/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.apache.felix.metatype;

import java.math.BigDecimal;
import java.math.BigInteger;

import org.osgi.service.metatype.AttributeDefinition;

/**
 * Provides various validation routines used by the {@link AD#validate(String)}
 * method.
 * 
 * @author <a href="mailto:dev@felix.apache.org">Felix Project Team</a>
 */
final class ADValidator
{
    /**
     * Validates a given input string according to the type specified by the given attribute 
     * definition.
     * <p>
     * The validation is done in the following way:
     * </p>
     * <ul>
     * <li>If the input is undefined (ie. <code>null</code>), and the attribute is mandatory, the 
     * validation fails due to a missing value. If the attribute is optional, the input is 
     * accepted;</li>
     * <li>If the input represents a <em>boolean</em> value, it is tested whether it is defined (in
     * case of non-zero cardinality) and represents either <tt>"true"</tt> or <tt>"false"</tt>. The
     * minimum and maximum parameters are <b>not</b> used in this validation;</li>
     * <li>If the input represents a <em>character</em> value, it is tested whether it is defined 
     * (in case of non-zero cardinality). The character value must be defined within the character 
     * range specified by the minimum and maximum parameters (if defined);</li>
     * <li>If the input represents a <em>numeric</em> value, it is tested whether it is defined (in
     * case of non-zero cardinality). The numeric value must be defined within the numeric range 
     * specified by the minimum and maximum parameters (if defined);</li>
     * <li>If the input represents a <em>string</em> or <em>password</em>, it is tested whether it
     * is defined (in case of non-zero cardinality). The length of the string value must be in the
     * range specified by the minimum and maximum parameters (if defined).</li>
     * </ul>
     * <p>
     * For all types of attributes, if it defines option values, the input should be present as one
     * of the defined option values. 
     * </p>
     * 
     * @param ad
     *            the attribute definition to use in the validation;
     * @param rawInput
     *            the raw input value to validate.
     * @return <code>null</code> if no validation is available, <tt>""</tt> if
     *         validation was successful, or any other non-empty string in case
     *         validation fails.
     */
    public static String validate(AD ad, String rawInput)
    {
        // Handle the case in which the given input is not defined...
        if (rawInput == null)
        {
            if (ad.isRequired())
            {
                return AD.VALIDATE_MISSING;
            }

            return ""; // accept null value...
        }

        // Raw input is defined, validate it further
        String[] input;
        if (ad.getCardinality() == 0)
        {
            input = new String[] { rawInput.trim() };
        }
        else
        {
            input = AD.splitList(rawInput);
        }

        int type = ad.getType();
        switch (type)
        {
            case AttributeDefinition.BOOLEAN:
                return validateBooleanValue(ad, input);

            case AttributeDefinition.CHARACTER:
                return validateCharacterValue(ad, input);

            case AttributeDefinition.BIGDECIMAL:
            case AttributeDefinition.BIGINTEGER:
            case AttributeDefinition.BYTE:
            case AttributeDefinition.DOUBLE:
            case AttributeDefinition.FLOAT:
            case AttributeDefinition.INTEGER:
            case AttributeDefinition.LONG:
            case AttributeDefinition.SHORT:
                return validateNumericValue(ad, input);

            case AttributeDefinition.PASSWORD:
            case AttributeDefinition.STRING:
                return validateString(ad, input);

            default:
                return null; // no validation present...
        }
    }

    /**
     * Searches for a given search value in a given array of options.
     * 
     * @param searchValue
     *            the value to search for;
     * @param optionValues
     *            the values to search in.
     * @return <code>null</code> if the given search value is not found in the
     *         given options, the searched value if found, or <tt>""</tt> if no
     *         search value or options were given.
     */
    private static String findOptionValue(String searchValue, String[] optionValues)
    {
        if ((searchValue == null) || (optionValues == null) || (optionValues.length == 0))
        {
            // indicates that we've not searched...
            return "";
        }

        for (int i = 0; i < optionValues.length; i++)
        {
            if (optionValues[i].equals(searchValue))
            {
                return optionValues[i];
            }
        }

