1 files changed, 220 insertions, 0 deletions
diff --git a/src/hero.mjs b/src/hero.mjs
new file mode 100644
index 0000000..a8532a8
--- /dev/null
+++ b/src/hero.mjs
@@ -0,0 +1,220 @@
+import assert from "node:assert";
+import crypto from "node:crypto";
+import http   from "node:http";
+
+import { assocIn, getIn, first, log } from "./utils.mjs";
+
+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();
+
+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(m => HTTP_METHODS.has(m)));
+
+	const segments = pathToSegments(path);
+	const kw = hasPathParams(segments) ? "dynamic" : "static";
+	return methods.reduce(
+		(acc, el) => assocIn(acc, [kw, el].concat(segments), handlerFn),
+		table,
+	);
+};
+
+export const buildRoutes = routes =>
+	routes.reduce(
+		(acc, [methods, path, handlerFn]) =>
+			addRoute(acc, methods, path, handlerFn),
+		{}
+	);
+
+export const findStaticHandler = (table, method, segments) => {
+	const handlerFn = getIn(table, ["static", 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();
+	return first(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) => {
+	const segments = pathToSegments(path);
+	return (
+		 findStaticHandler(table, method, segments) ||
+		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 handleRequest = async (table, method, url) => {
+	const [ path, queryParams ] = url.split("?");
+	const handler = findHandler(table, method, path);
+	if (!handler) {
+		return {
+			status: 404,
+			body: "Not Found",
+		};
+	}
+
+	const request = {
+		params: {
+			path: handler.params,
+			query: extractQueryParams(queryParams),
+		},
+		method,
+		path,
+		handler: handler.handlerFn,
+	};
+
+	return await handler.handlerFn(request);
+};
+
+export const makeRequestListener = table => async (req, res) => {
+	const response = await handleRequest(table, req.method, req.url);
+	res.writeHead(response.status, response.headers);
+	res.end(response.body);
+};
+
+export const interceptorsFn = ({
+	uuidFn,
+	logger,
+} = {
+	uuidFn: crypto.randomUUID,
+	logger: log,
+}) => ({
+	requestId: (req, next) => next({ ...req, id: uuidFn() }),
+	logged: async (req, next) => {
+		const { id, url, method } = req;
+		logger({
+			id,
+			url,
+			method,
+			type: "in-request",
+		});
+		const response = await next(req);
+		const { status } = response;
+		logger({
+			id,
+			status,
+			type: "in-response",
+		});
+		return response;
+	},
+	contentType: async (req, next) => {
+		const response = await next(req);
+		const [mimeType, body] = typeof response.body === "string" ?
+			["text/html",        response.body] :
+			["application/json", JSON.stringify(response.body) || ""];
+		return {
+			...response,
+			body,
+			headers: {
+				"Content-Type": mimeType,
+				"Content-Length": Buffer.byteLength(body),
+				...(response.headers || {})
+			},
+		};
+	},
+	serverError: async (req, next) => {
+		try {
+			const response = await next(req);
+			assert.ok("status" in response, `Missing "status"`);
+			return response;
+		} catch (error) {
+			logger({
+				id: req.id,
+				type: "server-error-interceptor",
+				message: error.message,
+			});
+			return {
+				status: 500,
+				body: "Internal Server Error",
+			};
+		}
+	},
+});
+
+export const interceptors = interceptorsFn();
+
+export const chainInterceptors = arr =>
+	req => arr.length === 0 ?
+		req :
+		arr[0](req, chainInterceptors(arr.slice(1)));
+
+export const wrapHandler = (fn, arr) =>
+	chainInterceptors(arr.concat([ (req, _next) => fn(req) ]));