From 66226b332b36ad707706c576b31700f80b68fa78 Mon Sep 17 00:00:00 2001
From: giles <giles.bradshaw@rose-ash.com>
Date: Sun, 7 Jun 2026 14:29:50 +0000
Subject: [PATCH] dream: router dispatch + path params + scopes + 27 tests

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 lib/dream/conformance.sh  |   4 +-
 lib/dream/router.sx       | 129 +++++++++++++++++++++
 lib/dream/tests/router.sx | 232 ++++++++++++++++++++++++++++++++++++++
 plans/dream-on-sx.md      |  11 +-
 4 files changed, 374 insertions(+), 2 deletions(-)
 create mode 100644 lib/dream/router.sx
 create mode 100644 lib/dream/tests/router.sx

diff --git a/lib/dream/conformance.sh b/lib/dream/conformance.sh
index 2ab78043..16de8614 100644
--- a/lib/dream/conformance.sh
+++ b/lib/dream/conformance.sh
@@ -23,11 +23,13 @@ VERBOSE="${1:-}"
 # Dream library modules loaded before any test suite.
 MODULES=(
   "lib/dream/types.sx"
+  "lib/dream/router.sx"
 )
 
 # Suites: NAME RUNNER-FN PATH
 SUITES=(
-  "types  dream-ty-tests-run!  lib/dream/tests/types.sx"
+  "types   dream-ty-tests-run!  lib/dream/tests/types.sx"
+  "router  dream-rt-tests-run!  lib/dream/tests/router.sx"
 )
 
 TMPFILE=$(mktemp); trap "rm -f $TMPFILE" EXIT
diff --git a/lib/dream/router.sx b/lib/dream/router.sx
new file mode 100644
index 00000000..723e69f6
--- /dev/null
+++ b/lib/dream/router.sx
@@ -0,0 +1,129 @@
+;; lib/dream/router.sx — Dream-on-SX routing.
+;; Routes are dicts {:method :path :handler}; a router is a handler that
+;; dispatches request -> response by method + path, extracting :name path
+;; params and binding a ** catch-all. No match -> 404. Depends on types.sx.
+
+;; ── route constructors (one per HTTP method) ───────────────────────
+(define dream-get (fn (path handler) (dream-route "GET" path handler)))
+(define dream-post (fn (path handler) (dream-route "POST" path handler)))
+(define dream-put (fn (path handler) (dream-route "PUT" path handler)))
+(define
+  dream-delete
+  (fn (path handler) (dream-route "DELETE" path handler)))
+(define dream-patch (fn (path handler) (dream-route "PATCH" path handler)))
+(define dream-head (fn (path handler) (dream-route "HEAD" path handler)))
+(define
+  dream-options
+  (fn (path handler) (dream-route "OPTIONS" path handler)))
+(define dream-any (fn (path handler) (dream-route "ANY" path handler)))
+
+;; ── path segmentation ──────────────────────────────────────────────
+;; "/users/42/" -> ("users" "42"); "/" -> ()
+(define
+  dr/segs
+  (fn (path) (filter (fn (s) (not (= s ""))) (split path "/"))))
+
+(define
+  dr/join-path
+  (fn
+    (prefix path)
+    (str "/" (join "/" (concat (dr/segs prefix) (dr/segs path))))))
+
+;; ── segment matching ───────────────────────────────────────────────
+;; Returns a params dict on match (possibly empty {}), nil on no match.
+(define
+  dr/match-segs
+  (fn
+    (pat path params)
+    (cond
+      ((and (empty? pat) (empty? path)) params)
+      ((empty? pat) nil)
+      (else
+        (let
+          ((ps (first pat)))
+          (cond
+            ((= ps "**") (assoc params "**" (join "/" path)))
+            ((empty? path) nil)
+            ((starts-with? ps ":")
+              (dr/match-segs
+                (rest pat)
+                (rest path)
+                (assoc params (substr ps 1) (first path))))
+            ((= ps (first path))
+              (dr/match-segs (rest pat) (rest path) params))
+            (else nil)))))))
+
+(define
+  dr/method-match?
+  (fn
+    (route-method req-method)
+    (or (= route-method "ANY") (= route-method req-method))))
+
+;; ── middleware pipeline (shared with middleware.sx) ────────────────
+;; m1 @@ m2 @@ handler = (m1 (m2 handler)); first in list is outermost.
