inventory-middleware/main.go

package main

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"
	"strconv"
	"strings"
	"time"
)

//Go Best practices: https://github.com/golovers/effective-go
type Item struct {
	ID                int32       `json:"id"`
	Name              int32       `json:"name"`
	ValueCents        int32       `json:"valueCents"`
	PurchaseCostCents int32       `json:"purchasedCostCents"`
	Aquired           time.Time   `json:"aquired"`
	Description       string      `json:"description"`
	Notes             string      `json:"notes"`
	SoldForCents      int32       `json:"soldForCents"`
	SoldTo            string      `json:"soldTo"`
	Category          Category    `json:"category"`
	Subcategory       Subcategory `json:"subcategory"`
}

func main() {
	http.HandleFunc("/categories", categories)
	//Note: seems adding a trailing slash allows routing URLs like /category/ID#
	//No need for query parameters.
	http.HandleFunc("/category/", category)
	http.HandleFunc("/subcategory/", subcategory)

	err := http.ListenAndServe(":8088", nil)

	if err != nil {
		panic(err)
	}

}

func categories(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case "GET":
		getCategoriesHandler(w, r)
	default:
		w.WriteHeader(http.StatusMethodNotAllowed)
		w.Write([]byte("Method not allowed"))
	}
}

func category(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case "GET":
		getCategoryHandler(w, r)
	case "POST":
		insertCategoryHandler(w, r)
	case "DELETE":
		deleteCategoryHandler(w, r)
	default:
		w.WriteHeader(http.StatusMethodNotAllowed)
		w.Write([]byte("Method not allowed"))
	}
}

func subcategory(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case "DELETE":
		deleteSubcategoryHandler(w, r)
	default:
		w.WriteHeader(http.StatusMethodNotAllowed)
		w.Write([]byte("Method not allowed"))
	}
}

func deleteSubcategoryHandler(w http.ResponseWriter, r *http.Request) {
	id := strings.TrimPrefix(r.URL.Path, "/subcategory/")

	value, err := strconv.ParseInt(id, 0, 64)

	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		w.Write([]byte(err.Error()))
		return
	}

	if !deleteSubcategory(value) {
		w.WriteHeader(http.StatusBadRequest)
		w.Write([]byte(fmt.Sprintf("Failed to delete %d", value)))
		return
	}

	w.WriteHeader(http.StatusOK)
}

func getCategoryHandler(w http.ResponseWriter, r *http.Request) {
	id := strings.TrimPrefix(r.URL.Path, "/category/")

	value, err := strconv.ParseInt(id, 0, 64)

	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		w.Write([]byte(err.Error()))
		return
	}

	category, ok := getCategoryByID(value)

	if !ok {
		w.WriteHeader(http.StatusInternalServerError)
		w.Write([]byte("Failed to get category."))
		return
	}

	jsonBytes, err := json.Marshal(&category)

	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		w.Write([]byte(err.Error()))
		return
	}

	w.WriteHeader(http.StatusOK)
	w.Write(jsonBytes)
}

func deleteCategoryHandler(w http.ResponseWriter, r *http.Request) {
	id := strings.TrimPrefix(r.URL.Path, "/category/")

	value, err := strconv.ParseInt(id, 0, 64)

	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		w.Write([]byte(err.Error()))
		return
	}

	if !deleteCategory(value) {
		w.WriteHeader(http.StatusBadRequest)
		w.Write([]byte(fmt.Sprintf("Failed to delete %d", value)))
		return
	}

	w.WriteHeader(http.StatusOK)
}

func getCategoriesHandler(w http.ResponseWriter, r *http.Request) {
	categories, ok := getAllCategories()

	if !ok {
		w.WriteHeader(http.StatusInternalServerError)
		w.Write([]byte("Failed to fetch a list of categories."))
		return
	}

	jsonBytes, err := json.Marshal(categories)

	if err != nil {
		w.WriteHeader(http.StatusInternalServerError)
		w.Write([]byte("Failed to get a list of categories."))
		return
	}

	w.WriteHeader(http.StatusOK)
	w.Write(jsonBytes)
}

func insertCategoryHandler(w http.ResponseWriter, r *http.Request) {
	ct := r.Header.Get("content-type")

	if ct != "application/json" {
		w.WriteHeader(http.StatusUnsupportedMediaType)
		w.Write([]byte(fmt.Sprintf("Unsupported media type '%s', expected application/json", ct)))
		return
	}

	bodyBytes, err := ioutil.ReadAll(r.Body)

	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		w.Write([]byte("Failed to parse request body"))
		return
	}

	defer r.Body.Close()

	var category Category

	err = json.Unmarshal(bodyBytes, &category)

	if err != nil {
		w.WriteHeader(http.StatusBadRequest)
		w.Write([]byte("Failed to unmarshal JSON"))
		return
	}

	id, ok := insertNewCategory(category.Name, category.Subcategories)

	if !ok {
		w.WriteHeader(http.StatusInternalServerError)
		w.Write([]byte("Failed to create the new category."))
		return
	}

	w.WriteHeader(http.StatusOK)
	w.Write([]byte(fmt.Sprintf("New Record: %d", id)))
}