markdown.ts

import path from 'node:path'

import {
  componentPlugin,
  type ComponentPluginOptions
} from '@mdit-vue/plugin-component'
import {
  frontmatterPlugin,
  type FrontmatterPluginOptions
} from '@mdit-vue/plugin-frontmatter'
import {
  headersPlugin,
  type HeadersPluginOptions
} from '@mdit-vue/plugin-headers'
import { sfcPlugin, type SfcPluginOptions } from '@mdit-vue/plugin-sfc'
import { titlePlugin } from '@mdit-vue/plugin-title'
import { tocPlugin, type TocPluginOptions } from '@mdit-vue/plugin-toc'
import { slugify as defaultSlugify } from '@mdit-vue/shared'
import { anchor as anchorPlugin, type AnchorOptions } from '@mdit/plugin-anchor'
import {
  attrs as attrsPlugin,
  type MarkdownItAttrsOptions
} from '@mdit/plugin-attrs'
import { fullEmoji as emojiPlugin } from '@mdit/plugin-emoji'
import { footnote as footnotePlugin } from '@mdit/plugin-footnote'
import {
  tasklist as tasklistPlugin,
  type MarkdownItTaskListOptions
} from '@mdit/plugin-tasklist'
import { MarkdownItAsync, type MarkdownItAsyncOptions } from 'markdown-it-async'
import mditCjkFriendly from 'markdown-it-cjk-friendly'
import type {
  BuiltinLanguage,
  BuiltinTheme,
  CodeToHastOptions,
  Highlighter,
  LanguageInput,
  ShikiTransformer,
  ThemeRegistrationAny
} from 'shiki'
import type { Logger } from 'vite'

import type {
  Awaitable,
  CodeCopyButtonOptions,
  LocaleConfig,
  MarkdownLocaleOptions
} from '../shared'
import {
  containerPlugin,
  gitHubAlertsPlugin,
  type ContainerOptions
} from './plugins/containers'
import { eagerFrontmatterInterpolationPlugin } from './plugins/eagerFrontmatterInterpolation'
import { highlight as createHighlighter } from './plugins/highlight'
import { imagePlugin, type Options as ImageOptions } from './plugins/image'
import {
  includePlugin,
  type Options as IncludePluginOptions
} from './plugins/include'
import { lineNumberPlugin } from './plugins/lineNumbers'
import { linkPlugin } from './plugins/link'
import { preWrapperPlugin } from './plugins/preWrapper'
import { restoreEntities } from './plugins/restoreEntities'
import {
  snippetPlugin,
  type Options as SnippetPluginOptions
} from './plugins/snippet'
import { tablePlugin } from './plugins/table'

export type { Header } from '../shared'

// not exported from @mdit/plugin-emoji, so derive it from the plugin signature
type EmojiPluginOptions = NonNullable<Parameters<typeof emojiPlugin>[1]>

export type ThemeOptions =
  | ThemeRegistrationAny
  | BuiltinTheme
  | {
      light: ThemeRegistrationAny | BuiltinTheme
      dark: ThemeRegistrationAny | BuiltinTheme
    }

// highlight is marked as any to avoid type conflicts with plugins expecting
// regular markdown-it which has sync highlight function. Such plugins will fail
// if they access highlight directly but currently none of the ones we use do that.
export type MarkdownRenderer = MarkdownItAsync & {
  options: { highlight?: any }
}

export interface MarkdownOptions extends MarkdownItAsyncOptions {
  /* ==================== General Options ==================== */

  /**
   * Configure the markdown-it instance before any plugins are applied.
   */
  preConfig?: (md: MarkdownRenderer) => Awaitable<void>
  /**
   * Configure the markdown-it instance after all built-in plugins are applied.
   */
  config?: (md: MarkdownRenderer) => Awaitable<void>
  /**
   * Disable cache (experimental)
   */
  cache?: boolean
  /**
   * HTML attributes applied to external links.
   * @default { target: '_blank', rel: 'noreferrer' }
   */
  externalLinks?: Record<string, string>
  /**
   * Per-locale overrides for build-time markdown strings (container titles
   * and the code copy button title), keyed by locale index. Populated
   * automatically from `locales.<index>.markdown` in the site config - pass
   * directly only when using `createMarkdownRenderer` standalone.
   */
  locales?: Record<string, MarkdownLocaleOptions>

