support staggard loading of tags

doc/api.oa3

@@ -2982,16 +2982,43 @@ paths:
           description: return updated topics since revision 
           required: false
           schema:
-            type: string
+            type: integer
+            format: int64
+        - name: count
+          in: query
+          description: limit number of latest from latest when revision not set
+          required: false
+          schema:
+            type: integer
+            format: int64
+        - name: begin
+          in: query
+          description: return tags after and including sequence marker
+          required: false
+          schema:
+            type: integer
+            format: int64
+        - name: end
+          in: query
+          description: return tags before and not including sequence marker
+          required: false
+          schema:
+            type: integer
+            format: int64
       responses:
         '200':
           description: successful operation
           headers:
-            X-Tag-Revision:
+            Tag-Revision:
               schema:
                 type: integer
                 format: int64
               description: current tag revision
+            Tag-Marker:
+              schema:
+                type: integer
+                format: int64
+              description: sequnce marker of first tag when count set
           content:
             application/json:
               schema:

net/server/internal/api_getChannelTopicTags.go

@@ -9,9 +9,23 @@ import (
   "databag/internal/store"
 )
 
+func reverseTags(input []store.TagSlot) []store.TagSlot {
+  var output []store.TagSlot
+  for i := len(input) - 1; i >= 0; i-- {
+    output = append(output, input[i])
+  }
+  return output
+}
+
 func GetChannelTopicTags(w http.ResponseWriter, r *http.Request) {
   var revisionSet bool
   var revision int64
+  var beginSet bool
+  var begin int64
+  var endSet bool
+  var end int64
+  var countSet bool
+  var count int
 
   // load channel slot
   channelSlot, _, err, code := getChannelSlot(r, false)
@@ -23,6 +37,7 @@ func GetChannelTopicTags(w http.ResponseWriter, r *http.Request) {
   // scan parameters
   params := mux.Vars(r)
   topicId := params["topicId"]
+
   rev := r.FormValue("revision")
   if rev != "" {
     revisionSet = true
@@ -32,6 +47,33 @@ func GetChannelTopicTags(w http.ResponseWriter, r *http.Request) {
     }
   }
 
+  cnt := r.FormValue("count")
+  if cnt != "" {
+    countSet = true
+    if count, err = strconv.Atoi(cnt); err != nil {
+      ErrResponse(w, http.StatusBadRequest, err)
+      return
+    }
+  }
+
+  bn := r.FormValue("begin")
+  if bn != "" {
+    beginSet = true
+    if begin, err = strconv.ParseInt(bn, 10, 64); err != nil {
+      ErrResponse(w, http.StatusBadRequest, err)
+      return
+    }
+  }
+
+  en := r.FormValue("end")
+  if en != "" {
+    endSet = true
+    if end, err = strconv.ParseInt(en, 10, 64); err != nil {
+      ErrResponse(w, http.StatusBadRequest, err)
+      return
+    }
+  }
+
   // load topic
   var topicSlot store.TopicSlot
   if err = store.DB.Preload("Topic").Where("channel_id = ? AND topic_slot_id = ?", channelSlot.Channel.ID, topicId).First(&topicSlot).Error; err != nil {
@@ -47,24 +89,75 @@ func GetChannelTopicTags(w http.ResponseWriter, r *http.Request) {
     return
   }
 
