schemagen cli

cmd/schemagen/schemagen.go

@@ -0,0 +1,162 @@
+package main
+
+import (
+	"bytes"
+	_ "embed"
+	"flag"
+	"fmt"
+	"go/format"
+	"html/template"
+	"io"
+	"log"
+	"os"
+	"path"
+	"strings"
+	"unicode"
+
+	"github.com/gocql/gocql"
+	"github.com/scylladb/gocqlx/v2"
+	_ "github.com/scylladb/gocqlx/v2/table"
+)
+
+var (
+	cmd          = flag.NewFlagSet(os.Args[0], flag.ExitOnError)
+	flagCluster  = cmd.String("cluster", "127.0.0.1", "a comma-separated list of host:port tuples")
+	flagKeyspace = cmd.String("keyspace", "", "keyspace to inspect")
+	flagPkgname  = cmd.String("pkgname", "models", "the name you wish to assign to your generated package")
+	flagOutput   = cmd.String("output", "models", "the name of the folder to output to")
+)
+
+var (
+	//go:embed keyspace.tmpl
+	keyspaceTmpl string
+)
+
+func main() {
+	err := cmd.Parse(os.Args[1:])
+	if err != nil {
+		log.Fatalln("can't parse flags")
+	}
+
+	if *flagKeyspace == "" {
+		log.Fatalln("missing required flag: keyspace")
+	}
+
+	schemagen()
+}
+
+func schemagen() {
+	err := os.MkdirAll(*flagOutput, os.ModePerm)
+	if err != nil {
+		log.Fatalln("unable to create output directory:", err)
+	}
+
+	outputPath := path.Join(*flagOutput, *flagPkgname+".go")
+	f, err := os.OpenFile(outputPath, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0755)
+	if err != nil {
+		log.Fatalln("unable to open output file:", err)
+	}
+
+	metadata := fetchMetadata(createSession())
+
+	if err = renderTemplate(f, metadata); err != nil {
+		log.Fatalln("unable to output template:", err)
+	}
+
+	if err = f.Close(); err != nil {
+		log.Fatalln("unable to close output file:", err)
+	}
+
+	log.Println("File written to", outputPath)
+}
+
+func fetchMetadata(s *gocqlx.Session) *gocql.KeyspaceMetadata {
+	md, err := s.KeyspaceMetadata(*flagKeyspace)
+	if err != nil {
+		log.Fatalln("unable to fetch keyspace metadata:", err)
+	}
+
+	return md
+}
+
+func renderTemplate(w io.Writer, md *gocql.KeyspaceMetadata) error {
+	t, err := template.
+		New("keyspace.tmpl").
+		Funcs(template.FuncMap{"camelize": camelize}).
+		Parse(keyspaceTmpl)
+
+	if err != nil {
+		log.Fatalln("unable to parse models template:", err)
+	}
+
+	buf := &bytes.Buffer{}
+	data := map[string]interface{}{
+		"PackageName": *flagPkgname,
+		"Tables":      md.Tables,
+	}
+
+	err = t.Execute(buf, data)
+	if err != nil {
+		log.Fatalln("unable to execute models template:", err)
+	}
+
+	res, err := format.Source(buf.Bytes())
+	if err != nil {
+		log.Fatalln("template output is not a valid go code:", err)
+	}
+
+	_, err = w.Write(res)
+
+	return err
+}
+
+func createSession() *gocqlx.Session {
+	cluster := createCluster()
+	s, err := gocqlx.WrapSession(cluster.CreateSession())
+	if err != nil {
+		log.Fatalln("unable to create scylla session:", err)
+	}
+	return &s
+}
+
+func createCluster() *gocql.ClusterConfig {
+	clusterHosts := getClusterHosts()
+	return gocql.NewCluster(clusterHosts...)
+}
+
+func getClusterHosts() []string {
+	return strings.Split(*flagCluster, ",")
+}
+
+func camelize(s string) string {
+	buf := []byte(s)
+	out := make([]byte, 0, len(buf))
+	underscoreSeen := false
+
+	l := len(buf)
+	for i := 0; i < l; i++ {
+		if !(allowedBindRune(buf[i]) || buf[i] == '_') {
+			panic(fmt.Sprint("not allowed name ", s))
+		}
+
+		b := rune(buf[i])
+
+		if b == '_' {
+			underscoreSeen = true
+			continue
+		}
+
+		if (i == 0 || underscoreSeen) && unicode.IsLower(b) {
+			b = unicode.ToUpper(b)
+			underscoreSeen = false
+		}
+
+		out = append(out, byte(b))
+	}
+
+	return string(out)
+}
+
+func allowedBindRune(b byte) bool {
+	return (b >= 'a' && b <= 'z') || (b >= 'A' && b <= 'Z') || (b >= '0' && b <= '9')
+}