old-bilal-vjezba-golang/server.go

package main

import (
	"fmt"
	"log"
	"net/http"
	"strconv"
	"strings"
	//"gopkg.in/headzoo/surf.v1"
	"github.com/PuerkitoBio/goquery"
	//"sourcegraph.com/sourcegraph/go-selenium"
	"github.com/benbjohnson/phantomjs"
)

const validNumberOfURLParams = 5
const sizeParamIndex = 3
const countParamIndex = 4
const validNumberOfSizeParams = 2

const maxExpectedNumberOfQuantities = 15

const stickerMuleURL = "https://www.stickermule.com/uk/products/die-cut-stickers"

const (
	invalidURL                    = "URL is not valid"
	invalidNumberOfParamsError    = "Number of params not correct, expected /WIDTHxLENGTH/count"
	invalidNumberOfSizeParamError = "Size not correct, expected /WIDTHxLENGTH/count"
	invalidParamsType             = "Params should be numbers"

	tooManyQuantities			  = "Too many quantities. Didn't expect this"
)

var listOfValidQuantities []int16
var stickerMuleWebPage *phantomjs.WebPage
var stickerMuleWebPageDocument *goquery.Document


func getListOfQuantities() error {
	result := make([]int16, maxExpectedNumberOfQuantities)
	resultCount := 0
	wasError := false
	whichError := error(nil)
	stickerMuleWebPageDocument.Find("label.quantity").Each(func(_ int, s *goquery.Selection){
		if wasError{
			return
		}

		numberWithoutComma := strings.Replace(s.Text(), ",","",-1)
		trimmedNumber := strings.TrimSpace(numberWithoutComma)


		if sizeInt64, err := strconv.ParseInt(trimmedNumber,10,16) ; err != nil {
			wasError = true
			whichError = err
		}else{
			result[resultCount] = int16(sizeInt64)
		}
		resultCount+=1
		if resultCount == 15 {
			wasError = true
			whichError = fmt.Errorf(tooManyQuantities)
		}
	})
	if wasError {
		return whichError
	}

	listOfValidQuantities = result[:resultCount]

	return nil
}

func errorResponse(w http.ResponseWriter, errType string) {
	fmt.Fprintf(w, errType)
}

func diecutHandler(w http.ResponseWriter, r *http.Request) {
	if params := strings.Split(r.URL.Path, "/"); len(params) == validNumberOfURLParams {
		if size := strings.Split(params[sizeParamIndex], "x"); len(size) == validNumberOfSizeParams {
			count := params[countParamIndex]

			width, wOk := strconv.ParseInt(size[0], 10, 16)
			height, hOk := strconv.ParseInt(size[1], 10, 16)
			countNumber, cOk := strconv.ParseInt(count, 10, 16)

			countNumber16 := int16(countNumber)

			foundValidQuantity := false
			for _, value := range(listOfValidQuantities){
				if value == countNumber16 {
					foundValidQuantity = true
					break
				} 
			}

			if wOk != nil || hOk != nil || cOk != nil || !foundValidQuantity {
				errorResponse(w, invalidParamsType)
			} else {

				fmt.Fprintf(w, "%dx%d | %d", width, height, countNumber)

			}

		} else {
			errorResponse(w, invalidNumberOfSizeParamError)
		}
	} else {
		errorResponse(w, invalidNumberOfParamsError)
	}
}

func defaultHandler(w http.ResponseWriter, r *http.Request) {
	errorResponse(w, invalidURL)
}

func initWebPage() error{
	p := phantomjs.DefaultProcess

	stickerMuleWebPage, err := p.CreateWebPage()
	if err != nil {
		return err
	}

	// Open a URL.
	if err := stickerMuleWebPage.Open(stickerMuleURL); err != nil {
		return err
	}

	content, err := stickerMuleWebPage.Content()
	if err != nil {
		return err
	}

	stickerMuleWebPageDocument,err = goquery.NewDocumentFromReader(strings.NewReader(content))
	if err != nil {
		return err
	}

	return nil
}

func closingCleanUp(){
	phantomjs.DefaultProcess.Close()
	stickerMuleWebPage.Close()
}

func main() {
	//init phantomJS
	if err:= phantomjs.DefaultProcess.Open(); err != nil {
		fmt.Println("Error : ", err)
		return
	}

	defer closingCleanUp()

	//init web page and document
	if err:= initWebPage() ; err != nil {
		fmt.Println("Error : ", err)
		return
	}

	//init valid values for stickers quantity
	if err:= getListOfQuantities() ; err != nil {
		fmt.Println("Error : ", err)
		return
	}

	http.HandleFunc("/prices/diecut/", diecutHandler)
	http.HandleFunc("/", defaultHandler)

	fmt.Println("Server running on localhost:8080")
	log.Fatal(http.ListenAndServe(":8080", nil))
	
	
}