class API {

	/**
	 * @type {!string}
	 */
	apiURL;

	/**
	 * @param {!string} apiURL
	 */
	constructor(apiURL) {
		this.apiURL = apiURL;
	}

	/**
	 * @param {"GET" | "POST" | "PUT"} method
	 * @param {!string} path
	 * @param {?Object.<string, string>} query
	 * @param {?any} body
	 * @returns {?any}
	 * @throws {APIError}
	 */
	async call(method, path, query, body) {
		let params = new URLSearchParams();
		if (query != null) {
			for (let key in query) {
				let value = query[key];
				if (value == null) continue;
				params.set(key, value);
			}
		}

		let response = await fetch(this.apiURL + path + (params.size > 0 ? "?" + params : ""),
			{
				method,
				headers: (body != null ? { "Content-Type": "application/json" } : undefined),
				body
			}
		);

		let json = null;
		try {
			json = await response.json();
		} catch (e) {
			throw "Failed to decode response";
		}

		if (!response.ok) {
			throw json?.error || "Request failed: " + response.status + " " + response.statusText;
		}

		return json
	}

	/**
	 * @param {?("series" | "author")} groupBy
	 * @returns {Library}
	 * @throws {APIError}
	 */
	async getLibrary(groupBy) {
		return await this.call("GET", "/library", { 'groupBy': groupBy }, null);
	}

	/**
	 * @param {!string} id
	 * @returns {Video}
	 * @throws {APIError}
	 */
	async getVideo(id) {
		return await this.call("GET", "/library/video/" + encodeURIComponent(id), null, null);
	}

	/**
	 * @param {string} id
	 * @returns {Video}
	 * @throws {APIError}
	 */
	async getVideoMetadata(id) {
		return await this.call("GET", "/library/video/" + encodeURIComponent(id) + "/metadata", null, null);
	}

}

class APIError {

	/**
	 * @type {string}
	 */
	errorMessage;

	/**
	 * @param {!string} errorMessage
	 */
	constructor(errorMessage) {
		this.errorMessage = errorMessage
	}

}

class Library {

	/**
	 * @type {Object<string, Video[]>}
	 */
	videos;

}

class Video {

	/**
	 * @type {string}
	 */
	id;

	/**
	 * @type {VideoMetadata}
	 */
	metadata;

}

/**
 * @typedef {{series:string, title: string, author: string, index: number, [key: string]: any}} VideoMetadata
 */

/**
 * @param {any} error
 * @returns {string}
 */
function errorToString(error) {
	if (typeof error == 'string') {
		return error;
	} else if (error.toString) {
		return error.toString();
	} else {
		return 'Unknown error';
	}
}