<?php

namespace SilverStripe\Assets;

use SilverStripe\Assets\Storage\DBFile;
use SilverStripe\Assets\Storage\AssetContainer;
use SilverStripe\Assets\Storage\AssetStore;
use SilverStripe\Core\Config\Config;
use SilverStripe\Core\Convert;
use SilverStripe\Core\Injector\Injector;
use SilverStripe\ORM\FieldType\DBField;
use SilverStripe\ORM\FieldType\DBHTMLText;
use InvalidArgumentException;

/**
 * Provides image manipulation functionality.
 * Provides limited thumbnail generation functionality for non-image files.
 * Should only be applied to implementors of AssetContainer
 *
 * Allows raw images to be resampled via Resampled()
 *
 * Image scaling manipluations, including:
 * - Fit()
 * - FitMax()
 * - ScaleWidth()
 * - ScaleMaxWidth()
 * - ScaleHeight()
 * - ScaleMaxHeight()
 * - ResizedImage()
 *
 * Image cropping manipulations, including:
 * - CropHeight()
 * - CropWidth()
 * - Fill()
 * - FillMax()
 *
 * Thumbnail generation methods including:
 * - Icon()
 * - CMSThumbnail()
 *
 * @mixin AssetContainer
 */
trait ImageManipulation
{

    /**
     * @return string Data from the file in this container
     */
    abstract public function getString();

    /**
     * @return resource Data stream to the asset in this container
     */
    abstract public function getStream();

    /**
     * @param bool $grant Ensures that the url for any protected assets is granted for the current user.
     * @return string public url to the asset in this container
     */
    abstract public function getURL($grant = true);

    /**
     * @return string The absolute URL to the asset in this container
     */
    abstract public function getAbsoluteURL();

    /**
     * Get metadata for this file
     *
     * @return array|null File information
     */
    abstract public function getMetaData();

    /**
     * Get mime type
     *
     * @return string Mime type for this file
     */
    abstract public function getMimeType();

    /**
     * Return file size in bytes.
     *
     * @return int
     */
    abstract public function getAbsoluteSize();

    /**
     * Determine if this container has a valid value
     *
     * @return bool Flag as to whether the file exists
     */
    abstract public function exists();

    /**
     * Get value of filename
     *
     * @return string
     */
    abstract public function getFilename();

    /**
     * Get value of hash
     *
     * @return string
     */
    abstract public function getHash();

    /**
     * Get value of variant
     *
     * @return string
     */
    abstract public function getVariant();

    /**
     * Determine if a valid non-empty image exists behind this asset
     *
     * @return bool
     */
    abstract public function getIsImage();

    /**
     * @config
     * @var bool Force all images to resample in all cases
     */
    private static $force_resample = true;

    /**
     * @config
     * @var int The width of an image thumbnail in a strip.
     */
    private static $strip_thumbnail_width = 50;

    /**
     * @config
     * @var int The height of an image thumbnail in a strip.
     */
    private static $strip_thumbnail_height = 50;

    /**
     * The width of an image thumbnail in the CMS.
     *
     * @config
     * @var int
     */
    private static $cms_thumbnail_width = 100;

    /**
     * The height of an image thumbnail in the CMS.
     *
     * @config
     * @var int
     */
    private static $cms_thumbnail_height = 100;

    /**
     * The width of an image preview in the Asset section
     *
     * @config
     * @var int
     */
    private static $asset_preview_width = 930; // max for mobile full-width

    /**
     * The height of an image preview in the Asset section
     *
     * @config
     * @var int
     */
    private static $asset_preview_height = 336;

    /**
     * Fit image to specified dimensions and fill leftover space with a solid colour (default white). Use in templates with $Pad.
     *
     * @param integer $width The width to size to
     * @param integer $height The height to size to
     * @param string $backgroundColor
     * @return AssetContainer
     */
    public function Pad($width, $height, $backgroundColor = 'FFFFFF')
    {
        if ($this->isSize($width, $height)) {
            return $this;
        }

        $variant = $this->variantName(__FUNCTION__, $width, $height, $backgroundColor);
        return $this->manipulateImage(
            $variant,
            function (Image_Backend $backend) use ($width, $height, $backgroundColor) {
                return $backend->paddedResize($width, $height, $backgroundColor);
            }
        );
    }

