import assert        from "node:assert/strict";
import child_process from "node:child_process";
import crypto        from "node:crypto";
import fs            from "node:fs";
import http          from "node:http";
import process       from "node:process";
import util          from "node:util";

import * as u from "./utils.mjs";


export const loggerDefaults = {
	pid:  process.pid,
	ppid: process.ppid,
	tool: "hero",
};

export let loggerGlobals = {};

export const configLogger = o => loggerGlobals = o;

export const logit = (writerFn, timestampFn, level, o) =>
	writerFn(JSON.stringify({
		...loggerDefaults,
		...loggerGlobals,
		level,
		timestamp: timestampFn(),
		...o,
	}));

const now = () => (new Date()).toISOString();
export const makeLogger = ({
	writerFn = console.error,
	timestampFn = now,
} = {}) => ({
	debug: (...args) => process.env.DEBUG ?
		logit(writerFn, timestampFn, "DEBUG", ...args) :
		null,
	info:  u.partial(logit, writerFn, timestampFn, "INFO"),
	warn:  u.partial(logit, writerFn, timestampFn, "WARN"),
	error: u.partial(logit, writerFn, timestampFn, "ERROR"),
});

export const log = makeLogger();

export const isValidMethod = method =>
	method === "GET";

export const isValidUpgrade = val =>
	val.toLowerCase() === "websocket";

export const isValidKey = key =>
	/^[0-9a-zA-Z+/]{22}==$/.test(key);

export const isValidVersion = n =>
	n === 13;

export const validateUpgrade = (method, headers) => {
	const upgrade    = headers["upgrade"];
	const key        = headers["sec-websocket-key"];
	const versionStr = headers["sec-websocket-version"];
	const version    = parseInt(versionStr);

	if (!isValidMethod(method)) {
		/// Unreachable by default, unless one is constructing tables
		/// manually.  Otherwise `findHandler()` will return a 404
		/// before the request gets here.
		return {
			isValid: false,
			response: {
				status: 405,
			},
		};
	}

	if (!upgrade) {
		return {
			isValid: false,
			response: {
				status: 400,
				body: 'Missing "Upgrade" header\n',
			},
		};
	}

	if (!isValidUpgrade(upgrade)) {
		return {
			isValid: false,
			response: {
				status: 400,
				body: 'Invalid "Upgrade" value\n',
			},
		};
	}

	if (!key) {
		return {
			isValid: false,
			response: {
				status: 400,
				body: 'Missing "Sec-WebSocket-Key" header\n',
			},
		};
	}

	if (!isValidKey(key)) {
		return {
			isValid: false,
			response: {
				status: 400,
				body: 'Invalid "Sec-WebSocket-Key" value\n',
			},
		};
	}

	if (!version) {
		return {
			isValid: false,
			response: {
				status: 400,
				body: 'Missing "Sec-WebSocket-Version" header\n',
			},
		};
	}

	if (!isValidVersion(version)) {
		return {
			isValid: false,
			response: {
				status: 400,
				body: 'Invalid "Sec-WebSocket-Version" value\n',
			},
		};
	}

	return {
		isValid: true,
	};
};

const GUID_MAGIC_NUMBER = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
export const computeHash = key =>
	crypto
		.createHash("SHA1")
		.update(key + GUID_MAGIC_NUMBER)
		.digest("base64");

export const interceptorsFn = ({
	uuidFn = crypto.randomUUID,
	logger = log,
} = {}) => ({
	requestId: (req, next) => next({ ...req, id: uuidFn() }),
	logged: async (req, next) => {
		const { id, url, method, upgrade } = req;
		logger.info({
			id,
			url,
			method,
			upgrade,
			type: "in-request",
		});
		const beforeDate = new Date();
		const response = await next(req);
		const afterDate = new Date();
		const { status } = response;