  /* ==================== Syntax Highlighting ==================== */

  /**
   * Custom theme for syntax highlighting.
   *
   * You can also pass an object with `light` and `dark` themes to support
   * dual themes.
   *
   * @example { theme: 'github-dark' }
   * @example { theme: { light: 'github-light', dark: 'github-dark' } }
   *
   * You can use an existing theme.
   * @see https://shiki.style/themes
   * Or add your own theme.
   * @see https://shiki.style/guide/load-theme
   */
  theme?: ThemeOptions
  /**
   * Custom languages for syntax highlighting or pre-load built-in languages.
   * @see https://shiki.style/languages
   */
  languages?: (LanguageInput | BuiltinLanguage)[]
  /**
   * Custom language aliases for syntax highlighting.
   * Maps custom language names to existing languages.
   * Alias lookup is case-insensitive and underscores in language names are
   * displayed as spaces.
   *
   * @example
   *
   * Maps `my_lang` to use Python syntax highlighting.
   * ```js
   * { 'my_lang': 'python' }
   * ```
   *
   * Usage in markdown:
   * ````md
   * ```My_Lang
   * # This will be highlighted as Python code
   * # and will show "My Lang" as the language label
   * print("Hello, World!")
   * ```
   * ````
   *
   * @see https://shiki.style/guide/load-lang#custom-language-aliases
   */
  languageAlias?: Record<string, string>
  /**
   * Fallback language used when the specified language is not available.
   */
  defaultHighlightLang?: string
  /**
   * Transformers applied to code blocks.
   * @see https://shiki.style/guide/transformers
   */
  codeTransformers?: ShikiTransformer[]
  /**
   * Color replacements applied during syntax highlighting.
   * Accepts either a flat color map or per-theme replacements.
   * @see https://shiki.style/guide/theme-colors#color-replacements
   */
  colorReplacements?: CodeToHastOptions['colorReplacements']
  /**
   * Configure the Shiki instance.
   */
  shikiSetup?: (shiki: Highlighter) => void | Promise<void>

  /* ==================== Code Blocks ==================== */

  /**
   * Wrap code blocks in a container carrying the language label and the
   * copy button. The default theme's code block styling relies on this
   * markup. Disabling it also disables `lineNumbers`.
   * @default true
   */
  preWrapper?: boolean
  /**
   * Strings for the copy button in code blocks: `tooltipText` is the
   * button's tooltip and `copiedText` is shown next to it after copying.
   * @default { tooltipText: 'Copy code', copiedText: 'Copied' }
   */
  codeCopyButton?: CodeCopyButtonOptions
  /**
   * Custom language labels for display.
   * Overrides the default language label shown in code blocks.
   * Keys are case-insensitive.
   *
   * @example { 'vue': 'Vue SFC' }
   */
  languageLabel?: Record<string, string>
  /**
   * Show line numbers in code blocks. Requires the `preWrapper` plugin.
   * @default false
   */
  lineNumbers?: boolean
  /**
   * Options for importing code snippets from files with `<<<`. Set to
   * `false` to disable.
   * @see https://vitepress.dev/guide/markdown#import-code-snippets
   */
  snippet?: SnippetPluginOptions | boolean
  /**
   * Options for including markdown files with `<!-- @include: path -->`.
   * Set to `false` to disable.
   * @see https://vitepress.dev/guide/markdown#markdown-file-inclusion
   */
  include?: IncludePluginOptions | boolean

