Refactored Blog API

main.go

package main

import (
	"encoding/json"
	"log"
	"net/http"

	"github.com/gorilla/mux"
	"gorm.io/driver/postgres"
	"gorm.io/gorm"
)

// Post is a GORM model representing a blog post.
type Post struct {
	gorm.Model
	Title string `json:"title"`
	Body  string `json:"body"`
}

func main() {
	var err error
	db, err := gorm.Open(postgres.Open("host=localhost user=postgres password=postgres dbname=myblog port=5432 sslmode=disable"), &gorm.Config{})
	if err != nil {
		log.Fatal(err)
	}

	router := mux.NewRouter()
	router.HandleFunc("/posts", listPostsHandler(db)).Methods("GET")
	router.HandleFunc("/posts", createPostHandler(db)).Methods("POST")
	router.HandleFunc("/posts/{id}", getPostHandler(db)).Methods("GET")

	log.Println("Listening on port 3000")
	log.Fatal(http.ListenAndServe(":3000", router))
}

// handleApiError renders a JSON error and sets the HTTP status code.
func handleApiError(w http.ResponseWriter, err error, code int) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(code)
	json.NewEncoder(w).Encode(map[string]string{"error": err.Error()})
}

func listPostsHandler(db *gorm.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		var posts []Post
		db.Find(&posts)

		// convert the posts to JSON
		postsJSON, err := json.Marshal(posts)
		if err != nil {
			handleApiError(w, err, 500)
		}

		w.Write(postsJSON)
	}
}

func createPostHandler(db *gorm.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		var post Post
		json.NewDecoder(r.Body).Decode(&post)
		db.Create(&post)

		// convert the post to JSON
		postJSON, err := json.Marshal(post)
		if err != nil {
			handleApiError(w, err, 500)
		}

		w.WriteHeader(201)
		w.Write(postJSON)
	}
}

func getPostHandler(db *gorm.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		vars := mux.Vars(r)
		var post Post
		db.First(&post, vars["id"])

		// convert the post to JSON
		postJSON, err := json.Marshal(post)
		if err != nil {
			handleApiError(w, err, 500)
		}

		w.Write(postJSON)
	}
}