Add example for iterating product id and product helper (#617)

* Add example for iterating product id and product helper

* simplify code a bit

* Remove newline

---------

Co-authored-by: Sascha L. Teichmann <sascha.teichmann@intevation.de>

examples/product_lister/main.go

@@ -0,0 +1,141 @@
+// Package main implements a simple demo program to
+// work with the csaf library.
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"log"
+	"os"
+
+	"github.com/gocsaf/csaf/v3/csaf"
+)
+
+func main() {
+	flag.Usage = func() {
+		if _, err := fmt.Fprintf(flag.CommandLine.Output(),
+			"Usage:\n  %s [OPTIONS] files...\n\nOptions:\n", os.Args[0]); err != nil {
+			log.Fatalf("error: %v\n", err)
+		}
+		flag.PrintDefaults()
+	}
+	printProductIdentHelper := flag.Bool("print_ident_helper", false, "print product helper mapping")
+	flag.Parse()
+
+	files := flag.Args()
+	if len(files) == 0 {
+		log.Println("No files given.")
+		return
+	}
+
+	var printer func(*csaf.Advisory) error
+	if *printProductIdentHelper {
+		printer = printProductIdentHelperMapping
+	} else {
+		printer = printProductIDMapping
+	}
+
+	if err := run(files, printer); err != nil {
+		log.Fatalf("error: %v\n", err)
+	}
+}
+
+// visitFullProductNames iterates all full product names in the advisory.
+func visitFullProductNames(
+	adv *csaf.Advisory,
+	visit func(*csaf.FullProductName),
+) {
+	// Iterate over all full product names
+	if fpns := adv.ProductTree.FullProductNames; fpns != nil {
+		for _, fpn := range *fpns {
+			if fpn != nil && fpn.ProductID != nil {
+				visit(fpn)
+			}
+		}
+	}
+
+	// Iterate over branches recursively
+	var recBranch func(b *csaf.Branch)
+	recBranch = func(b *csaf.Branch) {
+		if b == nil {
+			return
+		}
+		if fpn := b.Product; fpn != nil && fpn.ProductID != nil {
+			visit(fpn)
+
+		}
+		for _, c := range b.Branches {
+			recBranch(c)
+		}
+	}
+	for _, b := range adv.ProductTree.Branches {
+		recBranch(b)
+	}
+
+	// Iterate over relationships
+	if rels := adv.ProductTree.RelationShips; rels != nil {
+		for _, rel := range *rels {
+			if rel != nil {
+				if fpn := rel.FullProductName; fpn != nil && fpn.ProductID != nil {
+					visit(fpn)
+				}
+			}
+		}
+	}
+}
+
+// run applies fn to all loaded advisories.
+func run(files []string, fn func(*csaf.Advisory) error) error {
+	for _, file := range files {
+		adv, err := csaf.LoadAdvisory(file)
+		if err != nil {
+			return fmt.Errorf("loading %q failed: %w", file, err)
+		}
+		if err := fn(adv); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// printJSON serializes v as indented JSON to stdout.
+func printJSON(v any) error {
+	enc := json.NewEncoder(os.Stdout)
+	enc.SetIndent("", "  ")
+	return enc.Encode(v)
+}
+
+// printProductIDMapping prints all product ids with their name and identification helper.
+func printProductIDMapping(adv *csaf.Advisory) error {
+	type productNameHelperMapping struct {
+		FullProductName             *csaf.FullProductName             `json:"product"`
+		ProductIdentificationHelper *csaf.ProductIdentificationHelper `json:"product_identification_helper"`
+	}
+
+	productIDMap := map[csaf.ProductID][]productNameHelperMapping{}
+	visitFullProductNames(adv, func(fpn *csaf.FullProductName) {
+		productIDMap[*fpn.ProductID] = append(productIDMap[*fpn.ProductID], productNameHelperMapping{
+			FullProductName:             fpn,
+			ProductIdentificationHelper: fpn.ProductIdentificationHelper,
+		})
+	})
+	return printJSON(productIDMap)
+}
+
+// printProductIdentHelperMapping prints all product identifier helper with their product id.
+func printProductIdentHelperMapping(adv *csaf.Advisory) error {
+	type productIdentIDMapping struct {
+		ProductNameHelperMapping csaf.ProductIdentificationHelper `json:"product_identification_helper"`
+		ProductID                *csaf.ProductID                  `json:"product_id"`
+	}
+
+	productIdentMap := []productIdentIDMapping{}
+	visitFullProductNames(adv, func(fpn *csaf.FullProductName) {
+		productIdentMap = append(productIdentMap, productIdentIDMapping{
+			ProductNameHelperMapping: *fpn.ProductIdentificationHelper,
+			ProductID:                fpn.ProductID,
+		})
+	})
+	return printJSON(productIdentMap)
+}