/**
 *
 * Copyright 2014 Anno van Vliet, 2019-2020 Florian Schmaus
 *
 * 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.xdatavalidation.packet;

import java.math.BigInteger;

import javax.xml.namespace.QName;

import org.jivesoftware.smack.datatypes.UInt32;
import org.jivesoftware.smack.packet.FullyQualifiedElement;
import org.jivesoftware.smack.packet.XmlEnvironment;
import org.jivesoftware.smack.util.StringUtils;
import org.jivesoftware.smack.util.XmlStringBuilder;

import org.jivesoftware.smackx.xdata.AbstractSingleStringValueFormField;
import org.jivesoftware.smackx.xdata.FormField;
import org.jivesoftware.smackx.xdata.FormFieldChildElement;
import org.jivesoftware.smackx.xdata.packet.DataForm;
import org.jivesoftware.smackx.xdatavalidation.ValidationConsistencyException;

/**
 * DataValidation Extension according to XEP-0122: Data Forms Validation. This specification defines a
 * backwards-compatible extension to the XMPP Data Forms protocol that enables applications to specify additional
 * validation guidelines related to a {@link FormField} in a {@link DataForm}, such as validation of standard XML
 * datatypes, application-specific datatypes, value ranges, and regular expressions.
 *
 * @author Anno van Vliet
 */
public abstract class ValidateElement implements FormFieldChildElement {

    public static final String DATATYPE_XS_STRING = "xs:string";
    public static final String ELEMENT = "validate";
    public static final String NAMESPACE = "http://jabber.org/protocol/xdata-validate";

    public static final QName QNAME = new QName(NAMESPACE, ELEMENT);

    private final String datatype;

    private ListRange listRange;

    /**
     * The 'datatype' attribute specifies the datatype. This attribute is OPTIONAL, and when not specified, defaults to
     * "xs:string".
     *
     * @param datatype the data type of any value contained within the {@link FormField} element.
     */
    private ValidateElement(String datatype) {
        this.datatype = StringUtils.isNotEmpty(datatype) ? datatype : null;
    }

    /**
     * Specifies the data type of any value contained within the {@link FormField} element. It MUST meet one of the
     * following conditions:
     * <ul>
     * <li>Start with "xs:", and be one of the "built-in" datatypes defined in XML Schema Part 2 <a
     * href="http://www.xmpp.org/extensions/xep-0122.html#nt-idp1476016">[2]</a></li>
     * <li>Start with a prefix registered with the XMPP Registrar <a
     * href="http://www.xmpp.org/extensions/xep-0122.html#nt-idp1478544">[3]</a></li>
     * <li>Start with "x:", and specify a user-defined datatype <a
     * href="http://www.xmpp.org/extensions/xep-0122.html#nt-idp1477360">[4]</a></li>
     * </ul>
     *
     * @return the datatype
     */
    public String getDatatype() {
        return datatype != null ? datatype : DATATYPE_XS_STRING;
    }

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

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

    @Override
    public QName getQName() {
        return QNAME;
    }

    @Override
    public final boolean mustBeOnlyOfHisKind() {
        return true;
    }

    @Override
    public XmlStringBuilder toXML(org.jivesoftware.smack.packet.XmlEnvironment enclosingNamespace) {
        XmlStringBuilder buf = new XmlStringBuilder(this, enclosingNamespace);
        buf.optAttribute("datatype", datatype);
        buf.rightAngleBracket();
        appendXML(buf);
        buf.optAppend(getListRange());
        buf.closeElement(this);
        return buf;
    }

    /**
     * Append XML.
     *
     * @param buf TODO javadoc me please
     */
    protected abstract void appendXML(XmlStringBuilder buf);

    /**
     * Set list range.
     * @param listRange the listRange to set
     */
    public void setListRange(ListRange listRange) {
        this.listRange = listRange;
    }

    /**
     * Get list range.
     * @return the listRange
     */
    public ListRange getListRange() {
        return listRange;
    }

    /**
     * Check if this element is consistent according to the business rules in XEP-0122.
     *
     * @param formFieldBuilder the builder used to construct the form field.
     */
    @Override
    public abstract void checkConsistency(FormField.Builder<?, ?> formFieldBuilder);

    public static ValidateElement from(FormField formField) {
        return (ValidateElement) formField.getFormFieldChildElement(QNAME);
    }

    /**
     * Validation only against the datatype itself. Indicates that the value(s) should simply match the field type and
     * datatype constraints.
     *
     * @see ValidateElement
     */
    public static class BasicValidateElement extends ValidateElement {

        public static final String METHOD = "basic";