  /* ==================== Markdown Extensions ==================== */

  /**
   * Options for `@mdit/plugin-attrs`. Set to `false` to disable. The `fence`
   * rule is off by default so that curly attributes never consume code block
   * meta (e.g. line highlighting) - add classes to code blocks using shiki
   * transformers instead.
   * @see https://mdit-plugins.github.io/attrs.html
   */
  attrs?: MarkdownItAttrsOptions | boolean
  /**
   * Options for `@mdit/plugin-emoji`. Set to `false` to disable.
   * @see https://mdit-plugins.github.io/emoji.html
   */
  emoji?: EmojiPluginOptions | boolean
  /**
   * Options for `@mdit/plugin-tasklist` (GitHub-style task lists,
   * `- [ ] task`). Set to `false` to disable.
   * @see https://mdit-plugins.github.io/tasklist.html
   */
  tasklist?: MarkdownItTaskListOptions | boolean
  /**
   * Whether to enable footnotes (`[^1]` references with definitions, plus
   * inline `^[note]` syntax).
   * @default true
   * @see https://mdit-plugins.github.io/footnote.html
   */
  footnote?: boolean
  /**
   * Improves emphasis (`**bold**`) handling in Japanese, Chinese, and
   * Korean text.
   * @default true
   * @see https://github.com/tats-u/markdown-cjk-friendly
   */
  cjkFriendlyEmphasis?: boolean
  /**
   * Options for `@mdit/plugin-anchor`. Set to `false` to disable adding ids
   * and anchor links to headings. Note that the default theme's outline and
   * heading hash links rely on these ids.
   * @see https://mdit-plugins.github.io/anchor.html
   */
  anchor?: AnchorOptions | boolean
  /**
   * Options for `@mdit-vue/plugin-headers`. Set to `true` or pass options
   * to collect page headers into page data.
   * @default false
   * @see https://github.com/mdit-vue/mdit-vue/tree/main/packages/plugin-headers
   */
  headers?: HeadersPluginOptions | boolean
  /**
   * Options for `@mdit-vue/plugin-toc`. Set to `false` to disable the
   * `[[toc]]` syntax.
   * @see https://github.com/mdit-vue/mdit-vue/tree/main/packages/plugin-toc
   */
  toc?: TocPluginOptions | boolean
  /**
   * Math support.
   *
   * You need to install `markdown-it-mathjax3` and set `math` to `true` to
   * enable it. You can also pass options to `markdown-it-mathjax3` here.
   * @default false
   * @see https://vitepress.dev/guide/markdown#math-equations
   */
  math?: any | boolean
  /**
   * Custom labels for the built-in containers (`::: tip` etc.) and
   * additional user-defined containers. Labels are also used as the
   * default titles of GitHub-flavored alerts.
   * @see https://vitepress.dev/guide/markdown#custom-containers
   */
  container?: ContainerOptions | boolean
  /**
   * Whether to enable GitHub-flavored alerts (`> [!NOTE]`).
   * @default true
   * @see https://vitepress.dev/guide/markdown#github-flavored-alerts
   */
  gfmAlerts?: boolean
  /**
   * Add `tabindex="0"` to tables so keyboard users can focus and scroll
   * them.
   * @default true
   */
  tableTabIndex?: boolean
  /**
   * Options for the image plugin (resolves image sources against the public
   * directory, adds dimensions, and supports lazy loading). Set to `false`
   * to disable.
   * @see https://vitepress.dev/guide/markdown#image-lazy-loading
   */
  image?: ImageOptions | boolean

  /* ==================== Vue Integration ==================== */

  /**
   * Options for `@mdit-vue/plugin-component`. Set to `false` to disable.
   * @see https://github.com/mdit-vue/mdit-vue/tree/main/packages/plugin-component
   */
  component?: ComponentPluginOptions | boolean
  /**
   * Options for `@mdit-vue/plugin-frontmatter`.
   * @see https://github.com/mdit-vue/mdit-vue/tree/main/packages/plugin-frontmatter
   */
  frontmatter?: FrontmatterPluginOptions
  /**
   * Resolve `{{ $frontmatter.<path> }}` interpolations to their values while
   * rendering markdown, so the value also reaches consumers that never run
   * Vue - heading anchors and titles, the local search index, content loader
   * output, link destinations - and the compiled Vue template gets static
   * text instead of a runtime expression. Only bare property paths resolving
   * to simple primitive values in the page's own frontmatter are inlined -
   * anything else (complex expressions, missing keys, non-primitive values,
   * `v-pre` scopes) keeps its runtime interpolation. Set to `false` to leave
   * all interpolation to the Vue runtime - for example when
   * `transformPageData` rewrites frontmatter values that pages interpolate,
   * which would otherwise render the pre-transform value (a warning is
   * logged when that happens).
   *
   * @experimental
   * @default true
   */
  eagerFrontmatterInterpolation?: boolean
  /**
   * Options for `@mdit-vue/plugin-sfc`.
   * @see https://github.com/mdit-vue/mdit-vue/tree/main/packages/plugin-sfc
   */
  sfc?: SfcPluginOptions
}

