/**
 * 强调语法兼容插件
 *
 * v1 用 indexOf 顺序配对解析 ** / *，不校验 flanking 规则：
 *   - 「** 文本 **」这类星号内侧带空格的写法在 v1 中正常加粗/斜体
 *   - 标准 markdown 会因空格拒绝配对而原样输出星号，对存量简历是肉眼可见的回退
 *
 * 本插件按 v1 的顺序配对语义扫描 ** / * 标记对，
 * 把配对内容的首尾空白移到定界符外侧，使标准解析器能正确配对：
 *   ** 2021.12 - 至今 **  →  ` **2021.12 - 至今** `
 * 普通的 **加粗** / *斜体*（内容无首尾空白）完全不受影响。
 */

interface Run {
  index: number
  length: number // 2 = **, 1 = *
}

/** 找出所有标记 run 的位置（** 优先于 *） */
function findRuns(content: string, star: "**" | "*"): Run[] {
  const runs: Run[] = []
  if (star === "*") {
    // 单星：排除 ** 的成员
    for (let i = 0; i < content.length; i++) {
      if (content[i] === "*" && content[i - 1] !== "*" && content[i + 1] !== "*") {
        runs.push({ index: i, length: 1 })
      }
    }
  } else {
    let idx = content.indexOf("**")
    while (idx !== -1) {
      runs.push({ index: idx, length: 2 })
      idx = content.indexOf("**", idx + 2)
    }
  }
  return runs
}

/** v1 式顺序配对：run1-run2, run3-run4...，返回需要重写的区间 */
function collectReplacements(content: string, star: "**" | "*"): Array<{ start: number; end: number; lead: string; body: string; trail: string }> {
  const runs = findRuns(content, star)
  const result: Array<{ start: number; end: number; lead: string; body: string; trail: string }> = []
  const mark = star as string
  for (let i = 0; i + 1 < runs.length; i += 2) {
    const open = runs[i]
    const close = runs[i + 1]
    const body = content.slice(open.index + open.length, close.index)
    if (!body.trim()) continue
    const lead = body.slice(0, body.length - body.trimStart().length)
    const trail = body.slice(body.trimEnd().length)
    if (!lead && !trail) continue
    // 内容中间还有未配对的标记时不安全，跳过（保底为标准行为）
    if (body.slice(1, -1).includes(mark)) continue
    result.push({
      start: open.index,
      end: close.index + close.length,
      lead,
      body: body.trim(),
      trail,
    })
  }
  return result
}

function rewrite(content: string, star: "**" | "*"): string {
  const replacements = collectReplacements(content, star)
  if (!replacements.length) return content
  let result = content
  for (let i = replacements.length - 1; i >= 0; i--) {
    const { start, end, lead, body, trail } = replacements[i]
    result = result.slice(0, start) + lead + star + body + star + trail + result.slice(end)
  }
  return result
}

function emphasisCompatRule(state: any) {
  for (const token of state.tokens) {
    if (token.type !== "inline") continue
    const content = token.content
    if (!content || !content.includes("*")) continue
    let replaced = rewrite(content, "**")
    replaced = rewrite(replaced, "*")
    if (replaced !== content) token.content = replaced
  }
}

export function emphasisCompatPlugin(md: any) {
  // 锚定 block：无论 paragraphPerLine 是否开启都存在
  md.core.ruler.after("block", "resume_emphasis_compat", emphasisCompatRule)
}