import { computePosition, flip, inline, shift } from "@floating-ui/dom"

// from micromorph/src/utils.ts
// https://github.com/natemoo-re/micromorph/blob/main/src/utils.ts#L5
export function normalizeRelativeURLs(
  el: Element | Document,
  base: string | URL
) {
  const update = (el: Element, attr: string, base: string | URL) => {
    el.setAttribute(attr, new URL(el.getAttribute(attr)!, base).pathname)
  }

  el.querySelectorAll('[href^="./"], [href^="../"]').forEach((item) =>
    update(item, 'href', base)
  )

  el.querySelectorAll('[src^="./"], [src^="../"]').forEach((item) =>
    update(item, 'src', base)
  )
}

document.addEventListener("nav", () => {
  const links = [...document.getElementsByClassName("internal")] as HTMLLinkElement[]
  const p = new DOMParser()
  for (const link of links) {
    link.addEventListener("mouseenter", async ({ clientX, clientY }) => {
      async function setPosition(popoverElement: HTMLElement) {
        const { x, y } = await computePosition(link, popoverElement, {
          middleware: [
            inline({ x: clientX, y: clientY }),
            shift(),
            flip()
          ]
        })
        Object.assign(popoverElement.style, {
          left: `${x}px`,
          top: `${y}px`,
        })
      }

      if (link.dataset.fetchedPopover === "true") {
        return setPosition(link.lastChild as HTMLElement)
      }

      const thisUrl = new URL(document.location.href)
      thisUrl.hash = ""
      thisUrl.search = ""
      const targetUrl = new URL(link.href)
      const hash = targetUrl.hash
      targetUrl.hash = ""
      targetUrl.search = ""
      // prevent hover of the same page
      if (thisUrl.toString() === targetUrl.toString()) return

      const contents = await fetch(`${targetUrl}`)
        .then((res) => res.text())
        .catch((err) => {
          console.error(err)
        })

      if (!contents) return
      const html = p.parseFromString(contents, "text/html")
      normalizeRelativeURLs(html, targetUrl)
      const elts = [...html.getElementsByClassName("popover-hint")]
      if (elts.length === 0) return

      const popoverElement = document.createElement("div")
      popoverElement.classList.add("popover")
      const popoverInner = document.createElement("div")
      popoverInner.classList.add("popover-inner")
      popoverElement.appendChild(popoverInner)
      elts.forEach(elt => popoverInner.appendChild(elt))

      setPosition(popoverElement)
      link.appendChild(popoverElement)
      link.dataset.fetchedPopover = "true"

      if (hash !== "") {
        const heading = popoverInner.querySelector(hash) as HTMLElement | null
        if (heading) {
          // leave ~12px of buffer when scrolling to a heading
          popoverInner.scroll({ top: heading.offsetTop - 12, behavior: 'instant' })
        }
      }
    })
  }
})