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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
import { assertArg } from "../_common/normalize.ts";import { CHAR_COLON } from "../_common/constants.ts";import { normalizeString } from "../_common/normalize_string.ts";import { isPathSeparator, isWindowsDeviceRoot } from "./_util.ts";
/** * Normalize the `path`, resolving `'..'` and `'.'` segments. * Note that resolving these segments does not necessarily mean that all will be eliminated. * A `'..'` at the top-level will be preserved, and an empty path is canonically `'.'`. * @param path to be normalized */export function normalize(path: string): string {  assertArg(path);
  const len = path.length;  let rootEnd = 0;  let device: string | undefined;  let isAbsolute = false;  const code = path.charCodeAt(0);
  // Try to match a root  if (len > 1) {    if (isPathSeparator(code)) {      // Possible UNC root
      // If we started with a separator, we know we at least have an absolute      // path of some kind (UNC or otherwise)      isAbsolute = true;
      if (isPathSeparator(path.charCodeAt(1))) {        // Matched double path separator at beginning        let j = 2;        let last = j;        // Match 1 or more non-path separators        for (; j < len; ++j) {          if (isPathSeparator(path.charCodeAt(j))) break;        }        if (j < len && j !== last) {          const firstPart = path.slice(last, j);          // Matched!          last = j;          // Match 1 or more path separators          for (; j < len; ++j) {            if (!isPathSeparator(path.charCodeAt(j))) break;          }          if (j < len && j !== last) {            // Matched!            last = j;            // Match 1 or more non-path separators            for (; j < len; ++j) {              if (isPathSeparator(path.charCodeAt(j))) break;            }            if (j === len) {              // We matched a UNC root only              // Return the normalized version of the UNC root since there              // is nothing left to process
              return `\\\\${firstPart}\\${path.slice(last)}\\`;            } else if (j !== last) {              // We matched a UNC root with leftovers
              device = `\\\\${firstPart}\\${path.slice(last, j)}`;              rootEnd = j;            }          }        }      } else {        rootEnd = 1;      }    } else if (isWindowsDeviceRoot(code)) {      // Possible device root
      if (path.charCodeAt(1) === CHAR_COLON) {        device = path.slice(0, 2);        rootEnd = 2;        if (len > 2) {          if (isPathSeparator(path.charCodeAt(2))) {            // Treat separator following drive name as an absolute path            // indicator            isAbsolute = true;            rootEnd = 3;          }        }      }    }  } else if (isPathSeparator(code)) {    // `path` contains just a path separator, exit early to avoid unnecessary    // work    return "\\";  }
  let tail: string;  if (rootEnd < len) {    tail = normalizeString(      path.slice(rootEnd),      !isAbsolute,      "\\",      isPathSeparator,    );  } else {    tail = "";  }  if (tail.length === 0 && !isAbsolute) tail = ".";  if (tail.length > 0 && isPathSeparator(path.charCodeAt(len - 1))) {    tail += "\\";  }  if (device === undefined) {    if (isAbsolute) {      if (tail.length > 0) return `\\${tail}`;      else return "\\";    } else if (tail.length > 0) {      return tail;    } else {      return "";    }  } else if (isAbsolute) {    if (tail.length > 0) return `${device}\\${tail}`;    else return `${device}\\`;  } else if (tail.length > 0) {    return device + tail;  } else {    return device;  }}