import Mixin from 'ember-metal/mixin';
import run from 'ember-runloop';

export default Mixin.create({
    isLoading: false,
    triggerPoint: 100,

    /**
     * Determines if we are past a scroll point where we need to fetch the next page
     */
    _checkScroll() {
        let element = this.get('element');
        let triggerPoint = this.get('triggerPoint');
        let isLoading = this.get('isLoading');

        // If we haven't passed our threshold or we are already fetching content, exit
        if (isLoading || (element.scrollTop + element.clientHeight + triggerPoint <= element.scrollHeight)) {
            return;
        }

        this.sendAction('fetch');
    },

    didInsertElement() {
        this._super(...arguments);

        let el = this.get('element');

        el.onscroll = run.bind(this, this._checkScroll);

        // run on load, on the offchance that the initial load
        // did not fill the view.
        this._checkScroll();
    },

    willDestroyElement() {
        this._super(...arguments);

        // turn off the scroll handler
        this.get('element').onscroll = null;
    }
});