Caches of outside APIs live in /var/cache/sww (closes #314)

The answers of GeoJS, the lists fetched by URL, the DNS blocklists,
AbuseIPDB and routewatch each go in a cache file in SWW_CACHE_DIR
(default /var/cache/sww): lookups.json, lists.json, dnsbl.json,
abuseipdb-scores.json and routewatch.json. reputation.json is gone. The
AbuseIPDB checks spent today are a count, not a cache, and stay in
SWW_STATE_DIR as abuseipdb-checks-spent.json.

A cache file never stops the start: one that does not parse is set
aside as an edit is, one that cannot be read is written over, and its
cache starts empty. An unwritable SWW_CACHE_DIR stops the start, as an
unwritable SWW_STATE_DIR does. Each directory is watched on its own.
The run script makes the cache directory and gives it to sww.

Model: opus-5-5

internal/sww/sww.go

@@ -1,9 +1,9 @@
 // Package sww runs the sww process, as the command it is given.
 // `sww waf` reads the settings, the rule files, the lookup database
-// and the state files, answers rproxy's questions until it is told to stop, and
-// then stops in an orderly way, writing the state files. `sww rproxy`
-// reads rproxy's settings alone, and runs the reverse proxy in front of one app
-// that asks waf about each request. `sww healthcheck` is the
+// and the state and cache files, answers rproxy's questions until it is told to
+// stop, and then stops in an orderly way, writing the state and cache files.
+// `sww rproxy` reads rproxy's settings alone, and runs the reverse proxy in
+// front of one app that asks waf about each request. `sww healthcheck` is the
 // container's health check.
 package sww
 
@@ -101,8 +101,8 @@ func printUsage(w io.Writer) int {
 }
 
 // RunWAF is `sww waf`: it reads the settings, the rule files,
-// the lookup database and the state files, then serves requests until ctx is
-// done. It returns the process's exit status, 1 when waf cannot start.
+// the lookup database and the state and cache files, then serves requests until
+// ctx is done. It returns the process's exit status, 1 when waf cannot start.
 func RunWAF(ctx context.Context, params Params) int {
 	// Until the settings are read, the one message is an invalid setting's
 	// error, which every SWW_LOG_LEVEL lets through.
@@ -171,7 +171,7 @@ func RunWAF(ctx context.Context, params Params) int {
 
 	files, err := loadStateFiles(cfg, server, alertQueue, now, processLog)
 	if err != nil {
-		processLog.Error("cannot use the state files", "error", err.Error())
+		processLog.Error("cannot use the state and cache files", "error", err.Error())
 
 		return 1
 	}
@@ -236,14 +236,15 @@ func newServer(
 	return server, nil
 }
 
-// loadStateFiles reads the state files into the parts of server and into
-// alertQueue, as state.Load does.
+// loadStateFiles reads the state and cache files into the parts of server and
+// into alertQueue, as state.Load does.
 func loadStateFiles(
 	cfg *config.Config, server *waf.Server, alertQueue *alerts.Queue,
 	now func() time.Time, processLog *slog.Logger,
 ) (*state.Files, error) {
 	return state.Load(state.Params{
 		Dir:             cfg.StateDir,
+		CacheDir:        cfg.CacheDir,
 		WriteDelay:      cfg.StateWriteDelay,
 		CounterInterval: cfg.StateCounterInterval,
 		Ledger:          server.Ledger,
@@ -252,6 +253,7 @@ func loadStateFiles(
 		Lists:           server.Lists,
 		DNSBL:           server.DNSBL,
 		AbuseIPDB:       server.AbuseIPDB,
+		RouteWatch:      server.RouteWatch,
 		Alerts:          alertQueue,
 		Anomalies:       server.Anomalies,
 		Now:             now,
@@ -317,13 +319,13 @@ func startSending(
 	}
 }
 
-// serve serves requests on listener, writes the state files as they are
-// due, takes in an admin's edits of them, reads the rule files again as
+// serve serves requests on listener, writes the state and cache files as they
+// are due, takes in an admin's edits of them, reads the rule files again as
 // they change, and the lookup database when it is replaced, fetches the
 // lists the settings name by URL as they are due, and sends the alerts,
 // until ctx is done. Then it gives the requests in progress
-// shutdownTimeout to finish, and writes every state file, alerts.json with
-// the alerts still waiting.
+// shutdownTimeout to finish, and writes every state and cache file,
+// alerts.json with the alerts still waiting.
 func serve(
 	ctx context.Context, server *waf.Server, listener net.Listener,
 	files *state.Files, ruleFiles *rules.Files, alertQueue *alerts.Queue,
@@ -393,7 +395,7 @@ func serve(
 
 	err = files.WriteAll()
 	if err != nil {
-		processLog.Error("writing the state files failed", "error", err.Error())
+		processLog.Error("writing the state and cache files failed", "error", err.Error())
 
 		return 1
 	}