feat: add core library

Author: timlrx

.eslintignore

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+dist/

.eslintrc

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+{
+  "extends": ["eslint:recommended", "prettier"],
+  "parserOptions": {
+    "ecmaVersion": 2020,
+    "sourceType": "module",
+    "ecmaFeatures": {
+      "jsx": true
+    }
+  },
+  "env": {
+    "node": true,
+    "es6": true,
+    "jest": true
+  },
+  "plugins": ["node"],
+  "rules": {
+    "no-unused-vars": ["warn"],
+    "node/no-missing-require": ["error"]
+  }
+}

.gitignore

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+node_modules
+*.log
+.DS_Store
+coverage
+dist/

index.js

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+import { visit } from 'unist-util-visit'
+import toString from 'hast-util-to-string'
+import { refractor } from 'refractor'
+import rangeParser from 'parse-numeric-range'
+
+const getLanguage = (node) => {
+  const className = node.properties.className || []
+
+  for (const classListItem of className) {
+    if (classListItem.slice(0, 9) === 'language-') {
+      return classListItem.slice(9).toLowerCase()
+    }
+  }
+  return null
+}
+
+// Create a closure that determines if we have to highlight the given index
+const calculateLinesToHighlight = (meta) => {
+  const RE = /{([\d,-]+)}/
+  if (RE.test(meta)) {
+    const strlineNumbers = RE.exec(meta)[1]
+    const lineNumbers = rangeParser(strlineNumbers)
+    return (index) => lineNumbers.includes(index + 1)
+  } else {
+    return () => false
+  }
+}
+
+const splitLine = (text) => {
+  // Xdm Markdown parser every code line with \n
+  const textArray = text.split(/\n/)
+
+  // Remove last line \n which results in empty array
+  if (textArray[textArray.length - 1].trim() === '') {
+    textArray.pop()
+  }
+
+  return textArray.map((line) => {
+    return {
+      type: 'element',
+      tagName: 'div',
+      properties: { className: ['code-line'] },
+      children: [{ type: 'text', value: line }],
+    }
+  })
+}
+
+const rehypePrism = (options) => {
+  options = options || {}
+
+  return (tree) => {
+    visit(tree, 'element', visitor)
+  }
+
+  function visitor(node, index, parent) {
+    if (!parent || parent.tagName !== 'pre' || node.tagName !== 'code') {
+      return
+    }
+
+    const lang = getLanguage(node)
+    const meta = node.data && node.data.meta ? node.data.meta : ''
+    const shouldHighlightLine = calculateLinesToHighlight(meta)
+
+    if (lang) {
+      parent.properties.className = (parent.properties.className || []).concat('language-' + lang)
+    }
+
+    const codeLineArray = splitLine(toString(node))
+
+    for (const [i, line] of codeLineArray.entries()) {
+      // Code lines
+      if (meta.includes('showLineNumbers') || options.showLineNumbers) {
+        line.properties.line = [(i + 1).toString()]
+        line.properties.className = [`${line.properties.className} line-number`]
+      }
+
+      // Line highlight
+      if (shouldHighlightLine(i)) {
+        line.properties.className = [`${line.properties.className} highlight-line`]
+      }
+
+      // Syntax highlight
+      if (lang) {
+        try {
+          line.children = refractor.highlight(line.children[0].value, lang).children
+        } catch (err) {
+          // eslint-disable-next-line no-empty
+          if (options.ignoreMissing && /Unknown language/.test(err.message)) {
+          } else {
+            throw err
+          }
+        }
+      }
+    }
+
+    node.children = codeLineArray
+  }
+}
+
+export default rehypePrism