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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
import { isPosixPathSeparator } from "./_util.ts";import { resolve } from "./resolve.ts";import { assertArgs } from "../_common/relative.ts";
/** * Return the relative path from `from` to `to` based on current working directory. * * @param from path in current working directory * @param to path in current working directory */export function relative(from: string, to: string): string {  assertArgs(from, to);
  from = resolve(from);  to = resolve(to);
  if (from === to) return "";
  // Trim any leading backslashes  let fromStart = 1;  const fromEnd = from.length;  for (; fromStart < fromEnd; ++fromStart) {    if (!isPosixPathSeparator(from.charCodeAt(fromStart))) break;  }  const fromLen = fromEnd - fromStart;
  // Trim any leading backslashes  let toStart = 1;  const toEnd = to.length;  for (; toStart < toEnd; ++toStart) {    if (!isPosixPathSeparator(to.charCodeAt(toStart))) break;  }  const toLen = toEnd - toStart;
  // Compare paths to find the longest common path from root  const length = fromLen < toLen ? fromLen : toLen;  let lastCommonSep = -1;  let i = 0;  for (; i <= length; ++i) {    if (i === length) {      if (toLen > length) {        if (isPosixPathSeparator(to.charCodeAt(toStart + i))) {          // We get here if `from` is the exact base path for `to`.          // For example: from='/foo/bar'; to='/foo/bar/baz'          return to.slice(toStart + i + 1);        } else if (i === 0) {          // We get here if `from` is the root          // For example: from='/'; to='/foo'          return to.slice(toStart + i);        }      } else if (fromLen > length) {        if (isPosixPathSeparator(from.charCodeAt(fromStart + i))) {          // We get here if `to` is the exact base path for `from`.          // For example: from='/foo/bar/baz'; to='/foo/bar'          lastCommonSep = i;        } else if (i === 0) {          // We get here if `to` is the root.          // For example: from='/foo'; to='/'          lastCommonSep = 0;        }      }      break;    }    const fromCode = from.charCodeAt(fromStart + i);    const toCode = to.charCodeAt(toStart + i);    if (fromCode !== toCode) break;    else if (isPosixPathSeparator(fromCode)) lastCommonSep = i;  }
  let out = "";  // Generate the relative path based on the path difference between `to`  // and `from`  for (i = fromStart + lastCommonSep + 1; i <= fromEnd; ++i) {    if (i === fromEnd || isPosixPathSeparator(from.charCodeAt(i))) {      if (out.length === 0) out += "..";      else out += "/..";    }  }
  // Lastly, append the rest of the destination (`to`) path that comes after  // the common path parts  if (out.length > 0) return out + to.slice(toStart + lastCommonSep);  else {    toStart += lastCommonSep;    if (isPosixPathSeparator(to.charCodeAt(toStart))) ++toStart;    return to.slice(toStart);  }}