ambiorix: Web Framework Inspired by 'Express.js'

#' Core Routing Class
#' 
#' Core routing class.
#' Do not use directly, see [Ambiorix], and [Router].
#' 
#' @field error Error handler.
#' @field basepath Basepath, read-only.
#' @field websocket Websocket handler.
#' 
#' @keywords export
Routing <- R6::R6Class(
  "Routing",
  public = list(
    error = NULL,
    #' @details Initialise
    #' @param path Prefix path.
    initialize = function(path = "") {
      private$.basepath <- path
      private$.is_router <- path != ""
    },
    #' @details GET Method
    #' 
    #' Add routes to listen to.
    #' 
    #' @param path Route to listen to, `:` defines a parameter.
    #' @param handler Function that accepts the request and returns an object 
    #' describing an httpuv response, e.g.: [response()].
    #' @param error Handler function to run on error.
    #' 
    #' @examples 
    #' app <- Ambiorix$new()
    #' 
    #' app$get("/", function(req, res){
    #'  res$send("Using {ambiorix}!")
    #' })
    #' 
    #' if(interactive())
    #'  app$start()
    get = function(path, handler, error = NULL){
      assert_that(valid_path(path))
      assert_that(not_missing(handler))
      assert_that(is_handler(handler))

      r <- list(
        route = Route$new(private$.make_path(path)), 
        path = path, 
        fun = handler, 
        method = "GET",
        error = error %error% self$error
      )
      private$.routes <- append(private$.routes, list(r))

      invisible(self)
    },
    #' @details PUT Method
    #' 
    #' Add routes to listen to.
    #' 
    #' @param path Route to listen to, `:` defines a parameter.
    #' @param handler Function that accepts the request and returns an object 
    #' describing an httpuv response, e.g.: [response()].
    #' @param error Handler function to run on error.
    put = function(path, handler, error = NULL){
      assert_that(valid_path(path))
      assert_that(not_missing(handler))
      assert_that(is_handler(handler))

      r <- list(
        route = Route$new(private$.make_path(path)), 
        path = path, 
        fun = handler, 
        method = "PUT",
        error = error %error% self$error
      )
      private$.routes <- append(private$.routes, list(r))

      invisible(self)
    },
    #' @details PATCH Method
    #' 
    #' Add routes to listen to.
    #' 
    #' @param path Route to listen to, `:` defines a parameter.
    #' @param handler Function that accepts the request and returns an object 
    #' describing an httpuv response, e.g.: [response()].
    #' @param error Handler function to run on error.
    patch = function(path, handler, error = NULL){
      assert_that(valid_path(path))
      assert_that(not_missing(handler))
      assert_that(is_handler(handler))

      r <- list(
        route = Route$new(private$.make_path(path)), 
        path = path, 
        fun = handler, 
        method = "PATCH",
        error = error %error% self$error
      )
      private$.routes <- append(private$.routes, list(r))

      invisible(self)
    },
    #' @details DELETE Method
    #' 
    #' Add routes to listen to.
    #' 
    #' @param path Route to listen to, `:` defines a parameter.
    #' @param handler Function that accepts the request and returns an object 
    #' describing an httpuv response, e.g.: [response()].
    #' @param error Handler function to run on error.
    delete = function(path, handler, error = NULL){
      assert_that(valid_path(path))
      assert_that(not_missing(handler))
      assert_that(is_handler(handler))

      r <- list(
        route = Route$new(private$.make_path(path)), 
        path = path, 
        fun = handler, 
        method = "DELETE",
        error = error %error% self$error
      )
      private$.routes <- append(private$.routes, list(r))

      invisible(self)
    },
    #' @details POST Method
    #' 
    #' Add routes to listen to.
    #' 
    #' @param path Route to listen to.
    #' @param handler Function that accepts the request and returns an object 
    #' describing an httpuv response, e.g.: [response()].
    #' @param error Handler function to run on error.
    post = function(path, handler, error = NULL){
      assert_that(valid_path(path))
      assert_that(not_missing(handler))
      assert_that(is_handler(handler))

