server.js

const express = require('express')
const app = express();
const morgan = require('morgan')
const PORT= 3001;

app.use(express.json())
app.use(morgan('tiny'))

morgan.token('object', function (req, res){
    return `${JSON.stringify(req.body)}`
})

app.use(morgan(':object'))

let persons= [
    { 
      "id": 1,
      "name": "Arto Hellas", 
      "number": "040-123456"
    },
    { 
      "id": 2,
      "name": "Ada Lovelace", 
      "number": "39-44-5323523"
    },
    { 
      "id": 3,
      "name": "Dan Abramov", 
      "number": "12-43-234345"
    },
    { 
      "id": 4,
      "name": "Mary Poppendieck", 
      "number": "39-23-6423122"
    }
]

app.get('/api/persons', (req, res) => {
    res.json(persons)
})

app.get('/info', (req, res) => {
    const currentDate = new Date();
    res.send(`<h2>Phonebook info for the ${persons.length} people</h2> <h2>${currentDate}</h2>`)
})

app.get('/api/persons/:id', (req, res) => {
    const id = req.params.id
    const entry = persons.find(entry => entry.id ==id)
    if(entry){
        res.json(entry)
    }else{
        res.status(404).end()
    }
})

app.delete('/api/persons/:id', (req, res) => {
    const id= Number(req.params.id)
    persons= persons.filter(entry => entry.id!==id)
    res.status(204).end()
})

const generateId = ()  => {
    const maxID= persons.length > 0 ?
    Math.max(...persons.map(n =>n.id)) : 0
    return maxID +1 
}

app.post('/api/persons', (req, res) => {
    const body= req.body

    if (!body.number){
        return res.status(400).json({ error: 'number missing'})
    } 
    if(!body.name){
        return res.status(400).json({ error: 'name missing'})
    }
    if (persons.some(entry => entry.name === body.name)){
        return res.status(401).json({ error: 'name must be unique'})
    }

    let entry = {
        id: generateId(),
        name: body.name,
        number: body.number
    }
    persons.push(entry)
    res.json(entry)
})

app.listen(PORT, () => {
    console.log(`Server active on ${PORT}`)
})