import { getBestMatch } from '@acusti/matchmaking';

import { BODY_SELECTOR } from './styles.js';

export const ITEM_SELECTOR = `[data-ukt-item], [data-ukt-value]`;

export const getItemElements = (dropdownElement: HTMLElement | null) => {
    if (!dropdownElement) return null;

    const bodyElement = dropdownElement.querySelector(BODY_SELECTOR);
    if (!bodyElement) return null;

    let items: HTMLCollection | NodeListOf<Element> =
        bodyElement.querySelectorAll(ITEM_SELECTOR);

    if (items.length) return items;
    // If no items found via [data-ukt-item] or [data-ukt-value] selector,
    // use first instance of multiple children found
    items = bodyElement.children;
    while (items.length === 1) {
        if (items[0].children == null) break;
        items = items[0].children;
    }
    // If unable to find an element with more than one child, treat direct child as items
    if (items.length === 1) {
        items = bodyElement.children;
    }
    return items;
};

export const getActiveItemElement = (dropdownElement: HTMLElement | null) => {
    if (!dropdownElement) return null;
    return dropdownElement.querySelector('[data-ukt-active]') as HTMLElement | null;
};

const clearItemElementsState = (itemElements: Array<HTMLElement>) => {
    itemElements.forEach((itemElement) => {
        if (itemElement.hasAttribute('data-ukt-active')) {
            delete itemElement.dataset.uktActive;
        }
    });
};

export const setActiveItem = ({
    dropdownElement,
    element,
    index,
    indexAddend,
    isExactMatch,
    text,
}:
    | {
          dropdownElement: HTMLElement;
          element: HTMLElement;
          index?: null;
          indexAddend?: null;
          isExactMatch?: null;
          text?: null;
      }
    | {
          dropdownElement: HTMLElement;
          element?: null;
          index: number;
          indexAddend?: null;
          isExactMatch?: null;
          text?: null;
      }
    | {
          dropdownElement: HTMLElement;
          element?: null;
          index?: null;
          indexAddend: number;
          isExactMatch?: null;
          text?: null;
      }
    | {
          dropdownElement: HTMLElement;
          element?: null;
          index?: null;
          indexAddend?: null;
          isExactMatch?: boolean;
          text: string;
      }) => {
    const items = getItemElements(dropdownElement);
    if (!items) return;

    const itemElements = Array.from(items) as Array<HTMLElement>;
    if (!itemElements.length) return;

    const lastIndex = itemElements.length - 1;
    const currentActiveIndex = itemElements.findIndex((itemElement) =>
        itemElement.hasAttribute('data-ukt-active'),
    );

    let nextActiveIndex = currentActiveIndex;
    if (typeof index === 'number') {
        // Negative index means count back from the end
        nextActiveIndex = index < 0 ? itemElements.length + index : index;
    }

    if (element) {
        nextActiveIndex = itemElements.findIndex(
            (itemElement) => itemElement === element,
        );
    } else if (typeof indexAddend === 'number') {
        // If there’s no currentActiveIndex and we are handling -1, start at lastIndex
        if (currentActiveIndex === -1 && indexAddend === -1) {
            nextActiveIndex = lastIndex;
        } else {
            nextActiveIndex += indexAddend;
        }
        // Keep it within the bounds of the items list
        if (nextActiveIndex < 0) {
            nextActiveIndex = 0;
        } else if (nextActiveIndex > lastIndex) {
            nextActiveIndex = lastIndex;
        }
    } else if (typeof text === 'string') {
        // If text is empty, clear existing active items and early return
        if (!text) {
            clearItemElementsState(itemElements);
            return;
        }

        const itemTexts = itemElements.map((itemElement) => itemElement.innerText);
        if (isExactMatch) {
            const textToCompare = text.toLowerCase();
            nextActiveIndex = itemTexts.findIndex((itemText) =>
                itemText.toLowerCase().startsWith(textToCompare),
            );
            // If isExactMatch is required and no exact match was found, clear active items
            if (nextActiveIndex === -1) {
                clearItemElementsState(itemElements);
            }
        } else {
            const bestMatch = getBestMatch({ items: itemTexts, text });
            nextActiveIndex = itemTexts.findIndex((itemText) => itemText === bestMatch);
        }
    }

    if (nextActiveIndex === -1 || nextActiveIndex === currentActiveIndex) return;

    // Clear any existing active dropdown body item state
    clearItemElementsState(itemElements);

    const nextActiveItem = items[nextActiveIndex];
    if (nextActiveItem != null) {
        nextActiveItem.setAttribute('data-ukt-active', '');
        // Find closest scrollable parent and ensure that next active item is visible
        let { parentElement } = nextActiveItem;
        let scrollableParent = null;
        while (!scrollableParent && parentElement && parentElement !== dropdownElement) {
            const isScrollable =
                parentElement.scrollHeight > parentElement.clientHeight + 15;
            if (isScrollable) {
                scrollableParent = parentElement;
            } else {
                parentElement = parentElement.parentElement;
            }
        }

        if (scrollableParent) {
            const parentRect = scrollableParent.getBoundingClientRect();
            const itemRect = nextActiveItem.getBoundingClientRect();
            const isAboveTop = itemRect.top < parentRect.top;
            const isBelowBottom = itemRect.bottom > parentRect.bottom;
            if (isAboveTop || isBelowBottom) {
                let { scrollTop } = scrollableParent;
                // Item isn’t fully visible; adjust scrollTop to put item within closest edge
                if (isAboveTop) {
                    scrollTop -= parentRect.top - itemRect.top;
                } else {
                    scrollTop += itemRect.bottom - parentRect.bottom;
                }
                scrollableParent.scrollTop = scrollTop;
            }
        }
    }
};