/**
 * `materialSearch`: the behaviour of `<x-search>` — a search bar that opens into a search view.
 *
 * Focus or a press on the bar opens the view; Escape, the back arrow, a press outside, focus
 * leaving the search, or choosing a result closes it. ArrowDown from the input moves into the
 * results and the arrow keys walk them; ArrowUp past the first result returns to the input. On a
 * compact window (below `medium`, 600px) the view is full screen and modal: focus stays in it and
 * the page behind does not scroll — M3 docks the view from medium upwards. The results themselves
 * are the caller's, rendered by Livewire into the view as the query changes.
 *
 * Because the results arrive from the server, nothing in the page tells a screen reader they are
 * there; M3 asks that it be told. A MutationObserver counts the list items whenever the view's DOM
 * settles and writes "N results" into the polite live region the view renders, which is the one
 * announcement M3's search accessibility page names. With a `suggestions` slot, whichever of the
 * two lists is on screen is the one counted, and the suggestions are named as such.
 *
 * `trigger` is M3's entry point: the bar itself, or `icon` — a single search icon button that
 * expands into the full-screen view wherever the window is wide enough to dock, because an icon
 * button has nowhere to dock under.
 *
 * A full-screen view closes back into the bar or the icon it came from (M3's search view), so the
 * full-screen layout outlives `open` by the view's own exit: `leaving` holds `fullScreen` — and with
 * it `data-md-full-screen`, the fixed header bar and the back arrow — until the view's closing
 * transition has run, while the header bar fades out with it (search.css). Without it the bar went
 * back to its resting form, or to nothing behind the icon, on the first frame of the exit, and the
 * fading view dropped to the docked layout. The focus trap lets go at the close itself, not at the
 * end of the exit, so `returning` (close()) covers its return of focus like the field's own.
 */
import { upTo } from './breakpoints.js'
import { ms } from './util.js'

const FOCUSABLE = 'a[href], button:not([disabled]), input:not([disabled]), select:not([disabled]), textarea:not([disabled]), [tabindex]:not([tabindex="-1"])'

const CHOOSES = 'a[href], button:not([disabled]), [data-md-list-open]'

// A Livewire morph replaces the results in several mutations; wait for the batch to end before
// counting, so the live region speaks once.
const SETTLE_MS = 120

document.addEventListener('alpine:init', () => {
    window.Alpine.data('materialSearch', (docked = false, announce = {}, trigger = 'bar') => ({
        open: false,
        // A full-screen view on its way out; see the file's header.
        leaving: false,
        leavings: 0,
        compact: false,
        // A close is handing focus back; see close().
        returning: false,
        announcement: '',
        // What is in the field, which is what tells suggestions from results.
        query: '',
        observer: null,
        settle: null,

        init() {
            const media = upTo('medium')

            this.compact = media.matches
            media.addEventListener('change', (event) => (this.compact = event.matches))

            // Alpine registers x-ref as it walks the children, which is after this runs.
            this.$nextTick(() => {
                this.query = this.$refs.input?.value ?? ''
                this.observer = new MutationObserver(() => this.countLater())
                this.observer.observe(this.$refs.view, { childList: true, subtree: true, characterData: true })
            })

            this.$watch('open', () => this.countLater())
        },

        destroy() {
            this.observer?.disconnect()
            clearTimeout(this.settle)
        },

        countLater() {
            clearTimeout(this.settle)
            this.settle = setTimeout(() => this.count(), SETTLE_MS)
        },

        count() {
            if (! this.open || ! this.$refs.view) {
                this.announcement = ''

                return
            }

            // Suggestions and results never show together; count whichever one is on screen.
            const list = [...this.$refs.view.querySelectorAll('[data-md-search-results], [data-md-search-suggestions]')]
                .find((element) => element.getClientRects().length > 0)
            const items = list ? list.querySelectorAll('[role="listitem"], li') : []
            const total = items.length || (list ? this.results().length : 0)
            const suggesting = Boolean(list?.hasAttribute('data-md-search-suggestions'))

            this.announcement = total === 0
                ? (announce.none ?? '')
                : total === 1
                    ? ((suggesting ? announce.suggestionOne : announce.one) ?? '')
                    : ((suggesting ? announce.suggestionMany : announce.many) ?? '').replace(':count', total)
        },

        get fullScreen() {
            // An icon button has nothing to dock under, so M3's icon entry point always expands.
            return (this.open || this.leaving) && (trigger === 'icon' || (this.compact && !docked))
        },

        show() {
            this.leavings++
            this.leaving = false
            this.open = true
        },

