import MarkdownIt from 'markdown-it'
import hljs from 'highlight.js'
import DOMPurify from 'isomorphic-dompurify'
import { stripFrontMatter } from './markdown-front-matter'

const escapeHtml = (value: string): string =>
  value
    .replaceAll('&', '&')
    .replaceAll('<', '&lt;')
    .replaceAll('>', '&gt;')
    .replaceAll('"', '&quot;')
    .replaceAll("'", '&#39;')

const toSafeLanguageClass = (lang: string): string => {
  const normalized = lang.trim().toLowerCase().replaceAll(/[^a-z0-9_-]/g, '')
  return normalized || 'text'
}

const getHighlightedCode = (source: string, lang: string): string => {
  const normalizedLang = lang.trim().toLowerCase()
  if (normalizedLang && hljs.getLanguage(normalizedLang)) {
    return hljs.highlight(source, { language: normalizedLang, ignoreIllegals: true }).value
  }
  if (normalizedLang) {
    return hljs.highlightAuto(source).value
  }
  return escapeHtml(source)
}

const md = new MarkdownIt({
  html: false,
  linkify: true,
  typographer: false,
  breaks: true,
  // 开启代码块语言识别
  highlight: function (str: string, lang: string) {
    // 处理语言标签（如果没有指定语言，默认 text）
    const language = toSafeLanguageClass(lang || 'text')
    const highlightedCode = getHighlightedCode(str, lang || '')
    // 生成带语言标识 + 复制按钮的代码块外壳
    return (
      `<div class="code-block-wrapper"><div class="code-header"><span class="code-lang">${language}</span>` +
      `<button class="copy-btn" type="button" data-copy-code>复制</button></div>` +
      `<pre><code class="hljs language-${language}">${highlightedCode}</code></pre></div>`
    )
  },
})

/** 全局复制代码函数与事件绑定标记 */
declare global {
  interface Window {
    copyCode: (btn: HTMLButtonElement) => void
    __markdownCopyBound?: boolean
  }
}

// 只在客户端环境注册复制函数
if (typeof window !== 'undefined') {
  window.copyCode = function (btn: HTMLButtonElement) {
    const codeBlock = btn.closest('.code-block-wrapper')!.querySelector('code')!
    const text = codeBlock.textContent || ''
    
    navigator.clipboard.writeText(text).then(() => {
      const originalText = btn.textContent
      btn.textContent = '已复制'
      btn.classList.add('is-copied')
      
      // 2秒后恢复按钮文字
      setTimeout(() => {
        btn.textContent = originalText
        btn.classList.remove('is-copied')
      }, 2000)
    })
  }

  if (!window.__markdownCopyBound) {
    document.addEventListener('click', (event) => {
      const target = event.target
      if (!(target instanceof Element)) {
        return
      }
      const btn = target.closest<HTMLButtonElement>('button[data-copy-code]')
      if (!btn) {
        return
      }
      window.copyCode(btn)
    })
    window.__markdownCopyBound = true
  }
}

/** 将 Markdown 转为可安全用于 `v-html` 的 HTML（禁用源码中的原始 HTML）。 */
export function renderSafeMarkdown(src: string): string {
  if (!src.trim()) {
    return ''
  }
  return DOMPurify.sanitize(md.render(stripFrontMatter(src)), { USE_PROFILES: { html: true } })
}