`module System`

Maps individual URL path segments to and from local filesystem components.

Unlike generic URL decoding, this encoding rejects values which would turn one URL segment into multiple local path components.

Definitions

`def self.escape(component)`

Encode one local filesystem component as one URL path segment.

Signature

parameter　component　String: The local filesystem component.
returns　String: The encoded URL segment.
raises　ArgumentError: If the component cannot be converted or contains a system path separator.

Implementation

def self.escape(component)
	validate(component)
	Encoding.escape(transcode(component, ::Encoding::UTF_8))
end

`def self.unescape(segment)`

Decode one URL path segment as one local filesystem component.

Signature

parameter　segment　String: The encoded URL segment.
returns　String: The local filesystem component.
raises　ArgumentError: If the segment cannot map to one local filesystem component.

Implementation

def self.unescape(segment)
	component = Encoding.unescape(segment, ::Encoding::UTF_8)
	validate(component)
	transcode(component, ENCODING)
end

`def self.transcode(component, encoding)`

Transcode a path component to the requested character encoding.

Implementation

def self.transcode(component, encoding)
	component.encode(encoding)
rescue ::Encoding::InvalidByteSequenceError, ::Encoding::UndefinedConversionError
	raise ArgumentError, "Path component could not be transcoded!"
end

`def self.validate(component)`

Validate that a string can represent exactly one local filesystem component.

Implementation

def self.validate(component)
	unless component.valid_encoding?
		raise ArgumentError, "Path component has invalid encoding!"
	end
	
	if INVALID_CHARACTER_PATTERN.match?(component)
		raise ArgumentError, "Path component contains invalid characters!"
	end
end