index.js

const express = require('express')
const app = express()

app.use(express.json())

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

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

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

app.post('/api/persons', (request, response) => {
  const body = request.body

  if (!body.content) {
    return response.status(400).json({ 
      error: 'content missing' 
    })
  }

  const note = {
    content: body.content,
    important: body.important || false,
    date: new Date(),
    id: generateId(),
  }

  notes = notes.concat(note)

  response.json(note)
})

app.get('/api/persons/:id', (request, response) => {
  const id = Number(request.params.id)
  console.log(id)
  const person = persons.find(person => person.id === id)
  console.log(person)
  if (person) {
    response.json(person)
  } else {
    response.status(404).end()
  }
})

app.delete('/api/persons/:id', (request, response) => {
  console.log("Before", persons)
  const id = Number(request.params.id)
  persons = persons.filter(person => person.id !== id)
  console.log("after", persons)

  response.status(204).end()
})

const PORT = 3001
app.listen(PORT, () => {
  console.log(`Server running on port ${PORT}`)
})