class Sizer {
    constructor(container, vertical, reverse) {
        this.container = container;
        this.reverse = reverse;
        this.vertical = vertical;
    }

    getItemPercentage(item) {
        /*
        const flexGrow = window.getComputedStyle(item).flexGrow;
        if (flexGrow === "") {
            return null;
        }
        return parseInt(flexGrow) / 1000;
        */
        const style = window.getComputedStyle(item);
        const sizeStr = this.vertical ? style.height : style.width;
        const size = parseInt(sizeStr, 10);
        return size / this.getTotalSize();
    }

    setItemPercentage(item, percent) {
        item.style.flexGrow = Math.round(percent * 1000);
    }

    /** returns how far the edge of the item is from the edge of the container */
    getItemOffset(item) {
        const offset = (this.vertical ? item.offsetTop : item.offsetLeft) - this._getOffset();
        if (this.reverse) {
            return this.getTotalSize() - (offset + this.getItemSize(item));
        } else {
            return offset;
        }
    }

    /** returns the width/height of an item in the container */
    getItemSize(item) {
        return this.vertical ? item.offsetHeight : item.offsetWidth;
    }

    /** returns the width/height of the container */
    getTotalSize() {
        return this.vertical ? this.container.offsetHeight : this.container.offsetWidth;
    }

    /** container offset to offsetParent */
    _getOffset() {
        return this.vertical ? this.container.offsetTop : this.container.offsetLeft;
    }

    setItemSize(item, size) {
        if (this.vertical) {
            item.style.height = `${Math.round(size)}px`;
        } else {
            item.style.width = `${Math.round(size)}px`;
        }
    }

    /** returns the position of cursor at event relative to the edge of the container */
    offsetFromEvent(event) {
        const pos = this.vertical ? event.pageY : event.pageX;
        if (this.reverse) {
            return (this._getOffset() + this.getTotalSize()) - pos;
        } else {
            return pos - this._getOffset();
        }
    }
}

module.exports = {Sizer};