        return null;
    }

    /**
     * Parses a given string value into a numeric type.
     * 
     * @param type
     *            the type to parse;
     * @param value
     *            the value to parse.
     * @return a {@link Number} representation of the given value, or
     *         <code>null</code> if the input was <code>null</code>, empty, or
     *         not a numeric type.
     * @throws NumberFormatException
     *             in case the given value cannot be parsed as numeric value.
     */
    private static Comparable parseNumber(int type, String value) throws NumberFormatException
    {
        if ((value != null) && (value.length() > 0))
        {
            switch (type)
            {
                case AttributeDefinition.BIGDECIMAL:
                    return new BigDecimal(value);
                case AttributeDefinition.BIGINTEGER:
                    return new BigInteger(value);
                case AttributeDefinition.BYTE:
                    return Byte.valueOf(value);
                case AttributeDefinition.SHORT:
                    return Short.valueOf(value);
                case AttributeDefinition.INTEGER:
                    return Integer.valueOf(value);
                case AttributeDefinition.LONG:
                    return Long.valueOf(value);
                case AttributeDefinition.FLOAT:
                    return Float.valueOf(value);
                case AttributeDefinition.DOUBLE:
                    return Double.valueOf(value);
                default:
                    return null;
            }
        }
        return null;
    }

    /**
     * Parses a given string value as character, allowing <code>null</code>
     * -values and empty values to be given as input.
     * 
     * @param value
     *            the value to parse as character, can be <code>null</code> or
     *            an empty value.
     * @return the character value if, and only if, the given input was non-
     *         <code>null</code> and a non-empty string.
     */
    private static Character parseOptionalChar(String value)
    {
        if ((value != null) && (value.length() > 0))
        {
            return Character.valueOf(value.charAt(0));
        }
        return null;
    }

    /**
     * Parses a given string value as numeric value, allowing 
     * <code>null</code>-values and invalid numeric values to be given as 
     * input.
     * 
     * @param type the type of number, should only be a numeric type;
     * @param value
     *            the value to parse as integer, can be <code>null</code> or a
     *            non-numeric value.
     * @return the integer value if, and only if, the given input was non-
     *         <code>null</code> and a valid integer representation.
     */
    private static Comparable parseOptionalNumber(int type, String value)
    {
        if (value != null)
        {
            try
            {
                return parseNumber(type, value);
            }
            catch (NumberFormatException e)
            {
                // Ignore; invalid value...
            }
        }
        return null;
    }

    /**
     * Validates a given input string as boolean value.
     * 
     * @param ad
     *            the attribute definition to use in the validation;
     * @param input
     *            the array with input values to validate.
     * @return <code>null</code> if no validation is available, <tt>""</tt> if
     *         validation was successful, or any other non-empty string in case
     *         validation fails.
     */
    private static String validateBooleanValue(AD ad, String[] input)
    {
        for (int i = 0; i < input.length; i++)
        {
            String value = input[i];
            int length = (value == null) ? 0 : value.length();

            if ((length == 0) && ad.isRequired())
            {
                return AD.VALIDATE_MISSING;
            }
            else if (length > 0 && !"true".equalsIgnoreCase(value) && !"false".equalsIgnoreCase(value))
            {
                return AD.VALIDATE_INVALID_VALUE;
            }
        }

        String[] optionValues = ad.getOptionValues();
        if ((optionValues != null) && (optionValues.length > 0))
        {
            return null; // no validation possible for this type...
        }

        return ""; // accept given value...
    }

    /**
     * Validates a given input string as character value.
     * 
     * @param ad
     *            the attribute definition to use in the validation;
     * @param input
     *            the array with input values to validate.
     * @return <code>null</code> if no validation is available, <tt>""</tt> if
     *         validation was successful, or any other non-empty string in case
     *         validation fails.
     */
    private static String validateCharacterValue(AD ad, String[] input)
    {
        Character min = parseOptionalChar(ad.getMin());
        Character max = parseOptionalChar(ad.getMax());
        String[] optionValues = ad.getOptionValues();

        for (int i = 0; i < input.length; i++)
        {
            Character ch = null;