        /**
         * Basic validate element constructor.
         * @param datatype TODO javadoc me please
         * @see #getDatatype()
         */
        public BasicValidateElement(String datatype) {
            super(datatype);
        }

        @Override
        protected void appendXML(XmlStringBuilder buf) {
            buf.emptyElement(METHOD);
        }

        @Override
        public void checkConsistency(FormField.Builder<?, ?> formField) {
            checkListRangeConsistency(formField);
            if (formField.getType() != null) {
                switch (formField.getType()) {
                case hidden:
                case jid_multi:
                case jid_single:
                    throw new ValidationConsistencyException(String.format(
                                    "Field type '%1$s' is not consistent with validation method '%2$s'.",
                                    formField.getType(), BasicValidateElement.METHOD));
                default:
                    break;
                }
            }
        }

    }

    /**
     * For "list-single" or "list-multi", indicates that the user may enter a custom value (matching the datatype
     * constraints) or choose from the predefined values.
     *
     * @see ValidateElement
     */
    public static class OpenValidateElement extends ValidateElement {

        public static final String METHOD = "open";

        /**
         * Open validate element constructor.
         * @param datatype TODO javadoc me please
         * @see #getDatatype()
         */
        public OpenValidateElement(String datatype) {
            super(datatype);
        }

        @Override
        protected void appendXML(XmlStringBuilder buf) {
            buf.emptyElement(METHOD);
        }

        @Override
        public void checkConsistency(FormField.Builder<?, ?> formField) {
            checkListRangeConsistency(formField);
            if (formField.getType() != null) {
                switch (formField.getType()) {
                case hidden:
                    throw new ValidationConsistencyException(String.format(
                                    "Field type '%1$s' is not consistent with validation method '%2$s'.",
                                    formField.getType(), OpenValidateElement.METHOD));
                default:
                    break;
                }
            }
        }

    }

    /**
     * Indicate that the value should fall within a certain range.
     *
     * @see ValidateElement
     */
    public static class RangeValidateElement extends ValidateElement {

        public static final String METHOD = "range";
        private final String min;
        private final String max;

        /**
         * Range validate element constructor.
         * @param datatype TODO javadoc me please
         * @param min the minimum allowable value. This attribute is OPTIONAL. The value depends on the datatype in use.
         * @param max the maximum allowable value. This attribute is OPTIONAL. The value depends on the datatype in use.
         * @see #getDatatype()
         *
         */
        public RangeValidateElement(String datatype, String min, String max) {
            super(datatype);
            this.min = min;
            this.max = max;
        }

        @Override
        protected void appendXML(XmlStringBuilder buf) {
            buf.halfOpenElement(METHOD);
            buf.optAttribute("min", getMin());
            buf.optAttribute("max", getMax());
            buf.closeEmptyElement();
        }

        /**
         * The 'min' attribute specifies the minimum allowable value.
         *
         * @return the minimum allowable value. This attribute is OPTIONAL. The value depends on the datatype in use.
         */
        public String getMin() {
            return min;
        }

        /**
         * The 'max' attribute specifies the maximum allowable value.
         *
         * @return the maximum allowable value. This attribute is OPTIONAL. The value depends on the datatype in use.
         */
        public String getMax() {
            return max;
        }

        @Override
        public void checkConsistency(FormField.Builder<?, ?> formField) {
            checkNonMultiConsistency(formField, METHOD);
            if (getDatatype().equals(ValidateElement.DATATYPE_XS_STRING)) {
                throw new ValidationConsistencyException(String.format(
                                "Field data type '%1$s' is not consistent with validation method '%2$s'.",
                                getDatatype(), RangeValidateElement.METHOD));
            }
        }

        @Override
        public void validate(FormField formField) {
            AbstractSingleStringValueFormField singleValueFormField = formField.ifPossibleAs(AbstractSingleStringValueFormField.class);
            if (singleValueFormField == null) {
                // We currently only implement validation for single value fields.
                return;
            }
            String valueString = singleValueFormField.getValue();

            switch (getDatatype()) {
            case "xs:int":
            case "xs:integer":
                BigInteger value = new BigInteger(valueString);

                String minString = getMin();
                if (minString != null) {
                    BigInteger min = new BigInteger(minString);
                    if (value.compareTo(min) < 0) {
                        throw new IllegalArgumentException("The provided value " + valueString + " is lower than the allowed minimum of " + minString);
                    }
                }

