/*
 * %CopyrightBegin%
 * 
 * Copyright Ericsson AB 2000-2009. All Rights Reserved.
 * 
 * The contents of this file are subject to the Erlang Public License,
 * Version 1.1, (the "License"); you may not use this file except in
 * compliance with the License. You should have received a copy of the
 * Erlang Public License along with this software. If not, it can be
 * retrieved online at http://www.erlang.org/.
 * 
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
 * the License for the specific language governing rights and limitations
 * under the License.
 * 
 * %CopyrightEnd%
 */
package com.ericsson.otp.erlang;

import java.io.Serializable;

/**
 * Provides a Java representation of Erlang tuples. Tuples are created from one
 * or more arbitrary Erlang terms.
 * 
 * <p>
 * The arity of the tuple is the number of elements it contains. Elements are
 * indexed from 0 to (arity-1) and can be retrieved individually by using the
 * appropriate index.
 */
public class OtpErlangTuple extends OtpErlangObject implements Serializable,
	Cloneable {
    // don't change this!
    static final long serialVersionUID = 9163498658004915935L;

    private static final OtpErlangObject[] NO_ELEMENTS = new OtpErlangObject[0];

    private OtpErlangObject[] elems = NO_ELEMENTS;

    /**
     * Create a unary tuple containing the given element.
     * 
     * @param elem
     *                the element to create the tuple from.
     * 
     * @exception java.lang.IllegalArgumentException
     *                    if the element is null.
     */
    public OtpErlangTuple(final OtpErlangObject elem) {
	if (elem == null) {
	    throw new java.lang.IllegalArgumentException(
		    "Tuple element cannot be null");
	} else {
	    elems = new OtpErlangObject[] { elem };
	}
    }

    /**
     * Create a tuple from an array of terms.
     * 
     * @param elems
     *                the array of terms to create the tuple from.
     * 
     * @exception java.lang.IllegalArgumentException
     *                    if the array is empty (null) or contains null
     *                    elements.
     */
    public OtpErlangTuple(final OtpErlangObject[] elems) {
	this(elems, 0, elems.length);
    }

    /**
     * Create a tuple from an array of terms.
     * 
     * @param elems
     *                the array of terms to create the tuple from.
     * @param start
     *                the offset of the first term to insert.
     * @param count
     *                the number of terms to insert.
     * 
     * @exception java.lang.IllegalArgumentException
     *                    if the array is empty (null) or contains null
     *                    elements.
     */
    public OtpErlangTuple(OtpErlangObject[] elems, final int start,
	    final int count) {
	if (elems == null) {
	    throw new java.lang.IllegalArgumentException(
		    "Tuple content can't be null");
	} else if (count < 1) {
	    elems = NO_ELEMENTS;
	} else {
	    this.elems = new OtpErlangObject[count];
	    for (int i = 0; i < count; i++) {
		if (elems[start + i] != null) {
		    this.elems[i] = elems[start + i];
		} else {
		    throw new java.lang.IllegalArgumentException(
			    "Tuple element cannot be null (element"
				    + (start + i) + ")");
		}
	    }
	}
    }

    /**
     * Create a tuple from a stream containing an tuple encoded in Erlang
     * external format.
     * 
     * @param buf
     *                the stream containing the encoded tuple.
     * 
     * @exception OtpErlangDecodeException
     *                    if the buffer does not contain a valid external
     *                    representation of an Erlang tuple.
     */
    public OtpErlangTuple(final OtpInputStream buf)
	    throws OtpErlangDecodeException {
	final int arity = buf.read_tuple_head();

	if (arity > 0) {
	    elems = new OtpErlangObject[arity];

	    for (int i = 0; i < arity; i++) {
		elems[i] = buf.read_any();
	    }
	} else {
	    elems = NO_ELEMENTS;
	}
    }

    /**
     * Get the arity of the tuple.
     * 
     * @return the number of elements contained in the tuple.
     */
    public int arity() {
	return elems.length;
    }

    /**
     * Get the specified element from the tuple.
     * 
     * @param i
     *                the index of the requested element. Tuple elements are
     *                numbered as array elements, starting at 0.
     * 
     * @return the requested element, of null if i is not a valid element index.
     */
    public OtpErlangObject elementAt(final int i) {
	if (i >= arity() || i < 0) {
	    return null;
	}
	return elems[i];
    }

    /**
     * Get all the elements from the tuple as an array.
     * 
     * @return an array containing all of the tuple's elements.
     */
    public OtpErlangObject[] elements() {
	final OtpErlangObject[] res = new OtpErlangObject[arity()];
	System.arraycopy(elems, 0, res, 0, res.length);
	return res;
    }

    /**
     * Get the string representation of the tuple.
     * 
     * @return the string representation of the tuple.
     */
    @Override
    public String toString() {
	int i;
	final StringBuffer s = new StringBuffer();
	final int arity = elems.length;

	s.append("{");

	for (i = 0; i < arity; i++) {
	    if (i > 0) {
		s.append(",");
	    }
	    s.append(elems[i].toString());
	}

	s.append("}");

	return s.toString();
    }

    /**
     * Convert this tuple to the equivalent Erlang external representation.
     * 
     * @param buf
     *                an output stream to which the encoded tuple should be
     *                written.
     */
    @Override
    public void encode(final OtpOutputStream buf) {
	final int arity = elems.length;

	buf.write_tuple_head(arity);

	for (int i = 0; i < arity; i++) {
	    buf.write_any(elems[i]);
	}
    }

    /**
     * Determine if two tuples are equal. Tuples are equal if they have the same
     * arity and all of the elements are equal.
     * 
     * @param o
     *                the tuple to compare to.
     * 
     * @return true if the tuples have the same arity and all the elements are
     *         equal.
     */
    @Override
    public boolean equals(final Object o) {
	if (!(o instanceof OtpErlangTuple)) {
	    return false;
	}

	final OtpErlangTuple t = (OtpErlangTuple) o;
	final int a = arity();

	if (a != t.arity()) {
	    return false;
	}

	for (int i = 0; i < a; i++) {
	    if (!elems[i].equals(t.elems[i])) {
		return false; // early exit
	    }
	}

	return true;
    }
    
    protected int doHashCode() {
	OtpErlangObject.Hash hash = new OtpErlangObject.Hash(9);
	final int a = arity();
	hash.combine(a);
	for (int i = 0; i < a; i++) {
	    hash.combine(elems[i].hashCode());
	}
	return hash.valueOf();
    }
    
    @Override
    public Object clone() {
	final OtpErlangTuple newTuple = (OtpErlangTuple) super.clone();
	newTuple.elems = elems.clone();
	return newTuple;
    }
}
