text: const path = require(`path`)
  const { createFilePath } = require(`gatsby-source-filesystem`)
  
  exports.createPages = async ({ graphql, actions }) => {
    const { createPage } = actions
  
    const blogPost = path.resolve(`./src/templates/blog-post.js`)
    const result = await graphql(
      `
        {
          allMarkdownRemark(sort: { fields: [], order: DESC }, limit: 1000) {
            edges {
              node {
                fields {
                  slug
                }
                frontmatter {
                  title
                }
              }
            }
          }
        }
      `
    )
  
    if (result.errors) {
      throw result.errors
    }
  
    // Create blog posts pages.
    const posts = result.data.allMarkdownRemark.edges
  
    posts.forEach((post, index) => {
      const previous = index === posts.length - 1 ? null : posts[index + 1].node
      const next = index === 0 ? null : posts[index - 1].node
  
      createPage({
        path: post.node.fields.slug,
        component: blogPost,
        context: {
          slug: post.node.fields.slug,
          previous,
          next,
        },
      })
    })
  }
  
  exports.onCreateNode = ({ node, actions, getNode }) => {
    const { createNodeField } = actions
  
    if (node.internal.type === `MarkdownRemark`) {
      const value = createFilePath({ node, getNode })
      createNodeField({
        name: `slug`,
        node,
        value,
      })
    }
  }
  