gatsby-node.js

/**
 * Implement Gatsby's Node APIs in this file.
 *
 * See: https://www.gatsbyjs.org/docs/node-apis/
 */

const path = require("path")

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

 createRedirect({
 fromPath: `/osa-1/4-muuttujat`,
 isPermanent: true,
 redirectInBrowser: true,
 toPath: `/osa-1/4-laskentaa`,
 })

 const courseMaterialTemplate = path.resolve(
 `src/templates/CourseContentTemplate.js`,
 )

 const coursePartOverviewTemplate = path.resolve(
 `src/templates/CoursePartOverviewTemplate.js`,
 )

 const infoPageTemplate = path.resolve(`src/templates/InfoPageTemplate.js`)

 const query = `
 {
 allMarkdownRemark(
 sort: { order: DESC, fields: [frontmatter___path] }
 limit: 1000${
 process.env.NODE_ENV === "production"
 ? `, filter: { frontmatter: { hidden: { ne: true } } }`
 : ""
 }
 ) {
 edges {
 node {
 frontmatter {
 path
 overview
 information_page
 }
 }
 }
 }
 }
 `

 return graphql(query).then(result => {
 if (result.errors) {
 return Promise.reject(result.errors)
 }

 if (!result.data.allMarkdownRemark) {
 console.log("No markdown pages generated. Did you hide all of them?")
 return
 }

 result.data.allMarkdownRemark.edges.forEach(({ node }) => {
 let template = courseMaterialTemplate
 if (node.frontmatter.overview) {
 template = coursePartOverviewTemplate
 }
 if (node.frontmatter.information_page) {
 template = infoPageTemplate
 }
 if (!node.frontmatter.path) {
 // To prevent a bug that happens in development from time to time
 return;
 }
 createPage({
 path: node.frontmatter.path,
 component: template,
 context: {}, // additional data can be passed via context
 })
 })
 })
}