import pica from 'pica/dist/pica';

import { FileType } from '../data/file.js';

const THUMBNAIL_MAX_DIMENSION = 320;

export function maxLinearSize(width, height, max) {
	const ratio = width / height;
	if (width > height) {
		return {
			width: max,
			height: max / ratio
		};
	}
	return {
		width: max * ratio,
		height: max
	};
}

async function getLoadedImage(src) {
	return new Promise(resolve => {
		const i = new Image('image');
		i.onload = () => resolve(i);
		i.src = src;
	});
}

async function resizeImage(imageBlob, mimetype, width, height) {
	const url = URL.createObjectURL(imageBlob);
	const $img = await getLoadedImage(url);
	const $destinationCanvas = document.createElement('canvas');

	$destinationCanvas.width = width;
	$destinationCanvas.height = height;

	const afterResize = (resolve, reject) => err => {
		if (err) {
			return reject(err);
		}
		$destinationCanvas.toBlob(resolve, mimetype);
	};

	return new Promise((resolve, reject) => {
		pica.resizeCanvas($img, $destinationCanvas, {}, afterResize(resolve, reject));
	});
}

export async function generateThumbnailForImage(doc) {
	if (doc.sizes.thumbnail) {
		return;
	}

	const { width, height } = maxLinearSize(doc.width, doc.height, THUMBNAIL_MAX_DIMENSION);

	if (width < doc.width && height < doc.height) {
		console.log('generating thumbnail');
		// Thumbnail would be smaller
		const attachment = await FileType.getFromURL(doc.sizes.full);
		const mimetype = attachment.type;
		const resizedBlob = await resizeImage(attachment, mimetype, width, height);
		const thumbfile = await FileType.upload(resizedBlob);
		await doc.update({
			sizes: {
				thumbnail: FileType.getURL(thumbfile)
			}
		});
	} else {
		console.log('using original as thumbnail');
		// Thumbnail would be bigger so let's just use the original.
		await doc.update({
			sizes: {
				thumbnail: doc.sizes.full
			}
		});
	}
}