gatsby-node.js

const path = require('path');
const glob = require('glob');
const fs = require('fs');
const frontmatter = require('@github-docs/frontmatter');
const { v4: uuidv4 } = require('uuid');
const { createFilePath } = require('gatsby-source-filesystem');
const redirects = require('./src/redirects.json');
const leftNavTitle = require('./src/left-nav-title.json');

const ignorePaths = [];

exports.onCreateNode = ({ node, getNode, actions }) => {
    const { createNodeField } = actions;
    if (node.internal.type === 'MarkdownRemark') {
        const slug = createFilePath({ node, getNode, basePath: 'pages' });
        createNodeField({
            node,
            name: 'slug',
            value: slug,
        });
    }
};


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

    redirects.forEach(({ from, to }) => {
        createRedirect({
            fromPath: from,
            isPermanent: true,
            redirectInBrowser: true,
            toPath: to,
        });
    });

    const result = await graphql(`
    query {
      allMarkdownRemark(sort: {fields: frontmatter___order, order: ASC}) {
        edges {
          node {
            fields {
              slug
            }
            frontmatter {
              title
              meta_desc
              canonical
              keywords
              social_share_summary
              social_share_desc
              social_share_image
              noindex
            }
          }
        }
      }
    }
  `);
    result.data.allMarkdownRemark.edges.forEach(({ node }, index) => {
        if (node.fields.slug.includes('-')) {
            const underscoreSlug = node.fields.slug.replace(/-/g, '_');

            createRedirect({
                fromPath: underscoreSlug,
                isPermanent: true,
                redirectInBrowser: true,
                toPath: node.fields.slug,
            });
        }
        createPage({
            path: node.fields.slug,
            component: path.resolve('./src/templates/page.jsx'),
            context: {
                slug: node.fields.slug,
                prev: index === 0 ? null : result.data.allMarkdownRemark.edges[index - 1].node,
                next: index === result.data.allMarkdownRemark.edges.length - 1 ? null : result.data.allMarkdownRemark.edges[index + 1].node
            },
        });
    });
};



/* Create Header and Footer
/************************************************************************ */
exports.sourceNodes = async ({
                                 actions,
                                 createNodeId,
                                 createContentDigest,
                             }) => {
    const prepareNode = (obj, name) => {
        const data = {
            key: uuidv4(),
            value: JSON.stringify(obj),
        };
        const node = JSON.stringify(data);
        const nodeMeta = {
            id: createNodeId(`my-data-${data.key}`),
            parent: null,
            children: [],
            internal: {
                type: name,
                mediaType: 'text/json',
                content: node,
                contentDigest: createContentDigest(data),
            },
        };

        const output = { ...data, ...nodeMeta };
        return output;
    };

    const { createNode } = actions;

    const getDirectories = (src) => glob.sync(`${src}/**/*`);
    const paths = getDirectories('./src/pages/tutorials')
        .filter((val) => val.slice(-3) === '.md')
        .map((val) => {
            const { data } = frontmatter(fs.readFileSync(val));
            const order = data.order || 200;
            return [val, order];
        })
        .sort((a, b) => Number(a[1]) - Number(b[1]))
        .map((val) => {
            let newVal = '';
            newVal = val[0].replace(/\.\/src\/pages/g, '');
            newVal = newVal.substring(0, newVal.length - 3);
            newVal = newVal.slice(-5) === 'index' ? newVal.substring(0, newVal.length - 5) : newVal;
            return `${newVal}/`;
        })
        .filter((val) => !ignorePaths.includes(val));

    const output = {};

    paths.forEach((val) => {
        let split = val.split('/');
        split = split.filter((url) => url !== '');

        let current = output;
        split.forEach((part) => {
            if(current[part])
                current[part] = current[part];
            else {
                current[part] = {};
                if(leftNavTitle[part]) {
                    Object.keys(leftNavTitle[part]).forEach(key => {
                        if(val.indexOf(key) === 0) {
                            //console.log(key);
                            current[part] = {leftNavTitle: leftNavTitle[part][key]};
                        }
                    })
                }
            }
            current = current[part];
        });
        current.url = `/${split.join('/')}/`;
    });

    createNode(prepareNode(output.tutorials, 'leftNavLinks'));
};