-  var response []*Tag
+  response := []*Tag{}
   if revisionSet {
     var slots []store.TagSlot
+    if beginSet && !endSet {
+      if err := store.DB.Preload("Tag").Where("topic_id = ? AND revision > ? AND id >= ?", topicSlot.Topic.ID, revision, begin).Find(&slots).Error; err != nil {
+        ErrResponse(w, http.StatusInternalServerError, err)
+        return
+      }
+    } else if !beginSet && endSet {
+      if err := store.DB.Preload("Tag").Where("topic_id = ? AND revision > ? AND id < ?", topicSlot.Topic.ID, revision, end).Find(&slots).Error; err != nil {
+        ErrResponse(w, http.StatusInternalServerError, err)
+        return
+      }
+    } else if beginSet && endSet {
+      if err := store.DB.Preload("Tag").Where("topic_id = ? AND revision > ? AND id >= ? AND id < ?", topicSlot.Topic.ID, revision, begin, end).Find(&slots).Error; err != nil {
+        ErrResponse(w, http.StatusInternalServerError, err)
+        return
+      }
+    } else {
       if err := store.DB.Preload("Tag").Where("topic_id = ? AND revision > ?", topicSlot.Topic.ID, revision).Find(&slots).Error; err != nil {
         ErrResponse(w, http.StatusInternalServerError, err)
         return
       }
+    }
     for _, slot := range slots {
       response = append(response, getTagModel(&slot))
     }
   } else {
     var slots []store.TagSlot
+    if countSet {
+      if !endSet {
+        if err := store.DB.Preload("Tag").Where("topic_id = ?", topicSlot.Topic.ID).Order("id desc").Limit(count).Find(&slots).Error; err != nil {
+          ErrResponse(w, http.StatusInternalServerError, err)
+          return
+        }
+      } else {
+        if err := store.DB.Preload("Tag").Where("topic_id = ? AND id < ?", topicSlot.Topic.ID, end).Order("id desc").Limit(count).Find(&slots).Error; err != nil {
+          ErrResponse(w, http.StatusInternalServerError, err)
+          return
+        }
+      }
+      slots = reverseTags(slots)
+    } else if beginSet && !endSet {
+      if err := store.DB.Preload("Tag").Where("topic_id = ? AND id >= ?", topicSlot.Topic.ID, begin).Find(&slots).Error; err != nil {
+        ErrResponse(w, http.StatusInternalServerError, err)
+        return
+      }
+    } else if !beginSet && endSet {
+      if err := store.DB.Preload("Tag").Where("topic_id = ? AND id < ?", topicSlot.Topic.ID, end).Find(&slots).Error; err != nil {
+        ErrResponse(w, http.StatusInternalServerError, err)
+        return
+      }
+    } else if beginSet && endSet {
+      if err := store.DB.Preload("Tag").Where("topic_id = ? AND id >= ? AND id < ?", topicSlot.Topic.ID, begin, end).Find(&slots).Error; err != nil {
+        ErrResponse(w, http.StatusInternalServerError, err)
+        return
+      }
+    } else {
       if err := store.DB.Preload("Tag").Where("topic_id = ?", topicSlot.Topic.ID).Find(&slots).Error; err != nil {
         ErrResponse(w, http.StatusInternalServerError, err)
         return
       }
+    }
     for _, slot := range slots {
       if slot.Tag != nil {
+        if countSet {
+          w.Header().Set("Tag-Marker", strconv.FormatUint(uint64(slot.ID), 10))
+          countSet = false
+        }
         response = append(response, getTagModel(&slot))
       }
     }

net/server/internal/api_getChannelTopics.go

@@ -6,7 +6,7 @@ import (
   "databag/internal/store"
 )
 
-func reverse(input []store.TopicSlot) []store.TopicSlot {
+func reverseTopics(input []store.TopicSlot) []store.TopicSlot {
   var output []store.TopicSlot
   for i := len(input) - 1; i >= 0; i-- {
     output = append(output, input[i])
@@ -107,7 +107,7 @@ func GetChannelTopics(w http.ResponseWriter, r *http.Request) {
           return
         }
       }
-      slots = reverse(slots)
+      slots = reverseTopics(slots)
     } else if beginSet && !endSet {
       if err := store.DB.Preload("Topic.Assets").Where("channel_id = ? AND id >= ?", channelSlot.Channel.ID, begin).Find(&slots).Error; err != nil {
         ErrResponse(w, http.StatusInternalServerError, err)
@@ -132,7 +132,7 @@ func GetChannelTopics(w http.ResponseWriter, r *http.Request) {
     for _, slot := range slots {
       if slot.Topic != nil {
         if countSet {
-          w.Header().Set("Topic-Index", strconv.FormatUint(uint64(slot.ID), 10))
+          w.Header().Set("Topic-Marker", strconv.FormatUint(uint64(slot.ID), 10))
           countSet = false
         }
         response = append(response, getTopicModel(&slot))