/**
 *
 * Copyright © 2018 Paul Schaub
 *
 * 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 org.jivesoftware.smackx.message_markup.element;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Set;

import org.jivesoftware.smack.packet.ExtensionElement;
import org.jivesoftware.smack.util.XmlStringBuilder;

public class MarkupElement implements ExtensionElement {

    public static final String NAMESPACE = "urn:xmpp:markup:0";
    public static final String ELEMENT = "markup";

    private final List<MarkupChildElement> childElements;

    /**
     * Create a new MarkupElement.
     *
     * @param childElements child elements.
     */
    public MarkupElement(List<MarkupChildElement> childElements) {
        this.childElements = Collections.unmodifiableList(childElements);
    }

    /**
     * Return a new Builder for Message Markup elements.
     * @return builder.
     */
    public static Builder getBuilder() {
        return new Builder();
    }

    /**
     * Return a list of all child elements.
     * @return children TODO javadoc me please
     */
    public List<MarkupChildElement> getChildElements() {
        return childElements;
    }

    @Override
    public String getNamespace() {
        return NAMESPACE;
    }

    @Override
    public String getElementName() {
        return ELEMENT;
    }

    @Override
    public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
        XmlStringBuilder xml = new XmlStringBuilder(this).rightAngleBracket();

        for (MarkupChildElement child : getChildElements()) {
            xml.append(child.toXML());
        }

        xml.closeElement(this);
        return xml;
    }



    public static final class Builder {

        private final List<SpanElement> spans = new ArrayList<>();
        private final List<BlockQuoteElement> quotes = new ArrayList<>();
        private final List<CodeBlockElement> codes = new ArrayList<>();
        private final List<ListElement> lists = new ArrayList<>();

        private Builder() {

        }

        /**
         * Mark a section of a message as deleted.
         *
         * @param start start index
         * @param end end index
         * @return builder TODO javadoc me please
         */
        public Builder setDeleted(int start, int end) {
            return addSpan(start, end, Collections.singleton(SpanElement.SpanStyle.deleted));
        }

        /**
         * Mark a section of a message as emphasized.
         *
         * @param start start index
         * @param end end index
         * @return builder TODO javadoc me please
         */
        public Builder setEmphasis(int start, int end) {
            return addSpan(start, end, Collections.singleton(SpanElement.SpanStyle.emphasis));
        }

        /**
         * Mark a section of a message as inline code.
         *
         * @param start start index
         * @param end end index
         * @return builder TODO javadoc me please
         */
        public Builder setCode(int start, int end) {
            return addSpan(start, end, Collections.singleton(SpanElement.SpanStyle.code));
        }

        /**
         * Add a span element.
         *
         * @param start start index
         * @param end end index
         * @param styles list of text styles for that span
         * @return builder TODO javadoc me please
         */
        public Builder addSpan(int start, int end, Set<SpanElement.SpanStyle> styles) {
            verifyStartEnd(start, end);

            for (SpanElement other : spans) {
                if ((start >= other.getStart() && start <= other.getEnd()) ||
                        (end >= other.getStart() && end <= other.getEnd())) {
                    throw new IllegalArgumentException("Spans MUST NOT overlap each other.");
                }
            }

            spans.add(new SpanElement(start, end, styles));
            return this;
        }

        /**
         * Mark a section of a message as block quote.
         *
         * @param start start index
         * @param end end index
         * @return builder TODO javadoc me please
         */
        public Builder setBlockQuote(int start, int end) {
            verifyStartEnd(start, end);

            for (BlockQuoteElement other : quotes) {
                // 1 if out, 0 if on, -1 if in
                Integer s = start;
                Integer e = end;
                int startPos = s.compareTo(other.getStart()) * s.compareTo(other.getEnd());
                int endPos = e.compareTo(other.getStart()) * e.compareTo(other.getEnd());
                int allowed = startPos * endPos;

                if (allowed < 1) {
                    throw new IllegalArgumentException("BlockQuotes MUST NOT overlap each others boundaries");
                }
            }

            quotes.add(new BlockQuoteElement(start, end));
            return this;
        }

