const fs = require('fs')
const path = require('path')
const LRU = require('lru-cache')
const express = require('express')
const favicon = require('serve-favicon')
const compression = require('compression')
const microcache = require('route-cache')
const resolve = file => path.resolve(__dirname, file)
const { createBundleRenderer } = require('vue-server-renderer')

const isProd = process.env.NODE_ENV === 'production'
const useMicroCache = process.env.MICRO_CACHE !== 'false'
const serverInfo = 
    `express/${require('express/package.json').version} ` +
    `vue-server-renderer/${require('vue-server-renderer/package.json').version}`

const app = express()

function createRenderer (bundle, options) {
    return createBundleRenderer(bundle, Object.assign(options, {
        cache: LRU({
            max: 1000,
            maxAge: 1000 * 60 * 15
        }),
        basedir: resolve('./dist'),
        // 此配置项 优化性能
        runInNewContext: false
    }))
}

let renderer
let readyPromise
const templatePath = resolve('./src/index.html')
if(isProd) {
    const template = fs.readFileSync(templatePath, 'utf-8')
    const bundle = require('./dist/vue-ssr-server-bundle.json')
    const clientManifest = require('./dist/vue-ssr-client-manifest.json')

    renderer = createRenderer(bundle, {
        template,
        clientManifest
    })
} else {
    readyPromise = require('./build/setup-dev-server')(
        app,
        templatePath,
        (bundle, options) => {
            renderer = createRenderer(bundle, options)
        }
    )
}

const serve = (path, cache) => express.static(resolve(path), {
    maxAge: cache && isProd ? 1000 * 60 * 60 * 24 * 30 : 0
})

app.use(compression({ threshold: 0}))
app.use(favicon('./public/favicon.ico'))
app.use('/dist', serve('./dist', true))
app.use('/public', serve('./public', true))
app.use('/manifest.json', serve('./manifest.json', true))
app.use('/service-worker.js', serve('./dist/service-worker.js'))
app.use(microcache.cacheSeconds(1, req => useMicroCache && req.originalUrl))

function render (req, res) {
    const s = Date.now()

    res.setHeader("Content-type", "text/html")
    res.setHeader("Server", serverInfo)

    const handleError = err => {
        if(err.url) {
            res.redirect(err.url)
        } else if(err.code === 404) {
            res.status(404).send('404 | Page Not Found')
        } else {
            res.status(500).send('500 | Internal Server Error')
            console.error(`error during render : ${req.url}`)
            console.error(err.stack)
        }
    }

    const context = {
        title : '微剧院 - 作者后台',
        url : req.url
    }

    renderer.renderToString(context, (err, html) => {
        if(err) {
            return handleError(err)
        }

        res.send(html)

        if(!isProd) {
            console.log(`whole request: ${Date.now() - s}ms`)
        }
    })
}

app.get('*', isProd ? render : (req, res) => {
    readyPromise.then(() => render(req, res))
})

const port = process.env.PORT || 1024
app.listen(port, () => {
    console.log(`server started at localhost:${port}`)
})