const StringUtil = require('../util/string-util');
const log = require('../util/log');

const loadVector_ = function (costume, runtime, rotationCenter, optVersion) {
    return new Promise(resolve => {
        let svgString = costume.asset.decodeText();
        // SVG Renderer load fixes "quirks" associated with Scratch 2 projects
        if (optVersion && optVersion === 2 && !runtime.v2SvgAdapter) {
            log.error('No V2 SVG adapter present; SVGs may not render correctly.');
        } else if (optVersion && optVersion === 2 && runtime.v2SvgAdapter) {
            runtime.v2SvgAdapter.loadString(svgString, true /* fromVersion2 */);
            svgString = runtime.v2SvgAdapter.toString();
            // Put back into storage
            const storage = runtime.storage;
            costume.asset.encodeTextData(svgString, storage.DataFormat.SVG, true);
            costume.assetId = costume.asset.assetId;
            costume.md5 = `${costume.assetId}.${costume.dataFormat}`;
        }
        // createSVGSkin does the right thing if rotationCenter isn't provided, so it's okay if it's
        // undefined here
        costume.skinId = runtime.renderer.createSVGSkin(svgString, rotationCenter);
        costume.size = runtime.renderer.getSkinSize(costume.skinId);
        // Now we should have a rotationCenter even if we didn't before
        if (!rotationCenter) {
            rotationCenter = runtime.renderer.getSkinRotationCenter(costume.skinId);
            costume.rotationCenterX = rotationCenter[0];
            costume.rotationCenterY = rotationCenter[1];
            costume.bitmapResolution = 1;
        }

        resolve(costume);
    });
};

const canvasPool = (function () {
    /**
     * A pool of canvas objects that can be reused to reduce memory
     * allocations. And time spent in those allocations and the later garbage
     * collection.
     */
    class CanvasPool {
        constructor () {
            this.pool = [];
            this.clearSoon = null;
        }

        /**
         * After a short wait period clear the pool to let the VM collect
         * garbage.
         */
        clear () {
            if (!this.clearSoon) {
                this.clearSoon = new Promise(resolve => setTimeout(resolve, 1000))
                    .then(() => {
                        this.pool.length = 0;
                        this.clearSoon = null;
                    });
            }
        }

        /**
         * Return a canvas. Create the canvas if the pool is empty.
         * @returns {HTMLCanvasElement} A canvas element.
         */
        create () {
            return this.pool.pop() || document.createElement('canvas');
        }

        /**
         * Release the canvas to be reused.
         * @param {HTMLCanvasElement} canvas A canvas element.
         */
        release (canvas) {
            this.clear();
            this.pool.push(canvas);
        }
    }

    return new CanvasPool();
}());

/**
 * Return a promise to fetch a bitmap from storage and return it as a canvas
 * If the costume has bitmapResolution 1, it will be converted to bitmapResolution 2 here (the standard for Scratch 3)
 * If the costume has a text layer asset, which is a text part from Scratch 1.4, then this function
 * will merge the two image assets. See the issue LLK/scratch-vm#672 for more information.
 * @param {!object} costume - the Scratch costume object.
 * @param {!Runtime} runtime - Scratch runtime, used to access the v2BitmapAdapter
 * @param {?object} rotationCenter - optionally passed in coordinates for the center of rotation for the image. If
 *     none is given, the rotation center of the costume will be set to the middle of the costume later on.
 * @property {number} costume.bitmapResolution - the resolution scale for a bitmap costume.
 * @returns {?Promise} - a promise which will resolve to an object {canvas, rotationCenter, assetMatchesBase},
 *     or reject on error.
 *     assetMatchesBase is true if the asset matches the base layer; false if it required adjustment
 */
const fetchBitmapCanvas_ = function (costume, runtime, rotationCenter) {
    if (!costume || !costume.asset) {
        return Promise.reject('Costume load failed. Assets were missing.');
    }
    if (!runtime.v2BitmapAdapter) {
        return Promise.reject('No V2 Bitmap adapter present.');
    }

    return Promise.all([costume.asset, costume.textLayerAsset].map(asset => {
        if (!asset) {
            return null;
        }

        if (typeof createImageBitmap !== 'undefined') {
            return createImageBitmap(
                new Blob([asset.data], {type: asset.assetType.contentType})
            );
        }

        return new Promise((resolve, reject) => {
            const image = new Image();
            image.onload = function () {
                resolve(image);
                image.onload = null;
                image.onerror = null;
            };
            image.onerror = function () {
                reject('Costume load failed. Asset could not be read.');
                image.onload = null;
                image.onerror = null;
            };
            image.src = asset.encodeDataURI();
        });
    }))
        .then(([baseImageElement, textImageElement]) => {
            const mergeCanvas = canvasPool.create();