// folds `locales.<index>.markdown` entries from the site config into
// `MarkdownOptions.locales` so per-locale strings reach the renderer -
// site config entries win over directly passed ones
export function mergeMarkdownLocales(
  options: MarkdownOptions = {},
  locales?: LocaleConfig
): MarkdownOptions {
  const entries = Object.entries(locales ?? {}).filter(([, l]) => l?.markdown)
  if (!entries.length) return options
  const merged = { ...options.locales }
  for (const [index, { markdown }] of entries) {
    merged[index] = { ...merged[index], ...markdown }
  }
  return { ...options, locales: merged }
}

let md: MarkdownRenderer | undefined
let _disposeHighlighter: (() => void) | undefined

export function disposeMdItInstance() {
  if (md) {
    md = undefined
    _disposeHighlighter?.()
  }
}

/**
 * @experimental
 */
export async function createMarkdownRenderer(
  srcDir: string,
  options: MarkdownOptions = {},
  base = '/',
  logger: Pick<Logger, 'warn'> = console,
  publicDir?: string
): Promise<MarkdownRenderer> {
  if (md) return md

  publicDir ??= path.resolve(srcDir, 'public')

  const theme = options.theme ?? { light: 'github-light', dark: 'github-dark' }
  const codeCopyButton = {
    tooltipText: options.codeCopyButton?.tooltipText || 'Copy code',
    copiedText: options.codeCopyButton?.copiedText || 'Copied'
  }

  const [highlight, dispose] = options.highlight
    ? [options.highlight, () => {}]
    : await createHighlighter(theme, options, logger)

  _disposeHighlighter = dispose

  md = new MarkdownItAsync({ html: true, linkify: true, highlight, ...options })

  md.linkify.set({ fuzzyLink: false })
  restoreEntities(md)

  if (options.preConfig) {
    await options.preConfig(md)
  }

  const slugify =
    normalizePluginOptions(options.anchor)?.slugify ?? defaultSlugify

  // VitePress customizations
  if (options.preWrapper !== false) {
    preWrapperPlugin(md, {
      codeCopyButton,
      languageLabel: options.languageLabel,
      locales: options.locales
    })
    // must be applied after preWrapper as it augments its output
    lineNumberPlugin(md, options.lineNumbers)
  }
  if (options.snippet !== false) {
    snippetPlugin(md, srcDir, normalizePluginOptions(options.snippet), logger)
  }
  const containerOptions = normalizePluginOptions(options.container)
  if (options.container !== false) {
    containerPlugin(md, containerOptions, { locales: options.locales })
  }
  if (options.gfmAlerts !== false) {
    gitHubAlertsPlugin(md, containerOptions, { locales: options.locales })
  }
  if (options.image !== false) {
    imagePlugin(md, publicDir, normalizePluginOptions(options.image))
  }
  linkPlugin(
    md,
    { target: '_blank', rel: 'noreferrer', ...options.externalLinks },
    base,
    slugify
  )
  // must come after the image and link plugins so that url rebasing runs
  // before their href/src handling
  if (options.include !== false) {
    includePlugin(md, srcDir, normalizePluginOptions(options.include), logger)
  }
  if (options.tableTabIndex !== false) {
    tablePlugin(md)
  }

