writeonce/docs/examples/writeonce-framework/app.wo

-- app.wo — the assembly: an App holds the middleware chains and the route
-- table, satisfies internal's Dispatcher interface, and serves.
--
--   let app = App { middleware: [], gmw: [], afters: [], routes: [] };
--   app.use_mw(Mw { m: Auth { token: t } });
--   app.use_after(Aw { a: SecurityHeaders {} });
--   app.add(Route { method: "GET", pattern: "/products/:id", h: Show {} });
--   return app.serve("127.0.0.1", port);
--
-- Dispatch order: global middleware in registration order (a Resp
-- short-circuits), prefix-scoped group middleware next (framework v1
-- slice 2), then the first matching route (method + pattern), else the
-- framework 404/405 — and EVERY one of those responses passes the after
-- chain (security headers, CORS response headers) before it leaves.
-- The one exception is the WS hijack sentinel (status 101): that
-- response is never serialized, so afters skip it.
-- The serve loop wraps dispatch in `try`, so a trapping handler answers
-- 500 and the server survives.
use http
use router
-- iteration 17: the serve loop is library-internal now (internal/serve.wo).
-- Legal here: the `internal/` boundary refuses CONSUMERS, not the library.
use internal

pub class App {
  middleware: multi Mw
  -- v1 slice 2 additions carry defaults so the standing ctor literal
  -- `App { middleware: [], routes: [] }` keeps compiling everywhere.
  gmw:        multi Gmw = []
  afters:     multi Aw = []
  routes:     multi Route

  fn use_mw(take m: Mw) {
    push(self.middleware, m);
  }

  fn use_after(take a: Aw) {
    push(self.afters, a);
  }

  fn add(take r: Route) {
    push(self.routes, r);
  }

  -- Mount a group: its (already prefixed) routes join the table in
  -- order; its middleware becomes prefix-scoped entries.
  fn mount(take g: Group) {
    while len(g.routes) > 0 {
      push(self.routes, shift(g.routes));
    }
    while len(g.middleware) > 0 {
      let m = shift(g.middleware);
      push(self.gmw, Gmw { prefix: g.prefix, m: m.m });
    }
  }

  -- Registration helpers — the ctor-literal-into-take shape, per method.
  fn get(pattern: Text, take h: Handler) {
    push(self.routes, Route { method: "GET", pattern: pattern, h: h });
  }

  fn post(pattern: Text, take h: Handler) {
    push(self.routes, Route { method: "POST", pattern: pattern, h: h });
  }

  fn put(pattern: Text, take h: Handler) {
    push(self.routes, Route { method: "PUT", pattern: pattern, h: h });
  }

  fn delete_(pattern: Text, take h: Handler) {
    push(self.routes, Route { method: "DELETE", pattern: pattern, h: h });
  }

  -- The pre-after half of dispatch: first Resp wins.
  fn route_req(mut req: Req) -> Resp {
    for mw in self.middleware {
      let short = mw.m.before(req);
      if short != nil { return short; }
    }
    for g in self.gmw {
      if starts_with(req.path, g.prefix) {
        let short = g.m.before(req);
        if short != nil { return short; }
      }
    }
    -- Path-first matching so a wrong-method hit on a known path answers
    -- 405 with the Allow header (registration order) instead of a 404.
    let allow = "";
    for r in self.routes {
      let params: map<Text, Text> = {};
      if route_match(r.pattern, req.path, params) {
        if r.method == req.method {
          -- captures land on the borrowed request itself (mut) — a failed
          -- match above never touched it, since captures collect locally
          for k, v in params { req.params[k] = v; }
          return r.h.handle(req);
        }
        if allow == "" { allow = "${r.method}"; } else { allow = "${allow}, ${r.method}"; }
      }
    }
    if allow != "" { return method_not_allowed(allow); }
    return not_found();
  }

  fn dispatch(mut req: Req) -> Resp {
    let resp = self.route_req(req);
    if resp.status != 101 {
      for aw in self.afters {
        aw.a.after(req, resp);
      }
    }
    return resp;
  }

  fn serve(host: Text, port: Int) -> Int {
    return internal.serve(host, port, self);
  }

  -- iteration 35, the serving slice: serve ONE accepted connection to
  -- completion (the keep-alive loop with deadlines) — the body of an
  -- app-spawned per-connection actor. The app owns the accept loop and
  -- the spawn (a class literal, so the framework cannot spawn it);
  -- each worker builds its own App and calls this. See web-app's
  -- ConnWorker for the ten-line pattern.
  fn handle_conn(c: net.Conn, read_ms: Int, idle_ms: Int) {
    internal.serve_conn(c, self, read_ms, idle_ms);
  }
}