const findFocusable = (element: any, programmatic = false) => {
    if (!element) {
        return null
    }
    if (programmatic) {
        return element.querySelectorAll(`*[tabindex="-1"]`)
    }
    return element.querySelectorAll(`a[href]:not([tabindex="-1"]),
                                     area[href],
                                     input:not([disabled]),
                                     select:not([disabled]),
                                     textarea:not([disabled]),
                                     button:not([disabled]),
                                     iframe,
                                     object,
                                     embed,
                                     *[tabindex]:not([tabindex="-1"]),
                                     *[contenteditable]`)
}

let onKeyDown: any

const bind = (el: any, { value = true }) => {
    if (value) {
        let focusable = findFocusable(el)
        let focusableProg = findFocusable(el, true)

        if (focusable && focusable.length > 0) {
            onKeyDown = (event: any) => {
                // Need to get focusable each time since it can change between key events
                // ex. changing month in a datepicker
                focusable = findFocusable(el)
                focusableProg = findFocusable(el, true)
                const firstFocusable = focusable[0]
                const lastFocusable = focusable[focusable.length - 1]

                if (event.target === firstFocusable && event.shiftKey && event.key === 'Tab') {
                    event.preventDefault()
                    lastFocusable.focus()
                } else if ((event.target === lastFocusable || Array.from(focusableProg).indexOf(event.target) >= 0) && !event.shiftKey && event.key === 'Tab') {
                    event.preventDefault()
                    firstFocusable.focus()
                }
            }
            el.addEventListener('keydown', onKeyDown)
        }
    }
}

const unbind = (el: any) => {
    el.removeEventListener('keydown', onKeyDown)
}

const directive = {
    beforeMount: bind,
    beforeUnmount: unbind,
}

export default directive