cmd/rescached: add command "embed" and to run in development mode

This two commands is used internally for development.

The "embed" command embed all files inside "_www" directory into
Go file "memfs_generate.go".
This command replace "internal/generate_memfs.go".

The "dev" command run the rescached server in development mode using
"cmd/rescached/rescached.cfg.test" as the configuration.

The "dev" command listen on DNS port 5350, so to prevent conflict with
live rescached server, we run script _bin/nft_dnstest_chain.sh to redirect
UDP and TCP requests from port 53 to port 5350.

6 files changed, 128 insertions, 45 deletions

diff --git a/.gitignore b/.gitignore
index d5dba8e..cade8be 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,6 +1,7 @@
 /README.html
 /TODO
-/_bin
+/_bin/darwin_amd64
+/_bin/linux_amd64
 /_doc/benchmark.html
 /cover.html
 /cover.out
diff --git a/Makefile b/Makefile
index cceefb9..2a10f6a 100644
--- a/Makefile
+++ b/Makefile
@@ -56,7 +56,7 @@ lint:
 	-golangci-lint run --enable-all ./...
 
 memfs_generate.go: .FORCE
-	go run ./internal/generate_memfs.go
+	go run ./cmd/rescached embed
 
 doc: $(RESCACHED_MAN) $(RESCACHED_CFG_MAN) $(RESOLVER_MAN)
 
@@ -82,6 +82,17 @@ clean:
 	rm -f $(RESCACHED_BIN) $(RESOLVER_BIN) $(RESOLVERBENCH_BIN)
 
 ##
+## Development tasks
+##
+
+.PHONY: dev
+
+dev:
+	-sudo ./_bin/nft_dnstest_chain.sh; \
+		go run ./cmd/rescached -config=cmd/rescached/rescached.cfg.test dev; \
+		sudo ./_bin/nft_dnstest_chain.sh flush
+
+##
 ## Common tasks for installing and uninstalling program.
 ##
 
diff --git a/_bin/nft_dnstest_chain.sh b/_bin/nft_dnstest_chain.sh
new file mode 100755
index 0000000..8ab9a84
--- /dev/null
+++ b/_bin/nft_dnstest_chain.sh
@@ -0,0 +1,13 @@
+#!/bin/sh
+
+if [[ "$1" == "flush" ]]; then
+	echo "nft: delete chain dnstest";
+	nft delete chain ip nat dnstest;
+	exit 0
+fi
+
+## Forward port 53 to 5350 for testing.
+
+nft -- add chain ip nat dnstest { type nat hook output priority 0 \; }
+nft add rule ip nat dnstest tcp dport 53 redirect to 5350
+nft add rule ip nat dnstest udp dport 53 redirect to 5350
diff --git a/cmd/rescached/main.go b/cmd/rescached/main.go
index ebf0a62..8c9c8da 100644
--- a/cmd/rescached/main.go
+++ b/cmd/rescached/main.go
@@ -14,13 +14,22 @@ import (
 	"time"
 
 	"github.com/shuLhan/share/lib/debug"
+	libio "github.com/shuLhan/share/lib/io"
+	"github.com/shuLhan/share/lib/memfs"
+	"github.com/shuLhan/share/lib/mlog"
 
 	"github.com/shuLhan/rescached-go/v4"
 )
 
+const (
+	cmdEmbed = "embed" // Command to generate embedded files.
+	cmdDev   = "dev"   // Command to run rescached for local development.
+)
+
 func main() {
 	var (
 		fileConfig string
+		running    chan bool
 	)
 
 	log.SetFlags(0)
@@ -34,6 +43,21 @@ func main() {
 		log.Fatal(err)
 	}
 
+	cmd := flag.Arg(0)
+
+	switch cmd {
+	case cmdEmbed:
+		err = env.HttpdOptions.Memfs.GoEmbed()
+		if err != nil {
+			log.Fatal(err)
+		}
+		return
+
+	case cmdDev:
+		running = make(chan bool)
+		go watchWww(env, running)
+	}
+
 	rcd, err := rescached.New(env)
 	if err != nil {
 		log.Fatal(err)
@@ -52,7 +76,12 @@ func main() {
 	signal.Notify(c, syscall.SIGQUIT, syscall.SIGSEGV, syscall.SIGTERM,
 		syscall.SIGINT)
 	<-c
+	if cmd == cmdDev {
+		running <- false
+		<-running
+	}
 	rcd.Stop()
+	os.Exit(0)
 }
 
