/*
 *  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.
 */

/**
* @author Stepan M. Mishura
* @version $Revision$
*/

package org.apache.harmony.security.asn1;

import java.util.Arrays;

/**
 * Instance of this class represents ObjectIdentifier (OID).
 *
 * According to X.690:
 * OID is represented as a sequence of subidentifier.
 * Each subidentifier is represented as non negative integer value.
 * There are at least 2 subidentifiers in the sequence.
 *
 * Valid values for first subidentifier are 0, 1 and 2.
 * If the first subidentifier has 0 or 1 value the second
 * subidentifier must be less then 40.
 *
 * @see <a href="http://asn1.elibel.tm.fr/en/standards/index.htm">ASN.1</a>
 */
public final class ObjectIdentifier {

    /** OID as array of integers */
    private final int[] oid;

    /** OID as string */
    private String soid;

    /**
     * Creates ObjectIdentifier(OID) from array of integers.
     *
     * @param oid array of integers
     * @throws IllegalArgumentException if oid is invalid or null
     */
    public ObjectIdentifier(int[] oid) {
        validate(oid);
        this.oid = oid;
    }

    /**
     * Creates ObjectIdentifier(OID) from string representation.
     *
     * @param strOid oid string
     * @throws IllegalArgumentException if oid string is invalid or null
     */
    public ObjectIdentifier(String strOid) {
        this.oid = toIntArray(strOid);
        this.soid = strOid;
    }

    @Override public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || this.getClass() != o.getClass()) {
            return false;
        }
        return Arrays.equals(oid, ((ObjectIdentifier) o).oid);
    }

    @Override public String toString() {
        if (soid == null) {
            soid = toString(oid);
        }
        return soid;
    }

    @Override public int hashCode() {
        // FIXME change me to Arrays.hashCode(int[])
        int intHash = 0;
        for (int i = 0; i < oid.length && i < 4; i++) {
            intHash += oid[i] << (8 * i); //TODO what about to find better one?
        }
        return intHash & 0x7FFFFFFF; // only positive
    }

    /**
     * Validates ObjectIdentifier (OID).
     *
     * @param oid oid as array of integers
     * @throws IllegalArgumentException if oid is invalid or null
     */
    public static void validate(int[] oid) {
        if (oid == null) {
            throw new IllegalArgumentException("oid == null");
        }

        if (oid.length < 2) {
            throw new IllegalArgumentException("OID MUST have at least 2 subidentifiers");
        }

        if (oid[0] > 2) {
            throw new IllegalArgumentException(
                    "Valid values for first subidentifier are 0, 1 and 2");
        } else if (oid[0] != 2 && oid[1] > 39) {
            throw new IllegalArgumentException("If the first subidentifier has 0 or 1 value the "
                    + "second subidentifier value MUST be less than 40");
        }

        for (int anOid : oid) {
            if (anOid < 0) {
                throw new IllegalArgumentException("Subidentifier MUST have positive value");
            }
        }
    }

    /**
     * Returns string representation of OID.
     *
     * Note: it is supposed that passed array of integers
     * contains valid OID value, so no checks are performed.
     *
     * @param oid oid as array of integers
     * @return oid string representation
     */
    public static String toString(int[] oid) {
        StringBuilder sb = new StringBuilder(3 * oid.length);

        for (int i = 0; i < oid.length - 1; ++i) {
            sb.append(oid[i]);
            sb.append('.');
        }
        sb.append(oid[oid.length - 1]);
        return sb.toString();
    }

    /**
     * Gets ObjectIdentifier (OID) from string representation.
     *
     * String representation is defined by the following syntax:
     *     OID = subidentifier 1*("." subidentifier)
     *     subidentifier = 1*(digit)
     *
     * @param str string representation of OID
     * @return oid as array of integers
     * @throws IllegalArgumentException if oid string is invalid or null
     */
    public static int[] toIntArray(String str) {
        return toIntArray(str, true);
    }

    /**
     * Returns whether the given string is a valid ObjectIdentifier
     * (OID) representation.
     *
     * String representation is defined as for {@link #toIntArray}.
     *
     * @param str string representation of OID
     * @return true if oidString has valid syntax or false if not
     */
    public static boolean isOID(String str) {
        return toIntArray(str, false) != null;
    }

    /**
     * Gets ObjectIdentifier (OID) from string representation.
     *
     * String representation is defined by the following syntax:
     *     OID = subidentifier 1*("." subidentifier)
     *     subidentifier = 1*(digit)
     *
     * @param str string representation of OID
     * @return oid as array of integers or null if the oid string is
     * invalid or null and shouldThrow is false
     * @throws IllegalArgumentException if oid string is invalid or null and
     * shouldThrow is true
     */
    private static int[] toIntArray(String str, boolean shouldThrow) {
        if (str == null) {
            if (! shouldThrow) {
                return null;
            }
            throw new IllegalArgumentException("str == null");
        }

        int length = str.length();
        if (length == 0) {
            if (! shouldThrow) {
                return null;
            }
            throw new IllegalArgumentException("Incorrect syntax");
        }

        int count = 1; // number of subidentifiers
        boolean wasDot = true; // indicates whether char before was dot or not.
        char c; // current char
        for (int i = 0; i < length; i++) {
            c = str.charAt(i);
            if (c == '.') {
                if (wasDot) {
                    if (! shouldThrow) {
                        return null;
                    }
                    throw new IllegalArgumentException("Incorrect syntax");
                }
                wasDot = true;
                count++;
            } else if (c >= '0' && c <= '9') {
                wasDot = false;
            } else {
                if (! shouldThrow) {
                    return null;
                }
                throw new IllegalArgumentException("Incorrect syntax");
            }
        }

        if (wasDot) {
            // the last char is dot
            if (! shouldThrow) {
                return null;
            }
            throw new IllegalArgumentException("Incorrect syntax");
        }

        if (count < 2) {
            if (! shouldThrow) {
                return null;
            }
            throw new IllegalArgumentException("Incorrect syntax");
        }

        int[] oid = new int[count];
        for (int i = 0, j = 0; i < length; i++) {
            c = str.charAt(i);
            if (c == '.') {
                j++;
            } else {
                oid[j] = oid[j] * 10 + c - 48; // '0' = 48
            }
        }

        if (oid[0] > 2) {
            if (! shouldThrow) {
                return null;
            }
            throw new IllegalArgumentException("Incorrect syntax");
        } else if (oid[0] != 2 && oid[1] > 39) {
            if (! shouldThrow) {
                return null;
            }
            throw new IllegalArgumentException("Incorrect syntax");
        }

        return oid;
    }
}