<?php declare(strict_types=1);

namespace EmsApi;

use ArrayAccess;
use Countable;
use IteratorAggregate;
use Exception;
use Traversable;

/**
 * Class Params
 * @package EmsApi
 *
 * Implementation based on CMap class file from the Yii framework as follows:
 *
 * CMap implements a collection that takes key-value pairs.
 *
 * You can access, add or remove an item with a key by using
 * {@link itemAt}, {@link add}, and {@link remove}.
 * To get the number of the items in the map, use {@link getCount}.
 * CMap can also be used like a regular array as follows,
 * <pre>
 * $map[$key]=$value; // add a key-value pair
 * unset($map[$key]); // remove the value with the specified key
 * if(isset($map[$key])) // if the map contains the key
 * foreach($map as $key=>$value) // traverse the items in the map
 * $n=count($map);  // returns the number of items in the map
 * </pre>
 *
 * @property boolean $readOnly Whether this map is read-only or not. Defaults to false.
 * @property ParamsIterator $iterator An iterator for traversing the items in the list.
 * @property integer $count The number of items in the map.
 * @property array $keys The key list.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @package system.collections
 * @since 1.0
 */
class Params extends Base implements IteratorAggregate, ArrayAccess, Countable
{
    /**
     * @var array internal data storage
     */
    private $_data = [];
    
    /**
     * @var boolean whether this list is read-only
     */
    private $_readOnly = false;

    /**
     * Constructor.
     * Initializes the list with an array or an iterable object.
     * @param mixed $data the intial data. Default is null, meaning no initialization.
     * @param boolean $readOnly whether the list is read-only
     * @throws Exception If data is not null and neither an array nor an iterator.
     */
    public function __construct($data = null, $readOnly = false)
    {
        if ($data !== null) {
            $this->copyFrom($data);
        }
        $this->setReadOnly($readOnly);
    }

    /**
     * @return boolean whether this map is read-only or not. Defaults to false.
     */
    public function getReadOnly()
    {
        return $this->_readOnly;
    }

    /**
     * @param boolean $value whether this list is read-only or not
     * @return void
     */
    protected function setReadOnly($value)
    {
        $this->_readOnly = $value;
    }

    /**
     * Returns an iterator for traversing the items in the list.
     * This method is required by the interface IteratorAggregate.
     * @return ParamsIterator an iterator for traversing the items in the list.
     */
    #[\ReturnTypeWillChange]
    public function getIterator()
    {
        return new ParamsIterator($this->_data);
    }

    /**
     * Returns the number of items in the map.
     * This method is required by Countable interface.
     * @return integer number of items in the map.
     */
    #[\ReturnTypeWillChange]
    public function count()
    {
        return $this->getCount();
    }

    /**
     * Returns the number of items in the map.
     * @return integer the number of items in the map
     */
    public function getCount()
    {
        return count($this->_data);
    }

    /**
     * @return array the key list
     */
    public function getKeys()
    {
        return array_keys($this->_data);
    }

    /**
     * Returns the item with the specified key.
     * This method is exactly the same as {@link offsetGet}.
     * @param mixed $key the key
     * @return mixed the element at the offset, null if no element is found at the offset
     */
    public function itemAt($key)
    {
        return isset($this->_data[$key]) ? $this->_data[$key] : null;
    }

    /**
     * Adds an item into the map.
     * Note, if the specified key already exists, the old value will be overwritten.
     * @param mixed $key key
     * @param mixed $value value
     * @throws Exception if the map is read-only
     *
     * @return void
     */
    public function add($key, $value)
    {
        if (!$this->_readOnly) {
            if ($key === null) {
                $this->_data[] = $value;
            } else {
                $this->_data[$key] = $value;
            }
        } else {
            throw new Exception('The params map is read only.');
        }
    }

    /**
     * Removes an item from the map by its key.
     * @param mixed $key the key of the item to be removed
     * @return mixed the removed value, null if no such key exists.
     * @throws Exception if the map is read-only
     *
     * @return mixed
     */
    public function remove($key)
    {
        if (!$this->_readOnly) {
            if (isset($this->_data[$key])) {
                $value = $this->_data[$key];
                unset($this->_data[$key]);
                return $value;
            } else {
                // it is possible the value is null, which is not detected by isset
                unset($this->_data[$key]);
                return null;
            }
        } else {
            throw new Exception('The params map is read only.');
        }
    }

    /**
     * Removes all items in the map.
     *
     * @return void
     * @throws Exception
     */
    public function clear()
    {
        foreach (array_keys($this->_data) as $key) {
            $this->remove($key);
        }
    }

    /**
     * @param mixed $key the key
     * @return boolean whether the map contains an item with the specified key
     */
    public function contains($key)
    {
        return isset($this->_data[$key]) || array_key_exists($key, $this->_data);
    }

