Initial commit

.gitignore

+kohaprinter
+kohaprinter_mapping.json

README.md

+Kohaprinter
+==
+
+A Cups Backend and printer delegator for use in Koha Intra and other services attached.
+Purpose is to generate a simple connection between browser and thermal printers connected
+in local network, so that you can print any HTML slip or label to a printer in the network.
+
+Requirements
+==
+
+To build backend: golang
+
+* wkhtmltopdf (webkit html to pdf renderer) for rastering html
+  must be placed in /usr/bin on the cups server
+  https://github.com/wkhtmltopdf/wkhtmltopdf/releases
+* compiled backend (kohaprinter) must be placed in /usr/lib/cups/backend/ on the cups server
+* a json mapping file (see example) must be placed in same directory as backend and named kohaprinter_mapping.json
+* Cups is strict on permissions, so make sure backend is owned by root and chmod 0755
+* also beware that backend is run by user `lp` so main log turns up in /tmp/kohaprinter.log and
+  spool logs and output in /var/spool/cups/
+
+Setup and Testing
+==
+
+## 1. In Cups, a Raw Print Queue must be set up to point to backend.
+
+Make sure the Device URI corresponds with the backend, (kohaprinter), as this is picked up automagically by Cups
+
+e.g.
+
+```
+lpadmin -p KohaKvittPrinter -v kohaprinter:/kvitt -m raw -E
+```
+
+This means any job sent to this Queue on this Cups server will be passed along to the `kohaprinter` backend
+with the kohaprinter:/kvitt Device URI. Likewise a `kohaprinter:/label` queue could be made to handle label printing.
+
+If the Cups server was running on host, say, `cupsserver`, the queue would now be accessible as normal by Cups, e.g.
+
+```
+ipps://cupsserver/printers/KohaKvittPrinter
+```
+
+## 2. The Client Printer must be mapped to correct network printer
+
+
+On cups server: (See the example mapping file for examples)
+
+
+/usr/lib/cups/backend/kohaprinter_mapping.json:
+
+```
+{
+ "cupsclient": {
+    "name": "a koha staff client",
+    "kvittering": "lab-kvitt-10"
+  }
+}
+```
+
+## 3. The Client Must be configured with a Raw printer
+
+Setup a Raw Printer to the Queue created in #1
+
+Eg. in linux:
+
+```
+lpadmin -p IppKohaKvitt -v ipps://cupsserver/printers/KohaKvittPrinter8 -m raw -E
+```
+
+Now you should be able to print any html to the receipt printer. Eg. in linux:
+
+```
+lp -d IppKohaKvitt -o document-format=text/html test.html
+```
+
+Behind the scenes
+==
+
+What happens is that :
+
+* html document is sent raw to the Remote Print Queue KohaKvittPrinter
+* it is delegated to the kohaprinter backend which :
+  * fetches originating IP and DeviceURI from request
+  * rasters the html document to PDF with Webkit
+  * forwards generated PDF to Print Queue of Thermal Printer found in json mapping