    /**
     * Forces the image to be resampled, if possible
     *
     * @return AssetContainer
     */
    public function Resampled()
    {
        // If image is already resampled, return self reference
        $variant = $this->getVariant();
        if ($variant) {
            return $this;
        }

        // Resample, but fallback to original object
        $result = $this->manipulateImage(__FUNCTION__, function (Image_Backend $backend) {
            return $backend;
        });
        if ($result) {
            return $result;
        }
        return $this;
    }

    /**
     * Update the url to point to a resampled version if forcing
     *
     * @param string $url
     */
    public function updateURL(&$url)
    {
        // Skip if resampling is off, or is already resampled, or is not an image
        if (!Config::inst()->get(get_class($this), 'force_resample') || $this->getVariant() || !$this->getIsImage()) {
            return;
        }

        // Attempt to resample
        $resampled = $this->Resampled();
        if (!$resampled) {
            return;
        }

        // Only update if resampled file is a smaller file size
        if ($resampled->getAbsoluteSize() < $this->getAbsoluteSize()) {
            $url = $resampled->getURL();
        }
    }


    /**
     * Generate a resized copy of this image with the given width & height.
     * This can be used in templates with $ResizedImage but should be avoided,
     * as it's the only image manipulation function which can skew an image.
     *
     * @param integer $width Width to resize to
     * @param integer $height Height to resize to
     * @return AssetContainer
     */
    public function ResizedImage($width, $height)
    {
        if ($this->isSize($width, $height)) {
            return $this;
        }

        $variant = $this->variantName(__FUNCTION__, $width, $height);
        return $this->manipulateImage($variant, function (Image_Backend $backend) use ($width, $height) {
            return $backend->resize($width, $height);
        });
    }

    /**
     * Scale image proportionally to fit within the specified bounds
     *
     * @param integer $width The width to size within
     * @param integer $height The height to size within
     * @return AssetContainer
     */
    public function Fit($width, $height)
    {
        // Prevent divide by zero on missing/blank file
        if (!$this->getWidth() || !$this->getHeight()) {
            return null;
        }

        // Check if image is already sized to the correct dimension
        $widthRatio = $width / $this->getWidth();
        $heightRatio = $height / $this->getHeight();

        if ($widthRatio < $heightRatio) {
            // Target is higher aspect ratio than image, so check width
            if ($this->isWidth($width)) {
                return $this;
            }
        } else {
            // Target is wider or same aspect ratio as image, so check height
            if ($this->isHeight($height)) {
                return $this;
            }
        }

        // Item must be regenerated
        $variant = $this->variantName(__FUNCTION__, $width, $height);
        return $this->manipulateImage($variant, function (Image_Backend $backend) use ($width, $height) {
            return $backend->resizeRatio($width, $height);
        });
    }

    /**
     * Proportionally scale down this image if it is wider or taller than the specified dimensions.
     * Similar to Fit but without up-sampling. Use in templates with $FitMax.
     *
     * @uses ScalingManipulation::Fit()
     * @param integer $width The maximum width of the output image
     * @param integer $height The maximum height of the output image
     * @return AssetContainer
     */
    public function FitMax($width, $height)
    {
        return $this->getWidth() > $width || $this->getHeight() > $height
            ? $this->Fit($width, $height)
            : $this;
    }


    /**
     * Scale image proportionally by width. Use in templates with $ScaleWidth.
     *
     * @param integer $width The width to set
     * @return AssetContainer
     */
    public function ScaleWidth($width)
    {
        if ($this->isWidth($width)) {
            return $this;
        }

        $variant = $this->variantName(__FUNCTION__, $width);
        return $this->manipulateImage($variant, function (Image_Backend $backend) use ($width) {
            return $backend->resizeByWidth($width);
        });
    }

    /**
     * Proportionally scale down this image if it is wider than the specified width.
     * Similar to ScaleWidth but without up-sampling. Use in templates with $ScaleMaxWidth.
     *
     * @uses ScalingManipulation::ScaleWidth()
     * @param integer $width The maximum width of the output image
     * @return AssetContainer
     */
    public function ScaleMaxWidth($width)
    {
        return $this->getWidth() > $width
            ? $this->ScaleWidth($width)
            : $this;
    }