        /** M3's search-icon entry point: the button opens the view and hands over focus. */
        expand() {
            this.show()
            this.$nextTick(() => requestAnimationFrame(() => this.$refs.input?.focus()))
        },

        /** Every keystroke: the view opens, and the query decides suggestions or results. */
        typed(event) {
            this.query = event.target.value
            this.show()
        },

        focused() {
            if (!this.returning) {
                this.show()
            }
        },

        /**
         * `refocus` puts focus back where the view came from: the icon button, or the field itself.
         *
         * Either way a close hands focus back — the full-screen view's focus trap returns it as it
         * lets go, whether this asked for it or not — and that focus must not read as someone
         * coming to search, or the view would open again on its way out. `returning` covers it
         * until the hand-back has run, rather than for a fixed stretch of wall-clock time after
         * the close: both returns are scheduled on frames, and a runner painting a handful of
         * frames a second takes longer over one than any such guard would allow, which left the
         * view open for good.
         */
        close(refocus = false) {
            const fromFullScreen = this.open && this.fullScreen
            const back = refocus ? (this.$refs.trigger ?? this.$refs.input) : null

            this.open = false
            this.returning = true

            if (fromFullScreen) {
                this.hold()
            }

            // A frame after the tick, as `expand()` waits: the icon button is `x-show`n, and Alpine
            // only shows it on that frame, so a focus in the tick reaches a hidden button, which
            // Firefox and WebKit refuse (in Chrome the trap's own return had covered for it).
            this.$nextTick(() => requestAnimationFrame(() => {
                back?.focus()
                this.returning = false
            }))
        },

        /**
         * Keeps the full-screen layout for the length of the view's exit — the duration search.css
         * gives it, which is also the one Alpine's `x-transition` holds its `display` for, so the
         * two end together. Reopening, which counts `leavings` up, lets a pending end go by, and
         * reduced motion zeroes the token, which ends the hold on the next task, as it should.
         *
         * The duration rather than the exit's own animations: `getAnimations()` is empty both
         * before an engine has created the transitions and after they have finished, and nothing
         * on the element tells the two apart. Waiting a frame or two for them to appear only moves
         * the guess — a loaded engine can leave a second between two frames, and holding for what
         * it had not started yet ended the full-screen layout at once, mid-exit.
         */
        hold() {
            const leaving = ++this.leavings

            this.leaving = true

            setTimeout(() => {
                if (leaving === this.leavings) {
                    this.leaving = false
                }
            }, ms(this.$refs.view, '--md-sys-motion-spatial-fast-duration') ?? 0)
        },

        clear() {
            const input = this.$refs.input

            input.value = ''
            this.query = ''
            input.dispatchEvent(new Event('input', { bubbles: true }))
            input.focus()
        },

        results() {
            return [...this.$refs.view.querySelectorAll(FOCUSABLE)].filter((element) => element.getClientRects().length > 0)
        },

        step(delta) {
            const results = this.results()
            const index = results.indexOf(document.activeElement)

            if (results.length === 0) {
                return
            }

            if (index === -1) {
                results[delta > 0 ? 0 : results.length - 1].focus()
            } else if (index + delta < 0) {
                this.$refs.input.focus()
            } else {
                results[Math.min(index + delta, results.length - 1)].focus()
            }
        },

        choose(event) {
            if (event.target.closest(CHOOSES)) {
                this.close()
            }
        },

        leave(event) {
            if (event.relatedTarget && !this.$root.contains(event.relatedTarget)) {
                this.close()
            }
        },
    }))
})