  // community plugins
  if (options.attrs !== false) {
    attrsPlugin(md, {
      // no `fence` - code block meta (e.g. line highlighting) must reach
      // the highlighter intact
      rule: [
        'inline',
        'table',
        'list',
        'heading',
        'hr',
        'softbreak',
        'blockInfo',
        'blockEnd',
        'tasklist'
      ],
      ...normalizePluginOptions(options.attrs)
    })
  }
  if (options.emoji !== false) {
    emojiPlugin(md, normalizePluginOptions(options.emoji))
  }
  if (options.tasklist !== false) {
    tasklistPlugin(md, normalizePluginOptions(options.tasklist))
  }
  if (options.footnote !== false) {
    footnotePlugin(md)
  }
  if (options.cjkFriendlyEmphasis !== false) {
    mditCjkFriendly(md)
  }
  if (options.anchor !== false) {
    anchorPlugin(md, {
      slugify,
      getTokensText: (tokens) => {
        return tokens
          .filter((t) => !['html_inline', 'emoji'].includes(t.type))
          .map((t) => t.content)
          .join('')
      },
      permalink: (slug, _, state, idx) => {
        const title =
          state.tokens[idx + 1]?.children
            ?.filter((token) => ['text', 'code_inline'].includes(token.type))
            .reduce((acc, t) => acc + t.content, '')
            .trim() || ''

        const linkTokens = [
          Object.assign(new state.Token('text', '', 0), { content: ' ' }),
          Object.assign(new state.Token('link_open', 'a', 1), {
            attrs: [
              ['class', 'header-anchor'],
              ['href', `#${slug}`],
              ['aria-label', `Permalink to “${title}”`]
            ]
          }),
          Object.assign(new state.Token('html_inline', '', 0), {
            content: '&#8203;',
            meta: { isPermalinkSymbol: true }
          }),
          new state.Token('link_close', 'a', -1)
        ]

        state.tokens[idx + 1].children?.push(...linkTokens)
      },
      ...normalizePluginOptions(options.anchor)
    })
  }
  if (options.math) {
    try {
      const mathPlugin = await import('markdown-it-mathjax3')
      ;(mathPlugin.default ?? mathPlugin)(md, {
        ...normalizePluginOptions(options.math)
      })
      const origMathInline = md.renderer.rules.math_inline!
      md.renderer.rules.math_inline = function (...args) {
        return origMathInline
          .apply(this, args)
          .replace(/^<mjx-container /, '<mjx-container v-pre ')
      }
      const origMathBlock = md.renderer.rules.math_block!
      md.renderer.rules.math_block = function (...args) {
        return origMathBlock
          .apply(this, args)
          .replace(/^<mjx-container /, '<mjx-container v-pre tabindex="0" ')
      }
    } catch (error) {
      throw new Error(
        'You need to install `markdown-it-mathjax3@^4` to use math support.'
      )
    }
  }

  // mdit-vue plugins
  if (options.component !== false) {
    componentPlugin(md, normalizePluginOptions(options.component))
  }
  // pass an empty options object to gray-matter, otherwise it would memoize
  // the results in an unbounded cache, where the key is the full file content.
  // https://github.com/jonschlinkert/gray-matter/blob/310f9349381775d10a221cef903989eb5acc8843/index.js#L44-L47
  ;(options.frontmatter ??= {}).grayMatterOptions ??= {}
  frontmatterPlugin(md, options.frontmatter)
  if (options.headers) {
    headersPlugin(md, {
      level: [2, 3, 4, 5, 6],
      slugify,
      ...normalizePluginOptions(options.headers)
    })
  }
  sfcPlugin(md, options.sfc)
  titlePlugin(md)
  const tocOptions = normalizePluginOptions(options.toc)
  if (options.toc !== false) {
    tocPlugin(md, {
      slugify,
      ...tocOptions,
      format: (s) => {
        const title = s.replaceAll('&amp;', '&') // encoded twice because of restoreEntities
        return tocOptions?.format?.(title) ?? title
      }
    })
  }
  // applied after anchor/title so its finalize rule runs once their rules
  // have extracted the plain resolved text; its main rule is anchored right
  // after `text_join` regardless of when the plugin is applied
  if (options.eagerFrontmatterInterpolation !== false) {
    eagerFrontmatterInterpolationPlugin(md)
  }

  // apply user config
  if (options.config) {
    await options.config(md)
  }

  return md
}

// `true` and `undefined` enable a plugin with its default options - only an
// object carries user-provided plugin options
function normalizePluginOptions<T>(
  value: T | boolean | undefined
): T | undefined {
  return typeof value === 'boolean' ? undefined : value
}