[feature] Allow newly uploaded emojis to be placed in categories (#939)

* [feature] Add emoji categories GET
Serialize emojis in appropriate categories; make it possible to get categories via the admin API

* [feature] Create (or use existing) category for new emoji uploads

* fix lint issue

* update misleading line in swagger docs

internal/cache/emojicategory.go

@@ -0,0 +1,84 @@
+/*
+   GoToSocial
+   Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package cache
+
+import (
+	"strings"
+	"time"
+
+	"codeberg.org/gruf/go-cache/v2"
+	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
+)
+
+// EmojiCategoryCache is a cache wrapper to provide ID lookups for gtsmodel.EmojiCategory
+type EmojiCategoryCache struct {
+	cache cache.LookupCache[string, string, *gtsmodel.EmojiCategory]
+}
+
+// NewEmojiCategoryCache returns a new instantiated EmojiCategoryCache object
+func NewEmojiCategoryCache() *EmojiCategoryCache {
+	c := &EmojiCategoryCache{}
+	c.cache = cache.NewLookup(cache.LookupCfg[string, string, *gtsmodel.EmojiCategory]{
+		RegisterLookups: func(lm *cache.LookupMap[string, string]) {
+			lm.RegisterLookup("name")
+		},
+
+		AddLookups: func(lm *cache.LookupMap[string, string], emojiCategory *gtsmodel.EmojiCategory) {
+			lm.Set(("name"), strings.ToLower(emojiCategory.Name), emojiCategory.ID)
+		},
+
+		DeleteLookups: func(lm *cache.LookupMap[string, string], emojiCategory *gtsmodel.EmojiCategory) {
+			lm.Delete("name", strings.ToLower(emojiCategory.Name))
+		},
+	})
+	c.cache.SetTTL(time.Minute*5, false)
+	c.cache.Start(time.Second * 10)
+	return c
+}
+
+// GetByID attempts to fetch an emojiCategory from the cache by its ID, you will receive a copy for thread-safety
+func (c *EmojiCategoryCache) GetByID(id string) (*gtsmodel.EmojiCategory, bool) {
+	return c.cache.Get(id)
+}
+
+// GetByName attempts to fetch an emojiCategory from the cache by its name, you will receive a copy for thread-safety
+func (c *EmojiCategoryCache) GetByName(name string) (*gtsmodel.EmojiCategory, bool) {
+	return c.cache.GetBy("name", strings.ToLower(name))
+}
+
+// Put places an emojiCategory in the cache, ensuring that the object place is a copy for thread-safety
+func (c *EmojiCategoryCache) Put(emoji *gtsmodel.EmojiCategory) {
+	if emoji == nil || emoji.ID == "" {
+		panic("invalid emoji")
+	}
+	c.cache.Set(emoji.ID, copyEmojiCategory(emoji))
+}
+
+func (c *EmojiCategoryCache) Invalidate(emojiID string) {
+	c.cache.Invalidate(emojiID)
+}
+
+func copyEmojiCategory(emojiCategory *gtsmodel.EmojiCategory) *gtsmodel.EmojiCategory {
+	return &gtsmodel.EmojiCategory{
+		ID:        emojiCategory.ID,
+		CreatedAt: emojiCategory.CreatedAt,
+		UpdatedAt: emojiCategory.UpdatedAt,
+		Name:      emojiCategory.Name,
+	}
+}