      r <- list(
        route = Route$new(private$.make_path(path)), 
        path = path, 
        fun = handler, 
        method = "POST",
        error = error %error% self$error
      )
      private$.routes <- append(private$.routes, list(r))

      invisible(self)
    },
    #' @details OPTIONS Method
    #'
    #' Add routes to listen to.
    #'
    #' @param path Route to listen to.
    #' @param handler Function that accepts the request and returns an object
    #' describing an httpuv response, e.g.: [response()].
    #' @param error Handler function to run on error.
    options = function(path, handler, error = NULL){
      assert_that(valid_path(path))
      assert_that(not_missing(handler))
      assert_that(is_handler(handler))

      r <- list(
        route = Route$new(private$.make_path(path)), 
        path = path,
        fun = handler,
        method = "OPTIONS",
        error = error %error% self$error
      )
      private$.routes <- append(private$.routes, list(r))

      invisible(self)
    },
    #' @details All Methods
    #' 
    #' Add routes to listen to for all methods `GET`, `POST`, `PUT`, `DELETE`, and `PATCH`.
    #' 
    #' @param path Route to listen to.
    #' @param handler Function that accepts the request and returns an object 
    #' describing an httpuv response, e.g.: [response()].
    #' @param error Handler function to run on error.
    all = function(path, handler, error = NULL){
      assert_that(valid_path(path))
      assert_that(not_missing(handler))
      assert_that(is_handler(handler))

      r <- list(
        route = Route$new(private$.make_path(path)), 
        path = path, 
        fun = handler, 
        method = c("GET", "POST", "PUT", "DELETE", "PATCH"),
        error = error %error% self$error
      )
      private$.routes <- append(private$.routes, list(r))
      
      invisible(self)
    },
    #' @details Receive Websocket Message
    #' @param name Name of message.
    #' @param handler Function to run when message is received.
    #' 
    #' @examples 
    #' app <- Ambiorix$new()
    #' 
    #' app$get("/", function(req, res){
    #'  res$send("Using {ambiorix}!")
    #' })
    #' 
    #' app$receive("hello", function(msg, ws){
    #'  print(msg) # print msg received
    #'  
    #'  # send a message back
    #'  ws$send("hello", "Hello back! (sent from R)")
    #' })
    #' 
    #' if(interactive())
    #'  app$start()
    receive = function(name, handler){
      private$.receivers <- append(
        private$.receivers,
        list(WebsocketHandler$new(name, handler))
      )

      invisible(self)
    },
    #' @details Print
    print = function(){
      cli::cli_rule("Ambiorix", right = "web server")
      cli::cli_li("routes: {.val {private$n_routes()}}")
    },
    #' @details Engine to use for rendering templates.
    #' @param engine Engine function.
    engine = function(engine){
      if(!is_renderer_obj(engine))
        engine <- as_renderer(engine)

      self$use(engine)
      invisible(self)
    },
    #' @details Use a router or middleware
    #' @param use Either a router as returned by [Router], a function to use as middleware,
    #' or a `list` of functions.
    #' If a function is passed, it must accept two arguments (the request, and the response): 
    #' this function will be executed every time the server receives a request.
    #' _Middleware may but does not have to return a response, unlike other methods such as `get`_
    #' Note that multiple routers and middlewares can be used.
    use = function(use){
      assert_that(not_missing(use))
      
      # recurse through items
      if(is.list(use)) {
        for(i in seq_along(use)) {
          self$use(use[[i]])
        }
      }
      
