cache combos between pages

cache.go

@@ -0,0 +1,65 @@
+//
+// Copyright (c) 2019 Ted Unangst <tedu@tedunangst.com>
+//
+// Permission to use, copy, modify, and distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+package main
+
+import (
+	"reflect"
+	"sync"
+)
+
+type cacheFiller func(key interface{}) (interface{}, bool)
+
+type Cache struct {
+	cache  map[interface{}]interface{}
+	filler cacheFiller
+	lock   sync.Mutex
+}
+
+func cacheNew(filler cacheFiller) *Cache {
+	c := new(Cache)
+	c.cache = make(map[interface{}]interface{})
+	c.filler = filler
+	return c
+}
+
+func (cache *Cache) Get(key interface{}, value interface{}) bool {
+	cache.lock.Lock()
+	defer cache.lock.Unlock()
+	v, ok := cache.cache[key]
+	if !ok {
+		v, ok = cache.filler(key)
+		if ok {
+			cache.cache[key] = v
+		}
+	}
+	if ok {
+		ptr := reflect.ValueOf(v)
+		reflect.ValueOf(value).Elem().Set(ptr)
+	}
+	return ok
+}
+
+func (cache *Cache) Clear(key interface{}) {
+	cache.lock.Lock()
+	defer cache.lock.Unlock()
+	delete(cache.cache, key)
+}
+
+func (cache *Cache) Flush() {
+	cache.lock.Lock()
+	defer cache.lock.Unlock()
+	cache.cache = make(map[interface{}]interface{})
+}

web.go

@@ -1079,10 +1079,9 @@ func showhonkers(w http.ResponseWriter, r *http.Request) {
 	}
 }
 
-func showcombos(w http.ResponseWriter, r *http.Request) {
-	userinfo := login.GetUserInfo(r)
-	templinfo := getInfo(r)
-	honkers := gethonkers(userinfo.UserID)
+var combocache = cacheNew(func(key interface{}) (interface{}, bool) {
+	userid := key.(int64)
+	honkers := gethonkers(userid)
 	var combos []string
 	for _, h := range honkers {
 		combos = append(combos, h.Combos...)
@@ -1094,6 +1093,14 @@ func showcombos(w http.ResponseWriter, r *http.Request) {
 	}
 	combos = oneofakind(combos)
 	sort.Strings(combos)
+	return combos, true
+})
+
+func showcombos(w http.ResponseWriter, r *http.Request) {
+	userinfo := login.GetUserInfo(r)
+	var combos []string
+	combocache.Get(userinfo.UserID, &combos)
+	templinfo := getInfo(r)
 	templinfo["Combos"] = combos
 	err := readviews.Execute(w, "combos.html", templinfo)
 	if err != nil {
@@ -1109,6 +1116,8 @@ func submithonker(w http.ResponseWriter, r *http.Request) {
 	combos := r.FormValue("combos")
 	honkerid, _ := strconv.ParseInt(r.FormValue("honkerid"), 10, 0)
 
+	defer combocache.Clear(u.UserID)
+
 	if honkerid > 0 {
 		goodbye := r.FormValue("goodbye")
 		if goodbye == "F" {