Merge pull request #1 from senaduka/prices-getter

Prices getter

.gitignore

@@ -4,6 +4,9 @@
 *.so
 *.dylib
 
+# monitor binary
+gomon_spawn
+
 # Test binary, build with `go test -c`
 *.test
 

README.md

@@ -1,2 +1,6 @@
 # bilal-vjezba-golang
 bilal vjezba golang
+
+Requirements :
+
+phantomjs (apt-get install phantomjs)

server.go

@@ -0,0 +1,270 @@
+package main
+
+import (
+	"fmt"
+	"github.com/PuerkitoBio/goquery"
+	"github.com/benbjohnson/phantomjs"
+	"log"
+	"math"
+	"net/http"
+	"strconv"
+	"strings"
+)
+
+const validNumberOfURLParams = 5
+const sizeParamIndex = 3
+const countParamIndex = 4
+const validNumberOfSizeParams = 2
+
+const maxExpectedNumberOfQuantities = 15
+const numberOfTabsToSizeGroup = 12
+const numberOfArrowDownToCustomSize = 4
+
+const validMinWidth = 25.4
+const validMaxWidth = 914.4
+const validMinHeight = 25.4
+const validMaxHeigh = 609.59
+
+const epsilon = 0.1
+
+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"
+	invalidParamsSize             = "Params should be in range"
+
+	errorSimulatingInput = "Error with simulating user input"
+
+	tooManyQuantities = "Too many quantities. Didn't expect this"
+
+	failedToGetPrice = "Failed to get price"
+)
+
+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 floatToString(number float64) string {
+	return strconv.FormatFloat(number, 'f', 1, 64)
+}
+
+func getStickerPrice(width, height float64, quantity int) (int, error) {
+
+	//simulate click on "Custom size radio button"
+	if _, err := stickerMuleWebPage.Evaluate("function(){document.getElementById('variant_77').click();}"); err != nil {
+		return 0, err
+	}
+
+	//set value for width
+	if _, err := stickerMuleWebPage.Evaluate("function(){document.getElementById('width').value = " + floatToString(width) + ";}"); err != nil {
+		return 0, err
+	}
+
+	//set value for height
+	if _, err := stickerMuleWebPage.Evaluate("function(){document.getElementById('height').value = " + floatToString(height) + ";}"); err != nil {
+		return 0, err
+	}
+
+	//check if input boxes accepted passed values
+	valuesFromInputBoxes, err := stickerMuleWebPage.Evaluate("function(){return {width: document.getElementById('width').value, height: document.getElementById('height').value};}")
+	if err != nil {
+		return 0, err
+	}
+
+	valuesMap, ok := valuesFromInputBoxes.(map[string]interface{})
+	if !ok {
+		return 0, fmt.Errorf(invalidParamsType)
+	}
+
+	redWidthString, ok := valuesMap["width"].(string)
+	if !ok {
+		return 0, fmt.Errorf(invalidParamsType)
+	}
+
+	redHeightString, ok := valuesMap["height"].(string)
+	if !ok {
+		return 0, fmt.Errorf(invalidParamsType)
+	}
+
+	widthValue, err := strconv.ParseFloat(redWidthString, 64)
+	if err != nil {
+		return 0, fmt.Errorf(invalidParamsType)
+	}
+
+	heightValue, err := strconv.ParseFloat(redHeightString, 64)
+	if err != nil {
+		return 0, fmt.Errorf(invalidParamsType)
+	}
+
+	if math.Abs(widthValue-width) > epsilon || math.Abs(heightValue-height) > epsilon {
+		return 0, fmt.Errorf(invalidParamsType)
+	}
+
+	//Now read price for selected quantity
+	priceValue, err := stickerMuleWebPage.Evaluate("function(){return {price: document.getElementById('price_200_id').innerHTML};}")
+	//TODO : price is empty because setting value for width and height doesn't fire event listener
+	//on input fields and prices are not loaded. Find another way to simulate user input
+
+	priceMap, ok := priceValue.(map[string]interface{})
+	if !ok {
+		return 0, fmt.Errorf(failedToGetPrice)
+	}
+
+	_, ok = priceMap["price"].(string)
+	if !ok {
+		return 0, fmt.Errorf(failedToGetPrice)
+	}
+
+	return 100, 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.ParseFloat(size[0], 64)
+			height, hOk := strconv.ParseFloat(size[1], 64)
+			countNumber, cOk := strconv.ParseInt(count, 10, 16)
+
+			countNumber16 := int16(countNumber)
+
+			foundValidQuantity := false
+			for _, value := range listOfValidQuantities {
+				if value == countNumber16 {
+					foundValidQuantity = true
+					break
+				}
+			}
+
+			validWidth := width >= validMinWidth && width <= validMaxWidth
+			validHeight := height >= validMinHeight && height <= validMaxHeigh
+
+			if wOk != nil || hOk != nil || cOk != nil || !foundValidQuantity || !validWidth || !validHeight {
+				errorResponse(w, invalidParamsType)
+			} else {
+
+				price, err := getStickerPrice(width, height, int(countNumber))
+				if err != nil {
+					errorResponse(w, failedToGetPrice)
+				} else {
+					w.Header().Set("Content-Type", "application/json")
+					fmt.Fprintf(w, "{price:%d, currency: \"USD\"}", price)
+				}
+			}
+
+		} 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
+
+	localStickerMuleWebPage, err := p.CreateWebPage()
+	if err != nil {
+		return err
+	}
+
+	//keep pointer to web page in global space, so page is not re-created every time API is called
+	stickerMuleWebPage = localStickerMuleWebPage
+
+	// 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))
+
+}