import {
  getEditableCaretOffset,
  getEditableDomPointAtOffset,
  readEditableTextFromElement
} from './markdown-inline.js'

/** @type {import('vue').InjectionKey<{ extendSelection: Function, selectDocument: Function, deleteSelection: Function }>} */
export const LIVE_SELECTION_BRIDGE_KEY = Symbol('liveSelectionBridge')

/**
 * 컨테이너 안의 선택 가능한 contenteditable 요소 목록을 반환한다.
 * @param {HTMLElement|null} container - 탐색 루트
 * @returns {HTMLElement[]} 편집 요소 목록
 */
export const getSelectableEditableElements = (container) => {
  if (!container || !import.meta.client) {
    return []
  }

  return [...container.querySelectorAll('[data-source-line][contenteditable="true"]')]
    .filter((element) => element.getAttribute('contenteditable') === 'true')
    .sort((left, right) => Number(left.getAttribute('data-source-line')) - Number(right.getAttribute('data-source-line')))
}

/**
 * 노드가 속한 편집 요소를 반환한다.
 * @param {Node|null} node - 기준 노드
 * @param {HTMLElement[]} elements - 편집 요소 목록
 * @returns {HTMLElement|null}
 */
export const getEditableElementFromNode = (node, elements) => {
  if (!node) {
    return null
  }

  return elements.find((element) => element.contains(node)) ?? null
}

/**
 * 원본 줄 번호에 해당하는 편집 요소 인덱스를 찾는다.
 * @param {HTMLElement[]} elements - 편집 요소 목록
 * @param {number} sourceLine - 원본 줄 번호(0-based)
 * @returns {number} 인덱스(없으면 -1)
 */
export const findEditableIndexBySourceLine = (elements, sourceLine) => {
  return elements.findIndex((element) => {
    const start = Number(element.getAttribute('data-source-line'))
    const end = Number(element.getAttribute('data-source-line-end'))

    if (!Number.isInteger(start)) {
      return false
    }

    if (Number.isInteger(end) && end > start) {
      return sourceLine >= start && sourceLine <= end
    }

    return start === sourceLine
  })
}

/**
 * 편집 요소의 원본 줄 범위를 반환한다.
 * @param {HTMLElement} element - contenteditable 요소
 * @returns {{ startLine: number, endLine: number }}
 */
export const getEditableSourceLineRange = (element) => {
  const startLine = Number(element.getAttribute('data-source-line'))
  const endLine = Number(element.getAttribute('data-source-line-end'))

  if (!Number.isInteger(startLine)) {
    return { startLine: -1, endLine: -1 }
  }

  return {
    startLine,
    endLine: Number.isInteger(endLine) ? endLine : startLine
  }
}

/**
 * 선택 범위가 편집 요소와 겹치는지 확인한다.
 * @param {Range} range - 선택 범위
 * @param {HTMLElement} element - contenteditable 요소
 * @returns {boolean}
 */
export const rangeIntersectsElement = (range, element) => {
  const elementRange = document.createRange()
  elementRange.selectNodeContents(element)

  return range.compareBoundaryPoints(Range.START_TO_END, elementRange) < 0
    && range.compareBoundaryPoints(Range.END_TO_START, elementRange) > 0
}

/**
 * 편집 요소 안에서 선택 경계의 텍스트 오프셋을 계산한다.
 * @param {HTMLElement} element - contenteditable 요소
 * @param {Range} range - 선택 범위
 * @param {'start'|'end'} edge - 경계
 * @returns {number}
 */
export const getSelectionOffsetInElement = (element, range, edge) => {
  const partial = document.createRange()
  partial.selectNodeContents(element)

  if (edge === 'start') {
    partial.setEnd(range.startContainer, range.startOffset)
  } else {
    partial.setStart(range.endContainer, range.endOffset)
  }

  return getEditableCaretOffset(element, partial)
}

/**
 * 마크다운 줄에서 편집 본문 앞 접두사 길이를 반환한다.
 * @param {string} markdownLine - 마크다운 한 줄
 * @param {string} bodyText - 편집 본문
 * @returns {number}
 */
export const getMarkdownLineBodyPrefixLength = (markdownLine, bodyText) => {
  const line = String(markdownLine ?? '')
  const body = String(bodyText ?? '')

  if (line === body) {
    return 0
  }

  const prefixPatterns = [
    /^(#{1,6}\s+)/,
    /^(>\s*)/,
    /^([-*+]\s+)/,
    /^(\d+\.\s+)/
  ]

  for (const pattern of prefixPatterns) {
    const match = line.match(pattern)

    if (match && line.slice(match[0].length) === body) {
      return match[0].length
    }
  }

  if (line.endsWith(body)) {
    return line.length - body.length
  }

  return 0
}

/**
 * 마크다운 한 줄에 편집 본문 치환 결과를 반영한다.
 * @param {string} markdownLine - 마크다운 한 줄
 * @param {string} bodyText - 편집 본문
 * @param {string} nextBody - 치환 후 본문
 * @returns {string}
 */
export const rebuildMarkdownLineBody = (markdownLine, bodyText, nextBody) => {
  const prefixLength = getMarkdownLineBodyPrefixLength(markdownLine, bodyText)

