<?php
namespace lighter\models;


abstract class Model {
    /**
     * list of the models related to this one. Almost everytime results of a sql join.
     * @var array
     */
    protected $linkedModels = array();
    /**
     * the data of this model
     * @var array
     */
    protected $data = array();
    /**
     * list of errors generated by the validation
     * @var array
     */
    private $errors = array();
    /**
     * the filter to apply to clean data before returning it in getValues
     * @var array
     */
    private $filter = array();


    /**
     * set values of this model
     *
     * @param array $values
     * @param string $prefix
     */
    public function setValues(array $values) {
        $this->data = $values;
    }


    /**
     * return an array of the values contained within this model
     *
     * @param boolean $clean - default true
     * if true, only actual data is returned. If false, meta data, if it exists,
     * will also be returned. (id should be considered as meta data).
     * @return array
     */
    public function getValues($clean = true) {
        if ($clean) {
            return array_diff_key($this->data, $this->filter);
        } else {
            return $this->data;
        }
    }


    /**
     * return the errors generated by the validation process.
     *
     * @return array
     */
    public function getErrors()
    {
        return $this->errors;
    }


    /**
     * add an error
     *
     * @param string $message
     * @param string $field
     */
    protected function addError($message, $field) {
        $this->errors[$field] = $message;
    }


    /**
     * intialize the filter to use to clean data into getValues
     *
     * @param array $filter
     * the list of field to filter
     */
    protected function setFilter(array $filter) {
        $this->filter = array_flip($filter);
    }


    /**
     * same as setFilter but old values are kept
     *
     * @param array $filter
     */
    protected function addFilter(array $filter) {
        $this->filter = array_merge($this->filter, array_flip($filter));
    }


    /**
     * return the unique id of this model
     *
     * @return string | int
     */
    abstract public function getId();


    /**
     * validate data before storing it
     *
     * @return boolean
     */
    abstract public function validate();


    /**
     * a method to be called just before inserting the data in the DB.
     * Here you can check data validity, remove, add or change information
     *
     * @abstract
     * @param string $class
     */
    abstract public function prepareToStore();


    /**
     * say wether this object already exists in database or not
     *
     * @return boolean
     */
    abstract public function exists();


    /**
     * link another model to this one. Though this link is informal and can be used to a
     * variety of goals, it's designed with the sql join representation in mind.
     * Each model is added to a list of models depending on the linkid that identified a
     * kind of relation.
     *
     * @param Model $model
     * @param string $linkId
     */
    public function link(Model $model, $linkId)
    {
        if (isset($this->linkedModels[$linkId])) {
            $this->linkedModels[$linkId][] = $model;
        } else {
            $this->linkedModels[$linkId]= array($model);
        }
    }


    /**
     * return the list of model matching the linkid
     *
     * @param string $linkId
     * @return array
     */
    public function getLinkedModels($linkId = null)
    {
        if ($linkId == null) {
            $linkId = key($this->linkedModels);
        }
        return $this->linkedModels[$linkId];
    }

}