      # mount router
      if(inherits(use, "Router")){
        private$.routers <- append(private$.routers, use)
      } 
      
      if(is_renderer_obj(use) && private$.is_router){
        .globals$errorLog$log(
          "Cannot pass cookie preprocessor to `Router`, only to `Ambiorix`"
        )
        return(invisible(self))
      }

      if(is_renderer_obj(use)) {
        .Deprecated(
          "engine",
          package = "ambiorix",
          msg = "Use `engine` instead of `use` for custom renderers."
        )
        .globals$renderer <- use
        return(invisible(self))
      }
      
      if(is_cookie_parser(use) && private$.is_router){
        .globals$errorLog$log(
          "Cannot pass cookie parser to `Router`, only to `Ambiorix`"
        )
        return(invisible(self))
      }

      if(is_path_to_pattern(use) && private$.is_router){
        .globals$errorLog$log(
          "Cannot pass path to pattern converter to `Router`, only to `Ambiorix`"
        )
        return(invisible(self))
      }

      if(is_cookie_parser(use)) {
        .globals$cookieParser <- use
        return(invisible(self))
      }

      if(is_path_to_pattern(use)) {
        .globals$pathToPattern <- use
        return(invisible(self))
      }

      if(is_cookie_preprocessor(use) && private$.is_router){
        .globals$errorLog$log(
          "Cannot pass cookie preprocessor to `Router`, only to `Ambiorix`"
        )
        return(invisible(self))
      }

      if(is_cookie_preprocessor(use)) {
        .globals$cookiePreprocessors <- append(
          .globals$cookiePreprocessors,
          use
        )
        return(invisible(self))
      }

      # pass middleware
      if(is.function(use)) { 
        assert_that(is_handler(use))
        private$.middleware <- append(private$.middleware, use)
        return(invisible(self))
      }

      invisible(self)
    },
    #' @details Get the routes
    #' @param routes Existing list of routes.
    #' @param parent Parent path.
    get_routes = function(routes = list(), parent = ""){
      routes <- append(
        routes, 
        private$.routes |>
          lapply(\(route) {
            route$route$as_pattern(parent)
            route$route$decompose(parent)
            route
          })
      )

      if(!length(private$.routers)) return(routes)

      parent <- paste0(parent, private$.basepath)

      for(router in private$.routers) {
        routes <- router$get_routes(routes, parent)
      }

      return(routes)
    },
    #' @details Get the websocket receivers
    #' @param receivers Existing list of receivers
    get_receivers = function(receivers = list()){
      receivers <- append(receivers, private$.receivers)

      if(!length(private$.routers)) return(receivers)

      for(router in private$.routers) {
        receivers <- router$get_receivers(receivers)
      }

      return(receivers)
    },
    #' @details Get the middleware
    #' @param middlewares Existing list of middleswares
    #' @param parent Parent path
    get_middleware = function(middlewares = list(), parent = ""){
      middlewares <- append(
        middlewares,
        private$.middleware |>
          lapply(\(fn) {
            attr(fn, "basepath") <- paste0(parent, private$.basepath) 
            return(fn)
          })
      )

      if(!length(private$.routers)) return(middlewares)

      parent <- paste0(parent, private$.basepath)

      for(router in private$.routers) {
        middlewares <- router$get_middleware(middlewares, parent)
      }

      return(middlewares)
    },
    #' @details Prepare routes and decomposes paths
    prepare = function() {
      for(route in private$.routes) {
        route$route$as_pattern()
        route$route$decompose()
      }

      private$reorder_routes()
      if(!length(private$.routers)) return()

      for(route in private$.routers) {
        route$prepare()
      }
    }
  ),
  active = list(
    basepath = function(path) {
      if(!missing(path)){
        private$.basepath <- path
        return(path)
      }

      invisible(private$.basepath)
    },
    websocket = function(ws){
      if(missing(ws) && !is.null(private$.wss_custom))
        return(private$.wss_custom)

      if(missing(ws) && is.null(private$.wss_custom))
        return(private$.wss)

