21 lines
506 B
JavaScript
21 lines
506 B
JavaScript
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// @flow
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/**
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* Selector for calculating the number of unread chat messages.
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*
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* @param {Object} state - The redux state.
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* @returns {number} The number of unread messages.
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*/
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export function getUnreadCount(state: Object) {
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const { lastReadMessage, messages } = state['features/chat'];
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const messagesCount = messages.length;
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if (!messagesCount) {
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return 0;
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}
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const lastReadIndex = messages.lastIndexOf(lastReadMessage);
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return messagesCount - (lastReadIndex + 1);
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}
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