implement web handler for QR code generation

2020-06-20 09:39:06 +02:00
parent 8410782ab8
commit 8bf9d10964
5 changed files with 333 additions and 163 deletions
--- a/cmd/qrbill-example/example.go
+++ b/cmd/qrbill-example/example.go
@@ -1,14 +1,178 @@
 package main

 import (
+	"bytes"
+	"flag"
+	"fmt"
+	"image/png"
+	"io"
 	"log"
+	"net/http"
+	"regexp"
+	"strings"

+	"github.com/davecgh/go-spew/spew"
 	"github.com/stapelberg/qrbill"
+
+	_ "net/http/pprof"
 )

+func ifEmpty(s, alternative string) string {
+	if s == "" {
+		return alternative
+	}
+	return s
+}
+
+func qrchFromRequest(r *http.Request) *qrbill.QRCH {
+	return &qrbill.QRCH{
+		CdtrInf: qrbill.QRCHCdtrInf{
+			IBAN: ifEmpty(r.FormValue("criban"), "CH0209000000870913543"),
+			Cdtr: qrbill.Address{
+				AdrTp:            qrbill.AddressTypeStructured,
+				Name:             ifEmpty(r.FormValue("crname"), "Legalize it!"),
+				StrtNmOrAdrLine1: ifEmpty(r.FormValue("craddr1"), "Quellenstrasse 25"),
+				BldgNbOrAdrLine2: ifEmpty(r.FormValue("craddr2"), ""),
+				PstCd:            ifEmpty(r.FormValue("crpost"), "8005"),
+				TwnNm:            ifEmpty(r.FormValue("crcity"), "Zürich"),
+				Ctry:             ifEmpty(r.FormValue("crcountry"), "CH"),
+			},
+		},
+		CcyAmt: qrbill.QRCHCcyAmt{
+			Amt: "",
+			Ccy: "CHF",
+		},
+		UltmtDbtr: qrbill.Address{
+			AdrTp:            qrbill.AddressTypeStructured,
+			Name:             ifEmpty(r.FormValue("udname"), "Michael Stapelberg"),
+			StrtNmOrAdrLine1: ifEmpty(r.FormValue("udaddr1"), "Brahmsstrasse 21"),
+			BldgNbOrAdrLine2: ifEmpty(r.FormValue("udaddr2"), ""),
+			PstCd:            ifEmpty(r.FormValue("udpost"), "8003"),
+			TwnNm:            ifEmpty(r.FormValue("udcity"), "Zürich"),
+			Ctry:             ifEmpty(r.FormValue("udcountry"), "CH"),
+		},
+		RmtInf: qrbill.QRCHRmtInf{
+			Tp:  "NON", // Reference type
+			Ref: "",    // Reference
+			AddInf: qrbill.QRCHRmtInfAddInf{
+				Ustrd: ifEmpty(r.FormValue("message"), "Spende 6141"),
+			},
+		},
+	}
+}
+
+var fieldNameRe = regexp.MustCompile(`<br>(&nbsp;)*([^:]+):`)
+var stringLiteralRe = regexp.MustCompile(`"([^"]*)"`)
+
+func qrHandler(format string) http.Handler {
+	if format != "png" &&
+		format != "svg" &&
+		format != "txt" &&
+		format != "html" {
+		log.Fatalf("BUG: format must be either png, svg, txt or html")
+	}
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		prefix := "[" + r.RemoteAddr + "]"
+		log.Printf("%s handling request for %s", prefix, r.URL.Path)
+		defer log.Printf("%s done: %s", prefix, r.URL.Path)
+
+		qrch := qrchFromRequest(r)
+
+		bill, err := qrch.Encode()
+		if err != nil {
+			log.Print(err)
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+
+		var b []byte
+		switch format {
+		case "png":
+			code, err := bill.EncodeToImage()
+			if err != nil {
+				log.Print(err)
+				http.Error(w, err.Error(), http.StatusInternalServerError)
+				return
+			}
+
+			var buf bytes.Buffer
+			if err := png.Encode(&buf, code); err != nil {
+				log.Print(err)
+				http.Error(w, err.Error(), http.StatusInternalServerError)
+				return
+			}
+			b = buf.Bytes()
+			w.Header().Add("Content-Type", "image/png")
+
+		case "svg":
+			var err error
+			b, err = bill.EncodeToSVG()
+			if err != nil {
+				log.Print(err)
+				http.Error(w, err.Error(), http.StatusInternalServerError)
+				return
+			}
+
+			w.Header().Add("Content-Type", "image/svg+xml")
+
+		case "txt":
+			w.Header().Add("Content-Type", "text/plain; charset=utf-8")
+			spew.Fdump(w, qrch.Fill())
+
+		case "html":
+			w.Header().Add("Content-Type", "text/html; charset=utf-8")
+			fmt.Fprintf(w, `<html lang="en">
+<head>
+  <title>QR Bill HTML Debug Page</title>
+  <style type="text/css">
+.fieldname { font-weight: bold; }
+.stringliteral { color: blue; }
+  </style>
+</head>
+<body style="font-family: monospace">
+`)
+			sp := spew.Sdump(qrch.Fill())
+			sp = strings.ReplaceAll(sp, "\n", "<br>")
+			sp = strings.ReplaceAll(sp, " ", "&nbsp;")
+			sp = stringLiteralRe.ReplaceAllStringFunc(sp, func(stringLiteral string) string {
+				return `<span class="stringliteral">` + stringLiteral + "</span>"
+			})
+			sp = fieldNameRe.ReplaceAllStringFunc(sp, func(fieldName string) string {
+				return `<span class="fieldname">` + fieldName + "</span>"
+			})
+			fmt.Fprintf(w, "%s", sp)
+		}
+
+		// TODO: add cache control headers
+		if _, err := io.Copy(w, bytes.NewReader(b)); err != nil {
+			log.Print(err)
+			return
+		}
+	})
+}
+
 func logic() error {
-	return qrbill.Generate()
-	//return nil
+	var listen = flag.String("listen", "localhost:9933", "[host]:port to listen on")
+	flag.Parse()
+	http.Handle("/qr.png", qrHandler("png"))
+	http.Handle("/qr.svg", qrHandler("svg"))
+	http.Handle("/qr.txt", qrHandler("txt"))
+	http.Handle("/qr.html", qrHandler("html"))
+	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path != "/" {
+			http.Error(w, "not found", http.StatusNotFound)
+			return
+		}
+		w.Header().Add("Content-Type", "text/html; charset=utf-8")
+		// TODO: add explanation for how to construt a URL
+		// e.g. for usage in filemaker web view
+		fmt.Fprintf(w, "<ul>")
+		fmt.Fprintf(w, `<li>PNG referenz: <a href="/qr.png">qr.png</a>`+"\n")
+		fmt.Fprintf(w, `<li>SVG scalable: <a href="/qr.svg">qr.svg</a>`+"\n")
+		fmt.Fprintf(w, `<li>debug: <a href="/qr.txt">qr.txt</a>`+"\n")
+	})
+	log.Printf("listening on http://%s", *listen)
+	return http.ListenAndServe(*listen, nil)
 }

 func main() {