Passwd#remove_user(uid), Passwd#remove_group(gid)

src/passwd.cr

@@ -1,4 +1,5 @@
 require "csv"
+require "file_utils"
 
 # FIXME: Should we work on arrays and convert to CSV at the last second when adding rows?
 # FIXME: Use split, not CSV.
@@ -9,14 +10,11 @@ class Passwd
 	@group : String
 
 	# FIXME: Missing operations:
-	#   - Removing users.
 	#   - Reading groups.
 	#   - Adding and removing groups (ok, maybe admins can do that?)
 	#   - Adding users to group.
 	#   - Removing users from group.
 
-	# FIXME: Safety. Ensure passwd and group cannot be in a half-written state. (backups will probably work well enough in the mean-time)
-
 	def initialize(@passwd, @group)
 	end
 
@@ -188,6 +186,58 @@ class Passwd
 
 		File.write @passwd, new_passwd.join("\n") + "\n"
 	end
+
+	private def safe_rewrite(path : String, body : String)
+		tempfile = File.tempfile(File.basename path)
+		tempfile << body
+		tempfile.close
+
+		FileUtils.cp tempfile.path, path
+	end
+
+	def remove_user(uid)
+		user = get_user(uid)
+
+		return nil unless user
+
+		user_login = user.login
+
+		new_group = group_as_array.map do |line|
+			group = Group.new line
+
+			group.users.select! &.!=(user_login)
+
+			group.to_csv
+		end
+
+		safe_rewrite @group, new_group.join('\n') + '\n'
+
+		new_passwd = passwd_as_array.compact_map do |line|
+			user = User.new line
+
+			if uid == user.uid
+				nil
+			else
+				line.join ':'
+			end
+		end
+
+		safe_rewrite @passwd, new_passwd.join("\n") + "\n"
+	end
+
+	def remove_group(gid)
+		new_group = group_as_array.compact_map do |line|
+			group = Group.new line
+
+			if gid == group.gid
+				nil
+			else
+				line.join ':'
+			end
+		end
+
+		safe_rewrite @group, new_group.join('\n') + '\n'
+	end
 end
 
 class Passwd::Group