GraphQL CRM base

graph-ql-server.go

package main

import (
	"context"
	"database/sql"
	"log"
	"net/http"

	"github.com/graphql-go/graphql"
	"github.com/graphql-go/handler"
	_ "github.com/lib/pq"
)

type Customer struct {
	ID    int    `json:"id"`
	Name  string `json:"name"`
	Email string `json:"email"`
}

type Order struct {
	ID       int     `json:"id"`
	Customer Customer `json:"customer"`
	Amount   float64 `json:"amount"`
}

var (
	customerType = graphql.NewObject(
		graphql.ObjectConfig{
			Name: "Customer",
			Fields: graphql.Fields{
				"id": &graphql.Field{Type: graphql.Int},
				"name": &graphql.Field{Type: graphql.String},
				"email": &graphql.Field{Type: graphql.String},
			},
		},
	)

	orderType = graphql.NewObject(
		graphql.ObjectConfig{
			Name: "Order",
			Fields: graphql.Fields{
				"id": &graphql.Field{Type: graphql.Int},
				"customer": &graphql.Field{
					Type: customerType,
					Resolve: func(p graphql.ResolveParams) (interface{}, error) {
						order := p.Source.(Order)
						return order.Customer, nil
					},
				},
				"amount": &graphql.Field{Type: graphql.Float},
			},
		},
	)

	rootQuery = graphql.NewObject(
		graphql.ObjectConfig{
			Name: "Query",
			Fields: graphql.Fields{
				"customers": &graphql.Field{
					Type: graphql.NewList(customerType),
					Resolve: func(p graphql.ResolveParams) (interface{}, error) {
						db := p.Context.Value("db").(*sql.DB)
						rows, err := db.Query("SELECT id, name, email FROM customers")
						if err != nil {
							return nil, err
						}
						defer rows.Close()

						var customers []Customer
						for rows.Next() {
							var customer Customer
							err := rows.Scan(&customer.ID, &customer.Name, &customer.Email)
							if err != nil {
								return nil, err
							}
							customers = append(customers, customer)
						}
						return customers, nil
					},
				},
				"orders": &graphql.Field{
					Type: graphql.NewList(orderType),
					Resolve: func(p graphql.ResolveParams) (interface{}, error) {
						db := p.Context.Value("db").(*sql.DB)
						rows, err := db.Query("SELECT id, customer_id, amount FROM orders")
						if err != nil {
							return nil, err
						}
						defer rows.Close()

						var orders []Order
						for rows.Next() {
							var order Order
							err := rows.Scan(&order.ID, &order.Customer.ID, &order.Amount)
							if err != nil {
								return nil, err
							}
							orders = append(orders, order)
						}
						return orders, nil
					},
				},
			},
		},
	)

	schema, _ = graphql.NewSchema(
		graphql.SchemaConfig{
			Query: rootQuery,
		},
	)
)

func main() {
	db, err := sql.Open("postgres", "postgres://user:password@localhost/crm")
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	http.Handle("/graphql", &handler.Handler{
		Schema:   &schema,
		Pretty:   true,
		GraphiQL: true,
		ContextFunc: func(r *http.Request) context.Context {
			ctx := context.WithValue(r.Context(), "db", db)
			return ctx
		},
	})

	log.Fatal(http.ListenAndServe(":8080", nil))
}