import pica from 'pica/dist/pica';

import { generateAttachmentUrl, getDatabase } from '../services/db.js';
import { find, update, addAttachment } from '../data/image.js';

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(id) {
	const results = await find([id], { attachments: true, binary: true });
	const doc = results.rows[0].doc;

	if (doc.attachmentUrls.thumbnail && doc._attachments.thumbnail) {
		return;
	}

	const attachment = doc._attachments.image;
	const mimetype = attachment.content_type;
	const { width, height } = maxLinearSize(doc.width, doc.height, 320);
	const resizedBlob = await resizeImage(attachment.data, mimetype, width, height);
	const url = generateAttachmentUrl(getDatabase().name, id, 'thumbnail');

	await addAttachment(doc, 'thumbnail', resizedBlob);
	await update(doc._id, {
		attachmentUrls: {
			thumbnail: url
		}
	});

	return resizedBlob;
}

export const invoke = generateThumbnailForImage;