import type { Context } from '../context/grid-context'

const ensureVisibleVertical = (
    element: HTMLElement,
    scroller: HTMLDivElement,
    footerHeight: number,
    headerHeight: number
) => {
    const bounds = scroller.getBoundingClientRect()
    const scrollbarHeight = scroller.offsetHeight - scroller.clientHeight
    const adjustedTop = bounds.top + headerHeight
    const adjustedBottom = bounds.bottom - footerHeight - scrollbarHeight
    const availableHeight = adjustedBottom - adjustedTop
    const targetBounds = element.getBoundingClientRect()

    if (availableHeight > 0) {
        if (targetBounds.top < adjustedTop) {
            const diff = adjustedTop - targetBounds.top
            scroller.scrollTop -= diff
        } else if (targetBounds.bottom > adjustedBottom) {
            const diff = targetBounds.bottom - adjustedBottom
            scroller.scrollTop += diff
        }
    }
}

const ensureVisibleHorizontal = (
    element: HTMLElement,
    scroller: HTMLDivElement,
    stickyWidthLeft: number,
    stickyWidthRight: number
) => {
    const bounds = scroller.getBoundingClientRect()
    const scrollbarWidth = scroller.offsetWidth - scroller.clientWidth
    const adjustedLeft = bounds.left + stickyWidthLeft
    const adjustedRight = bounds.right - stickyWidthRight - scrollbarWidth
    const availableWidth = adjustedRight - adjustedLeft
    const targetBounds = element.getBoundingClientRect()

    if (availableWidth <= 0) {
        return
    }

    if (targetBounds.left < adjustedLeft) {
        /* Regardless of if the cell can fully fit on screen, align the left with the visible area */
        const diff = adjustedLeft - targetBounds.left
        scroller.scrollLeft -= diff
    } else if (targetBounds.right > adjustedRight) {
        if (availableWidth > targetBounds.width) {
            /* Full cell can fit in the available area. Move as little as needed
            to bring the cell fully into view */
            const diff = targetBounds.right - adjustedRight
            scroller.scrollLeft += diff
        } else {
            /* Full cell cannot fit on screen, align the left with the visible area */
            const diff = adjustedLeft - targetBounds.left
            scroller.scrollLeft -= diff
        }
    }
}

export function ensureRowIsVisible(
    row: HTMLTableRowElement,
    scroller: HTMLDivElement,
    grid: Context
) {
    const state = grid.getState()
    const area = grid.selectors.selectCurrentFocus(state).area
    const footerHeight = grid.selectors.selectAggregationEnabled(state)
        ? grid.selectors.selectRowHeight(state)
        : 0
    const headerHeight = grid.selectors.selectHeaderHeight(state)
    if (area === 'body') {
        ensureVisibleVertical(row, scroller, footerHeight, headerHeight)
    }
}

export function ensureCellIsVisible(
    cell: HTMLTableCellElement,
    scroller: HTMLDivElement,
    grid: Context
) {
    /* aria-column indexes are 1 based, so we subtract 1 */
    const columnIndex = Number(cell.getAttribute('aria-colindex')) - 1
    const state = grid.getState()
    const area = grid.selectors.selectCurrentFocus(state).area
    const footerHeight = grid.selectors.selectAggregationEnabled(state)
        ? grid.selectors.selectRowHeight(state)
        : 0
    const headerHeight = grid.selectors.selectHeaderHeight(state)
    const sticky = grid.selectors.selectStickyColumnDetails(state)
    const columnIsSticky = sticky.indexes.has(columnIndex)

    if (area === 'body') {
        ensureVisibleVertical(cell, scroller, footerHeight, headerHeight)
    }

    if (!columnIsSticky) {
        ensureVisibleHorizontal(
            cell,
            scroller,
            sticky.left.width,
            sticky.right.width
        )
    }
}