            const scale = costume.bitmapResolution === 1 ? 2 : 1;
            mergeCanvas.width = baseImageElement.width;
            mergeCanvas.height = baseImageElement.height;

            const ctx = mergeCanvas.getContext('2d');
            ctx.drawImage(baseImageElement, 0, 0);
            if (textImageElement) {
                ctx.drawImage(textImageElement, 0, 0);
            }
            // Track the canvas we merged the bitmaps onto separately from the
            // canvas that we receive from resize if scale is not 1. We know
            // resize treats mergeCanvas as read only data. We don't know when
            // resize may use or modify the canvas. So we'll only release the
            // mergeCanvas back into the canvas pool. Reusing the canvas from
            // resize may cause errors.
            let canvas = mergeCanvas;
            if (scale !== 1) {
                canvas = runtime.v2BitmapAdapter.resize(mergeCanvas, canvas.width * scale, canvas.height * scale);
            }

            // By scaling, we've converted it to bitmap resolution 2
            if (rotationCenter) {
                rotationCenter[0] = rotationCenter[0] * scale;
                rotationCenter[1] = rotationCenter[1] * scale;
                costume.rotationCenterX = rotationCenter[0];
                costume.rotationCenterY = rotationCenter[1];
            }
            costume.bitmapResolution = 2;

            // Clean up the costume object
            delete costume.textLayerMD5;
            delete costume.textLayerAsset;

            return {
                canvas,
                mergeCanvas,
                rotationCenter,
                // True if the asset matches the base layer; false if it required adjustment
                assetMatchesBase: scale === 1 && !textImageElement
            };
        })
        .catch(() => {
            // Clean up the text layer properties if it fails to load
            delete costume.textLayerMD5;
            delete costume.textLayerAsset;
        });
};

const loadBitmap_ = function (costume, runtime, _rotationCenter) {
    return fetchBitmapCanvas_(costume, runtime, _rotationCenter)
        .then(fetched => {
            const updateCostumeAsset = function (dataURI) {
                if (!runtime.v2BitmapAdapter) {
                    // TODO: This might be a bad practice since the returned
                    // promise isn't acted on. If this is something we should be
                    // creating a rejected promise for we should also catch it
                    // somewhere and act on that error (like logging).
                    //
                    // Return a rejection to stop executing updateCostumeAsset.
                    return Promise.reject('No V2 Bitmap adapter present.');
                }

                const storage = runtime.storage;
                costume.asset = storage.createAsset(
                    storage.AssetType.ImageBitmap,
                    storage.DataFormat.PNG,
                    runtime.v2BitmapAdapter.convertDataURIToBinary(dataURI),
                    null,
                    true // generate md5
                );
                costume.dataFormat = storage.DataFormat.PNG;
                costume.assetId = costume.asset.assetId;
                costume.md5 = `${costume.assetId}.${costume.dataFormat}`;
            };

            if (!fetched.assetMatchesBase) {
                updateCostumeAsset(fetched.canvas.toDataURL());
            }

            return fetched;
        })
        .then(({canvas, mergeCanvas, rotationCenter}) => {
            // createBitmapSkin does the right thing if costume.rotationCenter is undefined.
            // That will be the case if you upload a bitmap asset or create one by taking a photo.
            let center;
            if (rotationCenter) {
                // fetchBitmapCanvas will ensure that the costume's bitmap resolution is 2 and its rotation center is
                // scaled to match, so it's okay to always divide by 2.
                center = [
                    rotationCenter[0] / 2,
                    rotationCenter[1] / 2
                ];
            }

            // TODO: costume.bitmapResolution will always be 2 at this point because of fetchBitmapCanvas_, so we don't
            // need to pass it in here.
            costume.skinId = runtime.renderer.createBitmapSkin(canvas, costume.bitmapResolution, center);
            canvasPool.release(mergeCanvas);
            const renderSize = runtime.renderer.getSkinSize(costume.skinId);
            costume.size = [renderSize[0] * 2, renderSize[1] * 2]; // Actual size, since all bitmaps are resolution 2

            if (!rotationCenter) {
                rotationCenter = runtime.renderer.getSkinRotationCenter(costume.skinId);
                // Actual rotation center, since all bitmaps are resolution 2
                costume.rotationCenterX = rotationCenter[0] * 2;
                costume.rotationCenterY = rotationCenter[1] * 2;
                costume.bitmapResolution = 2;
            }
            return costume;
        });
};

