# Go

### app.go

package mainimport (
    "net/http"
    "mux-practice/routes"
)

func main() {
    r := routes.NewRouter()
    
    http.ListenAndServe(":8080", r)
}

- `net/http`: 提供前後端 http methods
- `mux-practice/routes`: 提供路由規則
- `HandleFunc`: API, 根據 URL 提供對應的 function
- `http.ListenAndServe` 根據 `mux.NewRouter()` 提供服務

### routes.go

package routes

import (
	"net/http"
	"mux-practice/controllers"
	"github.com/gorilla/mux"
)

type Route struct {
	Method     string
	Pattern    string
	Handler    http.HandlerFunc
	Middleware mux.MiddlewareFunc
}

var routes []Route

func init() {
	register("GET", "/movies", controllers.AllMovies, nil)
	register("GET", "/movies/{id}", controllers.FindMovie, nil)
	register("POST", "/movies", controllers.CreateMovie, nil)
	register("PUT", "/movies", controllers.UpdateMovie, nil)
	register("DELETE", "/movies", controllers.DeleteMovie, nil)
}

func NewRouter() *mux.Router {
	r := mux.NewRouter()
	for _, route := range routes {
		r.HandleFunc(route.Pattern, route.Handler).Methods(route.Method)
		
		if route.Middleware != nil {
			r.Use(route.Middleware)
		}
	}
	return r
}

func register(method, pattern string, handler http.HandlerFunc, middleware mux.MiddlewareFunc) {
	routes = append(routes, Route{method, pattern, handler, middleware})
}

- `routes` 是一個沒有限制長度的 slice (可變長度陣列)
- `register()` 的功能則是用 append 的方式新增 route 到 `routes` 中

---

#### 很好，讀一半才發現，這邊以下是 mangoDB

### models/db.go

package models

import (
	"log"
	"github.com/globalsign/mgo"
)

const (
	host = "127.0.0.1:27017"
	source = "admin"
	user = "user"
	pass = "1234"
)

var globalS *mgo.Session

func init() {
	dialInfo := &mgo.DialInfo{
		Addrs: []string{host},
		Source: source,
		Username: user,
		Password: pass,
	}

	s, err := mgo.DialWithInfo(dialInfo)
	if err != nil {
		log.Fatalln("create session error", err)
	}
	globalS = s
}

func connect(db, collection string) (*mgo.Session, *mgo.Collection) {
	s := globalS.Copy()
	c := s.DB(db).C(collection)
	return s, c
}

func Insert(db, collection string, docs ...interface{}) error {
	ms, c := connect(db, collection)
	defer ms.Close()
	return c.Insert(docs...)
}

func FindOne(db, collection string, query, selector, result interface{}) error {
	ms, c := connect(db, collection)
	defer ms.Close()
	return c.Find(query).Select(selector).One(result)
}

func FindAll(db, collection string, query, selector, result interface{}) error {
	ms, c := connect(db, collection)
	defer ms.Close()
	return c.Find(query).Select(selector).All(result)
}

func Update(db, collection string, query, update interface{}) error {
	ms, c := connect(db, collection)
	defer ms.Close()
	return c.Update(query, update)
}

func Remove(db, collection string, query interface{}) error {
	ms, c := connect(db, collection)
	defer ms.Close()
	return c.Remove(query)
}

### models/movies.go

package models

import "github.com/globalsign/mgo/bson"

type Movies struct {
	Id bson.ObjectId `bson:"_id" json:"id"`
	Name string `bson:"name" json:"name"`
	CoverImage string `bson:"cover_image" json:"cover_image"`
	Description string `bson:"description" json:"description"`
}

const (
	db = "Movies"
	collection = "MovieModel"
)

func (m *Movies) InsertMovie(movie Movies) error {
	return Insert(db, collection, movie)
}

func (m *Movies) FindAllMovies() ([]Movies, error) {
	var result []Movies
	err := FindAll(db, collection, nil, nil, &result)
	return result, err
}

func (m *Movies) FindMovieById(id string) (Movies, error) {
	var result Movies
	err := FindOne(db, collection, bson.M{"_id": bson.ObjectIdHex(id)}, nil, &result)
	return result, err
}

func (m *Movies) UpdateMovie(movie Movies) error {
	return Update(db, collection, bson.M{"_id": movie.Id}, movie)
}

func (m *Movies) RemoveMovie(id string) error {
	return Remove(db, collection, bson.M{"_id": bson.ObjectIdHex(id)})
}

### controllers/movies.go

package controllers

import (
	"fmt"
  "net/http"
)

func responseWithJson(w http.ResponseWriter, code int, payload interface{}) {
	response, _ := json.Marshal(payload)
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(code)
	w.Write(response)
}

func CreateMovie(w http.ResponseWriter, r *http.Request) {
	defer r.Body.Close()
	var movie models.Movies
	if err := json.NewDecoder(r.Body).Decode(&movie); err != nil {
		responseWithJson(w, http.StatusBadRequest, "Invalid request payload")
		return
	}
	movie.Id = bson.NewObjectId()
	if err := dao.InsertMovie(movie); err != nil {
		responseWithJson(w, http.StatusInternalServerError, err.Error())
		return
	}
	responseWithJson(w, http.StatusCreated, movie)
}

func AllMovies(w http.ResponseWriter, r *http.Request) {
	defer r.Body.Close()
	var movies []models.Movies
	movies, err := dao.FindAllMovies()
	if err != nil {
		responseWithJson(w, http.StatusInternalServerError, err.Error())
		return
	}
	responseWithJson(w, http.StatusOK, movies)
}

func FindMovie(w http.ResponseWriter, r *http.Request) {
	vars := mux.Vars(r)
	id := vars["id"]
	result, err := dao.FindMovieById(id)
	if err != nil {
		responseWithJson(w, http.StatusInternalServerError, err.Error())
		return
	}
	responseWithJson(w, http.StatusOK, result)
}

func UpdateMovie(w http.ResponseWriter, r *http.Request) {
	defer r.Body.Close()
	var params models.Movies
	if err := json.NewDecoder(r.Body).Decode(&params); err != nil {
		responseWithJson(w, http.StatusBadRequest, "Invalid request payload")
		return
	}
	if err := dao.UpdateMovie(params); err != nil {
		responseWithJson(w, http.StatusInternalServerError, err.Error())
		return
	}
	responseWithJson(w, http.StatusOK, map[string]string{"result": "success"})
}

func DeleteMovie(w http.ResponseWriter, r *http.Request) {
	vars := mux.Vars(r)
	id := vars["id"]
	if err := dao.RemoveMovie(id); err != nil {
		responseWithJson(w, http.StatusBadRequest, "Invalid request payload")
		return
	}

	responseWithJson(w, http.StatusOK, map[string]string{"result": "success"})
}

---
### Reference
[從這邊整理 ](https://medium.com/@intheblackworld/%E5%89%8D%E7%AB%AF%E6%94%BB%E5%9F%8E%E8%A9%A9-let-s-golang-6-golang-%E9%96%8B-api-%E4%B8%8A-5e82cde62853)

##### tags: `tutorial`