import { watchEffect } from 'vue';
export function useUpdateHead(route, siteDataByRouteRef) {
    let managedHeadTags = [];
    let isFirstUpdate = true;
    const updateHeadTags = (newTags) => {
        if (import.meta.env.PROD && isFirstUpdate) {
            // in production, the initial meta tags are already pre-rendered so we
            // skip the first update.
            isFirstUpdate = false;
            return;
        }
        const newEls = [];
        const commonLength = Math.min(managedHeadTags.length, newTags.length);
        for (let i = 0; i < commonLength; i++) {
            let el = managedHeadTags[i];
            const [tag, attrs, innerHTML = ''] = newTags[i];
            if (el.tagName.toLocaleLowerCase() === tag) {
                for (const key in attrs) {
                    if (el.getAttribute(key) !== attrs[key]) {
                        el.setAttribute(key, attrs[key]);
                    }
                }
                for (let i = 0; i < el.attributes.length; i++) {
                    const name = el.attributes[i].name;
                    if (!(name in attrs)) {
                        el.removeAttribute(name);
                    }
                }
                if (el.innerHTML !== innerHTML) {
                    el.innerHTML = innerHTML;
                }
            }
            else {
                document.head.removeChild(el);
                el = createHeadElement(newTags[i]);
                document.head.append(el);
            }
            newEls.push(el);
        }
        managedHeadTags
            .slice(commonLength)
            .forEach((el) => document.head.removeChild(el));
        newTags.slice(commonLength).forEach((headConfig) => {
            const el = createHeadElement(headConfig);
            document.head.appendChild(el);
            newEls.push(el);
        });
        managedHeadTags = newEls;
    };
    watchEffect(() => {
        const pageData = route.data;
        const siteData = siteDataByRouteRef.value;
        const pageTitle = pageData && pageData.title;
        const pageDescription = pageData && pageData.description;
        const frontmatterHead = pageData && pageData.frontmatter.head;
        // update title and description
        document.title = (pageTitle ? pageTitle + ` | ` : ``) + siteData.title;
        document
            .querySelector(`meta[name=description]`)
            .setAttribute('content', pageDescription || siteData.description);
        updateHeadTags([
            // site head can only change during dev
            ...(import.meta.env.DEV ? siteData.head : []),
            ...(frontmatterHead ? filterOutHeadDescription(frontmatterHead) : [])
        ]);
    });
}
function createHeadElement([tag, attrs, innerHTML]) {
    const el = document.createElement(tag);
    for (const key in attrs) {
        el.setAttribute(key, attrs[key]);
    }
    if (innerHTML) {
        el.innerHTML = innerHTML;
    }
    return el;
}
function isMetaDescription(headConfig) {
    return (headConfig[0] === 'meta' &&
        headConfig[1] &&
        headConfig[1].name === 'description');
}
function filterOutHeadDescription(head) {
    return head.filter((h) => !isMetaDescription(h));
}