<?php
/* Icinga Web 2 | (c) 2013-2015 Icinga Development Team | GPLv2+ */

namespace Icinga\Chart;

use DOMNode;
use DOMElement;
use DOMDocument;
use DOMImplementation;
use Icinga\Chart\Render\LayoutBox;
use Icinga\Chart\Render\RenderContext;
use Icinga\Chart\Primitive\Canvas;

/**
 * SVG Renderer component.
 *
 * Creates the basic DOM tree of the SVG to use
 */
class SVGRenderer
{
    const X_ASPECT_RATIO_MIN = 'xMin';

    const X_ASPECT_RATIO_MID = 'xMid';

    const X_ASPECT_RATIO_MAX = 'xMax';

    const Y_ASPECT_RATIO_MIN = 'YMin';

    const Y_ASPECT_RATIO_MID = 'YMid';

    const Y_ASPECT_RATIO_MAX = 'YMax';

    const ASPECT_RATIO_PAD = 'meet';

    const ASPECT_RATIO_CUTOFF = 'slice';

    /**
     * The XML-document
     *
     * @var DOMDocument
     */
    private $document;

    /**
     * The SVG-element
     *
     * @var DOMNode
     */
    private $svg;

    /**
     * The description of this SVG, useful for screen readers
     *
     * @var string
     */
    private $ariaDescription;

    /**
     * The title of this SVG, useful for screen readers
     *
     * @var string
     */
    private $ariaTitle;

    /**
     * The aria role used by this svg element
     *
     * @var string
     */
    private $ariaRole = 'img';

    /**
     * The root layer for all elements
     *
     * @var Canvas
     */
    private $rootCanvas;

    /**
     * The width of this renderer
     *
     * @var int
     */
    private $width = 100;

    /**
     * The height of this renderer
     *
     * @var int
     */
    private $height = 100;

    /**
     * Whether the aspect ratio is preversed
     *
     * @var bool
     */
    private $preserveAspectRatio = false;

    /**
     * Horizontal alignment of SVG element
     *
     * @var string
     */
    private $xAspectRatio = self::X_ASPECT_RATIO_MID;

    /**
     * Vertical alignment of SVG element
     *
     * @var string
     */
    private $yAspectRatio = self::Y_ASPECT_RATIO_MID;

    /**
     * Define whether aspect differences should be handled using padding (default) or cutoff
     *
     * @var string
     */
    private $xFillMode = "meet";


    /**
     * Create the root document and the SVG root node
     */
    private function createRootDocument()
    {
        $implementation = new DOMImplementation();
        $docType = $implementation->createDocumentType(
            'svg',
            '-//W3C//DTD SVG 1.1//EN',
            'http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd'
        );

        $this->document = $implementation->createDocument(null, null, $docType);
        $this->svg = $this->createOuterBox();
        $this->document->appendChild($this->svg);
    }

    /**
     * Create the outer SVG box  containing the root svg element and namespace and return it
     *
     * @return DOMElement The SVG root node
     */
    private function createOuterBox()
    {
        $ctx = $this->createRenderContext();
        $svg = $this->document->createElement('svg');
        $svg->setAttribute('xmlns', 'http://www.w3.org/2000/svg');
        $svg->setAttribute('xmlns:xlink', 'http://www.w3.org/1999/xlink');
        $svg->setAttribute('role', $this->ariaRole);
        $svg->setAttribute('width', '100%');
        $svg->setAttribute('height', '100%');
        $svg->setAttribute(
            'viewBox',
            sprintf(
                '0 0 %s %s',
                $ctx->getNrOfUnitsX(),
                $ctx->getNrOfUnitsY()
            )
        );
        if ($this->preserveAspectRatio) {
            $svg->setAttribute(
                'preserveAspectRatio',
                sprintf (
                    '%s%s %s',
                    $this->xAspectRatio,
                    $this->yAspectRatio,
                    $this->xFillMode
                )
            );
        }
        return $svg;
    }