/**
 * Initialize a costume from an asset asynchronously.
 * Do not call this unless there is a renderer attached.
 * @param {!object} costume - the Scratch costume object.
 * @property {int} skinId - the ID of the costume's render skin, once installed.
 * @property {number} rotationCenterX - the X component of the costume's origin.
 * @property {number} rotationCenterY - the Y component of the costume's origin.
 * @property {number} [bitmapResolution] - the resolution scale for a bitmap costume.
 * @property {!Asset} costume.asset - the asset of the costume loaded from storage.
 * @param {!Runtime} runtime - Scratch runtime, used to access the storage module.
 * @param {?int} optVersion - Version of Scratch that the costume comes from. If this is set
 *     to 2, scratch 3 will perform an upgrade step to handle quirks in SVGs from Scratch 2.0.
 * @returns {?Promise} - a promise which will resolve after skinId is set, or null on error.
 */
const loadCostumeFromAsset = function (costume, runtime, optVersion) {
    costume.assetId = costume.asset.assetId;
    const renderer = runtime.renderer;
    if (!renderer) {
        log.error('No rendering module present; cannot load costume: ', costume.name);
        return Promise.resolve(costume);
    }
    const AssetType = runtime.storage.AssetType;
    let rotationCenter;
    // Use provided rotation center and resolution if they are defined. Bitmap resolution
    // should only ever be 1 or 2.
    if (typeof costume.rotationCenterX === 'number' && !isNaN(costume.rotationCenterX) &&
            typeof costume.rotationCenterY === 'number' && !isNaN(costume.rotationCenterY)) {
        rotationCenter = [costume.rotationCenterX, costume.rotationCenterY];
    }
    if (costume.asset.assetType.runtimeFormat === AssetType.ImageVector.runtimeFormat) {
        return loadVector_(costume, runtime, rotationCenter, optVersion)
            .catch(error => {
                log.warn(`Error loading vector image: ${error.name}: ${error.message}`);
                // Use default asset if original fails to load
                costume.assetId = runtime.storage.defaultAssetId.ImageVector;
                costume.asset = runtime.storage.get(costume.assetId);
                costume.md5 = `${costume.assetId}.${AssetType.ImageVector.runtimeFormat}`;
                return loadVector_(costume, runtime);
            });
    }
    return loadBitmap_(costume, runtime, rotationCenter, optVersion);
};

/**
 * Load a costume's asset into memory asynchronously.
 * Do not call this unless there is a renderer attached.
 * @param {!string} md5ext - the MD5 and extension of the costume to be loaded.
 * @param {!object} costume - the Scratch costume object.
 * @property {int} skinId - the ID of the costume's render skin, once installed.
 * @property {number} rotationCenterX - the X component of the costume's origin.
 * @property {number} rotationCenterY - the Y component of the costume's origin.
 * @property {number} [bitmapResolution] - the resolution scale for a bitmap costume.
 * @param {!Runtime} runtime - Scratch runtime, used to access the storage module.
 * @param {?int} optVersion - Version of Scratch that the costume comes from. If this is set
 *     to 2, scratch 3 will perform an upgrade step to handle quirks in SVGs from Scratch 2.0.
 * @returns {?Promise} - a promise which will resolve after skinId is set, or null on error.
 */
const loadCostume = function (md5ext, costume, runtime, optVersion) {
    const idParts = StringUtil.splitFirst(md5ext, '.');
    const md5 = idParts[0];
    const ext = idParts[1].toLowerCase();
    costume.dataFormat = ext;

    if (costume.asset) {
        // Costume comes with asset. It could be coming from camera, image upload, drag and drop, or file
        return loadCostumeFromAsset(costume, runtime, optVersion);
    }

    // Need to load the costume from storage. The server should have a reference to this md5.
    if (!runtime.storage) {
        log.error('No storage module present; cannot load costume asset: ', md5ext);
        return Promise.resolve(costume);
    }

    if (!runtime.storage.defaultAssetId) {
        log.error(`No default assets found`);
        return Promise.resolve(costume);
    }

    const AssetType = runtime.storage.AssetType;
    const assetType = (ext === 'svg') ? AssetType.ImageVector : AssetType.ImageBitmap;

    const costumePromise = runtime.storage.load(assetType, md5, ext);
    if (!costumePromise) {
        log.error(`Couldn't fetch costume asset: ${md5ext}`);
        return;
    }

    let textLayerPromise;
    if (costume.textLayerMD5) {
        textLayerPromise = runtime.storage.load(AssetType.ImageBitmap, costume.textLayerMD5, 'png');
    } else {
        textLayerPromise = Promise.resolve(null);
    }

    return Promise.all([costumePromise, textLayerPromise]).then(assetArray => {
        costume.asset = assetArray[0];
        if (assetArray[1]) {
            costume.textLayerAsset = assetArray[1];
        }
        return loadCostumeFromAsset(costume, runtime, optVersion);
    });
};

module.exports = {
    loadCostume,
    loadCostumeFromAsset
};