build directory tree as String

FileManager+tree.swift

public extension FileManager {

	func makeTree(atPath path: String, level: Int) throws -> [String] {
		var strings = [String]()
		let items = try self.contentsOfDirectory(atPath: path)
		for item in items.sorted(by: { ($0 as NSString).lastPathComponent < ($1 as NSString).lastPathComponent }) {
			var isDirectory: ObjCBool = false
			let itemPath = (path as NSString).appendingPathComponent(item)
			if self.fileExists(atPath: itemPath, isDirectory: &isDirectory) && isDirectory.boolValue {
				strings.append("+ " + (item as NSString).lastPathComponent)
				if level > 1 || level == 0 {
					strings += (try self.makeTree(atPath: itemPath, level: level - 1)).map { "| " + $0 }
				}
			}
			
		}
		return strings.map { " \($0)" }
	}

	func tree(atPath path: String, level: Int) throws -> String {
		return try self.makeTree(atPath: path, level: level).joined(separator: "\n")
	}

}