+(define
+  dr/apply-middlewares
+  (fn (mws handler) (reduce (fn (h mw) (mw h)) handler (reverse mws))))
+
+;; ── scope: prefix mount + middleware chain ─────────────────────────
+;; Returns a flat list of routes; nested scopes flatten correctly.
+(define
+  dr/flatten-routes
+  (fn
+    (items)
+    (reduce
+      (fn
+        (acc it)
+        (if
+          (dream-route? it)
+          (concat acc (list it))
+          (concat acc (dr/flatten-routes it))))
+      (list)
+      items)))
+
+(define
+  dream-scope
+  (fn
+    (prefix middlewares routes)
+    (map
+      (fn
+        (r)
+        (dream-route
+          (dream-route-method r)
+          (dr/join-path prefix (dream-route-path r))
+          (dr/apply-middlewares middlewares (dream-route-handler r))))
+      (dr/flatten-routes routes))))
+
+;; ── dispatch ───────────────────────────────────────────────────────
+(define
+  dr/try-route
+  (fn
+    (r req)
+    (if
+      (dr/method-match? (dream-route-method r) (dream-method req))
+      (let
+        ((params (dr/match-segs (dr/segs (dream-route-path r)) (dr/segs (dream-path req)) {})))
+        (if
+          (nil? params)
+          :no-match (dream-coerce-response
+            ((dream-route-handler r) (dream-with-params req params)))))
+      :no-match)))
+
+(define
+  dr/dispatch
+  (fn
+    (routes req)
+    (if
+      (empty? routes)
+      (dream-not-found)
+      (let
+        ((res (dr/try-route (first routes) req)))
+        (if (= res :no-match) (dr/dispatch (rest routes) req) res)))))
+
+(define
+  dream-router
+  (fn
+    (routes)
+    (let
+      ((flat (dr/flatten-routes routes)))
+      (fn (req) (dr/dispatch flat req)))))
diff --git a/lib/dream/tests/router.sx b/lib/dream/tests/router.sx
new file mode 100644
index 00000000..fc6568fd
--- /dev/null
+++ b/lib/dream/tests/router.sx
@@ -0,0 +1,232 @@
+;; lib/dream/tests/router.sx — routing dispatch, path params, scopes.
+
+(define dream-rt-pass 0)
+(define dream-rt-fail 0)
+(define dream-rt-fails (list))
+
+(define
+  dream-rt-test
+  (fn
+    (name actual expected)
+    (if
+      (= actual expected)
+      (set! dream-rt-pass (+ dream-rt-pass 1))
+      (begin
+        (set! dream-rt-fail (+ dream-rt-fail 1))
+        (append! dream-rt-fails {:name name :actual actual :expected expected})))))
+
+(define
+  dream-rt-req
+  (fn (method target) (dream-request method target {} "")))
+
+;; ── basic dispatch ─────────────────────────────────────────────────
+(define
+  dream-rt-app
+  (dream-router
+    (list
+      (dream-get "/" (fn (req) (dream-text "home")))
+      (dream-get "/about" (fn (req) (dream-text "about")))
+      (dream-post "/submit" (fn (req) (dream-text "posted"))))))
+
+(dream-rt-test
+  "GET / -> home"
+  (dream-resp-body (dream-rt-app (dream-rt-req "GET" "/")))
+  "home")
+(dream-rt-test
+  "GET /about"
+  (dream-resp-body (dream-rt-app (dream-rt-req "GET" "/about")))
+  "about")
+(dream-rt-test
+  "POST /submit"
+  (dream-resp-body (dream-rt-app (dream-rt-req "POST" "/submit")))
+  "posted")
+(dream-rt-test
+  "unknown path 404"
+  (dream-status (dream-rt-app (dream-rt-req "GET" "/nope")))
+  404)
+(dream-rt-test
+  "wrong method 404"
+  (dream-status (dream-rt-app (dream-rt-req "GET" "/submit")))
+  404)
+(dream-rt-test
+  "trailing slash equiv"
+  (dream-resp-body (dream-rt-app (dream-rt-req "GET" "/about/")))
+  "about")
+(dream-rt-test
+  "query ignored for routing"
+  (dream-resp-body (dream-rt-app (dream-rt-req "GET" "/about?x=1")))
+  "about")
+
