/**
 * `<tab-group />`

A group of tabs, where only one can be visible at a time.

@privateRemarks TODO which form does the HTML document have? For CSS purposes

Each tab consists of two parts, a label which is used for selecting
it, and a tab-element, which contains the actual content. These two
should refer to each other as follows:

@example
```
+---------------+     +-----------------+
|   TabLabel    |     |       Tab       |
+---------------+     +-----------------+
|            id |<----| aria-labelledby |
| aria-controls |---->|              id |
+---------------+     +-----------------+
```

Further information about tabs in HTML can be found here:
https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/Roles/Tab_Role

#### CSS Variables

##### tabcount
Each tab element has the style property `--tabcount` set to how
many tabs it has. This is mostly useful to make sure the tab context
is large enough to fit all tab labels without overflowing.

 *
 * @category Web Components
 * @mergeTarget components
 * @module
 */

import { ComponentVEvent } from './vevent'
import { makeElement, gensym } from '../lib'
import { EditRRule } from './edit-rrule'
import { VEvent, isRedrawable } from '../vevent'
import { vcal_objects } from '../globals'

export { TabGroupElement }

/** Lacks a template, since it's trivial
   The initial children of this element all becomes tabs, each child may have
   the datapropertys 'label' and 'title' set, where label is what is shown in
   the tab bar, and title is the hower text.

   All additions and removals of tabs MUST go through addTab and removeTab!

   Information about how tabs should work from an accesability standpoint can be
   found here:
    https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/Roles/Tab_Role

   <tab-group/>
*/
class TabGroupElement extends ComponentVEvent {

    /** The container holding all the tabLabels */
    readonly menu: HTMLElement;

    /** Contents of each tab */
    tabs: HTMLElement[] = [];
    /** Label element of each tab */
    tabLabels: HTMLElement[] = [];

    constructor(uid?: string) {
        super(uid);

        this.menu = makeElement('div', {}, {
            role: 'tablist',
            'aria-label': 'Simple Tabs',
        })
    }

    redraw(data: VEvent) {
        /* Update our tabset to match data:s having or not having of rrule,
           but do nothing if we already match */
        let rrule_tab = this.has_rrule_tab()
        if (data.getProperty('rrule')) {
            if (!this.has_rrule_tab()) {
                /* Note that EditRRule register itself to be updated on changes
                to the event */
                this.addTab(new EditRRule(data.getProperty('uid')),
                    "↺", "Upprepningar");
            }
        } else {
            if (rrule_tab) this.removeTab(rrule_tab as HTMLElement);
        }

        /* TODO is there any case where we want to propagate the draw to any of
           our tabs? or are all our tabs independent? */
    }

    connectedCallback() {
        /* All pre-added children should become tabs, but start with removing
        them and storing them for later */
        let originalChildren: HTMLElement[] = [];
        while (this.firstChild) {
            originalChildren.push(this.removeChild(this.firstChild) as HTMLElement);
        }

        /* Add our tab label menu */
        this.appendChild(this.menu);

        /* Re-add our initial children, but as proper tab elements */
        for (let child of originalChildren) {
            this.addTab(child);
        }

        /* redraw might add or remove tabs depending on our data, so call it here */
        this.redraw(vcal_objects.get(this.uid)!);

        /* All tabs should now be ready, focus the first one */
        if (this.tabLabels.length > 0) {
            this.tabLabels[0].setAttribute('tabindex', '0');
            this.tabLabels[0].click();
        }

    } /* end connectedCallback */

    /**
       Adds a new tab to the group. The first parameter will make up the body
       of the tab. The label is whath should be shown in the tab selector,
       but defaults to the first letter of the text content of the body node.
       Title is the hoover text of the label.
    */
    addTab(child: HTMLElement, label?: string, title?: string) {

        /* First character of text is a good a guess as any for our label,
        but still defaut to '?' if no text is found */
        label = label || child.dataset.label || (child.textContent + '?')[0];
        title = title || child.dataset.title || '';
        let extra_attributes = {};
        /* Used to target a tab by name */
        if (child.dataset.originaltitle) {
            extra_attributes = { 'data-originaltitle': child.dataset.originaltitle }
        }

        let tab_id = gensym('tab_content_');
        let label_id = gensym('tab_label_');

        let tabLabel = makeElement('button', {
            textContent: label,
        }, {
            role: 'tab',
            id: label_id,
            tabindex: -1,
            title: title,
            'aria-selected': false,
            'aria-controls': tab_id,
            ...extra_attributes,
        })

        let tabContainer = makeElement('div', {}, {
            id: tab_id,
            role: 'tabpanel',
            tabindex: 0,
            hidden: 'hidden',
            'aria-labelledby': label_id,
        })

        tabContainer.replaceChildren(child);
        this.tabs.push(tabContainer);
        this.appendChild(tabContainer);

        this.tabLabels.push(tabLabel);
        this.menu.appendChild(tabLabel);

        tabLabel.addEventListener('click', () => this.#tabClickedCallback(tabLabel));

        this.style.setProperty('--tabcount', '' + this.tabs.length);
    }

    /**
       HTMLElement must be one of the tab bodies in this group. This method
       removes it, along with its TabLabel.
    */
    removeTab(tab: HTMLElement) {
        let id = tab.getAttribute('aria-labelledby')!
        let label = document.getElementById(id)
        if (label) {
            if (label.ariaSelected === 'true') {
                this.tabLabels[0].click();
            }
            this.tabLabels = this.tabLabels.filter(el => el !== label)
            label.remove();
        }
        /* remove tab */
        this.tabs = this.tabs.filter(el => el !== tab)
        this.removeChild(tab);
        if (tab.firstChild) {
            let child = tab.firstChild as HTMLElement;
            if (isRedrawable(child)) {
                vcal_objects.get(this.uid)?.unregister(child)
            }
        }

        this.style.setProperty('--tabcount', '' + this.tabs.length);
    }

    /* TODO replace querySelectors here with our already saved references */
    #tabClickedCallback(tab: Element) {

        /* hide all tab panels */
        for (let tabcontent of this.querySelectorAll('[role="tabpanel"]')) {
            tabcontent.setAttribute('hidden', 'hidden');
        }
        /* unselect all (selected) tab handles */
        for (let item of this.querySelectorAll('[aria-selected="true"]')) {
            item.setAttribute('aria-selected', 'false');
        }
        /* re-select ourselves */
        tab.setAttribute('aria-selected', 'true');

        /* unhide our target tab */
        this.querySelector('#' + tab.getAttribute('aria-controls'))!
            .removeAttribute('hidden')
    }


    /** Return our rrule tab if we have one */
    has_rrule_tab(): Element | false {
        for (let child of this.children) {
            if (child.firstChild! instanceof EditRRule) {
                return child;
            }
        }
        return false;
    }

}