LastNonDirectInteraction.ts

import { AttributionModel, Interaction } from '../types';

/**
 * This implements the "last non-direct interaction" attribution model
 * which returns the last non-direct interaction
 * as direct interactions may be logged after non-direct interactions once the specified session-timeout has passed
 *
 * Since only one interaction is returned, it is not weighted
 */
const lastNonDirectInteraction: AttributionModel = (interactions: Interaction[]): Interaction => {
    if (interactions.length === 0) {
        return null;
    }

    const nonExcludedInteractions = interactions.filter((interaction) => !interaction.excluded);
    const nonExcludedNonDirectInteractions = nonExcludedInteractions.filter((interaction) => !interaction.direct);

    // First, we attempt to return the last non-excluded non-direct interaction
    // Then if all we had were excluded and/or direct interactions we attempt to return the last non-excluded direct interaction
    // Then if all we had were excluded interactions we return the last one as it's better than nothing
    return nonExcludedNonDirectInteractions.pop()
        || nonExcludedInteractions.pop()
        || interactions.pop();
}

export default lastNonDirectInteraction;