. If an element has no text, then it is not included in the
     * result.
     * @return A list of each matched element's text content.
     * @see Element#text()
     * @see Element#hasText()
     * @see #text()
     */
    public List<String> eachText() {
        ArrayList<String> texts = new ArrayList<>(size());
        for (Element el: this) {
            if (el.hasText())
                texts.add(el.text());
        }
        return texts;
    }
    
    /**
     * Get the combined inner HTML of all matched elements.
     * @return string of all element's inner HTML.
     * @see #text()
     * @see #outerHtml()
     */
    public String html() {
        return stream()
            .map(Element::html)
            .collect(StringUtil.joining("\n"));
    }
    
    /**
     * Get the combined outer HTML of all matched elements.
     * @return string of all element's outer HTML.
     * @see #text()
     * @see #html()
     */
    public String outerHtml() {
        return stream()
            .map(Element::outerHtml)
            .collect(StringUtil.joining("\n"));
    }

    /**
     * Get the combined outer HTML of all matched elements. Alias of {@link #outerHtml()}.
     * @return string of all element's outer HTML.
     * @see #text()
     * @see #html()
     */
    @Override
    public String toString() {
        return outerHtml();
    }

    /**
     * Update (rename) the tag name of each matched element. For example, to change each {@code <i>} to a {@code <em>}, do
     * {@code doc.select("i").tagName("em");}
     *
     * @param tagName the new tag name
     * @return this, for chaining
     * @see Element#tagName(String)
     */
    public Elements tagName(String tagName) {
        for (Element element : this) {
            element.tagName(tagName);
        }
        return this;
    }
    
    /**
     * Set the inner HTML of each matched element.
     * @param html HTML to parse and set into each matched element.
     * @return this, for chaining
     * @see Element#html(String)
     */
    public Elements html(String html) {
        for (Element element : this) {
            element.html(html);
        }
        return this;
    }
    
    /**
     * Add the supplied HTML to the start of each matched element's inner HTML.
     * @param html HTML to add inside each element, before the existing HTML
     * @return this, for chaining
     * @see Element#prepend(String)
     */
    public Elements prepend(String html) {
        for (Element element : this) {
            element.prepend(html);
        }
        return this;
    }
    
    /**
     * Add the supplied HTML to the end of each matched element's inner HTML.
     * @param html HTML to add inside each element, after the existing HTML
     * @return this, for chaining
     * @see Element#append(String)
     */
    public Elements append(String html) {
        for (Element element : this) {
            element.append(html);
        }
        return this;
    }
    
    /**
     * Insert the supplied HTML before each matched element's outer HTML.
     * @param html HTML to insert before each element
     * @return this, for chaining
     * @see Element#before(String)
     */
    public Elements before(String html) {
        for (Element element : this) {
            element.before(html);
        }
        return this;
    }
    
    /**
     * Insert the supplied HTML after each matched element's outer HTML.
     * @param html HTML to insert after each element
     * @return this, for chaining
     * @see Element#after(String)
     */
    public Elements after(String html) {
        for (Element element : this) {
            element.after(html);
        }
        return this;
    }

    /**
     Wrap the supplied HTML around each matched elements. For example, with HTML
     {@code <p><b>This</b> is <b>Jsoup</b></p>},
     <code>doc.select("b").wrap("&lt;i&gt;&lt;/i&gt;");</code>
     becomes {@code <p><i><b>This</b></i> is <i><b>jsoup</b></i></p>}
     @param html HTML to wrap around each element, e.g. {@code <div class="head"></div>}. Can be arbitrarily deep.
     @return this (for chaining)
     @see Element#wrap
     */
    public Elements wrap(String html) {
        Validate.notEmpty(html);
        for (Element element : this) {
            element.wrap(html);
        }
        return this;
    }

    /**
     * Removes the matched elements from the DOM, and moves their children up into their parents. This has the effect of
     * dropping the elements but keeping their children.
     * <p>
     * This is useful for e.g removing unwanted formatting elements but keeping their contents.
     * </p>
     * 
     * E.g. with HTML: <p>{@code <div><font>One</font> <font><a href="/">Two</a></font></div>}</p>
     * <p>{@code doc.select("font").unwrap();}</p>
     * <p>HTML = {@code <div>One <a href="/">Two</a></div>}</p>
     *
     * @return this (for chaining)
     * @see Node#unwrap
     */
    public Elements unwrap() {
        for (Element element : this) {
            element.unwrap();
        }
        return this;
    }

