create-schema-customization.js

const _ = require(`lodash`)
const { GraphQLBoolean } = require(`gatsby/graphql`)
const remark = require(`remark`)
const english = require(`retext-english`)
const remark2retext = require(`remark-retext`)
const unified = require(`unified`)
const visit = require(`unist-util-visit`)
const remove = require(`unist-util-remove`)
const toString = require(`mdast-util-to-string`)
const generateTOC = require(`mdast-util-toc`)
const prune = require(`underscore.string/prune`)
const slugify = require(`slugify`)
const path = require(`path`)

const debug = require(`debug`)(`gatsby-plugin-mdx:extend-node-type`)
const getTableOfContents = require(`../utils/get-table-of-content`)
const defaultOptions = require(`../utils/default-options`)
const genMDX = require(`../utils/gen-mdx`)
const { mdxHTMLLoader: loader } = require(`../utils/render-html`)

async function getCounts({ mdast }) {
  const counts = {}

  // convert the mdxast to back to mdast
  remove(mdast, `import`)
  remove(mdast, `export`)
  visit(mdast, `jsx`, node => {
    node.type = `html`
  })

  await remark()
    .use(remark2retext, unified().use(english).use(count))
    .run(mdast)

  function count() {
    return counter
    function counter(tree) {
      visit(tree, visitor)
      function visitor(node) {
        counts[node.type] = (counts[node.type] || 0) + 1
      }
    }
  }

  return {
    paragraphs: counts.ParagraphNode || 0,
    sentences: counts.SentenceNode || 0,
    words: counts.WordNode || 0,
  }
}

module.exports = function createSchemaCustomization(
  {
    store,
    pathPrefix,
    getNode,
    getNodes,
    cache,
    reporter,
    actions,
    schema,
    ...helpers
  },
  pluginOptions
) {
  let mdxHTMLLoader
  const { createTypes } = actions

  const options = defaultOptions(pluginOptions)
  const headingsMdx = [`h1`, `h2`, `h3`, `h4`, `h5`, `h6`]

  /**
   * Support gatsby-remark parser plugins
   */
  for (const plugin of options.gatsbyRemarkPlugins) {
    debug(`requiring`, plugin.resolve)
    const requiredPlugin = plugin.module
    debug(`required`, plugin)
    if (_.isFunction(requiredPlugin.setParserPlugins)) {
      for (const parserPlugin of requiredPlugin.setParserPlugins(
        plugin.pluginOptions || {}
      )) {
        if (_.isArray(parserPlugin)) {
          const [parser, parserPluginOptions] = parserPlugin
          debug(`adding remarkPlugin with options`, plugin, parserPluginOptions)
          options.remarkPlugins.push([parser, parserPluginOptions])
        } else {
          debug(`adding remarkPlugin`, plugin)
          options.remarkPlugins.push(parserPlugin)
        }
      }
    }
  }

  const pendingPromises = new WeakMap()
  const processMDX = ({ node }) => {
    let promise = pendingPromises.get(node)
    if (!promise) {
      promise = genMDX({
        node,
        options,
        store,
        pathPrefix,
        getNode,
        getNodes,
        cache,
        reporter,
        actions,
        schema,
        ...helpers,
      })
      pendingPromises.set(node, promise)
      promise.then(() => {
        pendingPromises.delete(node)
      })
    }
    return promise
  }

  // New Code // Schema
  const MdxType = schema.buildObjectType({
    name: `Mdx`,
    fields: {
      rawBody: { type: `String!` },
      fileAbsolutePath: { type: `String!` },
      frontmatter: { type: `MdxFrontmatter` },
      slug: {
        type: `String`,
        async resolve(mdxNode, args, context) {
          const nodeWithContext = context.nodeModel.findRootNodeAncestor(
            mdxNode,
            node => node.internal && node.internal.type === `File`
          )

          if (!nodeWithContext) {
            return null
          }
          const fileRelativePath = nodeWithContext.relativePath

          const parsedPath = path.parse(fileRelativePath)

