From da4cb2f90aac299e3d958b8ebd08888fc76044d5 Mon Sep 17 00:00:00 2001
From: Albert Sverdlov <sverdlovalbert@gmail.com>
Date: Tue, 2 Jul 2019 00:37:30 +0300
Subject: [PATCH] router: route specificity by symbols known

Now we prioritize route (a) over (b) for some
request that matches both:

1. if it has more "constant" symbols (that is
symbols hardcoded in the path and not matched
in regexp group generated from : or * stashes),
or, if this number is equal,
2. if (a) has more specific filter on HTTP method
---
 http/router/matching.lua | 18 ++++++++++++++----
 test/http.test.lua       | 31 +++++++++++++++++++++++++++++--
 2 files changed, 43 insertions(+), 6 deletions(-)

diff --git a/http/router/matching.lua b/http/router/matching.lua
index 322c29c..2733779 100644
--- a/http/router/matching.lua
+++ b/http/router/matching.lua
@@ -77,9 +77,19 @@ local function matches(r, filter)
         return false
     end
 
+    -- how many symbols were not known (were hidden behind : and * patterns)
+    local symbols_didnt_know = 0
+    for _, matched_part in ipairs(regex_groups_matched) do
+        symbols_didnt_know = symbols_didnt_know + #matched_part
+    end
+
     return true, {
         route = r,
         stash = regex_groups_matched,
+
+        -- the more symbols were known in advance by route,
+        -- the more priority we give the route
+        specificity = -symbols_didnt_know,
     }
 end
 
@@ -91,10 +101,10 @@ local function better_than(newmatch, oldmatch)
         return true
     end
 
-    -- current match (route) is prioritized iff:
-    -- 1. it has less matched words, or
-    -- 2. if current match (route) has more specific method filter
-    if #oldmatch.stash > #newmatch.stash then
+    -- newmatch route is prioritized over oldmatch iff:
+    -- 1. its' path is more specific (see matches() function), or
+    -- 2. if current route has more specific method filter
+    if newmatch.specificity > oldmatch.specificity then
         return true
     end
     return newmatch.route.method ~= oldmatch.route.method and
diff --git a/test/http.test.lua b/test/http.test.lua
index a1fc1e9..4324c89 100755
--- a/test/http.test.lua
+++ b/test/http.test.lua
@@ -257,7 +257,7 @@ test:test("server url_for", function(test)
 end)
 
 test:test("server requests", function(test)
-    test:plan(42)
+    test:plan(43)
     local httpd, router = cfgserv()
     httpd:start()
 
@@ -501,7 +501,6 @@ test:test("server requests", function(test)
         test:is(parsed_body.read_cached, 'hello mister', 'non-json req:read_cached()')
     end)
 
-
     if is_builtin_test() then
         test:test('post body', function(test)
             test:plan(2)
@@ -569,6 +568,34 @@ test:test("server requests", function(test)
         test:ok(true, 'pong received - ignored on NGINX')
     end
 
+    test:test('prioritization of more specific routes', function(test)
+        test:plan(4)
+
+        router:route({method = 'GET', path = '*stashname'}, function(_)
+            return {
+                status = 200,
+                body = 'GET *',
+            }
+        end)
+        local r = http_client.get('http://127.0.0.1:12345/a/b/c')
+        test:is(r.status, 200, '/a/b/c request returns 200')
+        test:is(r.body, 'GET *', 'GET * matches')
+
+        router:route({method = 'ANY', path = '/a/:foo/:bar'}, function(_)
+            return {
+                status = 200,
+                body = 'ANY /a/:foo/:bar',
+            }
+        end)
+        local r = http_client.get('http://127.0.0.1:12345/a/b/c')
+        test:is(r.status, 200, '/a/b/c request returns 200')
+        test:is(
+            r.body,
+            'ANY /a/:foo/:bar',
+            '# of stashes matched doesnt matter - only # of known symbols by the route matters'
+        )
+    end)
+
     httpd:stop()
 end)