		const before   = beforeDate.getTime();
		const after    = afterDate.getTime();
		const duration = after - before;
		logger.info({
			id,
			status,
			type: "in-response",
			timings: {
				ms: { before, after, duration },
			},
		});
		return response;
	},
	contentType: async (req, next) => {
		const response = await next(req);
		const { status, body, headers } = response;
		assert.equal(typeof status, "number");
		const mappings = {
			string:    () => [ "text/html",        body                             ],
			undefined: () => [ "text/plain",       http.STATUS_CODES[status] + "\n" ],
			FALLBACK:  () => [ "application/json", JSON.stringify(body)             ],
		};
		const type = typeof body;
		assert.notEqual(type, "FALLBACK");
		const [mimeType, renderedBody] =
			(mappings[type] || mappings.FALLBACK)();
		return {
			...response,
			body: renderedBody,
			headers: {
				"Content-Type": mimeType,
				"Content-Length": Buffer.byteLength(renderedBody),
				...(response.headers || {})
			},
		};
	},
	serverError: async (req, next) => {
		try {
			const response = await next(req);
			assert.ok("status" in response, `Missing "status"`);
			return response;
		} catch (error) {
			logger.error({
				id: req.id,
				type: "server-error-interceptor",
				message: error.message,
				stacktrace: error.stack
			});
			return {
				status: 500,
				body: "Internal Server Error\n",
			};
		}
	},
	websocketHandshake: async (req, next) => {
		if (!req.upgrade) {
			return await next(req);
		}

		const { method, headers} = req;
		const { isValid, response } = validateUpgrade(method, headers);
		if (!isValid) {
			return response;
		}

		const _response = await next(req);
		const hash = computeHash(headers["sec-websocket-key"]);

		return {
			status: 101,
			headers: {
				"Connection": "Upgrade",
				"Upgrade": "websocket",
				"Sec-WebSocket-Accept": hash,
			},
		};
	},
});

export const interceptors = interceptorsFn();

export const defaultInterceptors = [
	interceptors.serverError,
	interceptors.requestId,
	interceptors.logged,
	interceptors.contentType,
	interceptors.websocketHandshake,
];

export const chainInterceptors = arr =>
	req => arr.length === 0 ?
		req :
		arr[0](req, chainInterceptors(arr.slice(1)));

export const wrapHandler = (fn, arr) =>
	arr.length === 0 ?
		fn :
		chainInterceptors(arr.concat([ (req, _next) => fn(req) ]));

export const normalizeSegments = segments =>
	segments.length === 1 && segments[0] === "" ?
		segments :
		segments.concat([""]);

export const pathToSegments = path =>
	normalizeSegments(path
		.replace(/^\/*/, "")
		.replace(/\/*$/, "")
		.replace(/\/+/, "/")
		.split("/"));

export const hasPathParams = segments =>
	segments.some(s => s.startsWith(":"));

const HTTP_METHODS = new Set([
	"GET",
	"HEAD",
	"POST",
	"PUT",
	"PATCH",
	"DELETE",
	"OPTIONS",
]);

const HTTP_METHODS_ARR = [...HTTP_METHODS.keys()].sort(u.strSortFn);

export const isValidLabel = name =>
	HTTP_METHODS.has(name) || name === "WEBSOCKET";

export const comboForLabel = (label, keyword) =>
	label === "WEBSOCKET" ?
		[ "websocket", "GET" ] :
		[ keyword, label ];

export const addRoute = (table, methods, path, handlerFn) => {
	if (methods === "*") {
		return addRoute(table, HTTP_METHODS_ARR, path, handlerFn);
	}

	if (!Array.isArray(methods)) {
		return addRoute(table, [methods], path, handlerFn);
	}

	assert.ok(methods.every(isValidLabel));

	const segments = pathToSegments(path);
	const kw = hasPathParams(segments) ? "dynamic" : "static";
	return methods.reduce(
		(acc, el) =>
			u.assocIn(
				acc,
				comboForLabel(el, kw).concat(segments),
				handlerFn,
			),
		table,
	);
};

export const findStaticHandler = (table, method, segments, section) => {
	const handlerFn = u.getIn(table, [section, method].concat(segments));
	return !handlerFn ? null : { handlerFn, params: {} };
};

/**
 *  "first" as is:
 *  - depth-first, as we look for a full match and use it instead of searching
 *    in parallel;
 *  - the first param in the same level to show up alphabetically, e.g.
 *    ":a-user" matches before ":id" does.
 */
export const firstParamMatch = (tree, segments, params) => {
	assert.notEqual(segments.length, 0);

	const [seg, ...nextSegments] = segments;

	if (segments.length === 1) {
		assert.equal(seg, "");
		const handlerFn = tree[""];

		return !handlerFn ? null : { handlerFn, params };
	}

	const subtree = tree[seg];
	if (subtree) {
		const submatch = firstParamMatch(subtree, nextSegments, params);
		/// propagation of the end of recursion
		if (submatch) {
			return submatch;
		}
	}

