package main

import (
    "net/http"
    "encoding/json"
    "database/sql"
    "github.com/gorilla/mux"
    _ "github.com/go-sql-driver/mysql"
)

type User struct {
    Id int64 `json:"id"`
    Name string `json:"name"`
    Email string `json:"email"`
}

func initDB() *sql.DB {
    db, err := sql.Open("mysql", "root@/golang?charset=utf8")
    if err != nil {
        panic(err)
    }
    return db
}

func main() {
    router := mux.NewRouter()
    router.HandleFunc("/users", getUsers).Methods("GET")
    router.HandleFunc("/users/{id}", getUser).Methods("GET")
    router.HandleFunc("/users", postUsers).Methods("POST")
    http.ListenAndServe(":3000", router)
}

func getUser(w http.ResponseWriter, r *http.Request) {
    db := initDB()
    w.Header().Set("Content-Type", "application/json")
    var user User
    err := db.QueryRow("SELECT * FROM users WHERE id=?", mux.Vars(r)["id"]).Scan(&user.Id, &user.Name, &user.Email)
    switch {
    case err == sql.ErrNoRows:
        http.Error(w, "User not found!", 400)
    case err != nil:
        panic(err)
    default:
        json.NewEncoder(w).Encode(user)
    }
}

func getUsers(w http.ResponseWriter, r *http.Request) {
    db := initDB()
    w.Header().Set("Content-Type", "application/json")
    rows, err := db.Query("SELECT * FROM users")
    if err != nil {
        panic(err)
    }
    var users = []User{}
    for rows.Next() {
        var user User
        rows.Scan(&user.Id, &user.Name, &user.Email)
        users = append(users, user)
    }
    json.NewEncoder(w).Encode(users)
}

func postUsers(w http.ResponseWriter, r *http.Request) {
    db := initDB()
    w.Header().Set("Content-Type", "application/json")
    query, err := db.Prepare("INSERT INTO users (name, email) VALUES (?, ?)")
    if err != nil {
        panic(err)
    }
    var user User
    json.NewDecoder(r.Body).Decode(&user)
    res, err := query.Exec(user.Name, user.Email)
    if err != nil {
        panic(err)
    }
    id, err := res.LastInsertId()
    if err != nil {
        panic(err)
    }
    user.Id = id
    json.NewEncoder(w).Encode(user)
}