class Sus::Identity

def self.current
	self.nested(nil, nil, caller_locations(1...2).first)
end

def self.file(parent, path, name = path, **options)
	self.new(path, name, nil, nil, **options)
end

def self.nested(parent, name, location = nil, **options)
	location ||= caller_locations(3...4).first
	
	self.new(location.path, name, location.lineno, parent, **options)
end

def append_unique_key(key, unique = @unique)
	if @parent
		@parent.append_unique_key(key)
	else
		key << @path
	end
	
	if unique == true
		# No key is needed because this identity is unique.
	else
		if unique
			key << unique
		elsif @line
			key << @line
		end
	end
end

def each(&block)
	@parent&.each(&block)
	
	yield self
end

def each_caller_location(&block)
	Thread.each_caller_location(&block)
end

def each_caller_location(&block)
	caller_locations(1).each(&block)
end

def initialize(path, name = nil, line = nil, parent = nil, unique: true)
	@path = path
	@name = name
	@line = line
	@parent = parent
	@unique = unique
	
	@key = nil
end

def inspect
	"\#<#{self.class} #{self.to_s}>"
end

def key
	unless @key
		key = Array.new
		
		# For a specific leaf node, the last part is not unique, i.e. it must be identified explicitly.
		append_unique_key(key, @unique == true ? false : @unique)
		
		@key = key.join(":")
	end
	
	return @key
end

def match?(other)
	if path = other.path
		return false unless path === @path
	end
	
	if name = other.name
		return false unless name === @name
	end
	
	if line = other.line
		return false unless line === @line
	end
end

def scoped(locations = nil)
	if locations
		# This code path is normally taken if we've got an exception with a backtrace:
		locations.each do |location|
			if location.path == @path
				return self.with_line(location.lineno)
			end
		end
	else
		# In theory this should be a bit faster:
		each_caller_location do |location|
			if location.path == @path
				return self.with_line(location.lineno)
			end
		end
	end
	
	return self
end

def to_location
	{
		path: ::File.expand_path(@path),
		line: @line,
	}
end

def to_s
	self.key
end

def with_line(line)
	self.class.new(@path, @name, line, @parent, unique: @unique)
end