    /**
     * Add aria title and description
     *
     * Adds an aria title and desc element to the given SVG node, which are used to describe this SVG by accessibility
     * tools such as screen readers.
     *
     * @param DOMNode $svg          The SVG DOMNode to which the aria attributes should be attached
     * @param         $title        The title text
     * @param         $description  The description text
     */
    private function addAriaDescription (DOMNode $svg, $titleText, $descriptionText)
    {
        $doc = $svg->ownerDocument;

        $titleId = $descId = '';
        if (isset ($this->ariaTitle)) {
            $titleId = 'aria-title-' . $this->stripNonAlphanumeric($titleText);
            $title = $doc->createElement('title');
            $title->setAttribute('id', $titleId);

            $title->appendChild($doc->createTextNode($titleText));
            $svg->appendChild($title);
        }

        if (isset ($this->ariaDescription)) {
            $descId = 'aria-desc-' . $this->stripNonAlphanumeric($descriptionText);
            $desc = $doc->createElement('desc');
            $desc->setAttribute('id', $descId);

            $desc->appendChild($doc->createTextNode($descriptionText));
            $svg->appendChild($desc);
        }

        $svg->setAttribute('aria-labelledby', join(' ', array($titleId, $descId)));
    }

    /**
     * Initialises the XML-document, SVG-element and this figure's root canvas
     *
     * @param int $width    The width ratio
     * @param int $height   The height ratio
     */
    public function __construct($width, $height)
    {
        $this->width = $width;
        $this->height = $height;
        $this->rootCanvas = new Canvas('root', new LayoutBox(0, 0));
    }

    /**
     * Render the SVG-document
     *
     * @return string The resulting XML structure
     */
    public function render()
    {
        $this->createRootDocument();
        $ctx = $this->createRenderContext();
        $this->addAriaDescription($this->svg, $this->ariaTitle, $this->ariaDescription);
        $this->svg->appendChild($this->rootCanvas->toSvg($ctx));
        $this->document->formatOutput = true;
        return $this->document->saveXML();
    }

    /**
     * Create a render context that will be used for rendering elements
     *
     * @return RenderContext The created RenderContext instance
     */
    public function createRenderContext()
    {
        return new RenderContext($this->document, $this->width, $this->height);
    }

    /**
     * Return the root canvas of this rendered
     *
     * @return Canvas The canvas that will be the uppermost element in this figure
     */
    public function getCanvas()
    {
        return $this->rootCanvas;
    }

    /**
     * Preserve the aspect ratio of the rendered object
     *
     * Do not deform the content of the SVG when the aspect ratio of the viewBox
     * differs from the aspect ratio of the SVG element, but add padding or cutoff
     * instead
     *
     * @param bool $preserve    Whether the aspect ratio should be preserved
     */
    public function preserveAspectRatio($preserve = true)
    {
        $this->preserveAspectRatio = $preserve;
    }

    /**
     * Change the horizontal alignment of the SVG element
     *
     * Change the horizontal alignment of the svg, when preserveAspectRatio is used and
     * padding is present. Defaults to
     */
    public function setXAspectRatioAlignment($alignment)
    {
        $this->xAspectRatio = $alignment;
    }

    /**
     * Change the vertical alignment of the SVG element
     *
     * Change the vertical alignment of the svg, when preserveAspectRatio is used and
     * padding is present.
     */
    public function setYAspectRatioAlignment($alignment)
    {
        $this->yAspectRatio = $alignment;
    }

    /**
     * Set the aria description, that is used as a title for this SVG in screen readers
     *
     * @param $text
     */
    public function setAriaTitle($text)
    {
        $this->ariaTitle = $text;
    }

    /**
     * Set the aria description, that is used to describe this SVG in screen readers
     *
     * @param $text
     */
    public function setAriaDescription($text)
    {
        $this->ariaDescription = $text;
    }

    /**
     * Set the aria role, that is used to describe the purpose of this SVG in screen readers
     *
     * @param $text
     */
    public function setAriaRole($text)
    {
        $this->ariaRole = $text;
    }


    private function stripNonAlphanumeric($str)
    {
        return preg_replace('/[^A-Za-z]+/', '', $str);
    }
}