/**
 * Adapted from https://github.com/facebook/react/blob/main/packages/react-dom-bindings/src/client/ReactInputSelection.js
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 * MIT License
 *
 * Eventually should be able to use moveBefore and won't need this at all.
 */

type SelectionInformation = {
  focusedElem: Element | null
  selectionRange: { start: number; end: number } | null
}

export function createDocumentState(_doc?: Document) {
  let doc = _doc ?? document

  function getActiveElement(): Element | null {
    return doc.activeElement || doc.body
  }

  function hasSelectionCapabilities(elem: Element): boolean {
    let nodeName = elem.nodeName.toLowerCase()
    return (
      (nodeName === 'input' &&
        'type' in elem &&
        (elem.type === 'text' ||
          elem.type === 'search' ||
          elem.type === 'tel' ||
          elem.type === 'url' ||
          elem.type === 'password')) ||
      nodeName === 'textarea' ||
      (elem instanceof HTMLElement && elem.contentEditable === 'true')
    )
  }

  function getSelection(input: Element): { start: number; end: number } | null {
    if (
      'selectionStart' in input &&
      typeof input.selectionStart === 'number' &&
      'selectionEnd' in input
    ) {
      let htmlInput = input as HTMLInputElement | HTMLTextAreaElement
      return {
        start: htmlInput.selectionStart ?? 0,
        end: htmlInput.selectionEnd ?? htmlInput.selectionStart ?? 0,
      }
    }
    // For contentEditable, we'd need more complex logic, but for now return null
    return null
  }

  function setSelection(input: Element, offsets: { start: number; end: number }): void {
    if ('selectionStart' in input && 'selectionEnd' in input) {
      try {
        let htmlInput = input as HTMLInputElement | HTMLTextAreaElement
        htmlInput.selectionStart = offsets.start
        htmlInput.selectionEnd = Math.min(offsets.end, htmlInput.value?.length ?? 0)
      } catch {
        // Ignore errors setting selection
      }
    }
  }

  function isInDocument(node: Node): boolean {
    return doc.documentElement.contains(node)
  }

  function getSelectionInformation(): SelectionInformation {
    let focusedElem = getActiveElement()
    return {
      focusedElem,
      selectionRange:
        focusedElem && hasSelectionCapabilities(focusedElem) ? getSelection(focusedElem) : null,
    }
  }

  function restoreSelection(priorSelectionInformation: SelectionInformation): void {
    let curFocusedElem = getActiveElement()
    let priorFocusedElem = priorSelectionInformation.focusedElem
    let priorSelectionRange = priorSelectionInformation.selectionRange

    if (curFocusedElem !== priorFocusedElem && priorFocusedElem && isInDocument(priorFocusedElem)) {
      // Save scroll positions before focusing (focusing can change scroll)
      let ancestors: Array<{ element: Element; left: number; top: number }> = []
      let ancestor: Node | null = priorFocusedElem
      while (ancestor) {
        if (ancestor.nodeType === Node.ELEMENT_NODE) {
          let el = ancestor as Element
          ancestors.push({
            element: el,
            left: el.scrollLeft ?? 0,
            top: el.scrollTop ?? 0,
          })
        }
        ancestor = ancestor.parentNode
      }

      // Restore selection if applicable
      if (priorSelectionRange !== null && hasSelectionCapabilities(priorFocusedElem)) {
        setSelection(priorFocusedElem, priorSelectionRange)
      }

      // Restore focus
      if (priorFocusedElem instanceof HTMLElement && typeof priorFocusedElem.focus === 'function') {
        priorFocusedElem.focus()
      }

      // Restore scroll positions
      for (let info of ancestors) {
        info.element.scrollLeft = info.left
        info.element.scrollTop = info.top
      }
    }
  }

  let selectionInfo: SelectionInformation | null = null

  function capture() {
    selectionInfo = getSelectionInformation()
  }

  function restore() {
    if (selectionInfo !== null) {
      restoreSelection(selectionInfo)
    }
    selectionInfo = null
  }

  return { capture, restore }
}