import type {
  PreviewItem,
  ProcessType,
  ResultItem,
  SourceLine,
  StructuredProcessOptions,
  UnstructuredProcessOptions,
} from './types'

export const DEFAULT_SOURCE_TEXT = [
  '问：如何看待当前的通货膨胀风险？',
  '答：当前通胀水平总体可控，但仍需关注能源价格与供给扰动。',
  '问：美联储下一次议息会议何时召开？',
  '答：会议时间以美联储官方日历为准，市场会重点关注利率路径指引。',
  '问：人民币汇率未来走势如何？',
  '答：人民币汇率取决于中美利差、经济基本面与政策预期。',
  '问：银行理财产品收益率为何持续走低？',
  '答：主要与市场利率下行、资产端收益下降以及风险偏好变化有关。',
  '问：什么是复利？',
  '答：复利是指在计算利息时，将上一期利息加入本金，再计算下一期利息。',
  '问：如何评估股票的投资价值？',
  '答：评估股票投资价值可以从以下几个方面进行：',
  '1. 公司基本面：分析公司的财务状况、盈利能力、成长性等。',
  '2. 行业前景：考察公司所处行业的发展趋势和竞争格局。',
  '3. 估值水平：通过市盈率、市净率等指标判断估值是否合理。',
  '4. 财务健康：关注公司的负债情况、现金流状况等。',
  '5. 管理团队：评估管理层的能力和过往业绩。',
  '此外，还需要关注宏观经济环境、政策变化等因素对股票市场的影响。',
  '问：债券和股票的主要区别是什么？',
  '答：债券收益相对稳定但上行有限，股票波动更大且承担更高风险。',
  '问：什么是市盈率？',
  '答：市盈率是股票价格与每股收益的比值，常用于衡量估值水平。',
  '问：如何进行资产配置？',
  '答：应根据投资目标、风险承受能力和市场环境合理分配资产。',
].join('\n')

export function sourceLines(sourceText: string): SourceLine[] {
  const rawLines = sourceText.split('\n')
  let cursor = 0

  return rawLines.map((content, index) => {
    const start = cursor
    const end = start + content.length
    cursor = end + (index < rawLines.length - 1 ? 1 : 0)
    return { number: index + 1, content, start, end }
  })
}

interface SourceRange {
  start: number
  end: number
}

interface ProtectedRange extends SourceRange {
  kind: 'code' | 'table' | 'list'
}

const DEFAULT_CHUNK_SIZE = 800
const DEFAULT_CHUNK_OVERLAP = 100
const DEFAULT_MIN_CHUNK_SIZE = 100

function finiteInteger(value: number | undefined, fallback: number, min: number): number {
  return Number.isFinite(value) ? Math.max(min, Math.round(value as number)) : fallback
}

function trimSourceRange(sourceText: string, start: number, end: number): SourceRange {
  let nextStart = Math.max(0, start)
  let nextEnd = Math.min(sourceText.length, end)

  while (nextStart < nextEnd && /\s/.test(sourceText[nextStart])) nextStart += 1
  while (nextEnd > nextStart && /\s/.test(sourceText[nextEnd - 1])) nextEnd -= 1

  return { start: nextStart, end: nextEnd }
}

function normalizeDelimiter(delimiter: string | undefined): string {
  return (delimiter ?? '').replace(/\\n/g, '\n').replace(/\\t/g, '\t')
}

function overlapsRange(line: SourceLine, range: SourceRange): boolean {
  return line.start < range.end && line.end > range.start
}

function isLineProtected(line: SourceLine, ranges: SourceRange[]): boolean {
  return ranges.some((range) => overlapsRange(line, range))
}

function detectCodeBlockRanges(sourceText: string, lines: SourceLine[]): ProtectedRange[] {
  const ranges: ProtectedRange[] = []
  let openFence: { start: number; marker: string; length: number } | null = null

  for (const line of lines) {
    const fence = line.content.match(/^\s*(`{3,}|~{3,})/)
    if (!fence) continue

    const marker = fence[1][0]
    if (!openFence) {
      openFence = { start: line.start, marker, length: fence[1].length }
      continue
    }

    if (marker === openFence.marker && fence[1].length >= openFence.length) {
      ranges.push({ start: openFence.start, end: line.end, kind: 'code' })
      openFence = null
    }
  }

  if (openFence) ranges.push({ start: openFence.start, end: sourceText.length, kind: 'code' })
  return ranges
}

function isTableSeparator(content: string): boolean {
  const normalized = content.trim().replace(/^\|/, '').replace(/\|$/, '')
  const cells = normalized.split('|').map((cell) => cell.trim())
  return cells.length >= 2 && cells.every((cell) => /^:?-{3,}:?$/.test(cell))
}

