Remove CLI flags; always use env vars

Provides a consistent public-facing API for Docker and direct usage.

README.md

@@ -12,7 +12,7 @@ Proxy version to MSC API specification:
 -   Version 0.1.x: [2022/04/01](https://github.com/matrix-org/matrix-spec-proposals/blob/615e8f5a7bfe4da813bc2db661ed0bd00bccac20/proposals/3575-sync.md)
     -   First release
 -   Version 0.2.x: [2022/06/09](https://github.com/matrix-org/matrix-spec-proposals/blob/3b2b3d547b41e4aeebbde2ad6e89606dd684a86c/proposals/3575-sync.md)
-    -   Reworked where lists and ops are situated in the response JSON. Added new filters like `room_name_like`. Added `slow_get_all_rooms`.
+    -   Reworked where lists and ops are situated in the response JSON. Added new filters like `room_name_like`. Added `slow_get_all_rooms`. Standardised on env vars for configuring the proxy.
 
 ## Usage
 
@@ -21,7 +21,7 @@ Requires Postgres 13+.
 ```bash
 $ createdb syncv3
 $ go build ./cmd/syncv3
-$ ./syncv3 -server "https://matrix-client.matrix.org" -db "user=$(whoami) dbname=syncv3 sslmode=disable"
+$ SYNCV3_SERVER="https://matrix-client.matrix.org" SYNCV3_DB="user=$(whoami) dbname=syncv3 sslmode=disable" SYNCV3_BINDADDR=0.0.0.0:8008 ./syncv3
 ```
 
 Then visit http://localhost:8008/client/ (with trailing slash) and paste in the `access_token` for any account on `-server`.
@@ -34,16 +34,6 @@ INF Poller: v2 poll loop started ip=::1 since= user_id=@kegan:matrix.org
 
 Wait for the first initial v2 sync to be processed (this can take minutes!) and then v3 APIs will be responsive.
 
-### Docker
-
-When running using the official docker container, these environment variables can be set:
-
-```
-SYNCV3_SERVER   equivalent of -server
-SYNCV3_DB       equivalent of -db
-SYNCV3_BINDADDR equivalent of -port, default: 0.0.0.0:8008
-```
-
 ### How can I help?
 
 At present, the best way to help would be to run a local v3 server pointed at a busy account and just leave it and a client running in the background. Look at it occasionally and submit any issues you notice. You can save console logs by right-clicking -> Save As.

cmd/syncv3/main.go

@@ -1,7 +1,6 @@
 package main
 
 import (
-	"flag"
 	"fmt"
 	"net/http"
 	_ "net/http/pprof"
@@ -17,17 +16,34 @@ var GitCommit string
 
 const version = "0.2.0rc2"
 
-var (
-	flagDestinationServer = flag.String("server", "", "The destination v2 matrix server")
-	flagBindAddr          = flag.String("port", ":8008", "Bind address")
-	flagPostgres          = flag.String("db", "user=postgres dbname=syncv3 sslmode=disable", "Postgres DB connection string (see lib/pq docs)")
+const (
+	EnvServer   = "SYNCV3_SERVER"
+	EnvDB       = "SYNCV3_DB"
+	EnvBindAddr = "SYNCV3_BINDADDR"
 )
 
+var helpMsg = fmt.Sprintf(`
+Environment var
+%s   Required. The destination homeserver to talk to (CS API HTTPS URL) e.g 'https://matrix-client.matrix.org'
+%s       Required. The postgres connection string: https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-CONNSTRING 
+%s (Default: 0.0.0.0:8008) The interface and port to listen on.
+`, EnvServer, EnvDB, EnvBindAddr)
+
+func defaulting(in, dft string) string {
+	if in == "" {
+		return dft
+	}
+	return in
+}
+
 func main() {
 	fmt.Printf("Sync v3 [%s] (%s)\n", version, GitCommit)
-	flag.Parse()
-	if *flagDestinationServer == "" {
-		flag.Usage()
+	flagDestinationServer := os.Getenv(EnvServer)
+	flagPostgres := os.Getenv(EnvDB)
+	flagBindAddr := defaulting(os.Getenv(EnvBindAddr), "0.0.0.0:8008")
+	if flagDestinationServer == "" || flagPostgres == "" {
+		fmt.Print(helpMsg)
+		fmt.Printf("\n%s and %s must be set\n", EnvServer, EnvBindAddr)
 		os.Exit(1)
 	}
 	// pprof
@@ -40,10 +56,10 @@ func main() {
 		Client: &http.Client{
 			Timeout: 5 * time.Minute,
 		},
-		DestinationServer: *flagDestinationServer,
-	}, *flagPostgres, os.Getenv("SYNCV3_DEBUG") == "1")
+		DestinationServer: flagDestinationServer,
+	}, flagPostgres, os.Getenv("SYNCV3_DEBUG") == "1")
 	if err != nil {
 		panic(err)
 	}
-	syncv3.RunSyncV3Server(h, *flagBindAddr, *flagDestinationServer)
+	syncv3.RunSyncV3Server(h, flagBindAddr, flagDestinationServer)
 }