gatsby-theme-try-ghost/plugins/gatsby-plugin-ghost-manifest/src/gatsby-node.js

A Gatsby theme for building flaring fast blogs from headless Ghost CMS.

const fs = require(`fs`)
const path = require(`path`)
const Promise = require(`bluebird`)
const sharp = require(`sharp`)
const { defaultIcons, doesIconExist } = require(`./common.js`)

sharp.simd(true)

function generateIcons(icons, srcIcon) {
    return Promise.map(icons, (icon) => {
        const size = parseInt(icon.sizes.substring(0, icon.sizes.lastIndexOf(`x`)))
        const imgPath = path.join(`public`, icon.src)

        return sharp(srcIcon)
            .resize(size)
            .toFile(imgPath)
            .then(() => { })
    })
}

exports.onPostBuild = async ({ graphql }, pluginOptions) => {
    let { icon, ...manifest } = pluginOptions

    const { data } = await graphql(pluginOptions.query)
    const siteTitle = data.allGhostSettings.edges[0].node.title || `No Title`
    manifest = {
        ...manifest,
        name: siteTitle,
    }

    // Delete options we won't pass to the manifest.webmanifest.
    delete manifest.plugins
    delete manifest.legacy
    delete manifest.theme_color_in_head
    delete manifest.query

    // If icons are not manually defined, use the default icon set.
    if (!manifest.icons) {
        manifest.icons = defaultIcons
    }

    // Determine destination path for icons.
    const iconPath = path.join(`public`, path.dirname(manifest.icons[0].src))

    //create destination directory if it doesn't exist
    if (!fs.existsSync(iconPath)) {
        fs.mkdirSync(iconPath)
    }

    fs.writeFileSync(
        path.join(`public`, `manifest.webmanifest`),
        JSON.stringify(manifest)
    )

    // Only auto-generate icons if a src icon is defined.
    if (icon !== undefined) {
        // Check if the icon exists
        if (!doesIconExist(icon)) {
            Promise.reject(
                `icon (${icon}) does not exist as defined in gatsby-config.js. Make sure the file exists relative to the root of the site.`
            )
        }
        generateIcons(manifest.icons, icon).then(() => {
            //images have been generated
            console.log(`done generating icons for manifest`)
            Promise.resolve()
        })
    } else {
        Promise.resolve()
    }
}