parse()

in src/vs/base/common/path.ts [914:1064]

• 109 lines of code
• 40 McCabe index (conditional complexity)

	parse(path) {
		validateString(path, 'path');

		const ret = { root: '', dir: '', base: '', ext: '', name: '' };
		if (path.length === 0) {
			return ret;
		}

		const len = path.length;
		let rootEnd = 0;
		let code = path.charCodeAt(0);

		if (len === 1) {
			if (isPathSeparator(code)) {
				// `path` contains just a path separator, exit early to avoid
				// unnecessary work
				ret.root = ret.dir = path;
				return ret;
			}
			ret.base = ret.name = path;
			return ret;
		}
		// Try to match a root
		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
				while (j < len && !isPathSeparator(path.charCodeAt(j))) {
					j++;
				}
				if (j < len && j !== last) {
					// Matched!
					last = j;
					// Match 1 or more path separators
					while (j < len && isPathSeparator(path.charCodeAt(j))) {
						j++;
					}
					if (j < len && j !== last) {
						// Matched!
						last = j;
						// Match 1 or more non-path separators
						while (j < len && !isPathSeparator(path.charCodeAt(j))) {
							j++;
						}
						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) && path.charCodeAt(1) === CHAR_COLON) {
			// Possible device root
			if (len <= 2) {
				// `path` contains just a drive root, exit early to avoid
				// unnecessary work
				ret.root = ret.dir = path;
				return ret;
			}
			rootEnd = 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;
					return ret;
				}
				rootEnd = 3;
			}
		}
		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 (end !== -1) {
			if (startDot === -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)) {
				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);
			}
		}

		// 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;
	},