    /**
     * Empty (remove all child nodes from) each matched element. This is similar to setting the inner HTML of each
     * element to nothing.
     * <p>
     * E.g. HTML: {@code <div><p>Hello <b>there</b></p> <p>now</p></div>}<br>
     * <code>doc.select("p").empty();</code><br>
     * HTML = {@code <div><p></p> <p></p></div>}
     * @return this, for chaining
     * @see Element#empty()
     * @see #remove()
     */
    public Elements empty() {
        for (Element element : this) {
            element.empty();
        }
        return this;
    }

    /**
     * Remove each matched element from the DOM. This is similar to setting the outer HTML of each element to nothing.
     * <p>The elements will still be retained in this list, in case further processing of them is desired.</p>
     * <p>
     * E.g. HTML: {@code <div><p>Hello</p> <p>there</p> <img /></div>}<br>
     * <code>doc.select("p").remove();</code><br>
     * HTML = {@code <div> <img /></div>}
     * <p>
     * Note that this method should not be used to clean user-submitted HTML; rather, use {@link org.jsoup.safety.Cleaner} to clean HTML.
     * @return this, for chaining
     * @see Element#empty()
     * @see #empty()
     * @see #clear()
     */
    public Elements remove() {
        for (Element element : this) {
            element.remove();
        }
        return this;
    }
    
    // filters
    
    /**
     * Find matching elements within this element list.
     * @param query A {@link Selector} query
     * @return the filtered list of elements, or an empty list if none match.
     */
    public Elements select(String query) {
        return Selector.select(query, this);
    }

    /**
     Find the first Element that matches the {@link Selector} CSS query within this element list.
     <p>This is effectively the same as calling {@code elements.select(query).first()}, but is more efficient as query
     execution stops on the first hit.</p>

     @param cssQuery a {@link Selector} query
     @return the first matching element, or <b>{@code null}</b> if there is no match.
     @see #expectFirst(String)
     @since 1.19.1
     */
    public @Nullable Element selectFirst(String cssQuery) {
        return Selector.selectFirst(cssQuery, this);
    }

    /**
     Just like {@link #selectFirst(String)}, but if there is no match, throws an {@link IllegalArgumentException}.

     @param cssQuery a {@link Selector} query
     @return the first matching element
     @throws IllegalArgumentException if no match is found
     @since 1.19.1
     */
    public Element expectFirst(String cssQuery) {
        return (Element) Validate.ensureNotNull(
            Selector.selectFirst(cssQuery, this),
            "No elements matched the query '%s' in the elements.", cssQuery
        );
    }

    /**
     * Remove elements from this list that match the {@link Selector} query.
     * <p>
     * E.g. HTML: {@code <div class=logo>One</div> <div>Two</div>}<br>
     * <code>Elements divs = doc.select("div").not(".logo");</code><br>
     * Result: {@code divs: [<div>Two</div>]}
     * <p>
     * @param query the selector query whose results should be removed from these elements
     * @return a new elements list that contains only the filtered results
     */
    public Elements not(String query) {
        Elements out = Selector.select(query, this);
        return Selector.filterOut(this, out);
    }
    
    /**
     * Get the <i>nth</i> matched element as an Elements object.
     * <p>
     * See also {@link #get(int)} to retrieve an Element.
     * @param index the (zero-based) index of the element in the list to retain
     * @return Elements containing only the specified element, or, if that element did not exist, an empty list.
     */
    public Elements eq(int index) {
        return size() > index ? new Elements(get(index)) : new Elements();
    }
    
    /**
     * Test if any of the matched elements match the supplied query.
     * @param query A selector
     * @return true if at least one element in the list matches the query.
     */
    public boolean is(String query) {
        Evaluator eval = QueryParser.parse(query);
        for (Element e : this) {
            if (e.is(eval))
                return true;
        }
        return false;
    }

    /**
     * Get the immediate next element sibling of each element in this list.
     * @return next element siblings.
     */
    public Elements next() {
        return siblings(null, true, false);
    }

    /**
     * Get the immediate next element sibling of each element in this list, filtered by the query.
     * @param query CSS query to match siblings against
     * @return next element siblings.
     */
    public Elements next(String query) {
        return siblings(query, true, false);
    }

