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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
/** Run a script for each new-line or otherwise delimited chunk of standard input. * * @module */
import { parse } from "../flags/mod.ts";import { TextDelimiterStream } from "../streams/delimiter.ts";
// See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/AsyncFunction.const AsyncFunction = Object.getPrototypeOf(async function () {})  .constructor;
const HELP_MSG = `xeval
Run a script for each new-line or otherwise delimited chunk of standard input.
Print all the usernames in /etc/passwd:  cat /etc/passwd | deno run -A https://deno.land/std/examples/xeval.ts "a = $.split(':'); if (a) console.log(a[0])"
A complicated way to print the current git branch:  git branch | deno run -A https://deno.land/std/examples/xeval.ts -I 'line' "if (line.startsWith('*')) console.log(line.slice(2))"
Demonstrates breaking the input up by space delimiter instead of by lines:  cat LICENSE | deno run -A https://deno.land/std/examples/xeval.ts -d " " "if ($ === 'MIT') console.log('MIT licensed')",
USAGE:  deno run -A https://deno.land/std/examples/xeval.ts [OPTIONS] <code>OPTIONS:  -d, --delim <delim>       Set delimiter, defaults to newline  -I, --replvar <replvar>   Set variable name to be used in eval, defaults to $ARGS:  <code>`;
export type XevalFunc = (v: string) => Promise<unknown>;
export interface XevalOptions {  delimiter?: string;}
const DEFAULT_DELIMITER = "\n";
export async function xeval(  readable: ReadableStream<Uint8Array>,  xevalFunc: XevalFunc,  { delimiter = DEFAULT_DELIMITER }: XevalOptions = {},) {  const chunks = readable    .pipeThrough(new TextDecoderStream())    .pipeThrough(new TextDelimiterStream(delimiter));  for await (const chunk of chunks) {    // Ignore empty chunks.    if (chunk.length > 0) {      await xevalFunc(chunk);    }  }}
async function main() {  const parsedArgs = parse(Deno.args, {    boolean: ["help"],    string: ["delim", "replvar"],    alias: {      delim: ["d"],      replvar: ["I"],      help: ["h"],    },    default: {      delim: DEFAULT_DELIMITER,      replvar: "$",    },  });  if (parsedArgs._.length != 1) {    console.error(HELP_MSG);    console.log(parsedArgs._);    Deno.exit(1);  }  if (parsedArgs.help) {    return console.log(HELP_MSG);  }
  const delimiter = parsedArgs.delim;  const replVar = parsedArgs.replvar;  const code = parsedArgs._[0];
  // new AsyncFunction()'s error message for this particular case isn't great.  if (!replVar.match(/^[_$A-z][_$A-z0-9]*$/)) {    console.error(`Bad replvar identifier: "${replVar}"`);    Deno.exit(1);  }
  const xEvalFunc = new AsyncFunction(replVar, code);
  await xeval(Deno.stdin.readable, xEvalFunc, { delimiter });}
if (import.meta.main) {  main();}