gatsby-node.js

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

// You can delete this file if you're not using it
const path = require(`path`)
const moment = require("moment")
const siteConfig = require("./site-config")
const { createFilePath } = require(`gatsby-source-filesystem`)

// This method adds the field slug to every markdown node
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 { createPage } = actions
    const template = path.resolve(`./src/templates/EventPageTemplate.tsx`)
    const result = await graphql(`
        query {
            allMarkdownRemark(
                filter: { frontmatter: { category: { eq: "event" } } }
            ) {
                edges {
                    node {
                        fields {
                            slug
                        }
                        frontmatter {
                            title
                            imgsrc
                            date
                        }
                    }
                }
            }
        }
    `)

    if (result.errors) {
        console.error(result.errors)
        throw result.errors
    }

    const postsEdges = result.data.allMarkdownRemark.edges

    postsEdges.sort((postA, postB) => {
        const dateA = moment(
            postA.node.frontmatter.date,
            siteConfig.dateFromFormat
        )

        const dateB = moment(
            postB.node.frontmatter.date,
            siteConfig.dateFromFormat
        )

        if (dateA.isBefore(dateB)) return 1
        if (dateB.isBefore(dateA)) return -1

        return 0
    })

    postsEdges.forEach((edge, index) => {
        let nextTitle = ""
        let nextSlug = ""
        let prevTitle = ""
        let prevSlug = ""

        if (index + 1 < postsEdges.length) {
            const nextEdge = postsEdges[index + 1]
            nextTitle = nextEdge.node.frontmatter.title
            nextSlug = nextEdge.node.fields.slug
        }

        if (index - 1 >= 0) {
            const prevEdge = postsEdges[index - 1]
            prevTitle = prevEdge.node.frontmatter.title
            prevSlug = prevEdge.node.fields.slug
        }

        createPage({
            path: edge.node.fields.slug,
            component: template,
            context: {
                // Data passed to context is available
                // in page queries as GraphQL variables.
                slug: edge.node.fields.slug,
                imgsrc: edge.node.frontmatter.imgsrc,
                nextTitle: nextTitle,
                nextSlug: nextSlug,
                prevTitle: prevTitle,
                prevSlug: prevSlug,
            },
        })
    })
}