    /**
     * Get each of the following element siblings of each element in this list.
     * @return all following element siblings.
     */
    public Elements nextAll() {
        return siblings(null, true, true);
    }

    /**
     * Get each of the following element siblings of each element in this list, that match the query.
     * @param query CSS query to match siblings against
     * @return all following element siblings.
     */
    public Elements nextAll(String query) {
        return siblings(query, true, true);
    }

    /**
     * Get the immediate previous element sibling of each element in this list.
     * @return previous element siblings.
     */
    public Elements prev() {
        return siblings(null, false, false);
    }

    /**
     * Get the immediate previous element sibling of each element in this list, filtered by the query.
     * @param query CSS query to match siblings against
     * @return previous element siblings.
     */
    public Elements prev(String query) {
        return siblings(query, false, false);
    }

    /**
     * Get each of the previous element siblings of each element in this list.
     * @return all previous element siblings.
     */
    public Elements prevAll() {
        return siblings(null, false, true);
    }

    /**
     * Get each of the previous element siblings of each element in this list, that match the query.
     * @param query CSS query to match siblings against
     * @return all previous element siblings.
     */
    public Elements prevAll(String query) {
        return siblings(query, false, true);
    }

    private Elements siblings(@Nullable String query, boolean next, boolean all) {
        Elements els = new Elements();
        Evaluator eval = query != null? QueryParser.parse(query) : null;
        for (Element e : this) {
            do {
                Element sib = next ? e.nextElementSibling() : e.previousElementSibling();
                if (sib == null) break;
                if (eval == null || sib.is(eval)) els.add(sib);
                e = sib;
            } while (all);
        }
        return els;
    }

    /**
     * Get all of the parents and ancestor elements of the matched elements.
     * @return all of the parents and ancestor elements of the matched elements
     */
    public Elements parents() {
        HashSet<Element> combo = new LinkedHashSet<>();
        for (Element e: this) {
            combo.addAll(e.parents());
        }
        return new Elements(combo);
    }

    // list-like methods
    /**
     Get the first matched element.
     @return The first matched element, or <code>null</code> if contents is empty.
     */
    public @Nullable Element first() {
        return isEmpty() ? null : get(0);
    }

    /**
     Get the last matched element.
     @return The last matched element, or <code>null</code> if contents is empty.
     */
    public @Nullable Element last() {
        return isEmpty() ? null : get(size() - 1);
    }

    /**
     * Perform a depth-first traversal on each of the selected elements.
     * @param nodeVisitor the visitor callbacks to perform on each node
     * @return this, for chaining
     */
    public Elements traverse(NodeVisitor nodeVisitor) {
        NodeTraversor.traverse(nodeVisitor, this);
        return this;
    }

    /**
     * Perform a depth-first filtering on each of the selected elements.
     * @param nodeFilter the filter callbacks to perform on each node
     * @return this, for chaining
     */
    public Elements filter(NodeFilter nodeFilter) {
        NodeTraversor.filter(nodeFilter, this);
        return this;
    }

    /**
     * Get the {@link FormElement} forms from the selected elements, if any.
     * @return a list of {@link FormElement}s pulled from the matched elements. The list will be empty if the elements contain
     * no forms.
     */
    public List<FormElement> forms() {
        ArrayList<FormElement> forms = new ArrayList<>();
        for (Element el: this)
            if (el instanceof FormElement)
                forms.add((FormElement) el);
        return forms;
    }

    /**
     * Get {@link Comment} nodes that are direct child nodes of the selected elements.
     * @return Comment nodes, or an empty list if none.
     */
    public List<Comment> comments() {
        return childNodesOfType(Comment.class);
    }

    /**
     * Get {@link TextNode} nodes that are direct child nodes of the selected elements.
     * @return TextNode nodes, or an empty list if none.
     */
    public List<TextNode> textNodes() {
        return childNodesOfType(TextNode.class);
    }

    /**
     * Get {@link DataNode} nodes that are direct child nodes of the selected elements. DataNode nodes contain the
     * content of tags such as {@code script}, {@code style} etc and are distinct from {@link TextNode}s.
     * @return Comment nodes, or an empty list if none.
     */
    public List<DataNode> dataNodes() {
        return childNodesOfType(DataNode.class);
    }

    private <T extends Node> List<T> childNodesOfType(Class<T> tClass) {
        ArrayList<T> nodes = new ArrayList<>();
        for (Element el: this) {
            for (int i = 0; i < el.childNodeSize(); i++) {
                Node node = el.childNode(i);
                if (tClass.isInstance(node))
                    nodes.add(tClass.cast(node));
            }
        }
        return nodes;
    }