    /**
     * @return array the list of items in array
     */
    public function toArray()
    {
        return $this->_data;
    }

    /**
     * Copies iterable data into the map.
     * Note, existing data in the map will be cleared first.
     * @param mixed $data the data to be copied from, must be an array or object implementing Traversable
     * @throws Exception If data is neither an array nor an iterator.
     *
     * @return void
     */
    public function copyFrom($data)
    {
        if (is_array($data) || $data instanceof Traversable) {
            if ($this->getCount()>0) {
                $this->clear();
            }
            if ($data instanceof Params) {
                $data = $data->_data;
            }
            foreach ($data as $key => $value) {
                $this->add($key, $value);
            }
        } elseif ($data !== null) {
            throw new Exception('Params map data must be an array or an object implementing Traversable.');
        }
    }

    /**
     * Merges iterable data into the map.
     *
     * Existing elements in the map will be overwritten if their keys are the same as those in the source.
     * If the merge is recursive, the following algorithm is performed:
     * <ul>
     * <li>the map data is saved as $a, and the source data is saved as $b;</li>
     * <li>if $a and $b both have an array indxed at the same string key, the arrays will be merged using this algorithm;</li>
     * <li>any integer-indexed elements in $b will be appended to $a and reindexed accordingly;</li>
     * <li>any string-indexed elements in $b will overwrite elements in $a with the same index;</li>
     * </ul>
     *
     * @param mixed $data the data to be merged with, must be an array or object implementing Traversable
     * @param boolean $recursive whether the merging should be recursive.
     *
     * @throws Exception If data is neither an array nor an iterator.
     *
     * @return void
     */
    public function mergeWith($data, $recursive=true)
    {
        if (is_array($data) || $data instanceof Traversable) {
            if ($data instanceof Params) {
                $data = $data->_data;
            }
            if ($recursive) {
                if ($data instanceof Traversable) {
                    $d=[];
                    foreach ($data as $key => $value) {
                        $d[$key] = $value;
                    }
                    $this->_data = self::mergeArray($this->_data, $d);
                } else {
                    $this->_data = self::mergeArray($this->_data, $data);
                }
            } else {
                foreach ($data as $key => $value) {
                    $this->add($key, $value);
                }
            }
        } elseif ($data !== null) {
            throw new Exception('Params map data must be an array or an object implementing Traversable.');
        }
    }

    /**
     * Merges two or more arrays into one recursively.
     * If each array has an element with the same string key value, the latter
     * will overwrite the former (different from array_merge_recursive).
     * Recursive merging will be conducted if both arrays have an element of array
     * type and are having the same key.
     * For integer-keyed elements, the elements from the latter array will
     * be appended to the former array.
     * @param array $a array to be merged to
     * @param array $b array to be merged from. You can specifiy additional
     * arrays via third argument, fourth argument etc.
     * @return array the merged array (the original arrays are not changed.)
     * @see mergeWith
     */
    public static function mergeArray($a, $b)
    {
        $args = func_get_args();
        $res = array_shift($args);
        while (!empty($args)) {
            $next = array_shift($args);
            foreach ($next as $k => $v) {
                if (is_integer($k)) {
                    isset($res[$k]) ? $res[] = $v : $res[$k] = $v;
                } elseif (is_array($v) && isset($res[$k]) && is_array($res[$k])) {
                    $res[$k] = self::mergeArray($res[$k], $v);
                } else {
                    $res[$k]=$v;
                }
            }
        }
        return $res;
    }

    /**
     * Returns whether there is an element at the specified offset.
     * This method is required by the interface ArrayAccess.
     * @param mixed $offset the offset to check on
     * @return boolean
     */
    #[\ReturnTypeWillChange]
    public function offsetExists($offset)
    {
        return $this->contains($offset);
    }

    /**
     * Returns the element at the specified offset.
     * This method is required by the interface ArrayAccess.
     * @param int $offset the offset to retrieve element.
     * @return mixed the element at the offset, null if no element is found at the offset
     */
    #[\ReturnTypeWillChange]
    public function offsetGet($offset)
    {
        return $this->itemAt($offset);
    }

    /**
     * Sets the element at the specified offset.
     * This method is required by the interface ArrayAccess.
     *
     * @param int $offset the offset to set element
     * @param mixed $item the element value
     *
     * @return void
     * @throws Exception
     */
    #[\ReturnTypeWillChange]
    public function offsetSet($offset, $item)
    {
        $this->add($offset, $item);
    }

    /**
     * Unsets the element at the specified offset.
     * This method is required by the interface ArrayAccess.
     *
     * @param mixed $offset the offset to unset element
     *
     * @return void
     * @throws Exception
     */
    #[\ReturnTypeWillChange]
    public function offsetUnset($offset)
    {
        $this->remove($offset);
    }
}