<?php

/**
 * Hoa
 *
 *
 * @license
 *
 * New BSD License
 *
 * Copyright © 2007-2015, Hoa community. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the Hoa nor the names of its contributors may be
 *       used to endorse or promote products derived from this software without
 *       specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS AND CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

namespace Hoa\Praspel\Model;

use Hoa\Iterator;
use Hoa\Praspel;
use Hoa\Realdom;

/**
 * Class \Hoa\Praspel\Model\Declaration.
 *
 * Represent a declaration.
 *
 * @copyright  Copyright © 2007-2015 Hoa community
 * @license    New BSD License
 */
abstract class Declaration
    extends    Clause
    implements Iterator\Aggregate,
               \ArrayAccess,
               \Countable
{
    /**
     * Declared variables.
     *
     * @var array
     */
    protected $_variables  = [];

    /**
     * Predicates.
     *
     * @var array
     */
    protected $_predicates = [];

    /**
     * Whether declaring a local variable or not.
     *
     * @var bool
     */
    protected $_let        = false;


    /**
     * Check if a variable exists.
     *
     * @param   string  $offset    Variable name.
     * @return  bool
     */
    public function offsetExists($offset)
    {
        return isset($this->_variables[$offset]);
    }

    /**
     * Get or create a variable.
     *
     * @param   string  $offset    Variable name.
     * @return  \Hoa\Praspel\Model\Variable
     */
    public function offsetGet($offset)
    {
        return $this->getVariable($offset);
    }

    /**
     * Declare or get a new variable.
     *
     * @param   string  $name         Variable name.
     * @param   bool    $borrowing    Borrowing variable or not.
     * @return  mixed
     */
    public function getVariable($name, $borrowing = false)
    {
        if (true === $borrowing) {
            $out        = new Variable\Borrowing($name, $this->_let, $this);
            $this->_let = false;

            return $out;
        }

        if ('\old(' === substr($name, 0, 5)) {
            $variable = $this->getVariable($name, true);

            return new Realdom\Crate\Constant(
                $variable->getBorrowedVariable(),
                function () use ($variable) {
                    return $variable->getName();
                },
                $this
            );
        }

        if (false === $this->offsetExists($name)) {
            $variable   = new Variable($name, $this->_let, $this);
            $this->_let = false;

            return $this->_variables[$name] = $variable;
        }

        return $this->_variables[$name];
    }

    /**
     * Add a variable.
     *
     * @param   string                       $name        Name.
     * @param   \Hoa\Praspel\Model\Variable  $variable    Variable.
     * @return  \Hoa\Praspel\Model\Variable
     */
    public function addVariable($name, Variable $variable)
    {
        return $this->_variables[$name] = $variable;
    }

    /**
     * Set a value to a variable.
     *
     * @param   string  $offset    Variable name.
     * @param   mixed   $value     Variable value.
     * @return  mixed
     */
    public function offsetSet($offset, $value)
    {
        $variable = $this->offsetGet($offset);
        $old      = $variable->getValue();
        $variable->setValue($value);

        return $old;
    }

    /**
     * Delete a variable.
     *
     * @param   string  $offset    Variable name.
     * @return  void
     */
    public function offsetUnset($offset)
    {
        unset($this->_variables[$offset]);

        return;
    }

    /**
     * Allow to write $clause->let['var'] = … to define a local variable (if
     * $name is not equal to "let", then it is a normal behavior).
     *
     * @param   string  $name     Name.
     * @return  \Hoa\Praspel\Model\Declaration
     */
    public function __get($name)
    {
        if ('let' !== $name) {
            return $this->$name;
        }

        $this->_let = true;

        return $this;
    }

    /**
     * Iterator over local variables.
     *
     * @return  \Hoa\Iterator\CallbackFilter
     */
    public function getIterator()
    {
        return new Iterator\CallbackFilter(
            new Iterator\Map($this->getLocalVariables()),
            function (Variable $variable) {
                return false === $variable->isLocal();
            }
        );
    }

    /**
     * Count number of variables.
     *
     * @return  int
     */
    public function count()
    {
        return count($this->_variables);
    }

    /**
     * Get local variables.
     *
     * @return  array
     */
    public function &getLocalVariables()
    {
        return $this->_variables;
    }

    /**
     * Get in-scope variables.
     *
     * @return  array
     */
    public function getInScopeVariables()
    {
        $out     = [];
        $clause  = $this->getName();
        $current = $this;

        while (null !== $current = $current->getParent()) {
            if (false === $current->clauseExists($clause)) {
                continue;
            }

            $localVariables = &$current->getClause($clause)->getLocalVariables();

            foreach ($localVariables as $name => &$variables) {
                $out[$name] = &$variables;
            }
        }

        return $out;
    }

    /**
     * Add a predicate.
     *
     * @param   string  $predicate    Predicate.
     * @return  \Hoa\Praspel\Model\Declaration
     */
    public function predicate($predicate)
    {
        $this->_predicates[] = $predicate;

        return $this;
    }

    /**
     * Get all predicates.
     *
     * @return  array
     */
    public function getPredicates()
    {
        return $this->_predicates;
    }
}