function detectTableRanges(lines: SourceLine[], codeRanges: SourceRange[]): ProtectedRange[] {
  const ranges: ProtectedRange[] = []

  for (let index = 0; index < lines.length - 1; index += 1) {
    const header = lines[index]
    const separator = lines[index + 1]
    if (
      isLineProtected(header, codeRanges)
      || isLineProtected(separator, codeRanges)
      || !header.content.includes('|')
      || !isTableSeparator(separator.content)
    ) {
      continue
    }

    let endIndex = index + 1
    while (
      endIndex + 1 < lines.length
      && !isLineProtected(lines[endIndex + 1], codeRanges)
      && lines[endIndex + 1].content.trim()
      && lines[endIndex + 1].content.includes('|')
    ) {
      endIndex += 1
    }

    ranges.push({ start: header.start, end: lines[endIndex].end, kind: 'table' })
    index = endIndex
  }

  return ranges
}

function isListItem(content: string): boolean {
  return /^\s*(?:[-+*]|\d+[.)])\s+\S/.test(content)
}

function isListContinuation(content: string): boolean {
  return /^\s{2,}\S/.test(content)
}

function detectListRanges(
  lines: SourceLine[],
  excludedRanges: SourceRange[],
): ProtectedRange[] {
  const ranges: ProtectedRange[] = []

  for (let index = 0; index < lines.length; index += 1) {
    if (isLineProtected(lines[index], excludedRanges) || !isListItem(lines[index].content)) continue

    let endIndex = index
    let itemCount = 1
    while (endIndex + 1 < lines.length && !isLineProtected(lines[endIndex + 1], excludedRanges)) {
      const nextContent = lines[endIndex + 1].content
      if (isListItem(nextContent)) {
        itemCount += 1
        endIndex += 1
        continue
      }
      if (isListContinuation(nextContent)) {
        endIndex += 1
        continue
      }
      break
    }

    if (itemCount >= 2) {
      ranges.push({ start: lines[index].start, end: lines[endIndex].end, kind: 'list' })
      index = endIndex
    }
  }

  return ranges
}

function mergeProtectedRanges(ranges: ProtectedRange[]): ProtectedRange[] {
  return ranges
    .sort((left, right) => left.start - right.start || left.end - right.end)
    .reduce<ProtectedRange[]>((merged, range) => {
      const previous = merged[merged.length - 1]
      if (previous && range.start < previous.end) {
        previous.end = Math.max(previous.end, range.end)
        return merged
      }
      merged.push({ ...range })
      return merged
    }, [])
}

function protectedRangesForOptions(
  sourceText: string,
  options?: UnstructuredProcessOptions,
): ProtectedRange[] {
  if (!options?.preserveCodeBlocks && !options?.preserveTables && !options?.preserveLists) return []

  const lines = sourceLines(sourceText)
  const codeRanges = detectCodeBlockRanges(sourceText, lines)
  const tableRanges = detectTableRanges(lines, codeRanges)
  const listRanges = detectListRanges(lines, [...codeRanges, ...tableRanges])
  const enabledRanges = [
    ...(options?.preserveCodeBlocks ? codeRanges : []),
    ...(options?.preserveTables ? tableRanges : []),
    ...(options?.preserveLists ? listRanges : []),
  ]

  return mergeProtectedRanges(enabledRanges)
}

function protectedRangeContaining(
  ranges: ProtectedRange[],
  offset: number,
): ProtectedRange | undefined {
  return ranges.find((range) => range.start < offset && offset < range.end)
}

function normalizeChunkStart(
  sourceText: string,
  cursor: number,
  protectedRanges: ProtectedRange[],
): number {
  let start = Math.max(0, Math.min(cursor, sourceText.length))
  const overlapBlock = protectedRangeContaining(protectedRanges, start)
  if (overlapBlock) start = overlapBlock.end

  while (start < sourceText.length && /\s/.test(sourceText[start])) start += 1

  // 去除块前空白时可能进入缩进代码块/列表；此时恢复到完整块起点。
  const blockAfterTrim = protectedRangeContaining(protectedRanges, start)
  if (blockAfterTrim) return cursor <= blockAfterTrim.start ? blockAfterTrim.start : blockAfterTrim.end

  return start
}

function protectChunkEnd(
  proposedEnd: number,
  start: number,
  minimumEnd: number,
  protectedRanges: ProtectedRange[],
): number {
  const splitBlock = protectedRangeContaining(protectedRanges, proposedEnd)
  if (!splitBlock) return proposedEnd