+;; ── path params ────────────────────────────────────────────────────
+(define
+  dream-rt-papp
+  (dream-router
+    (list
+      (dream-get
+        "/users/:id"
+        (fn (req) (dream-text (dream-param req "id"))))
+      (dream-get
+        "/users/:id/posts/:pid"
+        (fn
+          (req)
+          (dream-text
+            (str (dream-param req "id") "-" (dream-param req "pid")))))
+      (dream-get
+        "/files/**"
+        (fn (req) (dream-text (dream-param req "**")))))))
+
+(dream-rt-test
+  "single param"
+  (dream-resp-body (dream-rt-papp (dream-rt-req "GET" "/users/42")))
+  "42")
+(dream-rt-test
+  "two params"
+  (dream-resp-body (dream-rt-papp (dream-rt-req "GET" "/users/7/posts/9")))
+  "7-9")
+(dream-rt-test
+  "param no over-match"
+  (dream-status (dream-rt-papp (dream-rt-req "GET" "/users/7/extra")))
+  404)
+(dream-rt-test
+  "catch-all captures rest"
+  (dream-resp-body (dream-rt-papp (dream-rt-req "GET" "/files/a/b/c.txt")))
+  "a/b/c.txt")
+(dream-rt-test
+  "catch-all empty rest"
+  (dream-resp-body (dream-rt-papp (dream-rt-req "GET" "/files/")))
+  "")
+
+;; ── route order: first match wins ──────────────────────────────────
+(define
+  dream-rt-order
+  (dream-router
+    (list
+      (dream-get "/x/specific" (fn (req) (dream-text "specific")))
+      (dream-get "/x/:slug" (fn (req) (dream-text "generic"))))))
+(dream-rt-test
+  "first match wins"
+  (dream-resp-body (dream-rt-order (dream-rt-req "GET" "/x/specific")))
+  "specific")
+(dream-rt-test
+  "fallthrough to param"
+  (dream-resp-body (dream-rt-order (dream-rt-req "GET" "/x/other")))
+  "generic")
+
+;; ── ANY method ─────────────────────────────────────────────────────
+(define
+  dream-rt-any
+  (dream-router
+    (list (dream-any "/ping" (fn (req) (dream-text (dream-method req)))))))
+(dream-rt-test
+  "ANY matches GET"
+  (dream-resp-body (dream-rt-any (dream-rt-req "GET" "/ping")))
+  "GET")
+(dream-rt-test
+  "ANY matches DELETE"
+  (dream-resp-body (dream-rt-any (dream-rt-req "DELETE" "/ping")))
+  "DELETE")
+
+;; ── handler returns bare string (coerced) ──────────────────────────
+(define
+  dream-rt-coerce
+  (dream-router (list (dream-get "/s" (fn (req) "bare")))))
+(dream-rt-test
+  "string coerced to 200"
+  (dream-status (dream-rt-coerce (dream-rt-req "GET" "/s")))
+  200)
+(dream-rt-test
+  "string coerced body"
+  (dream-resp-body (dream-rt-coerce (dream-rt-req "GET" "/s")))
+  "bare")
+
+;; ── scope: prefix mount ────────────────────────────────────────────
+(define
+  dream-rt-scoped
+  (dream-router
+    (list
+      (dream-get "/" (fn (req) (dream-text "root")))
+      (dream-scope
+        "/api"
+        (list)
+        (list
+          (dream-get "/users" (fn (req) (dream-text "api-users")))
+          (dream-get
+            "/users/:id"
+            (fn
+              (req)
+              (dream-text (str "api-user-" (dream-param req "id"))))))))))
+(dream-rt-test
+  "scope root still works"
+  (dream-resp-body (dream-rt-scoped (dream-rt-req "GET" "/")))
+  "root")
+(dream-rt-test
+  "scope prefix path"
+  (dream-resp-body (dream-rt-scoped (dream-rt-req "GET" "/api/users")))
+  "api-users")
+(dream-rt-test
+  "scope prefix param"
+  (dream-resp-body (dream-rt-scoped (dream-rt-req "GET" "/api/users/5")))
+  "api-user-5")
+(dream-rt-test
+  "scope unprefixed 404"
+  (dream-status (dream-rt-scoped (dream-rt-req "GET" "/users")))
+  404)
+
+;; ── scope: middleware applied to all routes ────────────────────────
+(define
+  dream-rt-mw
