std/router

pub class Pattern
  # Two relations of parts (methods, then each segment) as the relation
  # of the whole: a superset in one part and a subset in another is
  # neither, an overlap.
  def self.combine(first : Int32, second : Int32) : Int32
  # The sentence refusing this pattern beside *other*, nil when the two
  # can be registered together: when they have the same host and match
  # the same requests, or some requests in common with neither more
  # specific. It names both and a request both match.
  def conflict(other : Pattern) : String | ::Nil
  # Whether this pattern matched *pieces* without its trailing wildcard
  # taking anything: `/x/` on `/x/`, not on `/x/y`. What decides whether
  # `/x` is redirected to `/x/`.
  def exact?(pieces : Array(String)) : Bool
  def host : String
  # A wildcard's name: an ASCII letter or `_`, then letters, digits, `_`.
  def self.identifier?(name : String) : Bool
  def initialize(text : String, method : String, host : String, kinds : Array(Int32), names : Array(String))
  protected def kinds : Array(Int32)
  # The wildcards' values when *path* - a request path, rooted and clean,
  # still percent-encoded - matches this pattern's path; nil when it does
  # not. The method and host are not looked at.
  def match(path : String) : Hash(String, String) | ::Nil
  # `match` on a path already cut into `pieces`.
  def match_pieces(pieces : Array(String)) : Hash(String, String) | ::Nil
  # Whether a request of *method* is one this pattern's method takes.
  def matches_method?(method : String) : Bool
  def method : String
  # Whether this pattern matches a strict subset of *other*'s requests,
  # methods and paths together; hosts are not compared.
  def more_specific?(other : Pattern) : Bool
  protected def names : Array(String)
  # *text* read as a pattern, or why it is not one: an invalid method, no
  # `/` to start the path, a `{` in the host, a path a request's cleaned
  # path never equals (`//`, `.`, `..`), a wildcard that is not a whole
  # segment, `{$}` or `{name...}` before the end, a name that is not an
  # identifier or is used twice, a malformed percent escape.
  def self.parse(text : String) : Pattern | RouterError
  # *path*'s segments after its first `/`, each percent-decoded: `/` is
  # one empty piece, and a trailing slash is a last empty one. Nil for a
  # path that is not rooted or holds a malformed escape. Decoded a segment
  # at a time, so `%2F` is inside a segment, never between two.
  def self.pieces(path : String) : Array(String) | ::Nil
  # How this pattern's requests relate to *other*'s, methods and paths
  # together: `EQUIVALENT`, `MORE_GENERAL`, `MORE_SPECIFIC`, `DISJOINT` or
  # `OVERLAPS`.
  def relation(other : Pattern) : Int32
  # The pattern as it was written.
  def to_s : String
end

  router = Router.new
  router.handle("GET /users/{id}") { |req, params| Response.new(200, params["id"]) }
  router.handle("/static/") { |req, params| FileServer.serve(root, req) }
  Server.serve(listener) { |req| router.call(req) }

pub class Router
  # The answer to *req*: its handler's, or the router's own 301, 400, 404
  # or 405.
  def call(req : Request) : Response
  # *path* - rooted - with `.` and empty segments dropped and `..` taking
  # the one before it off, its trailing slash kept: Go's `cleanPath`.
  def self.clean(path : String) : String
  # Sends the requests *pattern* matches to the block, with the request
  # and the wildcards' values by name.
  def handle(pattern : String, &handler : (Request, Hash(String, String) -> Response)) : Nil
  # A `Host` value without its port, as Go's `stripHostPort` has it: an
  # IPv6 address in brackets loses the brackets with the port.
  def self.host_of(value : String) : String
  def initialize
  # The patterns registered, in the order they were.
  def patterns : Array(Pattern)
  def self.plain(status : Int32, text : String) : Response
  def self.redirect(path : String, query : String | ::Nil) : Response
end

pub struct RouterError
  def initialize(reason : String)
  def reason : String
  def to_s : String
end

impl Error for RouterError
  def message : String
end