          let relevantPath
          if (parsedPath.name === `index`) {
            relevantPath = fileRelativePath.replace(parsedPath.base, ``)
          } else {
            relevantPath = fileRelativePath.replace(parsedPath.ext, ``)
          }
          return slugify(relevantPath, {
            remove: /[^\w\s$*_+~.()'"!\-:@/]/g, // this is the set of allowable characters
          })
        },
      },
      body: {
        type: `String!`,
        async resolve(mdxNode) {
          const { body } = await processMDX({ node: mdxNode })
          return body
        },
      },
      excerpt: {
        type: `String!`,
        args: {
          pruneLength: {
            type: `Int`,
            defaultValue: 140,
          },
          truncate: {
            type: GraphQLBoolean,
            defaultValue: false,
          },
        },
        async resolve(mdxNode, { pruneLength, truncate }) {
          if (mdxNode.excerpt) {
            return Promise.resolve(mdxNode.excerpt)
          }
          const { mdast } = await processMDX({ node: mdxNode })

          const excerptNodes = []
          visit(mdast, node => {
            if (node.type === `text` || node.type === `inlineCode`) {
              excerptNodes.push(node.value)
            }
            return
          })

          if (!truncate) {
            return prune(excerptNodes.join(` `), pruneLength, `…`)
          }

          return _.truncate(excerptNodes.join(` `), {
            length: pruneLength,
            omission: `…`,
          })
        },
      },
      headings: {
        type: `[MdxHeadingMdx]`,
        args: {
          depth: {
            type: `HeadingsMdx`,
          },
        },
        async resolve(mdxNode, { depth }) {
          // TODO: change this to operate on html instead of mdast
          const { mdast } = await processMDX({ node: mdxNode })
          let headings = []
          visit(mdast, `heading`, heading => {
            headings.push({
              value: toString(heading),
              depth: heading.depth,
            })
          })
          if (headingsMdx.includes(depth)) {
            headings = headings.filter(heading => `h${heading.depth}` === depth)
          }
          return headings
        },
      },
      html: {
        type: `String`,
        async resolve(mdxNode) {
          if (mdxNode.html) {
            return Promise.resolve(mdxNode.html)
          }
          const { body } = await processMDX({ node: mdxNode })
          try {
            if (!mdxHTMLLoader) {
              mdxHTMLLoader = loader({ reporter, cache, store })
            }
            const html = await mdxHTMLLoader.load({ ...mdxNode, body })
            return html
          } catch (e) {
            reporter.error(
              `gatsby-plugin-mdx: Error querying the \`html\` field.
This field is intended for use with RSS feed generation.
If you're trying to use it in application-level code, try querying for \`Mdx.body\` instead.
Original error:
${e}`
            )
            return undefined
          }
        },
      },
      mdxAST: {
        type: `JSON`,
        async resolve(mdxNode) {
          const { mdast } = await processMDX({ node: mdxNode })
          return mdast
        },
      },
      tableOfContents: {
        type: `JSON`,
        args: {
          maxDepth: {
            type: `Int`,
            default: 6,
          },
        },
        async resolve(mdxNode, { maxDepth }) {
          const { mdast } = await processMDX({ node: mdxNode })
          const toc = generateTOC(mdast, { maxDepth })

          return getTableOfContents(toc.map, {})
        },
      },
      timeToRead: {
        type: `Int`,
        async resolve(mdxNode) {
          const { mdast } = await processMDX({ node: mdxNode })
          const { words } = await getCounts({ mdast })
          let timeToRead = 0
          const avgWPM = 265
          timeToRead = Math.round(words / avgWPM)
          if (timeToRead === 0) {
            timeToRead = 1
          }
          return timeToRead
        },
      },
      wordCount: {
        type: `MdxWordCount`,
        async resolve(mdxNode) {
          const { mdast } = await processMDX({ node: mdxNode })
          return getCounts({ mdast })
        },
      },
    },
    interfaces: [`Node`],
    extensions: {
      childOf: {
        mimeTypes: options.mediaTypes,
      },
    },
  })

  createTypes([
    `
  type MdxFrontmatter {
    title: String!
  }

  type MdxHeadingMdx {
    value: String
    depth: Int
  }

  enum HeadingsMdx {
    ${headingsMdx}
  }

  type MdxWordCount {
    paragraphs: Int
    sentences: Int
    words: Int
  }
`,
    MdxType,
  ])
}