<?php

namespace SilverStripe\Assets\Tests;

use SilverStripe\Assets\GDBackend;
use Psr\SimpleCache\CacheInterface;
use SilverStripe\Core\Injector\Injector;
use SilverStripe\Dev\SapphireTest;

/**
 * Tests for the {@link GD} class.
 */
class GDTest extends SapphireTest
{

    public static $filenames = array(
        'gif' => 'test_gif.gif',
        'jpg' => 'test_jpg.jpg',
        'png8' => 'test_png8.png',
        'png32' => 'test_png32.png'
    );

    public function setUp()
    {
        parent::setUp();
        GDBackend::flush();
    }

    public function tearDown()
    {
        GDBackend::flush();
        parent::tearDown();
    }

    /**
     * Loads all images into an associative array of GD objects.
     * Optionally applies an operation to each GD
     *
     * @param  callable $callback Action to perform on each GD
     * @return array List of GD
     */
    protected function applyToEachImage($callback = null)
    {
        $gds = array();
        foreach (self::$filenames as $type => $file) {
            $fullPath = realpath(__DIR__ . '/GDTest/images/' . $file);
            $gd = new GDBackend();
            $gd->loadFrom($fullPath);
            if ($callback) {
                $gd = $callback($gd);
            }
            $gds[$type] = $gd;
        }
        return $gds;
    }

    /**
     * Takes samples from the given GD at 5 pixel increments
     *
     * @param  GDBackend $gd         The source image
     * @param  integer   $horizontal Number of samples to take horizontally
     * @param  integer   $vertical   Number of samples to take vertically
     * @return array List of colours for each sample, each given as an associative
     * array with red, blue, green, and alpha components
     */
    protected function sampleAreas(GDBackend $gd, $horizontal = 4, $vertical = 4)
    {
        $samples = array();
        for ($y = 0; $y < $vertical; $y++) {
            for ($x = 0; $x < $horizontal; $x++) {
                $colour = imagecolorat($gd->getImageResource(), $x * 5, $y * 5);
                $samples[] = imagecolorsforindex($gd->getImageResource(), $colour);
            }
        }
        return $samples;
    }

    /**
     * Asserts that two colour channels are equivalent within a given tolerance range
     *
     * @param integer $expected
     * @param integer $actual
     * @param integer $tolerance
     */
    protected function assertColourEquals($expected, $actual, $tolerance = 0)
    {
        $match =
            ($expected + $tolerance >= $actual) &&
            ($expected - $tolerance <= $actual);
        $this->assertTrue($match);
    }

    /**
     * Asserts that all samples given correctly correspond to a greyscale version
     * of the test image pattern
     *
     * @param array $samples   List of 16 colour samples representing each of the 8 x 8 squares on the image pattern
     * 8 x 8 squares on the image pattern
     * @param int   $alphaBits Depth of alpha channel in bits
     * @param int   $tolerance Reasonable tolerance level for colour comparison
     */
    protected function assertGreyscale($samples, $alphaBits = 0, $tolerance = 0)
    {

        // Check that all colour samples match
        foreach ($samples as $sample) {
            $matches =
                ($sample['red'] === $sample['green']) &&
                ($sample['blue'] === $sample['green']);
            $this->assertTrue($matches, 'Assert colour is greyscale');
            if (!$matches) {
                return;
            }
        }

        // check various sample points
        $this->assertColourEquals(76, $samples[0]['red'], $tolerance);
        $this->assertColourEquals(149, $samples[2]['red'], $tolerance);
        $this->assertColourEquals(0, $samples[8]['red'], $tolerance);
        $this->assertColourEquals(127, $samples[9]['red'], $tolerance);

        // check alpha of various points
        switch ($alphaBits) {
            case 0:
                $this->assertColourEquals(0, $samples[2]['alpha'], $tolerance);
                $this->assertColourEquals(0, $samples[12]['alpha'], $tolerance);
                break;
            case 1:
                $this->assertColourEquals(0, $samples[2]['alpha'], $tolerance);
                $this->assertColourEquals(127, $samples[12]['alpha'], $tolerance);
                break;
            default:
                $this->assertColourEquals(63, $samples[2]['alpha'], $tolerance);
                $this->assertColourEquals(127, $samples[12]['alpha'], $tolerance);
                break;
        }
    }

    /**
     * Tests that images are correctly transformed to greyscale
     */
    function testGreyscale()
    {

        // Apply greyscaling to each image
        $images = $this->applyToEachImage(
            function (GDBackend $gd) {
                return $gd->greyscale();
            }
        );

        // Test GIF (256 colour, transparency)
        $samplesGIF = $this->sampleAreas($images['gif']);
        $this->assertGreyscale($samplesGIF, 1);

        // Test JPG
        $samplesJPG = $this->sampleAreas($images['jpg']);
        $this->assertGreyscale($samplesJPG, 0, 4);

        // Test PNG 8 (indexed with alpha transparency)
        $samplesPNG8 = $this->sampleAreas($images['png8']);
        $this->assertGreyscale($samplesPNG8, 8, 4);

        // Test PNG 32 (full alpha transparency)
        $samplesPNG32 = $this->sampleAreas($images['png32']);
        $this->assertGreyscale($samplesPNG32, 8);
    }

    /**
     * Tests that GD doesn't attempt to load images when they're deemed unavailable
     *
     * @return void
     */
    public function testImageSkippedWhenUnavailable()
    {
        $fullPath = realpath(__DIR__ . '/GDTest/images/test_jpg.jpg');
        $gd = new GDTest\ImageUnavailable();
        $gd->loadFrom($fullPath);

        /* Ensure no image resource is created if the image is unavailable */
        $this->assertNull($gd->getImageResource());
    }

    /**
     * Tests the integrity of the manipulation cache when an error occurs
     */
    public function testCacheIntegrity()
    {
        $fullPath = realpath(__DIR__ . '/GDTest/images/nonimagedata.jpg');

        // Load invalid file
        $gd = new GDBackend();
        $gd->loadFrom($fullPath);

        // Cache should refer to this file
        $cache = Injector::inst()->get(CacheInterface::class . '.GDBackend_Manipulations');
        $key = sha1(implode('|', array($fullPath, filemtime($fullPath))));
        $data = $cache->get($key);
        $this->assertEquals('1', $data);
    }

    /**
     * Test that GD::failedResample() returns true for the current image
     * manipulation only if it previously failed
     *
     * @return void
     */
    public function testFailedResample()
    {
        $fullPath = realpath(__DIR__ . '/GDTest/images/nonimagedata.jpg');
        $fullPath2 = realpath(__DIR__ . '/GDTest/images/test_gif.gif');

        // Load invalid file
        $gd = new GDBackend();
        $gd->loadFrom($fullPath);

        // Cache should refre to this file
        $this->assertTrue($gd->failedResample($fullPath, filemtime($fullPath)));
        $this->assertFalse($gd->failedResample($fullPath2, filemtime($fullPath2)));
    }
}