const http = require ('http')
const fs   = require ('fs')
const path = require ('path')
const S    = require ('sanctuary')
const $    = require ('sanctuary-def')
const show = require ('sanctuary-show')
const {
    State,
}          = require ('monastic')

const setContentType = response => filePath => {
    switch (path.extname (filePath)) {
        case '.html':
        case '.htm':
            response.setHeader ('Content-Type', 'text/html; charset=utf-8')
            break
        case '.js':
        case '.mjs':
            response.setHeader ('Content-Type', 'application/javascript; charset=utf-8')
            break
        case '.json':
        case '.json5':
        case '.jsonc':
            response.setHeader ('Content-Type', 'application/json; charset=utf-8')
        default:
            response.setHeader ('Content-Type', 'text/plain; charset=utf-8')
    }

    return filePath
}

const readFile = cb => path => {
    fs.readFile (path, { encoding: 'utf-8' }, cb)
    return path
}

const payload = response => (error, data) => {
    if (error) {
        response.statusCode = 500
        response.end (JSON.stringify (error))
    } else {
        response.statusCode = 200
        response.end (String (data))
    }
}

const notAllowed = response => x => {
    response.statusCode = 403
    response.setHeader ('Content-Type', 'text/plain')
    response.end ('Not in allowed list')

    return x
}

// ---------------------------------------------->

const hostname   = '127.0.0.1'
const port       = 3000
const allowed    = {
    '/': path.resolve (__dirname, 'index.html'),
    '/text.txt'  : path.resolve (__dirname, 'text.txt'),
}

const serve = (request, response) => {
    S.pipe ([
        S.flip (S.get (S.is ($.String))) (allowed),
        S.map  (setContentType (response)),
        S.map  (readFile (payload (response))),
        S.when (S.isNothing)
               (notAllowed (response)),
    ])
    (request.url)
}

const server = http.createServer (serve)

server.listen (port, hostname, () => {
    console.log (`Server running at http://${hostname}:${port}/`)
})