go-handson/ex6/main.go

package main

import (
	"encoding/json"
	"fmt"
	"github.com/jinzhu/gorm"
	_ "github.com/jinzhu/gorm/dialects/sqlite"
	"log"
	"net/http"
	"strings"
	"strconv"
)

type server struct {
	name string
	db   *gorm.DB
}

type Message struct {
	ID      uint
	Name    string
	Content string
}

func main() {
	db, err := gorm.Open("sqlite3", "sqlite.db")
	if err != nil {
		log.Fatal("Could not open database", err)
	}
	defer db.Close()

	db.DropTableIfExists(&Message{})
	db.AutoMigrate(&Message{})

	s := server{name: "Golang Hands-on", db: db}
	http.Handle("/", http.FileServer(http.Dir("resources")))
	http.HandleFunc("/api/greet/", s.titleHandler)
	http.HandleFunc("/api/sum/", s.sumHandler)
	http.HandleFunc("/api/store/", s.storeHandler)

	if err != nil {
		log.Fatal(err)
	}

	log.Println("Listening on http://localhost:8080")
	err = http.ListenAndServe(":8080", nil)
	log.Fatal(err)
}

type greet struct {
	Title    string `json:"title"`
	Subtitle string `json:"subtitle"`
}

func (s server) titleHandler(w http.ResponseWriter, r *http.Request) {
	var err error

	if strings.Contains(r.Header.Get("Accept"), "application/json") {
		w.Header().Set("Content-Type", "application/json; charset=utf8")
		e := json.NewEncoder(w)
		err = e.Encode(greet{Title: s.name, Subtitle: "Hallo Quintor!"})
	} else {
		w.Header().Set("Content-Type", "text/plain; charset=utf8")
		_, err = fmt.Fprint(w, s.name)
	}

	if err != nil {
		log.Println(err)
	}
}

type sumRequest struct {
	Start   int   `json:"start"`
	End     int   `json:"end"`
	Numbers []int `json:"numbers"`
}
type sumResponse struct {
	Answer int `json:"answer"`
	Count  int `json:"contributers"`
}

func (s server) sumHandler(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json; charset=utf8")

	var sreq sumRequest
	d := json.NewDecoder(r.Body)
	err := d.Decode(&sreq)
	if err != nil {
		log.Println(err)
		http.Error(w, "Bad request", http.StatusBadRequest)
		return
	}

	var sresp sumResponse
	for _, val := range sreq.Numbers[sreq.Start:sreq.End] {
		sresp.Answer += val
		sresp.Count++
	}

	e := json.NewEncoder(w)
	err = e.Encode(sresp)
	if err != nil {
		log.Println(err)
	}
}

type storeMessage struct {
	Name    string `json:"name"`
	Content string `json:"message"`
}

type storeResponse struct {
	Id uint `json:"id"`
}

func (s server) storeHandler(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json; charset=utf8")
	if r.Method == http.MethodPost {
		storeHandlePost(s.db, w, r)
	} else {
		storeHandleGet(s.db, w, r)
	}
}

func storeHandlePost(db *gorm.DB, w http.ResponseWriter, r *http.Request) {
	var sm storeMessage
	d := json.NewDecoder(r.Body)
	err := d.Decode(&sm)
	if err != nil {
		log.Println(err)
		http.Error(w, "Bad request", http.StatusBadRequest)
		return
	}

	m := Message{Name: sm.Name, Content: sm.Content}
	db.Create(&m)
	log.Println("message id", m.ID)

	e := json.NewEncoder(w)
	err = e.Encode(storeResponse{Id: m.ID})
	if err != nil {
		log.Println(err)
	}
}

func storeHandleGet(db *gorm.DB, w http.ResponseWriter, r *http.Request) {
	log.Println(r.URL.Path, strings.TrimPrefix(r.URL.Path, "/api/store/"))
	id, err := strconv.Atoi(strings.TrimPrefix(r.URL.Path, "/api/store/"))
	if err != nil {
		http.NotFound(w, r)
		return
	}
	var m Message
	if err := db.First(&m, id).Error; err != nil {
		log.Println(err)
		http.NotFound(w, r)
		return
	}

	e := json.NewEncoder(w)
	err = e.Encode(storeMessage{m.Name, m.Content})
	if err != nil {
		log.Println(err)
	}
}