            int length = (input[i] == null) ? 0 : input[i].length();
            if (length > 1)
            {
                return AD.VALIDATE_GREATER_THAN_MAXIMUM;
            }
            else if ((length == 0) && ad.isRequired())
            {
                return AD.VALIDATE_MISSING;
            }
            else if (length == 1)
            {
                ch = Character.valueOf(input[i].charAt(0));
                // Check whether the minimum value is adhered for all values...
                if ((min != null) && (ch.compareTo(min) < 0))
                {
                    return AD.VALIDATE_LESS_THAN_MINIMUM;
                }
                // Check whether the maximum value is adhered for all values...
                if ((max != null) && (ch.compareTo(max) > 0))
                {
                    return AD.VALIDATE_GREATER_THAN_MAXIMUM;
                }
            }

            if (findOptionValue(input[i], optionValues) == null)
            {
                return AD.VALIDATE_NOT_A_VALID_OPTION;
            }
        }

        return ""; // accept given value...
    }

    /**
     * Validates a given input string as numeric value.
     * 
     * @param ad
     *            the attribute definition to use in the validation;
     * @param input
     *            the array with input values to validate.
     * @return <code>null</code> if no validation is available, <tt>""</tt> if
     *         validation was successful, or any other non-empty string in case
     *         validation fails.
     */
    private static String validateNumericValue(AD ad, String[] input)
    {
        Comparable min = parseOptionalNumber(ad.getType(), ad.getMin());
        Comparable max = parseOptionalNumber(ad.getType(), ad.getMax());
        String[] optionValues = ad.getOptionValues();

        for (int i = 0; i < input.length; i++)
        {
            Comparable value = null;
            try
            {
                value = parseNumber(ad.getType(), input[i]);
            }
            catch (NumberFormatException e)
            {
                return AD.VALIDATE_INVALID_VALUE;
            }

            if ((value == null) && ad.isRequired())
            {
                // Possible if the cardinality != 0 and input was something like
                // "0,,1"...
                return AD.VALIDATE_MISSING;
            }
            // Check whether the minimum value is adhered for all values...
            if ((min != null) && (value != null) && (value.compareTo(min) < 0))
            {
                return AD.VALIDATE_LESS_THAN_MINIMUM;
            }
            // Check whether the maximum value is adhered for all values...
            if ((max != null) && (value != null) && (value.compareTo(max) > 0))
            {
                return AD.VALIDATE_GREATER_THAN_MAXIMUM;
            }

            if (findOptionValue(input[i], optionValues) == null)
            {
                return AD.VALIDATE_NOT_A_VALID_OPTION;
            }
        }

        return ""; // accept given value...
    }

    /**
     * Validates a given input string as string (or password).
     * 
     * @param ad
     *            the attribute definition to use in the validation;
     * @param input
     *            the array with input values to validate.
     * @return <code>null</code> if no validation is available, <tt>""</tt> if
     *         validation was successful, or any other non-empty string in case
     *         validation fails.
     */
    private static String validateString(AD ad, String[] input)
    {
        // The length() method of a string yields an Integer, so the maximum string length is 2^31-1...
        Integer min = (Integer) parseOptionalNumber(AttributeDefinition.INTEGER, ad.getMin());
        Integer max = (Integer) parseOptionalNumber(AttributeDefinition.INTEGER, ad.getMax());
        String[] optionValues = ad.getOptionValues();

        for (int i = 0; i < input.length; i++)
        {
            String value = input[i];
            int length = (value == null) ? 0 : value.length();

            if (ad.isRequired() && ((value == null) || (length == 0)))
            {
                // Possible if the cardinality != 0 and input was something like
                // "0,,1"...
                return AD.VALIDATE_MISSING;
            }
            // Check whether the minimum length is adhered for all values...
            if ((min != null) && (length < min.intValue()))
            {
                return AD.VALIDATE_LESS_THAN_MINIMUM;
            }
            // Check whether the maximum length is adhered for all values...
            if ((max != null) && (length > max.intValue()))
            {
                return AD.VALIDATE_GREATER_THAN_MAXIMUM;
            }

            if (findOptionValue(value, optionValues) == null)
            {
                return AD.VALIDATE_NOT_A_VALID_OPTION;
            }
        }

        return ""; // accept given value...
    }
}