 func debugRuntime() {
@@ -69,3 +98,71 @@ func debugRuntime() {
 			memHeap.DiffHeapObjects)
 	}
 }
+
+//
+// watchWww watch any changes to files inside _www directory and regenerate
+// the embed file "memfs_generate.go".
+//
+func watchWww(env *rescached.Environment, running chan bool) {
+	var (
+		logp    = "watchWww"
+		changeq = make(chan *libio.NodeState, 64)
+		dw      = libio.DirWatcher{
+			Options: *env.HttpdOptions.Memfs.Opts,
+			Callback: func(ns *libio.NodeState) {
+				changeq <- ns
+			},
+		}
+		node      *memfs.Node
+		nChanges  int
+		err       error
+		isRunning bool = true
+	)
+
+	dw.Start()
+
+	tick := time.NewTicker(5 * time.Second)
+
+	for isRunning {
+		select {
+		case ns := <-changeq:
+			node, err = env.HttpdOptions.Memfs.Get(ns.Node.Path)
+			if err != nil {
+				log.Printf("%s: %q: %s", logp, ns.Node.Path, err)
+				continue
+			}
+			if node != nil {
+				err = node.Update(nil, 0)
+				if err != nil {
+					mlog.Errf("%s: %q: %s", logp, node.Path, err)
+					continue
+				}
+				nChanges++
+			}
+
+		case <-tick.C:
+			if nChanges > 0 {
+				fmt.Printf("--- %d changes\n", nChanges)
+				err = env.HttpdOptions.Memfs.GoEmbed()
+				if err != nil {
+					log.Printf("%s", err)
+				}
+				nChanges = 0
+			}
+
+		case <-running:
+			isRunning = false
+		}
+	}
+
+	// Run GoEmbed for the last time.
+	if nChanges > 0 {
+		fmt.Printf("--- %d changes\n", nChanges)
+		err = env.HttpdOptions.Memfs.GoEmbed()
+		if err != nil {
+			log.Printf("%s", err)
+		}
+	}
+	dw.Stop()
+	running <- false
+}
diff --git a/cmd/rescached/rescached.cfg.test b/cmd/rescached/rescached.cfg.test
index 5a03d6d..41c43a3 100644
--- a/cmd/rescached/rescached.cfg.test
+++ b/cmd/rescached/rescached.cfg.test
@@ -6,7 +6,7 @@
 
 [rescached]
 file.resolvconf=
-debug=3
+debug=2
 wui.listen = 127.0.0.1:5381
 
 hosts_block = http://pgl.yoyo.org/adservers/serverlist.php?hostformat=hosts&showintro=0&startdate[day]=&startdate[month]=&startdate[year]=&mimetype=plaintext
@@ -15,10 +15,10 @@ hosts_block = http://winhelp2002.mvps.org/hosts.txt
 hosts_block = http://someonewhocares.org/hosts/hosts
 
 [dns "server"]
-#parent=udp://18.136.35.199
-#parent=tcp://18.136.35.199
+#parent=udp://62.171.181.13
+#parent=tcp://62.171.181.13
 ## DNS over TLS
-parent=https://18.136.35.199
+parent=https://62.171.181.13
 ## DNS over HTTPS
 #parent=https://kilabit.info/dns-query
 
diff --git a/internal/generate_memfs.go b/internal/generate_memfs.go
deleted file mode 100644
index 7d34285..0000000
--- a/internal/generate_memfs.go
+++ /dev/null
@@ -1,39 +0,0 @@
-// Copyright 2020, Shulhan <ms@kilabit.info>. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build ignore
-// +build ignore
-
-package main
-
-import (
-	"log"
-
-	"github.com/shuLhan/share/lib/memfs"
-)
-
-func main() {
-	opts := memfs.Options{
-		Root: "_www",
-		Includes: []string{
-			`.*\.html`,
-			`.*\.js`,
-			`.*\.css`,
-			`.*\.png`,
-		},
-		Embed: memfs.EmbedOptions{
-			PackageName: "rescached",
-			VarName:     "memFS",
-			GoFileName:  "memfs_generate.go",
-		},
-	}
-	mfs, err := memfs.New(&opts)
-	if err != nil {
-		log.Fatal(err)
-	}
-	err = mfs.GoEmbed()
-	if err != nil {
-		log.Fatal(err)
-	}
-}