stream-chat-react-native-core/lib/module/hooks/usePrunableMessageList.js

The official React Native and Expo components for Stream Chat, a service for building chat applications

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.usePrunableMessageList = usePrunableMessageList;
var _react = require("react");
var _useStableCallback = require("./useStableCallback");
var calculateSafeGap = maximumMessages => 0.2 * maximumMessages;
var isNearEnd = ({
  rangeConfig,
  maximumMessageLimit
}) => {
  var first = rangeConfig.first,
    last = rangeConfig.last,
    inverted = rangeConfig.inverted;
  var safeGap = calculateSafeGap(maximumMessageLimit);
  if (!inverted) return first <= safeGap;
  return last >= maximumMessageLimit - 1 - safeGap;
};
function usePrunableMessageList({
  setMessages: rawSetMessages,
  maximumMessageLimit
}) {
  var visibleRangeConfigRef = (0, _react.useRef)({
    first: 0,
    inverted: true,
    last: -1
  });
  var viewabilityChangedCallback = (0, _useStableCallback.useStableCallback)(({
    viewableItems,
    inverted = true
  }) => {
    if (!viewableItems?.length || maximumMessageLimit == null) return;
    var first = Infinity;
    var last = -1;
    for (var v of viewableItems) {
      if (v.index == null) continue;
      if (v.index < first) first = v.index;
      if (v.index > last) last = v.index;
    }
    if (first !== Infinity) visibleRangeConfigRef.current = {
      first,
      inverted,
      last
    };
  });
  var setMessages = (0, _useStableCallback.useStableCallback)(channel => {
    var rangeConfig = visibleRangeConfigRef.current;
    if (maximumMessageLimit == null || channel.state.messages.length <= maximumMessageLimit || isNearEnd({
      maximumMessageLimit,
      rangeConfig
    })) {
      rawSetMessages(channel);
      return;
    }
    channel.state.pruneOldest(maximumMessageLimit);
    rawSetMessages(channel);
  });
  return {
    setMessages,
    viewabilityChangedCallback
  };
}
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