WDI Wk2D5 - Sinatra and SQL - products,users and wishlists

```
require 'sinatra'
require 'sinatra/reloader'
require 'json'
require 'sqlite3'

before do
  @db = SQLite3::Database.new './store.sqlite3'
end

get '/products' do
  rs = @db.execute 'SELECT * FROM products;'
  return rs.to_json
end

get '/products/:id' do
  id = params[:id]
  rs = @db.execute 'SELECT * FROM products WHERE id = ?;', [id]
  rs.first.to_json
end

get '/users' do
  rs = @db.execute 'SELECT * FROM users;'
  return rs.to_json
end

get '/users/:id' do
  id = params[:id]
  rs = @db.execute 'SELECT * FROM users WHERE id = ?;', [id]
  return rs.to_json
end


get '/wishlists' do
  rs = @db.execute 'SELECT users.name, products.name FROM products, users, wishlists WHERE products.id = wishlists.product_id AND wishlists.user_id = users.id;'
  w = reduce_wishlist rs
  w.to_json
end

get '/users/:id/wishlist' do
  id = params[:id]
  rs = @db.execute 'SELECT users.name, products.name FROM products, users, wishlists WHERE products.id = wishlists.product_id AND wishlists.user_id = users.id AND users.id = ? ;', id
  w = reduce_wishlist rs
  w.to_json
end

private
  def reduce_wishlist result_set
    result_set.inject({}) do |all, pair|
      u = pair[0]
      p = pair[1]
      all[u] ||= []
      all[u] << p
      all
    end
  end
```