  // 优先在块前结束；块前不足最小切片长度时，将整个块收入当前切片。
  return splitBlock.start > start && splitBlock.start >= minimumEnd
    ? splitBlock.start
    : splitBlock.end
}

function restoreProtectedEdges(
  range: SourceRange,
  rawStart: number,
  rawEnd: number,
  protectedRanges: ProtectedRange[],
): SourceRange {
  const nextRange = { ...range }
  const startBlock = protectedRangeContaining(protectedRanges, nextRange.start)
  if (startBlock && rawStart <= startBlock.start) nextRange.start = startBlock.start

  const endBlock = protectedRangeContaining(protectedRanges, nextRange.end)
  if (endBlock && rawEnd >= endBlock.end) nextRange.end = endBlock.end
  return nextRange
}

function lastBoundaryInRange(
  sourceText: string,
  idealEnd: number,
  minimumEnd: number,
): number | null {
  const candidates: number[] = []
  const boundaryTokens = ['\n\n', '\n', '。', '！', '？', '；', '.', '!', '?', ';']

  boundaryTokens.forEach((token) => {
    const tokenStart = sourceText.lastIndexOf(token, idealEnd - token.length)
    const boundary = tokenStart === -1 ? -1 : tokenStart + token.length
    if (boundary >= minimumEnd && boundary <= idealEnd) candidates.push(boundary)
  })

  return candidates.length ? Math.max(...candidates) : null
}

function lastHeadingBoundary(
  sourceText: string,
  start: number,
  idealEnd: number,
  minimumEnd: number,
): number | null {
  const section = sourceText.slice(start, idealEnd)
  const headingPattern = /^(?:#{1,6}\s+|第[一二三四五六七八九十百]+[章节篇部分]|\d+(?:\.\d+)*[、.\s])/gm
  let boundary: number | null = null
  let match: RegExpExecArray | null

  while ((match = headingPattern.exec(section))) {
    const absoluteStart = start + match.index
    if (absoluteStart >= minimumEnd) boundary = absoluteStart
  }

  return boundary
}

function resolveChunkEnd(
  sourceText: string,
  start: number,
  idealEnd: number,
  minimumEnd: number,
  options: UnstructuredProcessOptions | undefined,
): number {
  const method = options?.chunkMethod ?? 'semantic'

  if (method === 'fixed') return idealEnd

  if (method === 'custom') {
    const delimiter = normalizeDelimiter(options?.customDelimiter)
    if (!delimiter) return idealEnd

    const delimiterStart = sourceText.lastIndexOf(delimiter, idealEnd - delimiter.length)
    const boundary = delimiterStart === -1 ? -1 : delimiterStart + delimiter.length
    return boundary >= minimumEnd ? boundary : idealEnd
  }

  if (method === 'heading') {
    const headingBoundary = lastHeadingBoundary(sourceText, start, idealEnd, minimumEnd)
    if (headingBoundary !== null) return headingBoundary
  }

  return lastBoundaryInRange(sourceText, idealEnd, minimumEnd) ?? idealEnd
}

function buildUnstructuredRanges(
  sourceText: string,
  options?: UnstructuredProcessOptions,
): SourceRange[] {
  // 预览统一沿用“约 2 个字符 = 1 token”的轻量估算，避免引入分词器依赖。
  const targetCharacters = finiteInteger(options?.chunkSize, DEFAULT_CHUNK_SIZE, 1) * 2
  const minimumCharacters = Math.min(
    targetCharacters,
    finiteInteger(options?.minChunkSize, DEFAULT_MIN_CHUNK_SIZE, 1) * 2,
  )
  const requestedOverlap = finiteInteger(options?.chunkOverlap, DEFAULT_CHUNK_OVERLAP, 0) * 2
  const protectedRanges = protectedRangesForOptions(sourceText, options)
  const ranges: SourceRange[] = []
  let cursor = 0

  while (cursor < sourceText.length) {
    const start = normalizeChunkStart(sourceText, cursor, protectedRanges)
    if (start >= sourceText.length) break

    const idealEnd = Math.min(sourceText.length, start + targetCharacters)
    const minimumEnd = Math.min(idealEnd, start + minimumCharacters)
    let end = idealEnd === sourceText.length
      ? idealEnd
      : resolveChunkEnd(sourceText, start, idealEnd, minimumEnd, options)
    end = protectChunkEnd(end, start, minimumEnd, protectedRanges)

