// Copyright (c) 2019 Florian Klampfer <https://qwtel.com/>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

import { EMPTY, of } from "rxjs";
import { catchError, finalize, map, switchMap } from "rxjs/operators";

import { animate, fetchRx } from "./common";

const RE_CSS_URL = /url\s*\(['"]?(([^'"\\]|\\.)*)['"]?\)/u;

/** @param {Document} doc */
const calcHash = (doc) => {
	const sidebar = doc.getElementById("_sidebar");
	const sidebarBg = sidebar?.querySelector(".sidebar-bg");
	const pageStyle = doc.getElementById("_pageStyle");
	const source = doc.getElementById("source");
	// const rule = Array.from(pageStyle?.sheet?.rules ?? []).find(r => r.selectorText === 'html');
	// const accentColor = rule?.style.getPropertyValue('--accent-color') ?? '';
	// const themeColor = rule?.style.getPropertyValue('--theme-color') ?? '';
	return [
		pageStyle?.innerText?.trim(),
		sidebar?.classList,
		sidebarBg?.classList,
		sidebarBg?.style.backgroundImage,
		source?.src,
	].join("\n");
};

/**
 * Consider a URL external if either the protocol, hostname or port is different.
 * @param {URL} param0
 * @param {Location=} location
 */
function isExternal({ protocol, host }, location = window.location) {
	return protocol !== location.protocol || host !== location.host;
}

const objectURLs = new WeakMap();

export class CrossFader {
	/** @param {number} fadeDuration */
	constructor(fadeDuration) {
		this.sidebar = document.getElementById("_sidebar");
		this.fadeDuration = fadeDuration;
		this.prevHash = calcHash(document);
		this.themeColorEl = document.querySelector('meta[name="theme-color"]');
	}

	/** @param {Document} newDocument */
	fetchImage2(newDocument) {
		const sidebarBg = newDocument.querySelector(".sidebar-bg");
		const video = sidebarBg?.querySelector("source");
		const { backgroundImage = "" } = sidebarBg?.style ?? {};
		const result = RE_CSS_URL.exec(backgroundImage);
		const videoUrl = video?.src;
		if (!result) {
			return of("");
		}

		const url = new URL(result[1], window.location.origin);

		return fetchRx(url.href, {
			method: "GET",
			headers: { Accept: "image/*" },
			...(isExternal(url) ? { mode: "cors" } : {}),
		}).pipe(
			switchMap((r) => r.blob()),
			map((blob) => [URL.createObjectURL(blob), videoUrl]),
			catchError(() => of(url.href)),
		);
	}

	/** @param {Document} newDocument */
	fetchImage(newDocument) {
		const hash = calcHash(newDocument);
		if (hash === this.prevHash) return EMPTY;

		return this.fetchImage2(newDocument).pipe(
			map(([objectUrl, videoUrl]) => {
				/** @type {HTMLDivElement} */
				const div =
					newDocument.querySelector(".sidebar-bg") ??
					document.createElement("div");

				if (objectUrl) {
					div.style.backgroundImage = `url(${objectUrl})`;
					objectURLs.set(div, objectUrl);
				}

				const video = div.querySelector("video");

				if (video && videoUrl) {
					video.querySelector("source").src = videoUrl;
				}

				return [div, hash, newDocument];
			}),
		);
	}

	/** @param {Document} newDocument */
	updateStyle(newDocument) {
		const classList = newDocument.getElementById("_sidebar")?.classList;
		if (classList) this.sidebar.setAttribute("class", classList);

		if (this.themeColorEl) {
			const themeColor = newDocument.head.querySelector(
				'meta[name="theme-color"]',
			)?.content;
			if (themeColor) {
				window.setTimeout(() => {
					if (this.themeColorEl) {
						this.themeColorEl.content = themeColor;
					}
				}, 250);
			}
		}

		try {
			const pageStyle = document.getElementById("_pageStyle");
			const newPageStyle = newDocument.getElementById("_pageStyle");
			if (!newPageStyle) return;
			pageStyle?.parentNode?.replaceChild(newPageStyle, pageStyle);
		} catch (e) {
			if (process.env.DEBUG) console.error(e);
		}
	}

	/**
	 * @param {[HTMLDivElement]} param0
	 * @param {[HTMLDListElement, string, Document]} param1
	 */
	fade([prevDiv], [div, hash, newDocument]) {
		prevDiv?.parentNode?.insertBefore(div, prevDiv.nextElementSibling);

		this.updateStyle(newDocument);

		// Only update the prev hash after we're actually in the fade stage
		this.prevHash = hash;

		return animate(div, [{ opacity: 0 }, { opacity: 1 }], {
			duration: this.fadeDuration,
			easing: "ease",
		}).pipe(
			finalize(() => {
				if (objectURLs.has(prevDiv))
					URL.revokeObjectURL(objectURLs.get(prevDiv));
				prevDiv?.parentNode?.removeChild(prevDiv);

				div.querySelector("video").play();
			}),
		);
	}
}