module Protocol::HTTP::URL

def self.assign(keys, value, parent)

@parameter parent [Hash] The parent hash.
@parameter value [Object] The value to assign.
@parameter keys [Array(String)] The parts of the key.

Assign a value to a nested hash. 
def self.assign(keys, value, parent)
	top, *middle = keys
	
	middle.each_with_index do |key, index|
		if key.nil? or key.empty?
			parent = (parent[top] ||= Array.new)
			top = parent.size
			
			if nested = middle[index+1] and last = parent.last
				top -= 1 unless last.include?(nested)
			end
		else
			parent = (parent[top] ||= Hash.new)
			top = key
		end
	end
	
	parent[top] = value
end

def self.decode(string, maximum = 8, symbolize_keys: false)

@returns [Hash] The decoded query string.
@parameter symbolize_keys [Boolean] Whether to symbolize keys.
@parameter maximum [Integer] The maximum number of keys in a path.
@parameter string [String] The query string to decode.

Decode a URL-encoded query string into a hash. 
def self.decode(string, maximum = 8, symbolize_keys: false)
	parameters = {}
	
	self.scan(string) do |name, value|
		keys = self.split(name)
		
		if keys.empty?
			raise ArgumentError, "Invalid key path: #{name.inspect}!"
		end
		
		if keys.size > maximum
			raise ArgumentError, "Key length exceeded limit!"
		end
		
		if symbolize_keys
			keys.collect!{|key| key.empty? ? nil : key.to_sym}
		end
		
		self.assign(keys, value, parameters)
	end
	
	return parameters
end

def self.encode(value, prefix = nil)

@parameter prefix [String] The prefix to use for keys.
@parameter value [Hash | Array | Nil] The value to encode.

Encodes a hash or array into a query string. This method is used to encode query parameters in a URL. For example, `{"a" => 1, "b" => 2}` is encoded as `a=1&b=2`. 
def self.encode(value, prefix = nil)
	case value
	when Array
		return value.map {|v|
			self.encode(v, "#{prefix}[]")
		}.join("&")
	when Hash
		return value.map {|k, v|
			self.encode(v, prefix ? "#{prefix}[#{escape(k.to_s)}]" : escape(k.to_s))
		}.reject(&:empty?).join("&")
	when nil
		return prefix
	else
		raise ArgumentError, "value must be a Hash" if prefix.nil?
		
		return "#{prefix}=#{escape(value.to_s)}"
	end
end

def self.escape(string, encoding = string.encoding)

@returns [String] The escaped string.
@parameter string [String] The string to escape.

Escapes a string using percent encoding, e.g. `a b` -> `a%20b`. 
def self.escape(string, encoding = string.encoding)
	string.b.gsub(/([^a-zA-Z0-9_.\-]+)/) do |m|
		"%" + m.unpack("H2" * m.bytesize).join("%").upcase
	end.force_encoding(encoding)
end

def self.escape_path(path)

@returns [String] The escaped path.
@parameter path [String] The path to escape.

Escapes non-path characters using percent encoding. In other words, this method escapes characters that are not allowed in a URI path segment. According to RFC 3986 Section 3.3 (https://tools.ietf.org/html/rfc3986#section-3.3), a valid path segment consists of "pchar" characters. This method percent-encodes characters that are not "pchar" characters. 
def self.escape_path(path)
	encoding = path.encoding
	path.b.gsub(NON_PATH_CHARACTER_PATTERN) do |m|
		"%" + m.unpack("H2" * m.bytesize).join("%").upcase
	end.force_encoding(encoding)
end

def self.scan(string)

@parameter value [String] The unescaped key.
@parameter key [String] The unescaped key.
@yields {|key, value| ...}
Scan a string for URL-encoded key/value pairs. 
def self.scan(string)
	string.split("&") do |assignment|
		next if assignment.empty?
		
		key, value = assignment.split("=", 2)
		
		yield unescape(key), value.nil? ? value : unescape(value)
	end
end

def self.split(name)

@returns [Array(String)] The parts of the key.
@parameter name [String] The key to split.

Split a key into parts, e.g. `a[b][c]` -> `["a", "b", "c"]`. 
def self.split(name)
	name.scan(/([^\[]+)|(?:\[(.*?)\])/)&.tap do |parts|
		parts.flatten!
		parts.compact!
	end
end

def self.unescape(string, encoding = string.encoding)

@returns [String] The unescaped string.
@parameter string [String] The string to unescape.

Unescapes a percent encoded string, e.g. `a%20b` -> `a b`. 
def self.unescape(string, encoding = string.encoding)
	string.b.gsub(/%(\h\h)/) do |hex|
		Integer($1, 16).chr
	end.force_encoding(encoding)
end