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// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
import { CHAR_BACKWARD_SLASH } from "../_common/constants.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. * * An example in windws, for instance: *  from = 'C:\\orandea\\test\\aaa' *  to = 'C:\\orandea\\impl\\bbb' * The output of the function should be: '..\\..\\impl\\bbb' * * @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);
  const fromOrig = resolve(from);  const toOrig = resolve(to);
  if (fromOrig === toOrig) return "";
  from = fromOrig.toLowerCase();  to = toOrig.toLowerCase();
  if (from === to) return "";
  // Trim any leading backslashes  let fromStart = 0;  let fromEnd = from.length;  for (; fromStart < fromEnd; ++fromStart) {    if (from.charCodeAt(fromStart) !== CHAR_BACKWARD_SLASH) break;  }  // Trim trailing backslashes (applicable to UNC paths only)  for (; fromEnd - 1 > fromStart; --fromEnd) {    if (from.charCodeAt(fromEnd - 1) !== CHAR_BACKWARD_SLASH) break;  }  const fromLen = fromEnd - fromStart;
  // Trim any leading backslashes  let toStart = 0;  let toEnd = to.length;  for (; toStart < toEnd; ++toStart) {    if (to.charCodeAt(toStart) !== CHAR_BACKWARD_SLASH) break;  }  // Trim trailing backslashes (applicable to UNC paths only)  for (; toEnd - 1 > toStart; --toEnd) {    if (to.charCodeAt(toEnd - 1) !== CHAR_BACKWARD_SLASH) 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 (to.charCodeAt(toStart + i) === CHAR_BACKWARD_SLASH) {          // We get here if `from` is the exact base path for `to`.          // For example: from='C:\\foo\\bar'; to='C:\\foo\\bar\\baz'          return toOrig.slice(toStart + i + 1);        } else if (i === 2) {          // We get here if `from` is the device root.          // For example: from='C:\\'; to='C:\\foo'          return toOrig.slice(toStart + i);        }      }      if (fromLen > length) {        if (from.charCodeAt(fromStart + i) === CHAR_BACKWARD_SLASH) {          // We get here if `to` is the exact base path for `from`.          // For example: from='C:\\foo\\bar'; to='C:\\foo'          lastCommonSep = i;        } else if (i === 2) {          // We get here if `to` is the device root.          // For example: from='C:\\foo\\bar'; to='C:\\'          lastCommonSep = 3;        }      }      break;    }    const fromCode = from.charCodeAt(fromStart + i);    const toCode = to.charCodeAt(toStart + i);    if (fromCode !== toCode) break;    else if (fromCode === CHAR_BACKWARD_SLASH) lastCommonSep = i;  }
  // We found a mismatch before the first common path separator was seen, so  // return the original `to`.  if (i !== length && lastCommonSep === -1) {    return toOrig;  }
  let out = "";  if (lastCommonSep === -1) lastCommonSep = 0;  // Generate the relative path based on the path difference between `to` and  // `from`  for (i = fromStart + lastCommonSep + 1; i <= fromEnd; ++i) {    if (i === fromEnd || from.charCodeAt(i) === CHAR_BACKWARD_SLASH) {      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 + toOrig.slice(toStart + lastCommonSep, toEnd);  } else {    toStart += lastCommonSep;    if (toOrig.charCodeAt(toStart) === CHAR_BACKWARD_SLASH) ++toStart;    return toOrig.slice(toStart, toEnd);  }}