app.js

let express = require('express')
let app = express()

let {open} = require('sqlite')
let sqlite3 = require('sqlite3')
let path = require('path')
let dbPath = path.join(__dirname, 'userData.db')

let bcrypt = require('bcrypt')

let db = null

let initializeDBAndServer = async () => {
  try {
    db = await open({filename: dbPath, driver: sqlite3.Database})
    app.listen(3000, () => {
      console.log('server running on http://localhost:3000')
    })
  } catch (error) {
    console.log(error.message)
    process.exit(1)
  }
}

initializeDBAndServer()

app.use(express.json())

app.post('/register', async (request, response) => {
  let {username, name, password, gender, location} = request.body
  let userExistOrNotQuery = `select * from user where username = '${username}';`
  let userData = await db.get(userExistOrNotQuery)
  if (userData !== undefined) {
    //user exist
    response.status(400)
    response.send('User already exists')
  } else {
    //user not exist
    if (password.length < 5) {
      response.status(400)
      response.send('Password is too short')
    } else {
      let hashedPassword = await bcrypt.hash(password, 10)
      let insertQuery = `insert into user(username,name,password,gender,location) values('${username}','${name}','${hashedPassword}','${gender}','${location}');`
      await db.run(insertQuery)
      response.status(200)
      response.send('User created successfully')
    }
  }
})

//api 2

app.post('/login', async (request, response) => {
  let {username, password} = request.body
  let userExistOrNotQuery = `select * from user where username = '${username}';`
  let userExistOrNot = await db.get(userExistOrNotQuery)
  if (userExistOrNot === undefined) {
    //user not exist
    response.status(400)
    response.send('Invalid user')
  } else {
    //user exist
    let isCorrectPassword = await bcrypt.compare(
      password,
      userExistOrNot.password,
    )
    if (isCorrectPassword) {
      // we dont need to put response.status(200) here
      response.send('Login success!')
    } else {
      response.status(400)
      response.send('Invalid password')
    }
  }
})

//api 3
app.put('/change-password', async (request, response) => {
  let {username, oldPassword, newPassword} = request.body
  let userExistOrNotQuery = `select * from user where username = '${username}';`
  let userData = await db.get(userExistOrNotQuery)
  if (userData === undefined) {
    response.status(400)
    response.send('User Not Found')
  } else {
    //user exist
    let isCorrectPassword = await bcrypt.compare(oldPassword, userData.password)
    if (isCorrectPassword) {
      if (newPassword.length < 5) {
        response.status(400)
        response.send('Password is too short')
      } else {
        let newHashedPassword = await bcrypt.hash(newPassword, 10)
        let updatePasswordQuery = `update user set password = '${newHashedPassword}' where username = '${username}';`
        await db.run(updatePasswordQuery)
        response.send('Password updated')
      }
    } else {
      response.status(400)
      response.send('Invalid current password')
    }
  }
})

module.exports = app