                String maxString = getMax();
                if (maxString != null) {
                    BigInteger max = new BigInteger(maxString);
                    if (value.compareTo(max) > 0) {
                        throw new IllegalArgumentException("The provided value " + valueString + " is higher than the allowed maximum of " + maxString);
                    }
                }
                break;
            }
        }
    }

    /**
     * Indicates that the value should be restricted to a regular expression. The regular expression must be that
     * defined for <a href="http://www.xmpp.org/extensions/xep-0122.html#nt-idp1501344"> POSIX extended regular
     * expressions </a> including support for <a
     * href="http://www.xmpp.org/extensions/xep-0122.html#nt-idp1502496">Unicode</a>.
     *
     * @see ValidateElement
     */
    public static class RegexValidateElement extends ValidateElement {

        public static final String METHOD = "regex";
        private final String regex;

        /**
         * Regex validate element.
         * @param datatype TODO javadoc me please
         * @param regex TODO javadoc me please
         * @see #getDatatype()
         */
        public RegexValidateElement(String datatype, String regex) {
            super(datatype);
            this.regex = regex;
        }

        /**
         * the expression is that defined for POSIX extended regular expressions, including support for Unicode.
         *
         * @return the regex
         */
        public String getRegex() {
            return regex;
        }

        @Override
        protected void appendXML(XmlStringBuilder buf) {
            buf.element("regex", getRegex());
        }

        @Override
        public void checkConsistency(FormField.Builder<?, ?> formField) {
            checkNonMultiConsistency(formField, METHOD);
        }

    }

    /**
     * This element indicates for "list-multi", that a minimum and maximum number of options should be selected and/or
     * entered.
     */
    public static class ListRange implements FullyQualifiedElement {

        public static final String ELEMENT = "list-range";
        private final UInt32 min;
        private final UInt32 max;

        public ListRange(Long min, Long max) {
            this(min != null ? UInt32.from(min) : null, max != null ? UInt32.from(max) : null);
        }

        /**
         * The 'max' attribute specifies the maximum allowable number of selected/entered values. The 'min' attribute
         * specifies the minimum allowable number of selected/entered values. Both attributes are optional, but at
         * least one must bet set, and the value must be within the range of a unsigned 32-bit integer.
         *
         * @param min TODO javadoc me please
         * @param max TODO javadoc me please
         */
        public ListRange(UInt32 min, UInt32 max) {
            if (max == null && min == null) {
                throw new IllegalArgumentException("Either min or max must be given");
            }
            this.min = min;
            this.max = max;
        }

        @Override
        public XmlStringBuilder toXML(XmlEnvironment enclosingXmlEnvironment) {
            XmlStringBuilder buf = new XmlStringBuilder(this, enclosingXmlEnvironment);
            buf.optAttributeCs("min", getMin());
            buf.optAttributeCs("max", getMax());
            buf.closeEmptyElement();
            return buf;
        }

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

        /**
         * The minimum allowable number of selected/entered values.
         *
         * @return a positive integer, can be null
         */
        public UInt32 getMin() {
            return min;
        }

        /**
         * The maximum allowable number of selected/entered values.
         *
         * @return a positive integer, can be null
         */
        public UInt32 getMax() {
            return max;
        }

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

    }

    /**
     * The &gt;list-range/&lt; element SHOULD be included only when the &lt;field/&gt; is of type "list-multi" and SHOULD be ignored
     * otherwise.
     *
     * @param formField TODO javadoc me please
     */
    protected void checkListRangeConsistency(FormField.Builder<?, ?> formField) {
        ListRange listRange = getListRange();
        if (listRange == null) {
            return;
        }

        Object max = listRange.getMax();
        Object min = listRange.getMin();
        if ((max != null || min != null) && formField.getType() != FormField.Type.list_multi) {
            throw new ValidationConsistencyException(
                            "Field type is not of type 'list-multi' while a 'list-range' is defined.");
        }
    }

    /**
     * Check that the field being build is not of type multi (or hidden).
     *
     * @param formField TODO javadoc me please
     * @param method TODO javadoc me please
     */
    protected void checkNonMultiConsistency(FormField.Builder<?, ?> formField, String method) {
        checkListRangeConsistency(formField);
        if (formField.getType() != null) {
            switch (formField.getType()) {
            case hidden:
            case jid_multi:
            case list_multi:
            case text_multi:
                throw new ValidationConsistencyException(String.format(
                                "Field type '%1$s' is not consistent with validation method '%2$s'.",
                                formField.getType(), method));
            default:
                break;
            }
        }
    }
}