<?php

namespace Icinga\Backend\DataView;
/**
 * Dataview that maps generic field names to storage specific fields or requests them via handlers.
 *
 * When accessing objects, every storage api returns them with other names. You can't simply say $object->service_state,
 * because this field is, e.g. under status.current_state in the status.dat view, while IDO uses servicestate->current_state.
 *
 * This view is intended for normalizing these changes, so a request of service_state returns the right field for the backend.
 * When implementing it, you have to fill the mappedParameters and/or the handlerParameters array. While mappedParameters
 * simply translate logic field names to storage specific ones, handlerParameters determins functions that handle data
 * retrieval for the specific fields.
 *
 */
class ObjectRemappingView implements AbstractAccessorStrategy
{

    /**
     * When implementing your own Mapper, this contains the static mapping rules.
     * @see Icinga\Backend\Statusdat\DataView\StatusdatServiceView for an example
     *
     * @var array
     */
    protected $mappedParameters = array();

    /**
     * When implementing your own Mapper, this contains the handler for specific fields and allows you to lazy load
     * different fields if necessary. The methods are strings that will be mapped to methods of this class
     *
     * @see Icinga\Backend\Statusdat\DataView\StatusdatServiceView for an example
     *
     * @var array
     */
    protected $handlerParameters = array();

    /**
     *
     * @see Icinga\Backend\DataView\AbstractAccessorStrategy
     *
     * @param The $item
     * @param The $field
     * @return The|string
     * @throws \InvalidArgumentException
     */
    public function get(&$item, $field)
    {

        if (isset($item->$field))
            return $item->$field;
        if (isset($this->mappedParameters[$field])) {
            $mapped = explode(".",$this->mappedParameters[$field]);
            $res = $item;

            foreach($mapped as $map) {
                if(!isset($res->$map))
                    return "";
                $res = $res->$map;
            }
            return $res;
        }

        if (isset($this->handlerParameters[$field])) {
            $hdl = $this->handlerParameters[$field];
            return $this->$hdl($item);
        }
        throw new \InvalidArgumentException("Field $field does not exist for status.dat services");
    }

    /**
     *
     * @see Icinga\Backend\DataView\AbstractAccessorStrategy
     *
     * @param The $field
     * @return The|string
     */
    public function getNormalizedFieldName($field)
    {
        if(isset($this->mappedParameters[$field]))
            return $this->mappedParameters[$field];
        return $field;
    }

    /**
     *
     * @see Icinga\Backend\DataView\AbstractAccessorStrategy
     *
     * @param The $item
     * @param The $field
     * @return bool
     */
    public function exists(&$item, $field)
    {
        return (isset($item->$field)
            || isset($this->mappedParameters[$field])
            || isset($this->handlerParameters[$field])
        );
    }

}