app.js

const express = require('express')
const { engine } = require('express-handlebars')
const app = express()
const port = 3000
const fs = require('fs')
const shortUrl = require('./shortUrl/randomURL')


// View:樣版引擎負責畫面呈現
app.engine('.hbs',engine({extname:'.hbs'}))
app.set('view engine','.hbs')
app.set('views','./views')

// Model:載入靜態文件
app.use(express.static('public'))
app.use(express.urlencoded({extended: true}))


// Controller:set router
app.get('/', (req, res) =>{
  res.redirect('/URL_Shortener')
})
app.get('/URL_Shortener',(req, res) =>{
  res.render('index')
})

let urldata = {}   //讀取json檔案 
if (fs.existsSync('./data.json')) {
  try {
    const jsonData = fs.readFileSync('./data.json')
    urldata = JSON.parse(jsonData)

  }
  catch (error) {
    console.error(error)
  }
}

app.post('/URL_Shortener', (req, res) => {
  const originalURL = req.body.inputURL

  if (!originalURL || !originalURL.toLowerCase().trim().startsWith("http")) {   //防止輸入空字串或是不是http開頭的
    res.render('index', { error: '請輸入正確的URL' })

    return
  }


  if (Object.keys(urldata).includes(originalURL)) {   //辨認是否有同樣的縮網址
    useshortUrl = urldata[originalURL]
    res.render('index', { useshortUrl })
  }

  else {
    const useshortUrl = shortUrl() //執行 randomURL檔案內的函數
    urldata[originalURL] = useshortUrl
    fs.writeFileSync('./data.json', JSON.stringify(urldata)) //輸入進data.json檔案裡

    res.render('index', { useshortUrl })
  } 

})

app.get('/:ShortUrl', (req, res) => {
  const url = req.params.ShortUrl
  for (const key in urldata) {
    if (url === urldata[key]) {
      res.redirect(key)  //[key] 匹配到 url 這時可以直接使用key來代表相對應的鍵
      return
    }
  }
  res.status(404).send('Short URL not found')
})

app.listen(port,(req,res)=>{
  console.log(`express sever is running on http://localhost:${port}`)
})