	/// literal matching failed, we now look for patterns that might match
	const paramOptions = Object.keys(tree)
		.filter(s => s.startsWith(":"))
		.sort(u.strSortFn);
	return u.findFirst(paramOptions, param => firstParamMatch(tree[param], nextSegments, {
		...params,
		[param.slice(1)]: seg
	}));
};

export const findDynamicHandler = (table, method, segments) => {
	const tree = table?.dynamic?.[method];
	return !tree ? null : firstParamMatch(tree, segments, {});
};

export const findHandler = (table, method, path, upgrade) => {
	const segments = pathToSegments(path);
	return upgrade ?
		findStaticHandler(table, method, segments, "websocket") :
		(
			 findStaticHandler(table, method, segments, "static") ||
			findDynamicHandler(table, method, segments)
		);
};

export const extractQueryParams = s => {
	const ret = {};
	for (const [k, v] of new URLSearchParams(s)) {
		ret[k] = v;
	}
	return ret;
};

export const renderStatus = code =>
	`HTTP/1.1 ${code} ${http.STATUS_CODES[code]}`

export const renderHeaders = (obj = {}) =>
	Object.keys(obj)
		.sort(u.strSortFn)
		.map(name => `${name}: ${obj[name]}`);

export const buildHeader = (status, headers) =>
	[renderStatus(status)]
		.concat(renderHeaders(headers))
		.concat(["\r\n"])
		.join("\r\n");

export const writeHead = (socket, status, headers) =>
	socket.write(buildHeader(status, headers));

export const handle404 = _req => ({
	status: 404,
	body: "Not Found\n",
});

export const make404Handler = interceptors => ({
	params: {},
	handlerFn: wrapHandler(handle404, interceptors),
});

export const handleRequest = async (table, reqHandle) => {
	const { method, url, headers, upgrade, socket } = reqHandle;
	const [ path, queryParams ] = url.split("?");
	const { params, handlerFn } = (
		findHandler(table, method, path, upgrade) ||
		make404Handler(table.interceptors)
	);

	const request = {
		params: {
			path: params,
			query: extractQueryParams(queryParams),
		},
		method,
		path,
		headers,
		upgrade,
		socket,
		handler: handlerFn,
		ref: reqHandle,
	};

	return await handlerFn(request);
};

export const makeRequestListener = table => async (req, res) => {
	const { status, headers, body } = await handleRequest(table, {
		...req,
		upgrade: false,
		socket: null,
		headers: req.headers,  /// API docs mention getHeaders(), but req doesn't have it...
	});
	res.writeHead(status, headers);
	res.end(body);
};

export const makeUpgradeListener = table => async (req, socket, _head) => {
	assert.ok(req.upgrade);
	const { status, headers, body } = await handleRequest(table, {
		...req,
		socket,
		headers: req.headers,
	});
	writeHead(socket, status, headers);
	socket.write(body);
	if (status !== 101) {
		socket.end();
	}
};

export const actionsFn = ({
	logger = log,
} = {}) => ({
	"toggle-debug-env": action => {
		const before = process.env.DEBUG;
		if (process.env.DEBUG) {
			delete process.env.DEBUG;
		} else {
			process.env.DEBUG = "1";
		}
		const after = process.env.DEBUG;

		logger.info({
			type: "action-response",
			action,
			message: "toggle process.env.DEBUG",
			before: u.undefinedAsNull(before),
			after:  u.undefinedAsNull(after),
		});
	},
	"config-dump": action => logger.info({
		type: "action-response",
		action,
		data: {
			...loggerDefaults,
			...loggerGlobals,
		},
	}),
	"ping": _ => logger.info({ message: "pong" }),
});

export const actions = actionsFn();

export const lineHandlerFn = ({
	logger     = log,
	actionsMap = actions,
} = {}) => line => {
	let cmd = null;
	try {
		cmd = JSON.parse(line);
	} catch (e) {
		logger.info({
			type: "invalid-cmd-input",
			message: e.message,
		});
		return;
	}