    // list methods that update the DOM:

    /**
     Replace the Element at the specified index in this list, and in the DOM.
     * @param index index of the element to replace
     * @param element element to be stored at the specified position
     * @return the old Element at this index
     * @since 1.17.1
     */
    @Override public Element set(int index, Element element) {
        Validate.notNull(element);
        Element old = super.set(index, element);
        old.replaceWith(element);
        return old;
    }

    /**
     Remove the Element at the specified index in this ist, and from the DOM.
     @param index the index of the element to be removed
     @return the old element at this index
     @see #deselect(int)
     @since 1.17.1
     */
    @Override public Element remove(int index) {
        Element old = super.remove(index);
        old.remove();
        return old;
    }

    /**
     Remove the specified Element from this list, and from the DOM.
     @param o element to be removed from this list, if present
     @return if this list contained the Element
     @see #deselect(Object)
     @since 1.17.1
     */
    @Override public boolean remove(Object o) {
        int index = super.indexOf(o);
        if (index == -1) {
            return false;
        } else {
            remove(index);
            return true;
        }
    }

    /**
     Remove the Element at the specified index in this list, but not from the DOM.
     @param index the index of the element to be removed
     @return the old element at this index
     @see #remove(int) 
     @since 1.19.2
     */
    public Element deselect(int index) {
        return super.remove(index);
    }

    /**
     Remove the specified Element from this list, but not from the DOM.
     @param o element to be removed from this list, if present
     @return if this list contained the Element
     @see #remove(Object) 
     @since 1.19.2
     */
    public boolean deselect(Object o) {
        return super.remove(o);
    }

    /**
     Removes all the elements from this list, and each of them from the DOM.
     @since 1.17.1
     @see #deselectAll()
     */
    @Override public void clear() {
        remove();
        super.clear();
    }

    /**
     Like {@link #clear()}, removes all the elements from this list, but not from the DOM.
     @see #clear()
     @since 1.19.2
     */
    public void deselectAll() {
        super.clear();
    }

    /**
     Removes from this list, and from the DOM, each of the elements that are contained in the specified collection and
     are in this list.
     * @param c collection containing elements to be removed from this list
     * @return {@code true} if elements were removed from this list
     * @since 1.17.1
     */
    @Override public boolean removeAll(Collection<?> c) {
        boolean anyRemoved = false;
        for (Object o : c) {
            anyRemoved |= this.remove(o);
        }
        return anyRemoved;
    }

    /**
     Retain in this list, and in the DOM, only the elements that are in the specified collection and are in this list.
     In other words, remove elements from this list and the DOM any item that is in this list but not in the specified
     collection.
     * @param c collection containing elements to be retained in this list
     * @return {@code true} if elements were removed from this list
     * @since 1.17.1
     */
    @Override public boolean retainAll(Collection<?> c) {
        boolean anyRemoved = false;
        for (Iterator<Element> it = this.iterator(); it.hasNext(); ) {
            Element el = it.next();
            if (!c.contains(el)) {
                it.remove();
                anyRemoved = true;
            }
        }
        return anyRemoved;
    }

    /**
     Remove from the list, and from the DOM, all elements in this list that mach the given filter.
     * @param filter a predicate which returns {@code true} for elements to be removed
     * @return {@code true} if elements were removed from this list
     * @since 1.17.1
     */
    @Override public boolean removeIf(Predicate<? super Element> filter) {
        boolean anyRemoved = false;
        for (Iterator<Element> it = this.iterator(); it.hasNext(); ) {
            Element el = it.next();
            if (filter.test(el)) {
                it.remove();
                anyRemoved = true;
            }
        }
        return anyRemoved;
    }

    /**
     Replace each element in this list with the result of the operator, and update the DOM.
     * @param operator the operator to apply to each element
     * @since 1.17.1
     */
    @Override public void replaceAll(UnaryOperator<Element> operator) {
        for (int i = 0; i < this.size(); i++) {
            this.set(i, operator.apply(this.get(i)));
        }
    }
}