barcodes/web/generate.route.go

package web

import (
	"encoding/json"
	"errors"
	"fmt"
	"image"
	"image/png"
	"net/http"

	"git.fjla.uk/fred.boniface/barcodes/generation"
	"git.fjla.uk/fred.boniface/barcodes/validation"
	"github.com/boombuler/barcode"
)

// Generates a barcode from the data and options provided in the request
func generateBarcode(w http.ResponseWriter, r *http.Request) {

	if r.Method != http.MethodPost && r.Method != http.MethodGet {
		http.Error(w, "Use a POST or GET request for barcode generation. See the help page for more information", http.StatusMethodNotAllowed)
		return
	}

	var req *BarcodeRequest
	var err error

	if r.Method == http.MethodGet {
		req, err = generateFromGet(r)
		if err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}
	} else {
		err := json.NewDecoder(r.Body).Decode(&req)
		if err != nil {
			http.Error(w, err.Error(), http.StatusBadRequest)
			return
		}
	}

	parameters := generation.Parameters{
		Format:   generation.BarcodeType(req.BarcodeType),
		ECCLevel: generation.ECCLevel(req.ECCLevel),
		Content:  req.Content,
	}

	validate := validation.Validate(parameters)
	if !validate {
		fmt.Println("Validation Failed")
		http.Error(w, "Validation Failed", http.StatusBadRequest)
		return
	}

	barcodeGen, err := generation.Generate(parameters)
	if err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	if barcodeGen == nil {
		fmt.Println("Generation failed, no barcode created")
		http.Error(w, "Barcode Generation Failed", http.StatusInternalServerError)
		return
	}

	barcodeGen, _ = barcode.Scale(barcodeGen, int(req.Width), int(req.Height))

	image, isImage := barcodeGen.(image.Image)
	if !isImage {
		fmt.Println("Generation failed - no image")
		http.Error(w, "Generated Barcode is not an image", http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "image/png")

	err = png.Encode(w, image)
	if err != nil {
		http.Error(w, "Error streaming barcode", http.StatusInternalServerError)
	}
}

func generateFromGet(r *http.Request) (*BarcodeRequest, error) {
	//var parameters generation.Parameters
	if r.Method == http.MethodGet {
		validTypes := map[string]bool{
			"qr":         true,
			"aztec":      true,
			"datamatrix": true,
		}

		typeParam := r.URL.Query().Get("type")
		content := r.URL.Query().Get("text")

		if typeParam == "" || content == "" {
			return nil, errors.New("both 'type' and 'text' parameters are required")
		}

		if !validTypes[typeParam] {
			return nil, errors.New("'type' must be 'qr', 'aztec', or 'datamatrix'")
		}

		barcodeReq := &BarcodeRequest{
			BarcodeType: typeParam,
			Width:       300,
			Height:      300,
			ECCLevel:    2,
			Content:     content,
		}

		return barcodeReq, nil
	} else {
		return nil, errors.New("incorrect request type passed to function")
	}
}