    /**
     * Scale image proportionally by height. Use in templates with $ScaleHeight.
     *
     * @param int $height The height to set
     * @return AssetContainer
     */
    public function ScaleHeight($height)
    {
        if ($this->isHeight($height)) {
            return $this;
        }

        $variant = $this->variantName(__FUNCTION__, $height);
        return $this->manipulateImage($variant, function (Image_Backend $backend) use ($height) {
            return $backend->resizeByHeight($height);
        });
    }

    /**
     * Proportionally scale down this image if it is taller than the specified height.
     * Similar to ScaleHeight but without up-sampling. Use in templates with $ScaleMaxHeight.
     *
     * @uses ScalingManipulation::ScaleHeight()
     * @param integer $height The maximum height of the output image
     * @return AssetContainer
     */
    public function ScaleMaxHeight($height)
    {
        return $this->getHeight() > $height
            ? $this->ScaleHeight($height)
            : $this;
    }


    /**
     * Crop image on X axis if it exceeds specified width. Retain height.
     * Use in templates with $CropWidth. Example: $Image.ScaleHeight(100).$CropWidth(100)
     *
     * @uses CropManipulation::Fill()
     * @param integer $width The maximum width of the output image
     * @return AssetContainer
     */
    public function CropWidth($width)
    {
        return $this->getWidth() > $width
            ? $this->Fill($width, $this->getHeight())
            : $this;
    }

    /**
     * Crop image on Y axis if it exceeds specified height. Retain width.
     * Use in templates with $CropHeight. Example: $Image.ScaleWidth(100).CropHeight(100)
     *
     * @uses CropManipulation::Fill()
     * @param integer $height The maximum height of the output image
     * @return AssetContainer
     */
    public function CropHeight($height)
    {
        return $this->getHeight() > $height
            ? $this->Fill($this->getWidth(), $height)
            : $this;
    }

    /**
     * Crop this image to the aspect ratio defined by the specified width and height,
     * then scale down the image to those dimensions if it exceeds them.
     * Similar to Fill but without up-sampling. Use in templates with $FillMax.
     *
     * @uses ImageManipulation::Fill()
     * @param integer $width The relative (used to determine aspect ratio) and maximum width of the output image
     * @param integer $height The relative (used to determine aspect ratio) and maximum height of the output image
     * @return AssetContainer
     */
    public function FillMax($width, $height)
    {
        // Prevent divide by zero on missing/blank file
        if (!$this->getWidth() || !$this->getHeight()) {
            return null;
        }

        // Is the image already the correct size?
        if ($this->isSize($width, $height)) {
            return $this;
        }

        // If not, make sure the image isn't upsampled
        $imageRatio = $this->getWidth() / $this->getHeight();
        $cropRatio = $width / $height;
        // If cropping on the x axis compare heights
        if ($cropRatio < $imageRatio && $this->getHeight() < $height) {
            return $this->Fill($this->getHeight() * $cropRatio, $this->getHeight());
        }

        // Otherwise we're cropping on the y axis (or not cropping at all) so compare widths
        if ($this->getWidth() < $width) {
            return $this->Fill($this->getWidth(), $this->getWidth() / $cropRatio);
        }

        return $this->Fill($width, $height);
    }

    /**
     * Resize and crop image to fill specified dimensions.
     * Use in templates with $Fill
     *
     * @param integer $width Width to crop to
     * @param integer $height Height to crop to
     * @return AssetContainer
     */
    public function Fill($width, $height)
    {
        if ($this->isSize($width, $height)) {
            return $this;
        }

        // Resize
        $variant = $this->variantName(__FUNCTION__, $width, $height);
        return $this->manipulateImage($variant, function (Image_Backend $backend) use ($width, $height) {
            return $backend->croppedResize($width, $height);
        });
    }

    /**
     * Default CMS thumbnail
     *
     * @return DBFile|DBHTMLText Either a resized thumbnail, or html for a thumbnail icon
     */
    public function CMSThumbnail()
    {
        $width = (int)Config::inst()->get(__CLASS__, 'cms_thumbnail_width');
        $height = (int)Config::inst()->get(__CLASS__, 'cms_thumbnail_height');
        return $this->ThumbnailIcon($width, $height);
    }

