gatsby-node.js

const _ = require('lodash')
const path = require('path')
const { createFilePath } = require('gatsby-source-filesystem')
const { fmImagesToRelative } = require('gatsby-remark-relative-images')

exports.createPages = ({ boundActionCreators, graphql }) => {
  const { createPage } = boundActionCreators

  return graphql(`
    {
      allMarkdownRemark(limit: 1000) {
        edges {
          node {
            id
            fields {
              slug
            }
            frontmatter {
              tags
              templateKey
            }
          }
        }
      }
    }
  `).then(result => {
    if (result.errors) {
      result.errors.forEach(e => console.error(e.toString()))
      return Promise.reject(result.errors)
    }

    const posts = result.data.allMarkdownRemark.edges

    posts.forEach(edge => {
      const id = edge.node.id
      createPage({
        path: edge.node.fields.slug,
        tags: edge.node.frontmatter.tags,
        component: path.resolve(
          `src/templates/${String(edge.node.frontmatter.templateKey)}.js`
        ),
        // additional data can be passed via context
        context: {
          id,
        },
      })
    })

    // Tag pages:
    let tags = []
    // Iterate through each post, putting all found tags into `tags`
    posts.forEach(edge => {
      if (_.get(edge, `node.frontmatter.tags`)) {
        tags = tags.concat(edge.node.frontmatter.tags)
      }
    })
    // Eliminate duplicate tags
    tags = _.uniq(tags)

    // Make tag pages
    tags.forEach(tag => {
      const tagPath = `/tags/${_.kebabCase(tag)}/`

      createPage({
        path: tagPath,
        component: path.resolve(`src/templates/tags.js`),
        context: {
          tag,
        },
      })
    })
  })
}

exports.onCreateNode = ({ node, boundActionCreators, getNode }) => {
  fmImagesToRelative(node)
  const { createNodeField } = boundActionCreators

  if (node.internal.type === `MarkdownRemark`) {
    const value = createFilePath({ node, getNode })
    createNodeField({
      name: `slug`,
      node,
      value,
    })
  }
}

// link collections
exports.sourceNodes = ({ boundActionCreators, getNodes, getNode }) => {
  const { createNodeField } = boundActionCreators

  const nodes = getNodes()

  // link scenes to collections
  // first, build an index
  const scenesByPlaylistIndex = {}
  // Playlist -> Scenes Index build
  nodes
    .filter(
      node =>
        node.internal.type === `MarkdownRemark` &&
        !!node.frontmatter &&
        node.frontmatter.templateKey === `playlist`
    )
    .forEach(playlist => {
      // console.log(playlist)
      if (!!playlist.frontmatter.scenes) {
        playlist.frontmatter.scenes.forEach(sceneLink => {
          // console.log(sceneLink)
          const match = nodes.find(
            scene =>
              scene.internal.type === `MarkdownRemark` &&
              !!scene.frontmatter &&
              scene.frontmatter.templateKey === `scene` &&
              scene.frontmatter.title === sceneLink.title
          )

          if (!!match) {
            // console.log(match)
            if (!scenesByPlaylistIndex[playlist.id])
              scenesByPlaylistIndex[playlist.id] = []

            scenesByPlaylistIndex[playlist.id].push(match.id)
          }
        })
      }
    })

  // next, use the index to create the links
  Object.entries(scenesByPlaylistIndex).forEach(([playlistId, sceneIds]) => {
    // link in graphql
    createNodeField({
      node: getNode(playlistId),
      name: `scenes`,
      value: sceneIds,
    })
  })

  // link scenes/playlists to screens
  // nodes
  //   .filter(
  //     node =>
  //       node.internal.type === `MarkdownRemark` &&
  //       !!node.frontmatter &&
  //       node.frontmatter.templateKey === `screen`
  //   )
  //   .forEach(screen => {
  //     // console.log(screen)
  //     if (!!screen.frontmatter.scene) {
  //       // console.log('checking scene')
  //       const match = nodes.find(
  //         scene =>
  //           scene.internal.type === `MarkdownRemark` &&
  //           !!scene.frontmatter &&
  //           scene.frontmatter.templateKey === `scene` &&
  //           scene.frontmatter.title === screen.frontmatter.scene
  //       )
  //
  //       if (!!match) {
  //         // console.log(match)
  //         // link in graphql
  //         createNodeField({
  //           node: screen,
  //           name: `scene`,
  //           value: match.id,
  //         })
  //       }
  //     }
  //
  //     if (!!screen.frontmatter.playlist) {
  //       const match = nodes.find(
  //         playlist =>
  //           playlist.internal.type === `MarkdownRemark` &&
  //           !!playlist.frontmatter &&
  //           playlist.frontmatter.templateKey === `playlist` &&
  //           playlist.frontmatter.title === screen.frontmatter.playlist
  //       )
  //
  //       if (!!match) {
  //         // console.log(match)
  //         // link in graphql
  //         createNodeField({
  //           node: screen,
  //           name: `playlist`,
  //           value: match.id,
  //         })
  //       }
  //     }
  //   })
}