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// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.import {  BinaryEncodings,  Encodings,  notImplemented,  TextEncodings,} from "../_utils.ts";
export type CallbackWithError = (err?: Error | null) => void;
export interface FileOptions {  encoding?: Encodings;  flag?: string;}
export type TextOptionsArgument =  | TextEncodings  | ({ encoding: TextEncodings } & FileOptions);export type BinaryOptionsArgument =  | BinaryEncodings  | ({ encoding: BinaryEncodings } & FileOptions);export type FileOptionsArgument = Encodings | FileOptions;
export interface WriteFileOptions extends FileOptions {  mode?: number;}
export function isFileOptions(  fileOptions: string | WriteFileOptions | undefined,): fileOptions is FileOptions {  if (!fileOptions) return false;
  return (    (fileOptions as FileOptions).encoding != undefined ||    (fileOptions as FileOptions).flag != undefined ||    (fileOptions as WriteFileOptions).mode != undefined  );}
export function getEncoding(  optOrCallback?:    | FileOptions    | WriteFileOptions    // deno-lint-ignore no-explicit-any    | ((...args: any[]) => any)    | Encodings    | null,): Encodings | null {  if (!optOrCallback || typeof optOrCallback === "function") {    return null;  }
  const encoding = typeof optOrCallback === "string"    ? optOrCallback    : optOrCallback.encoding;  if (!encoding) return null;  return encoding;}
export function checkEncoding(encoding: Encodings | null): Encodings | null {  if (!encoding) return null;
  encoding = encoding.toLowerCase() as Encodings;  if (["utf8", "hex", "base64"].includes(encoding)) return encoding;
  if (encoding === "utf-8") {    return "utf8";  }  if (encoding === "binary") {    return "binary";    // before this was buffer, however buffer is not used in Node    // node -e "require('fs').readFile('../world.txt', 'buffer', console.log)"  }
  const notImplementedEncodings = ["utf16le", "latin1", "ascii", "ucs2"];
  if (notImplementedEncodings.includes(encoding as string)) {    notImplemented(`"${encoding}" encoding`);  }
  throw new Error(`The value "${encoding}" is invalid for option "encoding"`);}
export function getOpenOptions(flag: string | undefined): Deno.OpenOptions {  if (!flag) {    return { create: true, append: true };  }
  let openOptions: Deno.OpenOptions;  switch (flag) {    case "a": {      // 'a': Open file for appending. The file is created if it does not exist.      openOptions = { create: true, append: true };      break;    }    case "ax": {      // 'ax': Like 'a' but fails if the path exists.      openOptions = { createNew: true, write: true, append: true };      break;    }    case "a+": {      // 'a+': Open file for reading and appending. The file is created if it does not exist.      openOptions = { read: true, create: true, append: true };      break;    }    case "ax+": {      // 'ax+': Like 'a+' but fails if the path exists.      openOptions = { read: true, createNew: true, append: true };      break;    }    case "r": {      // 'r': Open file for reading. An exception occurs if the file does not exist.      openOptions = { read: true };      break;    }    case "r+": {      // 'r+': Open file for reading and writing. An exception occurs if the file does not exist.      openOptions = { read: true, write: true };      break;    }    case "w": {      // 'w': Open file for writing. The file is created (if it does not exist) or truncated (if it exists).      openOptions = { create: true, write: true, truncate: true };      break;    }    case "wx": {      // 'wx': Like 'w' but fails if the path exists.      openOptions = { createNew: true, write: true };      break;    }    case "w+": {      // 'w+': Open file for reading and writing. The file is created (if it does not exist) or truncated (if it exists).      openOptions = { create: true, write: true, truncate: true, read: true };      break;    }    case "wx+": {      // 'wx+': Like 'w+' but fails if the path exists.      openOptions = { createNew: true, write: true, read: true };      break;    }    case "as": {      // 'as': Open file for appending in synchronous mode. The file is created if it does not exist.      openOptions = { create: true, append: true };      break;    }    case "as+": {      // 'as+': Open file for reading and appending in synchronous mode. The file is created if it does not exist.      openOptions = { create: true, read: true, append: true };      break;    }    case "rs+": {      // 'rs+': Open file for reading and writing in synchronous mode. Instructs the operating system to bypass the local file system cache.      openOptions = { create: true, read: true, write: true };      break;    }    default: {      throw new Error(`Unrecognized file system flag: ${flag}`);    }  }
  return openOptions;}