src/lib/markdown.js

import Util from './util.js'

/**
 * Convert the HTML DOM Node to Markdown text.
 * @type {MdConverter[]}
 * @see https://github.com/domchristie/to-markdown/blob/master/lib/md-converters.js
 */
const MarkdownConverters = [
  // Paragraph
  {
    filter: 'p',
    replacement: (node, content) => {
      return '\n\n' + content + '\n\n'
    }
  },
  // Line break
  {
    filter: 'br',
    replacement: () => {
      return '  \n'
    }
  },
  // Header
  {
    filter: [ 'h1', 'h2', 'h3', 'h4', 'h5', 'h6' ],
    replacement: (node, content, modes) => {
      const level  = node.nodeName.charAt(1)
      let   prefix = ''
      for (let i = 0; i < level; ++i) {
        prefix += '#'
      }

      // Inter link (Markdown Extra)
      if (node.id && !(modes.noMELink)) {
        return '\n\n' + prefix + ' ' + content + ' {#' + node.id + '}\n\n'
      }

      return '\n\n' + prefix + ' ' + content + '\n\n'
    }
  },
  // Line
  {
    filter: 'hr',
    replacement: () => {
      return '\n\n* * *\n\n'
    }
  },
  // Italic
  {
    filter: ['em', 'i'],
    replacement: (node, content) => {
      return '_' + content + '_'
    }
  },
  // Strong
  {
    filter: [ 'strong', 'b' ],
    replacement: (node, content) => {
      return '**' + content + '**'
    }
  },
  // Inline code
  {
    filter: (node) => {
      const hasSiblings = node.previousSibling || node.nextSibling
      const isCodeBlock = (node.parentNode.nodeName === 'PRE' && !(hasSiblings))

      return (node.nodeName === 'CODE' && !(isCodeBlock))
    },
    replacement: (node, content) => {
      return '`' + content + '`'
    }
  },
  // Link
  {
    filter: (node) => {
      return (node.nodeName === 'A' && node.getAttribute('href'))
    },
    replacement: (node, content) => {
      const titlePart = node.title ? ' "' + node.title + '"' : ''
      return '[' + content + '](' + node.getAttribute('href') + titlePart + ')'
    }
  },
  // Image
  {
    filter: 'img',
    replacement: (node) => {
      const alt       = node.alt || ''
      const src       = node.getAttribute('src') || ''
      const title     = node.title || ''
      const titlePart = title ? ' "' + title + '"' : ''

      return src ? '![' + alt + '](' + src + titlePart + ')' : ''
    }
  },
  // Code blocks
  {
    filter: (node) => {
      return node.nodeName === 'PRE' && node.firstChild.nodeName === 'CODE'
    },
    replacement: (node) => {
      return '\n\n    ' + node.firstChild.textContent.replace(/\n/g, '\n    ') + '\n\n'
    }
  },
  // Block quote
  {
    filter: 'blockquote',
    replacement: (node, content) => {
      let result = Util.trim(content)
      result = result.replace(/\n{3,}/g, '\n\n')
      result = result.replace(/^/gm, '> ')
      return '\n\n' + result + '\n\n'
    }
  },
  // List item
  {
    filter: 'li',
    replacement: (node, content) => {
      const text   = content.replace(/^\s+/, '').replace(/\n/gm, '\n    ')
      const parent = node.parentNode
      const index  = Util.arrayIndexOf(parent.children, node) + 1
      const ol     = /ol/i
      const prefix = ol.test(parent.nodeName) ? index + '. ' : '* '
      return prefix + text
    }
  },
  // List
  {
    filter: [ 'ul', 'ol' ],
    replacement: (node) => {
      const strings = []
      for (let i = 0, max = node.childNodes.length; i < max; ++i) {
        if (node.childNodes[i]._replacement) {
          strings.push(node.childNodes[i]._replacement)
        }
      }

      const li = /li/i
      if (li.test(node.parentNode.nodeName)) {
        return '\n' + strings.join('\n')
      }

      return '\n\n' + strings.join('\n') + '\n\n'
    }
  },
  // Block element
  {
    filter: (node) => {
      return Util.isBlockElement(node)
    },
    replacement: (node, content) => {
      return '\n\n' + Util.outerHTML(node, content) + '\n\n'
    }
  },
  // Anything else!
  {
    filter: () => {
      return true
    },
    replacement: (node, content) => {
      return Util.outerHTML(node, content)
    }
  }
]

export default MarkdownConverters