  return `${String(markdownLine ?? '').slice(0, prefixLength)}${nextBody}`
}

/**
 * 마크다운 한 줄에서 본문 일부를 삭제한다.
 * @param {string} markdownLine - 마크다운 한 줄
 * @param {string} bodyText - 편집 본문
 * @param {number} startOffset - 시작 오프셋
 * @param {number} endOffset - 끝 오프셋
 * @returns {string}
 */
export const applyBodyEditToMarkdownLine = (markdownLine, bodyText, startOffset, endOffset) => {
  const prefixLength = getMarkdownLineBodyPrefixLength(markdownLine, bodyText)
  const line = String(markdownLine ?? '')
  const absoluteStart = prefixLength + startOffset
  const absoluteEnd = prefixLength + endOffset

  return `${line.slice(0, absoluteStart)}${line.slice(absoluteEnd)}`
}

/**
 * 인접 블록 선택 확장 대상 오프셋을 계산한다.
 * @param {string} text - 대상 편집 요소 텍스트
 * @param {number} direction - 이동 방향
 * @param {number} column - 유지할 열
 * @returns {number}
 */
export const getTargetSelectionOffset = (text, direction, column) => {
  const source = String(text ?? '')
  const lines = source.length ? source.split('\n') : ['']
  const safeColumn = Math.max(0, column)

  if (direction > 0) {
    const lineText = lines[0] ?? ''
    return Math.min(safeColumn, lineText.length)
  }

  const lineText = lines[lines.length - 1] ?? ''
  const previousLength = lines.slice(0, -1).reduce((sum, line) => sum + line.length + 1, 0)

  return previousLength + Math.min(safeColumn, lineText.length)
}

/**
 * 편집 요소 본문 전체를 선택한다.
 * @param {HTMLElement} element - contenteditable 요소
 * @returns {void}
 */
export const selectEditableElementContents = (element) => {
  if (!element || !import.meta.client) {
    return
  }

  const selection = window.getSelection()

  if (!selection) {
    return
  }

  const range = document.createRange()
  range.selectNodeContents(element)
  selection.removeAllRanges()
  selection.addRange(range)
}

/**
 * 편집 요소 목록 전체를 하나의 선택 범위로 만든다.
 * @param {HTMLElement[]} elements - 편집 요소 목록
 * @returns {void}
 */
export const selectAllEditableElements = (elements) => {
  if (!import.meta.client || !elements.length) {
    return
  }

  const selection = window.getSelection()

  if (!selection) {
    return
  }

  const first = elements[0]
  const last = elements[elements.length - 1]
  const startPoint = getEditableDomPointAtOffset(first, 0)
  const endText = readEditableTextFromElement(last)
  const endPoint = getEditableDomPointAtOffset(last, endText.length)

  if (!startPoint || !endPoint) {
    return
  }

  selection.setBaseAndExtent(
    startPoint.node,
    startPoint.offset,
    endPoint.node,
    endPoint.offset
  )
}

/**
 * 인접 편집 블록으로 선택 범위를 확장한다.
 * @param {{ container: HTMLElement|null, sourceLine: number, direction: number, column?: number }} options - 확장 옵션
 * @returns {boolean} 확장 여부
 */
export const extendSelectionAcrossBlocks = ({
  container,
  sourceLine,
  direction,
  column = 0
}) => {
  if (!import.meta.client || !container || !direction) {
    return false
  }

  const elements = getSelectableEditableElements(container)
  const currentIndex = findEditableIndexBySourceLine(elements, sourceLine)

  if (currentIndex < 0) {
    return false
  }

  const selection = window.getSelection()

  if (!selection || selection.rangeCount === 0) {
    return false
  }

  const focusedElement = getEditableElementFromNode(selection.focusNode, elements)
  const focusedIndex = focusedElement ? elements.indexOf(focusedElement) : -1
  const resolvedCurrentIndex = focusedIndex >= 0 ? focusedIndex : currentIndex
  const targetIndex = resolvedCurrentIndex + direction

  if (targetIndex < 0 || targetIndex >= elements.length) {
    return false
  }

  const target = elements[targetIndex]
  const targetText = readEditableTextFromElement(target)
  const anchorPoint = {
    node: selection.anchorNode,
    offset: selection.anchorOffset
  }
  const focusPoint = getEditableDomPointAtOffset(
    target,
    getTargetSelectionOffset(targetText, direction, column)
  )

  if (!anchorPoint?.node || !focusPoint) {
    return false
  }

  selection.setBaseAndExtent(
    anchorPoint.node,
    anchorPoint.offset,
    focusPoint.node,
    focusPoint.offset
  )