      private$.wss_custom <- ws
      invisible(self)
    }
  ),
  private = list(
    .basepath = "/",
    .is_router = FALSE,
    .routes = list(),
    .static = list(),
    .receivers = list(),
    .middleware = list(),
    .is_running = FALSE,
    .wss_custom = NULL,
    .routers = list(),
    # we reorder the routes before launching the app
    # we make sure the longest patterns are checked first
    # this makes sure /:id/x matches BEFORE /:id does
    # howerver we also want to try to match extact paths
    # BEFORE dynamic once
    # e.g. /hello should be matched before /:id
    # TODO https://github.com/devOpifex/ambiorix/issues/47
    reorder_routes = function() {
      indices <- seq_along(private$.routes)
      pats <- lapply(private$.routes, \(route) {
        data.frame(
          pattern = route$route$pattern,
          dynamic = route$route$dynamic
        )
      })
      df <- do.call(rbind, pats)
      df$order <- seq_len(nrow(df))
      df$nchar <- nchar(df$pattern)
      df <- df[order(df$dynamic, -df$nchar), ]

      new_routes <- as.list(c(seq_len(nrow(df))))
      for(i in seq_len(nrow(df))) {
        new_routes[[i]] <- private$.routes[[df$order[i]]]
      }

      private$.routes <- new_routes
    },
    .call = function(req){

      request <- Request$new(req)
      res <- Response$new()

      if(length(private$.middleware) > 0L){
        for(i in seq_along(private$.middleware)) {
          mid_basepath <- attr(private$.middleware[[i]], "basepath")

          mid_res <- NULL
          if(grepl(mid_basepath, req$PATH_INFO))
            mid_res <- private$.middleware[[i]](request, res)

          if(is_response(mid_res))
            return(mid_res)
        }
      }
      
      # loop over routes
      for(i in seq_along(private$.routes)){
        # if path matches pattern and method
        if(grepl(private$.routes[[i]]$route$pattern, req$PATH_INFO) &&
            req$REQUEST_METHOD %in% private$.routes[[i]]$method){
          
          .globals$infoLog$log(req$REQUEST_METHOD, "on", req$PATH_INFO)

          # parse request
          request$params <- set_params(request$PATH_INFO, private$.routes[[i]]$route)

          # get response
          response <- tryCatch(
            private$.routes[[i]]$fun(request, res),
            error = function(error){
              error
            }
          )

          if(inherits(response, "error") && !is.null(private$.routes[[i]]$error)){
            return(private$.routes[[i]]$error(request, res, response))
          }

          if(inherits(response, "error") && !is.null(self$error)){
            return(self$error(request, res, response))
          }

          if(promises::is.promising(response)){
            return(
              promises::then(
                response, 
                onFulfilled = function(response){
                  return(
                    response %response% response("Must return a response", status = 206L)
                  )
                },
                onRejected = function(error){
                  message(error)
                  .globals$errorLog$log(req$REQUEST_METHOD, "on", req$PATH_INFO, "-", "Server error")
                  private$.routes[[i]]$error(request, res, error)
                }
              )
            )
          }

          if(is_forward(response))
            next

          # if not a response return something that is
          return(
            response %response% response("Must return a response", status = 206L)
          )
        }
      }

      .globals$errorLog$log(request$REQUEST_METHOD, "on", request$PATH_INFO, "- Not found")

      # return 404
      request$params <- set_params(request$PATH_INFO, Route$new(request$PATH_INFO))
      return(self$not_found(request, res))
    },
    .wss = function(ws){

      # receive
      ws$onMessage(function(binary, message) {
        # don't run if no receiver
        if(length(private$.receivers) == 0) return(NULL)

        message <- jsonlite::fromJSON(message)

        for(i in seq_along(private$.receivers)){
          if(private$.receivers[[i]]$is_handler(message)){
            .globals$infoLog$log("Received message from websocket:", message$name)
            return(private$.receivers[[i]]$receive(message, ws))
          }
        }

      })
    }, 
    n_routes = function(){
      length(private$.routes)
    },
    .make_path = function(path){
      paste0(private$.basepath, path)
    }
  )
)