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// We actually don't rely and use /favicon.ico but it's nevertheless a

// very common request. Same with /apple-touch-icon.png.

// Because we store our images, including those not for the Markdown text,

// in the `assets/images/site` directory, we will use a custom

// solution to serve this directly.

import fs from 'fs'

import { SURROGATE_ENUMS, setFastlySurrogateKey } from './set-fastly-surrogate-key.js'

import { cacheControlFactory } from './cache-control.js'

const cacheControl = cacheControlFactory(60 * 60 * 24 * 7, { immutable: true })

const MAP = {

'/favicon.ico': {

contentType: 'image/x-icon',

buffer: getBuffer('assets/images/site/favicon.ico'),

},

'/apple-touch-icon.png': {

contentType: 'image/png',

buffer: getBuffer('assets/images/site/apple-touch-icon.png'),

},

}

function getBuffer(filePath) {

let buffer

if (!fs.existsSync(filePath)) {

throw new Error(`${filePath} not found on disk`)

}

return () => {

if (!buffer) {

// Yes, sync and a bit slow, but the headers we send will

// make sure these requests are rare because the payload

// will be sticky in the CDN and stickly in the browser too.

buffer = fs.readFileSync(filePath)

}

return buffer

}

}

export default function favicons(req, res, next) {

if (!MAP[req.path]) return next()

// This makes sure the CDN caching survives each production deployment.

setFastlySurrogateKey(res, SURROGATE_ENUMS.MANUAL)

// Manually settings a Cache-Control because no other middleware

// will get a chance to do this later since we terminate here.

cacheControl(res)

const { contentType, buffer } = MAP[req.path]

res.set('content-type', contentType)

res.send(buffer())

}