doFetchSubCount: batch support; fetch interval gap;

1. The API supports batching -- updated the code to use that. Retained string as the parameter (instead of changing it to array) so that existing clients won't be affected.

2. Make `doFetchSubCount` a batched command by default through an idle timer. This way, none of the clients need to collect IDs -- it's all done behind the scenes.

3. Added minimum of 5 minutes between each sub-count fetch for a claim ID.

extras/lbryinc/redux/actions/stats.js

@@ -2,6 +2,9 @@
 import { Lbryio } from 'lbryinc';
 import * as ACTIONS from 'constants/action_types';
 
+const FETCH_SUB_COUNT_MIN_INTERVAL_MS = 5 * 60 * 1000;
+const FETCH_SUB_COUNT_IDLE_FIRE_MS = 100;
+
 export const doFetchViewCount = (claimIdCsv: string) => (dispatch: Dispatch) => {
   dispatch({ type: ACTIONS.FETCH_VIEW_COUNT_STARTED });
 
@@ -10,23 +13,56 @@ export const doFetchViewCount = (claimIdCsv: string) => (dispatch: Dispatch) =>
       const viewCounts = result;
       dispatch({ type: ACTIONS.FETCH_VIEW_COUNT_COMPLETED, data: { claimIdCsv, viewCounts } });
     })
-    .catch(error => {
+    .catch((error) => {
       dispatch({ type: ACTIONS.FETCH_VIEW_COUNT_FAILED, data: error });
     });
 };
 
-export const doFetchSubCount = (claimId: string) => (dispatch: Dispatch) => {
+const executeFetchSubCount = (claimIdCsv: string) => (dispatch: Dispatch, getState: GetState) => {
+  const state = getState();
+  const subCountLastFetchedById = state.stats.subCountLastFetchedById;
+  const now = Date.now();
+
+  const claimIds = claimIdCsv.split(',').filter((id) => {
+    const prev = subCountLastFetchedById[id];
+    return !prev || now - prev > FETCH_SUB_COUNT_MIN_INTERVAL_MS;
+  });
+
+  if (claimIds.length === 0) {
+    return;
+  }
+
   dispatch({ type: ACTIONS.FETCH_SUB_COUNT_STARTED });
 
-  return Lbryio.call('subscription', 'sub_count', { claim_id: claimId })
+  return Lbryio.call('subscription', 'sub_count', { claim_id: claimIds.join(',') })
     .then((result: Array<number>) => {
-      const subCount = result[0];
+      const subCounts = result;
       dispatch({
         type: ACTIONS.FETCH_SUB_COUNT_COMPLETED,
-        data: { claimId, subCount },
+        data: { claimIdCsv, subCounts, fetchDate: now },
       });
     })
-    .catch(error => {
+    .catch((error) => {
       dispatch({ type: ACTIONS.FETCH_SUB_COUNT_FAILED, data: error });
     });
 };
+
+let fetchSubCountTimer;
+let fetchSubCountQueue = '';
+
+export const doFetchSubCount = (claimIdCsv: string) => (dispatch: Dispatch) => {
+  if (fetchSubCountTimer) {
+    clearTimeout(fetchSubCountTimer);
+  }
+
+  if (fetchSubCountQueue && !fetchSubCountQueue.endsWith(',')) {
+    fetchSubCountQueue += ',';
+  }
+
+  fetchSubCountQueue += claimIdCsv;
+
+  fetchSubCountTimer = setTimeout(() => {
+    dispatch(executeFetchSubCount(fetchSubCountQueue));
+    fetchSubCountQueue = '';
+  }, FETCH_SUB_COUNT_IDLE_FIRE_MS);
+};

extras/lbryinc/redux/reducers/stats.js

@@ -8,15 +8,18 @@ const defaultState = {
   fetchingSubCount: false,
   subCountError: undefined,
   subCountById: {},
+  subCountLastFetchedById: {},
 };
 
 export const statsReducer = handleActions(
   {
-    [ACTIONS.FETCH_VIEW_COUNT_STARTED]: state => ({ ...state, fetchingViewCount: true }),
+    [ACTIONS.FETCH_VIEW_COUNT_STARTED]: (state) => ({ ...state, fetchingViewCount: true }),
+
     [ACTIONS.FETCH_VIEW_COUNT_FAILED]: (state, action) => ({
       ...state,
       viewCountError: action.data,
     }),
+
     [ACTIONS.FETCH_VIEW_COUNT_COMPLETED]: (state, action) => {
       const { claimIdCsv, viewCounts } = action.data;
 
@@ -35,20 +38,43 @@ export const statsReducer = handleActions(
         viewCountById,
       };
     },
-    [ACTIONS.FETCH_SUB_COUNT_STARTED]: state => ({ ...state, fetchingSubCount: true }),
+
+    [ACTIONS.FETCH_SUB_COUNT_STARTED]: (state) => ({ ...state, fetchingSubCount: true }),
+
     [ACTIONS.FETCH_SUB_COUNT_FAILED]: (state, action) => ({
       ...state,
       subCountError: action.data,
     }),
-    [ACTIONS.FETCH_SUB_COUNT_COMPLETED]: (state, action) => {
-      const { claimId, subCount } = action.data;
 
-      const subCountById = { ...state.subCountById, [claimId]: subCount };
-      return {
+    [ACTIONS.FETCH_SUB_COUNT_COMPLETED]: (state, action) => {
+      const { claimIdCsv, subCounts, fetchDate } = action.data;
+
+      const subCountById = Object.assign({}, state.subCountById);
+      const subCountLastFetchedById = Object.assign({}, state.subCountLastFetchedById);
+      const claimIds = claimIdCsv.split(',');
+      let dataChanged = false;
+
+      if (claimIds.length === subCounts.length) {
+        claimIds.forEach((claimId, index) => {
+          if (subCountById[claimId] !== subCounts[index]) {
+            subCountById[claimId] = subCounts[index];
+            dataChanged = true;
+          }
+          subCountLastFetchedById[claimId] = fetchDate;
+        });
+      }
+
+      const newState = {
         ...state,
         fetchingSubCount: false,
-        subCountById,
+        subCountLastFetchedById,
       };
+
+      if (dataChanged) {
+        newState.subCountById = subCountById;
+      }
+
+      return newState;
     },
   },
   defaultState