+  (fn (next) (fn (req) (dream-add-header (next req) "X-Scope" "on"))))
+(define
+  dream-rt-mwapp
+  (dream-router
+    (list
+      (dream-scope
+        "/v1"
+        (list dream-rt-mw)
+        (list (dream-get "/a" (fn (req) (dream-text "a"))))))))
+(dream-rt-test
+  "scope mw header"
+  (dream-resp-header (dream-rt-mwapp (dream-rt-req "GET" "/v1/a")) "x-scope")
+  "on")
+(dream-rt-test
+  "scope mw body intact"
+  (dream-resp-body (dream-rt-mwapp (dream-rt-req "GET" "/v1/a")))
+  "a")
+
+;; ── nested scopes ──────────────────────────────────────────────────
+(define
+  dream-rt-outer
+  (fn (next) (fn (req) (dream-add-header (next req) "X-Outer" "1"))))
+(define
+  dream-rt-inner
+  (fn (next) (fn (req) (dream-add-header (next req) "X-Inner" "1"))))
+(define
+  dream-rt-nested
+  (dream-router
+    (list
+      (dream-scope
+        "/api"
+        (list dream-rt-outer)
+        (list
+          (dream-scope
+            "/v2"
+            (list dream-rt-inner)
+            (list (dream-get "/thing" (fn (req) (dream-text "thing"))))))))))
+(dream-rt-test
+  "nested path"
+  (dream-resp-body (dream-rt-nested (dream-rt-req "GET" "/api/v2/thing")))
+  "thing")
+(dream-rt-test
+  "nested outer mw"
+  (dream-resp-header
+    (dream-rt-nested (dream-rt-req "GET" "/api/v2/thing"))
+    "x-outer")
+  "1")
+(dream-rt-test
+  "nested inner mw"
+  (dream-resp-header
+    (dream-rt-nested (dream-rt-req "GET" "/api/v2/thing"))
+    "x-inner")
+  "1")
+
+(define dream-rt-tests-run! (fn () {:total (+ dream-rt-pass dream-rt-fail) :passed dream-rt-pass :failed dream-rt-fail :fails dream-rt-fails}))
diff --git a/plans/dream-on-sx.md b/plans/dream-on-sx.md
index 3cc80f94..555d54f6 100644
--- a/plans/dream-on-sx.md
+++ b/plans/dream-on-sx.md
@@ -45,7 +45,7 @@ The user-facing story: rose-ash users who'd never touch s-expressions might writ
 The five types: `request`, `response`, `handler = request -> response`, `middleware = handler -> handler`, `route`. Everything else is a function over these.
 
 - [x] **Core types** in `lib/dream/types.sx`: request/response records, route record.
-- [ ] **Router** in `lib/dream/router.sx`:
+- [x] **Router** in `lib/dream/router.sx`:
       - `dream-get path handler`, `dream-post path handler`, etc. for all HTTP methods.
       - `dream-scope prefix middlewares routes` — prefix mount with middleware chain.
       - `dream-router routes` — dispatch tree, returns handler; no match → 404.
@@ -112,6 +112,15 @@ Confirm scope before starting; some of these may be addable as Dream-internal he
   constructors + accessors; smart response constructors (html/text/json/empty/
   not-found/redirect); `dream-coerce-response` wraps bare strings; query-string
   parsing. Conformance runner `lib/dream/conformance.sh` modelled on flow's.
+- **2026-06-07 — Router** (`lib/dream/router.sx`, 27 tests). `dream-get/post/put/
+  delete/patch/head/options/any` route constructors; `dream-router` flattens routes
+  (incl. nested scopes) and dispatches by method+path, first-match-wins, 404 on no
+  match. Path matching is recursive over `/`-split segments: literal, `:name` binds
+  a param, `**` catch-all binds remaining path under key `"**"`. Trailing slashes and
+  query strings are ignored for routing. `dream-scope prefix mws routes` prepends the
+  prefix and folds the middleware chain (`m1 @@ m2 @@ h`, first = outermost) onto each
+  route's handler; nests correctly (inner mw innermost). Shared `dr/apply-middlewares`
+  fold will back `dream-pipeline`.
 
 ## Blockers