    // 所有自定义边界都必须向前推进；异常配置回退到固定长度切分。
    if (end <= start) end = Math.min(sourceText.length, start + targetCharacters)

    let range = trimSourceRange(sourceText, start, end)
    range = restoreProtectedEdges(range, start, end, protectedRanges)
    if (end < sourceText.length && range.end - range.start < minimumCharacters) {
      range.end = Math.min(end, range.start + minimumCharacters)
    }
    if (range.end <= range.start) {
      cursor = Math.max(cursor + 1, end)
      continue
    }

    const isLastRange = end >= sourceText.length
    if (isLastRange && range.end - range.start < minimumCharacters && ranges.length) {
      ranges[ranges.length - 1].end = range.end
      break
    }

    ranges.push(range)
    if (isLastRange) break

    // overlap 是允许的最大重叠量；按当前切片动态收缩，保证每轮至少推进最小切片长度。
    const maximumOverlap = Math.max(0, range.end - range.start - minimumCharacters)
    const actualOverlap = Math.min(requestedOverlap, maximumOverlap)
    const nextCursor = range.end - actualOverlap
    cursor = nextCursor > start ? nextCursor : range.end
  }

  return ranges
}

function lineNumberAtOffset(lines: SourceLine[], offset: number): number | null {
  if (!lines.length) return null

  let low = 0
  let high = lines.length - 1
  let result = 0

  while (low <= high) {
    const middle = Math.floor((low + high) / 2)
    if (lines[middle].start <= offset) {
      result = middle
      low = middle + 1
    } else {
      high = middle - 1
    }
  }

  return lines[result].number
}

function previewItemFromRange(
  sourceText: string,
  lines: SourceLine[],
  range: SourceRange,
  sourceFileId: string,
  index: number,
): PreviewItem {
  const content = sourceText.slice(range.start, range.end)

  return {
    id: `preview-${sourceFileId}-${index + 1}`,
    sourceFileId,
    originalContent: content,
    editedContent: content,
    sourceStart: range.start,
    sourceEnd: range.end,
    sourceStartLine: lineNumberAtOffset(lines, range.start),
    sourceEndLine: lineNumberAtOffset(lines, Math.max(range.start, range.end - 1)),
    tokenCount: Math.max(1, Math.ceil(content.length / 2)),
    status: 'original',
  }
}

export function buildPreviewItems(
  sourceText: string,
  processType: ProcessType,
  sourceFileId = 'default-source',
  unstructuredOptions?: UnstructuredProcessOptions,
): PreviewItem[] {
  const lines = sourceLines(sourceText)

  if (processType === 'unstructured') {
    return buildUnstructuredRanges(sourceText, unstructuredOptions).map((range, index) => (
      previewItemFromRange(sourceText, lines, range, sourceFileId, index)
    ))
  }

  const meaningfulLines = lines.filter((line) => line.content.trim())
  const groupSize = processType === 'structured' ? 1 : 3
  const items: PreviewItem[] = []

  for (let index = 0; index < meaningfulLines.length; index += groupSize) {
    const group = meaningfulLines.slice(index, index + groupSize)
    if (!group.length) continue

    const sourceStart = group[0].start
    const sourceEnd = group[group.length - 1].end
    const content = sourceText.slice(sourceStart, sourceEnd)

    items.push({
      id: `preview-${sourceFileId}-${items.length + 1}`,
      sourceFileId,
      originalContent: content,
      editedContent: content,
      sourceStart,
      sourceEnd,
      sourceStartLine: group[0].number,
      sourceEndLine: group[group.length - 1].number,
      tokenCount: Math.max(1, Math.ceil(content.length / 2)),
      status: 'original',
    })
  }

  return items
}

const SEMANTIC_PREFIXES = [
  '请结合实际情况，说明一下：',
  '如果方便的话，请详细解答：',
  '请用通俗易懂的方式说明：',
  '请从实际应用角度说明：',
  '请简洁、自然地说明：',
]

export function createResults(
  items: PreviewItem[],
  options?: StructuredProcessOptions | UnstructuredProcessOptions,
): ResultItem[] {
  const resultCount = options && 'qaPairsPerChunk' in options
    ? Math.min(3, finiteInteger(options.qaPairsPerChunk, 1, 1))
    : Math.min(5, finiteInteger(options?.qaPairsPerRow, 1, 1))

  return items.flatMap((item, index) => {
    const [firstLine = '', ...rest] = item.editedContent.split('\n')
    const output = rest.join('\n').trim() || item.editedContent.trim()
    const baseInstruction = firstLine.replace(/^问[:：]\s*/, '').trim() || `数据条目 ${index + 1}`

    return Array.from({ length: resultCount }, (_, variantIndex) => {
      const instruction = options?.semanticEnrichment
        ? `${SEMANTIC_PREFIXES[variantIndex]}${baseInstruction}`
        : variantIndex === 0
          ? baseInstruction
          : `${baseInstruction}（问法 ${variantIndex + 1}）`

      return {
        id: resultCount === 1 ? `result-${index + 1}` : `result-${index + 1}-${variantIndex + 1}`,
        instruction,
        input: '',
        output,
        originalInstruction: instruction,
        originalInput: '',
        originalOutput: output,
        status: 'valid' as const,
      }
    })
  })
}