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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
import { CHAR_COLON, CHAR_DOT } from "../_common/constants.ts";import type { ParsedPath } from "../_interface.ts";import { assertPath } from "../_common/assert_path.ts";import { isPathSeparator, isWindowsDeviceRoot } from "./_util.ts";
/** * Return a `ParsedPath` object of the `path`. * @param path to process */export function parse(path: string): ParsedPath {  assertPath(path);
  const ret: ParsedPath = { root: "", dir: "", base: "", ext: "", name: "" };
  const len = path.length;  if (len === 0) return ret;
  let rootEnd = 0;  let code = path.charCodeAt(0);
  // Try to match a root  if (len > 1) {    if (isPathSeparator(code)) {      // Possible UNC root
      rootEnd = 1;      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) {          // 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
              rootEnd = j;            } else if (j !== last) {              // We matched a UNC root with leftovers
              rootEnd = j + 1;            }          }        }      }    } else if (isWindowsDeviceRoot(code)) {      // Possible device root
      if (path.charCodeAt(1) === CHAR_COLON) {        rootEnd = 2;        if (len > 2) {          if (isPathSeparator(path.charCodeAt(2))) {            if (len === 3) {              // `path` contains just a drive root, exit early to avoid              // unnecessary work              ret.root = ret.dir = path;              ret.base = "\\";              return ret;            }            rootEnd = 3;          }        } else {          // `path` contains just a relative drive root, exit early to avoid          // unnecessary work          ret.root = ret.dir = path;          return ret;        }      }    }  } else if (isPathSeparator(code)) {    // `path` contains just a path separator, exit early to avoid    // unnecessary work    ret.root = ret.dir = path;    ret.base = "\\";    return ret;  }
  if (rootEnd > 0) ret.root = path.slice(0, rootEnd);
  let startDot = -1;  let startPart = rootEnd;  let end = -1;  let matchedSlash = true;  let i = path.length - 1;
  // Track the state of characters (if any) we see before our first dot and  // after any path separator we find  let preDotState = 0;
  // Get non-dir info  for (; i >= rootEnd; --i) {    code = path.charCodeAt(i);    if (isPathSeparator(code)) {      // If we reached a path separator that was not part of a set of path      // separators at the end of the string, stop now      if (!matchedSlash) {        startPart = i + 1;        break;      }      continue;    }    if (end === -1) {      // We saw the first non-path separator, mark this as the end of our      // extension      matchedSlash = false;      end = i + 1;    }    if (code === CHAR_DOT) {      // If this is our first dot, mark it as the start of our extension      if (startDot === -1) startDot = i;      else if (preDotState !== 1) preDotState = 1;    } else if (startDot !== -1) {      // We saw a non-dot and non-path separator before our dot, so we should      // have a good chance at having a non-empty extension      preDotState = -1;    }  }
  if (    startDot === -1 ||    end === -1 ||    // We saw a non-dot character immediately before the dot    preDotState === 0 ||    // The (right-most) trimmed path component is exactly '..'    (preDotState === 1 && startDot === end - 1 && startDot === startPart + 1)  ) {    if (end !== -1) {      ret.base = ret.name = path.slice(startPart, end);    }  } else {    ret.name = path.slice(startPart, startDot);    ret.base = path.slice(startPart, end);    ret.ext = path.slice(startDot, end);  }
  // Fallback to '\' in case there is no basename  ret.base = ret.base || "\\";
  // If the directory is the root, use the entire root as the `dir` including  // the trailing slash if any (`C:\abc` -> `C:\`). Otherwise, strip out the  // trailing slash (`C:\abc\def` -> `C:\abc`).  if (startPart > 0 && startPart !== rootEnd) {    ret.dir = path.slice(0, startPart - 1);  } else ret.dir = ret.root;
  return ret;}