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// Copyright 2019 Yusuke Sakurai. All rights reserved. MIT license.import { listenAndServe, ServeOptions, ServerRequest } from "./server.ts";import { internalServerError, notFound } from "./responder.ts";import ListenOptions = Deno.ListenOptions;
export type RoutedServerRequest = ServerRequest & {  match?: RegExpMatchArray;};
/** Basic handler for http request */export type HttpHandler = (req: RoutedServerRequest) => unknown;
/** Global error handler for requests */export type ErrorHandler = (e: unknown, req: RoutedServerRequest) => unknown;
/** * Find the match that appeared in the nearest position to the beginning of word. * If positions are same, the longest one will be picked. * Return -1 and null if no match found. * */export function findLongestAndNearestMatch(  pathname: string,  patterns: (string | RegExp)[]): { index: number; match: RegExpMatchArray } {  let lastMatchIndex = pathname.length;  let lastMatchLength = 0;  let match: RegExpMatchArray | null = null;  let index = -1;  for (let i = 0; i < patterns.length; i++) {    const pattern = patterns[i];    if (pattern instanceof RegExp) {      const m = pathname.match(pattern);      if (!m) continue;      if (        m.index < lastMatchIndex ||        (m.index === lastMatchIndex && m[0].length > lastMatchLength)      ) {        index = i;        match = m;        lastMatchIndex = m.index;        lastMatchLength = m[0].length;      }    } else if (      pathname.startsWith(pattern) &&      pattern.length > lastMatchLength    ) {      index = i;      match = [pattern];      lastMatchIndex = 0;      lastMatchLength = pattern.length;    }  }  return { index, match };}
export interface HttpRouter {  /** Set global middleware */  use(handler: HttpHandler);
  handle(pattern: string | RegExp, handlers: HttpHandler);
  /** Set global error handler. Only one handler can be set at same time */  handleError(handler: ErrorHandler);
  listen(addr: string | ListenOptions, opts?: ServeOptions): void;}
/** create HttpRouter object */export function createRouter(): HttpRouter {  const middlewares: HttpHandler[] = [];  const finalErrorHandler = async (e: unknown, req: RoutedServerRequest) => {    if (e) {      console.error(e);    }    await req.respond(internalServerError());  };  let errorHandler: ErrorHandler = finalErrorHandler;  const routes: { pattern: string | RegExp; handlers: HttpHandler[] }[] = [];  function handle(pattern: string | RegExp, ...handlers: HttpHandler[]) {    routes.push({ pattern, handlers });  }  function use(middleware: HttpHandler) {    middlewares.push(middleware);  }  function handleError(handler: ErrorHandler) {    errorHandler = handler;  }  function listen(addr: string, opts?: ServeOptions) {    const handleInternal = async req => {      let { pathname } = new URL(req.url, "http://localhost");      for (const middleware of middlewares) {        await middleware(req);        if (req.isResponded()) {          return;        }      }      const { index, match } = findLongestAndNearestMatch(        pathname,        routes.map(v => v.pattern)      );      if (index > -1) {        const { handlers } = routes[index];        for (const handler of handlers) {          await handler(Object.assign(req, { match }));          if (req.isResponded()) {            break;          }        }        if (!req.isResponded()) {          return await req.respond(notFound());        }      } else {        return await req.respond(notFound());      }    };    const handler = async req => {      const onError = async (e: unknown) => {        try {          await errorHandler(e, req);        } catch (e) {          if (!req.isResponded()) {            await finalErrorHandler(e, req);          }        } finally {          if (!req.isResponded()) {            await finalErrorHandler(undefined, req);          }        }      };      return handleInternal(req).catch(onError);    };    listenAndServe(addr, handler, opts);  }  return { handle, use, handleError, listen };}