kohaprinter.go

+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"os"
+	"os/exec"
+	"strings"
+
+	wkhtml "github.com/SebastiaanKlippert/go-wkhtmltopdf"
+)
+
+type Printer struct {
+	Name, Kvittering, Etikett string
+}
+
+var (
+	Log *log.Logger
+)
+
+/*
+ * Prerequisites:
+ *   wkhtmltopdf binary MUST be downloaded to /usr/bin
+ *   this file needs to be chown root and chmod 755 executable in /usr/lib/cups/backend/
+ *   job needs job-originating-host-name
+ *   kohaprint.json mapping must exist beside this file
+ */
+func main() {
+
+	lfile, err := os.Create("/tmp/kohaprint.log")
+	if err != nil {
+		fail(err)
+	}
+	Log = log.New(lfile, "", log.LstdFlags|log.Lshortfile)
+
+	var mapping map[string]Printer
+	cfgFile, err := os.Open("/usr/lib/cups/backend/kohaprinter_mapping.json")
+	defer cfgFile.Close()
+	if err != nil {
+		fail(err)
+	}
+	dec := json.NewDecoder(cfgFile)
+	dec.Decode(&mapping)
+
+	Log.Printf("[INFO  ] MAPPING: %v", mapping)
+	// No args? Return status line as cups expects this to discover backend
+	if len(os.Args) == 1 {
+		fmt.Println("network kohaprint \"Unknown\" \"Print any job to queue specified in device-URI\"")
+		os.Exit(0)
+	} else if len(os.Args) < 6 {
+		fmt.Println("Usage: kohaprint job-id user title copies options [file]")
+		os.Exit(0)
+	}
+
+	opts := os.Args[5]
+	Log.Printf("[INFO  ] OPTS: %s", opts)
+
+	h := getOriginHostName(opts)
+	if h == "" {
+		fail(errors.New("Missing params: job-originating-host-name"))
+	}
+	if _, ok := mapping[h]; !ok {
+		fail(errors.New("Originating Host IP missing from mapping file"))
+	}
+
+	pdfg, err := wkhtml.NewPDFGenerator()
+	if err != nil {
+		fail(err)
+	}
+	// Read job data from stdin
+	data, err := ioutil.ReadAll(os.Stdin)
+	if err != nil {
+		fail(err)
+	}
+
+	Log.Printf("[INFO  ] DATA: %s", data)
+	pdfg.AddPage(wkhtml.NewPageReader(strings.NewReader(string(data))))
+	err = pdfg.Create()
+	if err != nil {
+		fail(err)
+	}
+
+	tmpf, err := ioutil.TempFile("", "kohaprintpdf")
+	if err != nil {
+		fail(err)
+	}
+
+	defer os.Remove(tmpf.Name())
+
+	if _, err := tmpf.Write(pdfg.Bytes()); err != nil {
+		fail(err)
+	}
+	if err := tmpf.Close(); err != nil {
+		fail(err)
+	}
+
+	args := []string{"-d", mapping[h].Kvittering, tmpf.Name()}
+	Log.Printf("[INFO  ] ARGS: %s\n", args)
+	out, err := exec.Command("lp", args...).Output()
+	if err != nil {
+		Log.Printf("[INFO  ] CMD OUTPUT: %s\n", out)
+		fail(err)
+	}
+	os.Exit(0)
+}
+
+func getOriginHostName(opts string) string {
+	arr := strings.Split(opts, " ")
+	for _, a := range arr {
+		p := strings.Split(a, "=")
+		if p[0] == "job-originating-host-name" {
+			return p[1]
+		}
+	}
+	return ""
+}
+
+func fail(err error) {
+	Log.Printf("[ERROR] %s", err.Error())
+	os.Exit(1)
+}

kohaprinter_mapping_example.json

+{
+  "10.172.2.10": {
+    "name": "a test client",
+    "kvittering": "printer-thermal-in-cups"
+  },
+  "10.172.2.11": {
+    "name": "another client",
+    "kvittering": "another-thermal-printer-in-cups",
+    "etikett": "label-printer-in-cups"
+  }
+}
\ No newline at end of file

test.html

+<!DOCTYPE html>
+<html><body><h1>It actually works!</h1>
+<p>Give me a <strong>Bloody Beer!</strong></p>
+<pre>
+
+                 /######\
+               /##########\
+              /   \###/    \
+             /     \#/      \
+          /\|               |/\
+          | | \ ==\    /== / | |
+           \|  \<|>\  /<|>/  |/     /|
+    \__     |    -   \  -    |     /#|
+     \#\     |        |      |   /###|
+      \##\   |       \|     |  /#####|
+       \###\  |   _______  | /######|
+        \####\ | / \/ \/ \|/#######|
+        |######\|        |#########|
+        |########\______/##########|
+        |#########\    /##########/
+        |##########\  |#########/\
+        /###########\/########/###\
+    /################\######/########\
+   /##################\###/###########\
+  /###################\#/##############\
+ /####################/#################\
+/###################/####################\
+</pre>
+</body></html>