        /**
         * Mark a section of a message as a code block.
         *
         * @param start start index
         * @param end end index
         * @return builder TODO javadoc me please
         */
        public Builder setCodeBlock(int start, int end) {
            verifyStartEnd(start, end);

            codes.add(new CodeBlockElement(start, end));
            return this;
        }

        /**
         * Begin a list.
         *
         * @return list builder
         */
        public Builder.ListBuilder beginList() {
            return new Builder.ListBuilder(this);
        }

        public static final class ListBuilder {
            private final Builder markup;
            private final ArrayList<ListElement.ListEntryElement> entries = new ArrayList<>();
            private int end = -1;

            private ListBuilder(Builder markup) {
                this.markup = markup;
            }

            /**
             * Add an entry to the list.
             * The start index of an entry must correspond to the end index of the previous entry
             * (if a previous entry exists.)
             *
             * @param start start index
             * @param end end index
             * @return list builder
             */
            public Builder.ListBuilder addEntry(int start, int end) {
                verifyStartEnd(start, end);

                ListElement.ListEntryElement last = entries.size() == 0 ? null : entries.get(entries.size() - 1);
                // Entries themselves do not store end values, that's why we store the last entries end value in this.end
                if (last != null && start != this.end) {
                    throw new IllegalArgumentException("Next entries start must be equal to last entries end (" + this.end + ").");
                }
                entries.add(new ListElement.ListEntryElement(start));
                this.end = end;

                return this;
            }

            /**
             * End the list.
             *
             * @return builder TODO javadoc me please
             */
            public Builder endList() {
                if (entries.size() > 0) {
                    ListElement.ListEntryElement first = entries.get(0);
                    ListElement list = new ListElement(first.getStart(), end, entries);
                    markup.lists.add(list);
                }

                return markup;
            }
        }

        /**
         * Build a Message Markup element.
         *
         * @return extension element
         */
        public MarkupElement build() {
            List<MarkupElement.MarkupChildElement> children = new ArrayList<>();
            children.addAll(spans);
            children.addAll(quotes);
            children.addAll(codes);
            children.addAll(lists);
            return new MarkupElement(children);
        }

        private static void verifyStartEnd(int start, int end) {
            if (start >= end || start < 0) {
                throw new IllegalArgumentException("Start value (" + start + ") MUST be greater equal than 0 " +
                        "and MUST be smaller than end value (" + end + ").");
            }
        }
    }

    /**
     * Interface for child elements.
     */
    public abstract static class MarkupChildElement implements ExtensionElement {

        public static final String ATTR_START = "start";
        public static final String ATTR_END = "end";

        private final int start, end;

        protected MarkupChildElement(int start, int end) {
            this.start = start;
            this.end = end;
        }

        /**
         * Return the start index of this element.
         *
         * @return start index
         */
        public final int getStart() {
            return start;
        }

        /**
         * Return the end index of this element.
         *
         * @return end index
         */
        public final int getEnd() {
            return end;
        }

        @Override
        public final String getNamespace() {
            return NAMESPACE;
        }

        @Override
        public final XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
            XmlStringBuilder xml = new XmlStringBuilder(this, enclosingNamespace);
            xml.attribute(ATTR_START, getStart());
            xml.attribute(ATTR_END, getEnd());

            afterXmlPrelude(xml);
            return xml;
        }

        protected abstract void afterXmlPrelude(XmlStringBuilder xml);
    }

    public abstract static class NonEmptyChildElement extends MarkupChildElement {

        protected NonEmptyChildElement(int start, int end) {
            super(start, end);
        }

        @Override
        protected final void afterXmlPrelude(XmlStringBuilder xml) {
            xml.rightAngleBracket();

            appendInnerXml(xml);

            xml.closeElement(this);
        }

        protected abstract void appendInnerXml(XmlStringBuilder xml);

    }

    /**
     * Interface for block level child elements.
     */
    public abstract static class BlockLevelMarkupElement extends MarkupChildElement {

        protected BlockLevelMarkupElement(int start, int end) {
            super(start, end);
        }

        @Override
        protected final void afterXmlPrelude(XmlStringBuilder xml) {
            xml.closeEmptyElement();
        }

    }
}