    /**
     * Generates a thumbnail for use in the gridfield view
     *
     * @return AssetContainer|DBHTMLText Either a resized thumbnail, or html for a thumbnail icon
     */
    public function StripThumbnail()
    {
        $width = (int)Config::inst()->get(__CLASS__, 'strip_thumbnail_width');
        $height = (int)Config::inst()->get(__CLASS__, 'strip_thumbnail_height');
        return $this->ThumbnailIcon($width, $height);
    }

    /**
     * Get preview for this file
     *
     * @return AssetContainer|DBHTMLText Either a resized thumbnail, or html for a thumbnail icon
     */
    public function PreviewThumbnail()
    {
        $width = (int)Config::inst()->get(__CLASS__, 'asset_preview_width');
        return $this->ScaleMaxWidth($width)  ?: $this->IconTag();
    }

    /**
     * Default thumbnail generation for Images
     *
     * @param int $width
     * @param int $height
     * @return AssetContainer
     */
    public function Thumbnail($width, $height)
    {
        return $this->Pad($width, $height);
    }

    /**
     * Thubnail generation for all file types.
     *
     * Resizes images, but returns an icon <img /> tag if this is not a resizable image
     *
     * @param int $width
     * @param int $height
     * @return AssetContainer|DBHTMLText
     */
    public function ThumbnailIcon($width, $height)
    {
        return $this->Thumbnail($width, $height) ?: $this->IconTag();
    }

    /**
     * Get HTML for img containing the icon for this file
     *
     * @return DBHTMLText
     */
    public function IconTag()
    {
        return DBField::create_field(
            'HTMLFragment',
            '<img src="' . Convert::raw2att($this->getIcon()) . '" />'
        );
    }

    /**
     * Get URL to thumbnail of the given size.
     *
     * May fallback to default icon
     *
     * @param int $width
     * @param int $height
     * @return string
     */
    public function ThumbnailURL($width, $height)
    {
        $thumbnail = $this->Thumbnail($width, $height);
        if ($thumbnail) {
            return $thumbnail->getURL();
        }
        return $this->getIcon();
    }

    /**
     * Return the relative URL of an icon for the file type,
     * based on the {@link appCategory()} value.
     * Images are searched for in "framework/images/app_icons/".
     *
     * @return string URL to icon
     */
    public function getIcon()
    {
        $filename = $this->getFilename();
        $ext = pathinfo($filename, PATHINFO_EXTENSION);
        return File::get_icon_for_extension($ext);
    }

    /**
     * Get Image_Backend instance for this image
     *
     * @return Image_Backend
     */
    public function getImageBackend()
    {
        if (!$this->getIsImage()) {
            return null;
        }

        // Create backend for this object
        /** @skipUpgrade */
        return Injector::inst()->createWithArgs('Image_Backend', array($this));
    }

    /**
     * Get the dimensions of this Image.
     *
     * @param string $dim One of the following:
     *  - "string": return the dimensions in string form
     *  - "array": it'll return the raw result
     *  - 0: return the height
     *  - 1: return the width
     * @return string|int|array|null
     */
    public function getDimensions($dim = "string")
    {
        if (!$this->getIsImage()) {
            return null;
        }

        $content = $this->getString();
        if (!$content) {
            return null;
        }

        // Get raw content
        $size = getimagesizefromstring($content);
        if ($size === false) {
            return null;
        }

        if ($dim === 'array') {
            return $size;
        }

        // Get single dimension
        if (is_numeric($dim)) {
            return $size[$dim];
        }

        return "$size[0]x$size[1]";
    }

    /**
     * Get the width of this image.
     *
     * @return int
     */
    public function getWidth()
    {
        return $this->getDimensions(0);
    }

    /**
     * Get the height of this image.
     *
     * @return int
     */
    public function getHeight()
    {
        return $this->getDimensions(1);
    }

    /**
     * Get the orientation of this image.
     *
     * @return int ORIENTATION_SQUARE | ORIENTATION_PORTRAIT | ORIENTATION_LANDSCAPE
     */
    public function getOrientation()
    {
        $width = $this->getWidth();
        $height = $this->getHeight();
        if ($width > $height) {
            return Image_Backend::ORIENTATION_LANDSCAPE;
        } elseif ($height > $width) {
            return Image_Backend::ORIENTATION_PORTRAIT;
        } else {
            return Image_Backend::ORIENTATION_SQUARE;
        }
    }