  return true
}

/**
 * 편집 요소가 현재 전체 선택 상태인지 확인한다.
 * @param {HTMLElement} element - contenteditable 요소
 * @returns {boolean}
 */
export const isEditableElementFullySelected = (element) => {
  if (!element || !import.meta.client) {
    return false
  }

  const selection = window.getSelection()

  if (!selection || selection.rangeCount === 0 || selection.isCollapsed) {
    return false
  }

  const range = selection.getRangeAt(0)
  const fullText = readEditableTextFromElement(element)

  if (!fullText.length) {
    return false
  }

  const startOffset = getSelectionOffsetInElement(element, range, 'start')
  const endOffset = getSelectionOffsetInElement(element, range, 'end')

  return startOffset === 0 && endOffset >= fullText.length
}

/**
 * 선택 삭제·잘라내기 단축키인지 확인한다.
 * @param {KeyboardEvent} event - 키보드 이벤트
 * @returns {boolean}
 */
export const isLiveSelectionDeleteKey = (event) => {
  if (event.key === 'Backspace' || event.key === 'Delete') {
    return true
  }

  return (event.metaKey || event.ctrlKey)
    && !event.shiftKey
    && !event.altKey
    && event.key.toLowerCase() === 'x'
}

/**
 * 라이브 선택을 마크다운에 반영해 삭제한다.
 * @param {string} markdown - 현재 마크다운
 * @param {HTMLElement|null} container - 렌더러 루트
 * @returns {string|null} 갱신된 마크다운(처리하지 않으면 null)
 */
export const applyLiveSelectionDelete = (markdown, container) => {
  if (!import.meta.client || !container) {
    return null
  }

  const selection = window.getSelection()

  if (!selection || selection.rangeCount === 0 || selection.isCollapsed) {
    return null
  }

  const range = selection.getRangeAt(0)
  const elements = getSelectableEditableElements(container)
  const affected = elements.filter((element) => rangeIntersectsElement(range, element))

  if (!affected.length) {
    return null
  }

  const lines = String(markdown ?? '').split('\n')

  if (affected.length === 1) {
    const element = affected[0]
    const startsIn = element.contains(range.startContainer)
    const endsIn = element.contains(range.endContainer)

    if (!startsIn || !endsIn) {
      return null
    }

    const bodyText = readEditableTextFromElement(element, { trimEnd: false })
    const startOffset = getSelectionOffsetInElement(element, range, 'start')
    const endOffset = getSelectionOffsetInElement(element, range, 'end')

    if (startOffset === 0 && endOffset >= bodyText.length) {
      const { startLine, endLine } = getEditableSourceLineRange(element)

      if (startLine < 0) {
        return null
      }

      const replacementLines = element.hasAttribute('data-empty-markdown-line')
        ? [element.getAttribute('data-empty-markdown-line') ?? '']
        : []

      return [
        ...lines.slice(0, startLine),
        ...replacementLines,
        ...lines.slice(endLine + 1)
      ].join('\n')
    }

    if (startOffset < endOffset) {
      const { startLine } = getEditableSourceLineRange(element)
      const nextLine = applyBodyEditToMarkdownLine(lines[startLine] ?? '', bodyText, startOffset, endOffset)

      return [
        ...lines.slice(0, startLine),
        nextLine,
        ...lines.slice(startLine + 1)
      ].join('\n')
    }

    return null
  }

  const first = affected[0]
  const last = affected[affected.length - 1]
  const { startLine: firstLine, endLine: firstEndLine } = getEditableSourceLineRange(first)
  const { startLine: lastLine, endLine: lastEndLine } = getEditableSourceLineRange(last)

  if (firstLine < 0 || lastLine < 0) {
    return null
  }

  const firstBody = readEditableTextFromElement(first, { trimEnd: false })
  const lastBody = readEditableTextFromElement(last, { trimEnd: false })
  const startOffset = getSelectionOffsetInElement(first, range, 'start')
  const endOffset = getSelectionOffsetInElement(last, range, 'end')
  const mergedBody = `${firstBody.slice(0, startOffset)}${lastBody.slice(endOffset)}`

  let replacementLines = []

  if (mergedBody.length) {
    const bodySegments = mergedBody.split('\n')

    replacementLines = bodySegments.map((segment, index) => {
      if (index === 0) {
        return rebuildMarkdownLineBody(lines[firstLine] ?? '', firstBody, segment)
      }

      if (index === bodySegments.length - 1 && firstLine !== lastLine) {
        return rebuildMarkdownLineBody(lines[lastLine] ?? '', lastBody, segment)
      }

      return segment
    })
  }

  return [
    ...lines.slice(0, firstLine),
    ...replacementLines,
    ...lines.slice(lastEndLine + 1)
  ].join('\n')
}

/**
 * 현재 문서 선택을 접는다.
 * @returns {void}
 */
export const collapseLiveSelection = () => {
  if (!import.meta.client) {
    return
  }

  window.getSelection()?.removeAllRanges()
}