tree-wide: use a standard project layout

Keep main.go files under cmd/ and internal libraries under internal/.
This will allow us to add more exutables under cmd/ (whereas only one
was possible when main.go was kept in the root).

Signed-off-by: Tom Gundersen <teg@jklm.no>

cmd/osbuild-composer/main.go

@@ -0,0 +1,122 @@
+package main
+
+import (
+	"context"
+	"flag"
+	"io/ioutil"
+	"log"
+	"net"
+	"net/http"
+	"os"
+	"os/signal"
+	"path/filepath"
+
+	"osbuild-composer/internal/rpmmd"
+	"osbuild-composer/internal/weldr"
+)
+
+const StateFile = "/var/lib/osbuild-composer/weldr-state.json"
+
+func main() {
+	var verbose bool
+	flag.BoolVar(&verbose, "v", false, "Print access log")
+	flag.Parse()
+
+	err := os.Remove("/run/weldr/api.socket")
+	if err != nil && !os.IsNotExist(err) {
+		panic(err)
+	}
+
+	listener, err := net.Listen("unix", "/run/weldr/api.socket")
+	if err != nil {
+		panic(err)
+	}
+
+	repo := rpmmd.RepoConfig{
+		Id:       "fedora-30",
+		Name:     "Fedora 30",
+		Metalink: "https://mirrors.fedoraproject.org/metalink?repo=fedora-30&arch=x86_64",
+	}
+
+	packages, err := rpmmd.FetchPackageList(repo)
+	if err != nil {
+		panic(err)
+	}
+
+	var logger *log.Logger
+	if verbose {
+		logger = log.New(os.Stdout, "", 0)
+	}
+
+	err = os.MkdirAll("/var/lib/osbuild-composer", 0755)
+	if err != nil {
+		panic(err)
+	}
+
+	state, err := ioutil.ReadFile(StateFile)
+	if err != nil && !os.IsNotExist(err) {
+		log.Fatalf("cannot read state: %v", err)
+	}
+
+	stateChannel := make(chan []byte, 10)
+	api := weldr.New(repo, packages, logger, state, stateChannel)
+	go func() {
+		for {
+			err := writeFileAtomically(StateFile, <-stateChannel, 0755)
+			if err != nil {
+				log.Fatalf("cannot write state: %v", err)
+			}
+		}
+	}()
+
+	server := http.Server{Handler: api}
+	shutdownDone := make(chan struct{}, 1)
+	go func() {
+		channel := make(chan os.Signal, 1)
+		signal.Notify(channel, os.Interrupt)
+		<-channel
+		server.Shutdown(context.Background())
+		close(shutdownDone)
+	}()
+
+	err = server.Serve(listener)
+	if err != nil && err != http.ErrServerClosed {
+		panic(err)
+	}
+
+	<-shutdownDone
+}
+
+func writeFileAtomically(filename string, data []byte, mode os.FileMode) error {
+	dir, name := filepath.Dir(filename), filepath.Base(filename)
+
+	tmpfile, err := ioutil.TempFile(dir, name + "-*.tmp")
+	if err != nil {
+		return err
+	}
+
+	_, err = tmpfile.Write(data)
+	if err != nil {
+		os.Remove(tmpfile.Name())
+		return err
+	}
+
+	err = tmpfile.Chmod(mode)
+	if err != nil {
+		return err
+	}
+
+	err = tmpfile.Close()
+	if err != nil {
+		os.Remove(tmpfile.Name())
+		return err
+	}
+
+	err = os.Rename(tmpfile.Name(), filename)
+	if err != nil {
+		os.Remove(tmpfile.Name())
+		return err
+	}
+
+	return nil
+}