require "http/server"
require "radix"

# Kemal::RouteHandler is the main handler which handles all the HTTP requests. Routing, parsing, rendering e.g
# are done in this handler.
class Kemal::RouteHandler < HTTP::Handler
  INSTANCE = new

  property tree

  def initialize
    @tree = Radix::Tree(Route).new
  end

  def call(context)
    context.response.content_type = "text/html" unless context.response.headers.has_key?("Content-Type")
    process_request(context)
  end

  # Adds a given route to routing tree. As an exception each `GET` route additionaly defines
  # a corresponding `HEAD` route.
  def add_route(method, path, &handler : HTTP::Server::Context -> _)
    add_to_radix_tree method, path, Route.new(method, path, &handler)
    add_to_radix_tree("HEAD", path, Route.new("HEAD", path, &handler)) if method == "GET"
  end

  # Check if a route is defined and returns the lookup
  def lookup_route(verb, path)
    @tree.find radix_path(verb, path)
  end

  # Processes the route if it's a match. Otherwise renders 404.
  def process_request(context)
    raise Kemal::Exceptions::RouteNotFound.new(context) unless context.route_defined?
    route = context.route_lookup.payload.as(Route)
    content = route.handler.call(context)
    if Kemal.config.error_handlers.has_key?(context.response.status_code)
      raise Kemal::Exceptions::CustomException.new(context)
    end
    context.response.print(content)
    context
  end

  private def radix_path(method : String, path)
    "/#{method.downcase}#{path}"
  end

  private def add_to_radix_tree(method, path, route)
    node = radix_path method, path
    @tree.add node, route
  end
end