class Grape::Router

def self.normalize_path(path)
  path = +"/#{path}"
  path.squeeze!('/')
  path.sub!(%r{/+\Z}, '')
  path = '/' if path == ''
  path
end

def self.supported_methods
  @supported_methods ||= Grape::Http::Headers::SUPPORTED_METHODS + ['*']
end

def append(route)
  map[route.request_method] << route
end

def associate_routes(pattern, **options)
  @neutral_regexes << Regexp.new("(?<_#{@neutral_map.length}>)#{pattern.to_regexp}")
  @neutral_map << Grape::Router::AttributeTranslator.new(**options, pattern: pattern, index: @neutral_map.length)
end

def call(env)
  with_optimization do
    response, route = identity(env)
    response || rotation(env, route)
  end
end

def call_with_allow_headers(env, route)
  prepare_env_from_route(env, route)
  env[Grape::Env::GRAPE_ALLOWED_METHODS] = route.allow_header.join(', ').freeze
  route.endpoint.call(env)
end

def cascade?(response)
  response && response[1][Grape::Http::Headers::X_CASCADE] == 'pass'
end

def compile!
  return if compiled
  @union = Regexp.union(@neutral_regexes)
  @neutral_regexes = nil
  self.class.supported_methods.each do |method|
    routes = map[method]
    @optimized_map[method] = routes.map.with_index do |route, index|
      route.index = index
      Regexp.new("(?<_#{index}>#{route.pattern.to_regexp})")
    end
    @optimized_map[method] = Regexp.union(@optimized_map[method])
  end
  @compiled = true
end

def default_response
  [404, { Grape::Http::Headers::X_CASCADE => 'pass' }, ['404 Not Found']]
end

def extract_input_and_method(env)
  input = string_for(env[Grape::Http::Headers::PATH_INFO])
  method = env[Grape::Http::Headers::REQUEST_METHOD]
  [input, method]
end

def greedy_match?(input)
  return unless @union.match(input)
  last_match = Regexp.last_match
  @neutral_map.detect { |route| last_match["_#{route.index}"] }
end

def identity(env)
  route = nil
  response = transaction(env) do |input, method|
    route = match?(input, method)
    process_route(route, env) if route
  end
  [response, route]
end

def initialize
  @neutral_map = []
  @neutral_regexes = []
  @map = Hash.new { |hash, key| hash[key] = [] }
  @optimized_map = Hash.new { |hash, key| hash[key] = // }
end

def make_routing_args(default_args, route, input)
  args = default_args || { route_info: route }
  args.merge(route.params(input) || {})
end

def match?(input, method)
  current_regexp = @optimized_map[method]
  return unless current_regexp.match(input)
  last_match = Regexp.last_match
  @map[method].detect { |route| last_match["_#{route.index}"] }
end

def prepare_env_from_route(env, route)
  input, = *extract_input_and_method(env)
  env[Grape::Env::GRAPE_ROUTING_ARGS] = make_routing_args(env[Grape::Env::GRAPE_ROUTING_ARGS], route, input)
end

def process_route(route, env)
  prepare_env_from_route(env, route)
  route.exec(env)
end

def recognize_path(input)
  any = with_optimization { greedy_match?(input) }
  return if any == default_response
  any.endpoint
end

def rotation(env, exact_route = nil)
  response = nil
  input, method = *extract_input_and_method(env)
  map[method].each do |route|
    next if exact_route == route
    next unless route.match?(input)
    response = process_route(route, env)
    break unless cascade?(response)
  end
  response
end

def string_for(input)
  self.class.normalize_path(input)
end

def transaction(env)
  input, method = *extract_input_and_method(env)
  response = yield(input, method)
  return response if response && !(cascade = cascade?(response))
  last_neighbor_route = greedy_match?(input)
  # If last_neighbor_route exists and request method is OPTIONS,
  # return response by using #call_with_allow_headers.
  return call_with_allow_headers(env, last_neighbor_route) if last_neighbor_route && method == Grape::Http::Headers::OPTIONS && !cascade
  route = match?(input, '*')
  return last_neighbor_route.endpoint.call(env) if last_neighbor_route && cascade && route
  if route
    response = process_route(route, env)
    return response if response && !(cascade = cascade?(response))
  end
  return call_with_allow_headers(env, last_neighbor_route) if !cascade && last_neighbor_route
  nil
end

def with_optimization
  compile! unless compiled
  yield || default_response
end