books.go

package main

import (
	"database/sql"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"time"

	"github.com/gorilla/mux"
	"github.com/jmoiron/sqlx"
)

const StatusHandled = 0

type Book struct {
	BookID      string
	CategoryID  string
	Title       string
	Slug        string
	Description string
	LikeCount   int
	Creation    time.Time
	LastUpdate  time.Time
	Deleted     bool
}

type NewBook struct {
	Title       string
	Description string
}

type Context struct {
	DB *sqlx.DB
}

func New(db *sql.DB) *Context {
	return &Context{DB}
}

func readjson(r io.ReadCloser, v interface{}) error {
	data, err := ioutil.ReadAll(r)
	if err != nil {
		return err
	}

	return json.Unmarshal(data, v)
}

func (c *Context) json(rw http.ResponseWriter, r *http.Request, v interface{}) (err string, code int) {
	data, err := json.Marshal(v)
	if err != nil {
		return err.Error(), http.StatusInternalServerError
	}

	rw.Header().Set("Content-Type", "application/json")
	rw.WriteHeader(http.StatusOK)
	rw.Write(data)
	return "", StatusHandled
}

func (c *Context) Books(rw http.ResponseWriter, r *http.Request) (err string, code int) {
	vars, db := mux.Vars(r), c.DB

	switch r.Method {
	case "GET":
		books := &Books{}
		category := vars["category"]
		if category == "" {
			http.Error(rw, fmt.Sprintf("Category cannot be empty."), http.StatusBadRequest)
			return
		}

		err := db.Select(books, "SELECT * FROM book WHERE categoryid=?", category)
		if err != nil {
			return fmt.Sprintf(`Error searching for books: %v`, err), http.StatusInternalServerError
		}

		return c.json(rw, r, books)
	default:
		return fmt.Sprintf("Invalid method: %s", r.Method), http.StatusForbidden
	}
}

func (c *Context) ByCategory(rw http.ResponseWriter, r *http.Request) (err string, code int) {
	vars, db := mux.Vars(r), c.DB

	slug := vars["slug"]
	category := vars["category"]

	switch r.Method {

	case "GET":
		book := &Book{}
		if slug == "" || cat == "" {
			return fmt.Sprintf("Slug or category cannot be empty."), http.StatusBadRequest
		}

		err = db.Get(book, "SELECT * FROM book WHERE slug=? AND categoryid=?", slug, cat)
		if err != nil {
			return fmt.Sprintf(`Error searching for books: %v`, err), http.StatusInternalServerError
		}
		return c.json(rw, r, book)

	case "POST":
		book := &NewBook{}
		err := readjson(r.Body, book)
		if err != nil {
			return fmt.Sprintf("Invalid book."), http.StatusBadRequest
		}

		_, err = db.Exec(`
			INSERT INTO book 
				(categoryid, title, slug, description, likecount, creation, lastupdate, deleted)
			VALUES 
				(?, ?, ?, ?, 0, NOW(), NOW(), false)`, category, book.Title, slug(book.Title), book.Description)
		if err != nil {
			return fmt.Sprintf("Error inserting the book: %s", err.Error()), http.StatusInternalServerError
		}

		return "", http.StatusOK
	default:
		return fmt.Sprintf("Invalid method: %s", r.Method), http.StatusForbidden
	}
}

func (c *Context) BookLike(rw http.ResponseWriter, r *http.Request) (err string, code int) {
	vars, db := mux.Vars(r), c.DB

	switch r.Method {
	case "POST":
		id := vars["bookid"]
		if id == "" {
			return fmt.Sprintf("Book id cannot be empty."), http.StatusBadRequest
		}

		_, err = db.Exec(`UPDATE book SET likecount=likecount+1 WHERE bookid=?`, id)
		if err != nil {
			return fmt.Sprintf("Error inserting the book: %s", err.Error()), http.StatusInternalServerError
		}

		return "", http.StatusOK
	default:
		return fmt.Sprintf("Invalid method: %s", r.Method), http.StatusForbidden
	}
}

var Router = mux.NewRouter()

type Handler func(rw http.ResponseWriter, r *http.Request) (err string, code int)

func route(path string, fn Handler) {
	Router.HandleFunc(path, func(rw http.ResponseWriter, r *http.Request) {
		err, code := fn(rw, r)
		if code != StatusHandled {
			http.Error(rw, err, code)
		}
	})
}

func main() {
	db := sqlx.Open("sqlite3", "memory")
	c := &Context{db}

	route("categories/{category}/books/{slug}", c.ByCategory)
	route("categories/{category}/books/{bookid}/like", c.BookLike)

	http.Handle("/api/", Router)
	http.ListenAndServe(":3000", nil)
}