    /**
     * Determine if this image is of the specified size
     *
     * @param integer $width Width to check
     * @param integer $height Height to check
     * @return boolean
     */
    public function isSize($width, $height)
    {
        return $this->isWidth($width) && $this->isHeight($height);
    }

    /**
     * Determine if this image is of the specified width
     *
     * @param integer $width Width to check
     * @return boolean
     */
    public function isWidth($width)
    {
        if (empty($width) || !is_numeric($width)) {
            throw new InvalidArgumentException("Invalid value for width");
        }
        return $this->getWidth() == $width;
    }

    /**
     * Determine if this image is of the specified width
     *
     * @param integer $height Height to check
     * @return boolean
     */
    public function isHeight($height)
    {
        if (empty($height) || !is_numeric($height)) {
            throw new InvalidArgumentException("Invalid value for height");
        }
        return $this->getHeight() == $height;
    }

    /**
     * Wrapper for manipulate that passes in and stores Image_Backend objects instead of tuples
     *
     * @param string $variant
     * @param callable $callback Callback which takes an Image_Backend object, and returns an Image_Backend result
     * @return DBFile The manipulated file
     */
    public function manipulateImage($variant, $callback)
    {
        return $this->manipulate(
            $variant,
            function (AssetStore $store, $filename, $hash, $variant) use ($callback) {
                /** @var Image_Backend $backend */
                $backend = $this->getImageBackend();

                // If backend isn't available
                if (!$backend || !$backend->getImageResource()) {
                    return null;
                }
                $backend = $callback($backend);
                if (!$backend) {
                    return null;
                }

                $return = $backend->writeToStore(
                    $store,
                    $filename,
                    $hash,
                    $variant,
                    array('conflict' => AssetStore::CONFLICT_USE_EXISTING)
                );

                // Enforce garbage collection on $backend, avoid increasing memory use on each manipulation
                // by holding on to the underlying GD image resource.
                // Even though it's a local variable with no other references,
                // PHP holds on to it for the entire lifecycle of the script,
                // which is potentially related to passing it into the $callback closure.
                gc_collect_cycles();

                return $return;
            }
        );
    }

    /**
     * Generate a new DBFile instance using the given callback if it hasn't been created yet, or
     * return the existing one if it has.
     *
     * @param string $variant name of the variant to create
     * @param callable $callback Callback which should return a new tuple as an array.
     * This callback will be passed the backend, filename, hash, and variant
     * This will not be called if the file does not
     * need to be created.
     * @return DBFile The manipulated file
     */
    public function manipulate($variant, $callback)
    {
        // Verify this manipulation is applicable to this instance
        if (!$this->exists()) {
            return null;
        }

        // Build output tuple
        $filename = $this->getFilename();
        $hash = $this->getHash();
        $existingVariant = $this->getVariant();
        if ($existingVariant) {
            $variant = $existingVariant . '_' . $variant;
        }

        // Skip empty files (e.g. Folder does not have a hash)
        if (empty($filename) || empty($hash)) {
            return null;
        }

        // Create this asset in the store if it doesn't already exist,
        // otherwise use the existing variant
        $store = Injector::inst()->get('AssetStore');
        $result = null;
        if (!$store->exists($filename, $hash, $variant)) {
            $result = call_user_func($callback, $store, $filename, $hash, $variant);
        } else {
            $result = array(
                'Filename' => $filename,
                'Hash' => $hash,
                'Variant' => $variant
            );
        }

        // Callback may fail to perform this manipulation (e.g. resize on text file)
        if (!$result) {
            return null;
        }

        // Store result in new DBFile instance
        /** @var DBFile $file */
        $file = DBField::create_field('DBFile', $result);
        return $file->setOriginal($this);
    }

    /**
     * Name a variant based on a format with arbitrary parameters
     *
     * @param string $format The format name.
     * @param mixed $arg,... Additional arguments
     * @return string
     * @throws InvalidArgumentException
     */
    public function variantName($format, $arg = null)
    {
        $args = func_get_args();
        array_shift($args);
        return $format . Convert::base64url_encode($args);
    }
}