	if (typeof cmd?.action !== "string") {
		logger.info({
			type: "missing-key-action",
			message: `missing the "action" key from the given object`,
		});
		return;
	}

	const fn = actionsMap[cmd.action];
	if (!fn) {
		logger.info({
			type: "unsupported-action",
			message: `can't run given action: ${cmd.action}`,
		});
		return;
	}

	return fn(cmd.action, ...(cmd?.args || []));
};

export const lineHandler = lineHandlerFn();

export const rmIf = path => {
	if (fs.existsSync(path)) {
		fs.unlinkSync(path);
	}
};

export const mkfifo = path =>
	child_process.execFileSync("mkfifo", [path]);

export const makeLineEmitter = fn => {
	let data = "";
	return chunk => {
		const segments = chunk.split("\n");
		assert.ok(segments.length > 0);

		if (segments.length === 1) {
			data += segments[0];
			return;
		}

		[
			data + u.first(segments),
			...u.butlast(u.rest(segments)),
		].forEach(fn);
		data = u.last(segments);
	};
};

export const makeReopeningPipeReader = (shouldReopenPipe, path, {
	lineFn,
	logger,
} = {}, out) => {
	const reader = fs.createReadStream(path, "UTF-8")
	out.ref = reader;
	reader.on("data", makeLineEmitter(lineFn));
	reader.on("close", () => {
		if (shouldReopenPipe.ref) {
			logger.debug({
				message: "pipe closed, reopening",
			});
			makeReopeningPipeReader(
				shouldReopenPipe,
				path,
				{ lineFn, logger },
				out,
			);
			return;
		}

		logger.debug({
			message: "pipe closed, NOT reopening",
		});
	});
};

export const makePipeReaderFn = ({
	lineFn = lineHandler,
	logger = log,
} = {}) => path => {
	mkfifo(path);
	let shouldReopenPipe = { ref: true };
	const pipe = {};
	makeReopeningPipeReader(
		shouldReopenPipe,
		path,
		{ lineFn, logger },
		pipe,
	);
	return () => new Promise((resolve, reject) => {
		shouldReopenPipe.ref = false;
		fs.createWriteStream(path).end().close();
		pipe.ref.on("close", resolve);
	});
};

export const makePipeReader = makePipeReaderFn();

export const buildRoutes = (routes, globalInterceptors = []) =>
	routes.reduce(
		(acc, [methods, path, handlerFn, interceptors = []]) =>
			addRoute(
				acc,
				methods,
				path,
				wrapHandler(
					handlerFn,
					globalInterceptors.concat(interceptors),
				),
			),
		{}
	);

export const buildTable = (routes, globalInterceptors = []) =>
	u.assocIn(
		buildRoutes(routes, globalInterceptors),
		["interceptors"],
		globalInterceptors,
	);

export const promisifyServer = (name, serverHandle, socket, pipe) => {
	let closePipeFn = null;
	return {
		ref:   serverHandle,
		start: util.promisify((...args) => {
			assert.equal(typeof socket, "string");
			assert.equal(typeof pipe,   "string");

			configLogger({ name });

			log.info({
				type: "starting-server",
				name,
				socket,
				pipe,
				node: {
					version:  process.version,
					versions: process.versions,
				},
			});

			rmIf(pipe);
			closePipeFn = makePipeReader(pipe);

			rmIf(socket);
			return serverHandle.listen(socket, ...args)
		}),
		stop:  util.promisify(async (...args) => {
			log.info({
				type: "stopping-server",
				name,
				socket,
				pipe,
				node: {
					version:  process.version,
					versions: process.versions,
				},
			});

			await closePipeFn();
			return serverHandle.close(...args);
		}),
		events: serverHandle,
	};
};

export const buildServer = ({
	name,
	routes = [],
	socket = `${name}.socket`,
	pipe = `${name}.pipe`,
	globalInterceptors = defaultInterceptors,
}) => {
	const table = buildTable(routes, globalInterceptors);
	const requestListener = makeRequestListener(table);
	const server = http.createServer(requestListener);
	return promisifyServer(name, server, socket, pipe);
};