<?php

namespace App\Model;

use App\Model\Model;
use ArrayAccess;
use Countable;
use Exception;
use Iterator;

/**
 * A collection of models
 *
 * @author Phil Burton <phil@pgburton.com>
 */
class Collection implements ArrayAccess, Iterator, Countable
{
    /**
     * Raw array of models
     *
     * @var Model[]
     */
    protected $models;

    /**
     * Current index of array
     *
     * @var int
     */
    protected $position;

    /**
     * Initalise the collection
     *
     * @author Phil Burton <phil@pgburton.com>
     * @param $array
     */
    public function __construct($array = [])
    {
        // Initalise Index
        $this->position = 0;

        // Initalise empty array
        $this->setFromArray($array);
    }

    /**
     * Reset array to a new array of models
     *
     * @author Phil Burton <phil@pgburton.com>
     * @param array $array
     */
    public function setFromArray(array $array)
    {
        $this->models = [];
        foreach ($array as $model) {
            $this->models[] = $model;
        }
    }

    /**
     * Set the offset
     * Only allow values that are an instance of User
     *
     * @author Phil Burton <phil@pgburton.com>
     * @param mixed $offset
     * @param mixed $value
     */
    public function offsetSet($offset, $value)
    {
        if (!$value instanceof Model) {
            throw new Exception(
                'Collection expects a value of type ' . Model::class . ', ' . gettype($value) . ' given'
            );
        }
        if (is_null($offset)) {
            $this->models[] = $value;
        } else {
            $this->models[$offset] = $value;
        }
    }

    /**
     * Return true if the given offset exists
     * Otherwise return false
     *
     * @author Phil Burton <phil@pgburton.com>
     * @param mixed $offset
     */
    public function offsetExists($offset)
    {
        return isset($this->models[$offset]);
    }

    /**
     * Unset a given offset
     *
     * @author Phil Burton <phil@pgburton.com>
     * @param mixed $offset
     */
    public function offsetUnset($offset)
    {
        unset($this->models[$offset]);
    }

    /**
     * Get the value at a given offset
     *
     * @author Phil Burton <phil@pgburton.com>
     * @param mixed $offset
     */
    public function offsetGet($offset)
    {
        return isset($this->models[$offset]) ? $this->models[$offset] : null;
    }

    /**
     * Return current user
     *
     * @author Phil Burton <phil@pgburton.com>
     * @return Model
     */
    public function current()
    {
        return $this->models[$this->position];
    }

    /**
     * Return true if the current index exists in user array
     * Otherwise return false
     *
     * @author Phil Burton <phil@pgburton.com>
     * @return bool
     */
    public function valid()
    {
        return isset($this->models[$this->position]);
    }

    /**
     * Reset index back to 0
     *
     * @author Phil Burton <phil@pgburton.com>
     */
    public function rewind()
    {
        $this->position = 0;
    }

    /**
     * Return the current index
     *
     * @author Phil Burton <phil@pgburton.com>
     * @return int
     */
    public function key()
    {
        return $this->position;
    }

    /**
     * Increment index by 1
     *
     * @author Phil Burton <phil@pgburton.com>
     */
    public function next()
    {
        ++$this->position;
    }

    /**
     * Create and return new collection of the merged arrays from thsi and a given collection
     *
     * @author Phil Burton <phil@pgburton.com>
     * @param Collection $collection
     * @return Collection
     */
    public function merge(Collection $collection): Collection
    {
        return new Collection(array_merge($collection->toArray(), $this->toArray()));
    }

    /**
     * Return count of users
     *
     * @author Phil Burton <phil@pgburton.com>
     * @return int
     */
    public function count(): int
    {
        return count($this->models);
    }
}