implement blorg serve command

Squashed commit of the following:

commit 5e3c3f35c73f884bbf89f5daabcdc2aec5e0af75
Author: facundoolano <facundo.olano@gmail.com>
Date:   Wed Feb 14 11:24:45 2024 -0300

    cleanup

commit e8881df9f27fc37c46120c946dfad107d551ef67
Author: facundoolano <facundo.olano@gmail.com>
Date:   Wed Feb 14 11:21:54 2024 -0300

    add basic src watching

commit 4e61add89c632b0cc7a740d15be671de3df12157
Author: facundoolano <facundo.olano@gmail.com>
Date:   Wed Feb 14 00:19:25 2024 -0300

    move serve command to a separate file

commit abc2100582b71179e0eade154d2af3e86b48574f
Author: facundoolano <facundo.olano@gmail.com>
Date:   Wed Feb 14 00:17:05 2024 -0300

    first stab at serve command

commands/commands.go

@@ -2,12 +2,13 @@ package commands
 
 import (
 	"fmt"
-	"github.com/facundoolano/blorg/site"
 	"io"
 	"io/fs"
 	"os"
 	"path/filepath"
 	"strings"
+
+	"github.com/facundoolano/blorg/site"
 )
 
 const SRC_DIR = "src"
@@ -98,11 +99,3 @@ func New() error {
 	fmt.Println("not implemented yet")
 	return nil
 }
-
-func Serve() error {
-	// build
-	// serve target with file server
-	// (later watch and live reload)
-	fmt.Println("not implemented yet")
-	return nil
-}

commands/serve.go

@@ -0,0 +1,120 @@
+package commands
+
+import (
+	"fmt"
+	"io/fs"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/fsnotify/fsnotify"
+)
+
+// Generate and serve the site, rebuilding when the source files change.
+func Serve() error {
+	// TODO tweak the building logic to inject js snippet that reloads the browser on rebuild
+
+	// first rebuild the target
+	if err := Build(); err != nil {
+		return err
+	}
+
+	// watch for changes in src and layouts, and trigger a rebuild
+	watcher, err := setupWatcher()
+	if err != nil {
+		return err
+	}
+	defer watcher.Close()
+
+	// serve the target dir with a file server
+	fs := http.FileServer(HTMLDir{http.Dir("target/")})
+	http.Handle("/", http.StripPrefix("/", fs))
+	fmt.Println("server listening at http://localhost:4001/")
+	http.ListenAndServe(":4001", nil)
+
+	return nil
+}
+
+// Tweaks the http file system to construct a server that hides the .html suffix from requests.
+// Based on https://stackoverflow.com/a/57281956/993769
+type HTMLDir struct {
+	d http.Dir
+}
+
+func (d HTMLDir) Open(name string) (http.File, error) {
+	// Try name as supplied
+	f, err := d.d.Open(name)
+	if os.IsNotExist(err) {
+		// Not found, try with .html
+		if f, err := d.d.Open(name + ".html"); err == nil {
+			return f, nil
+		}
+	}
+	return f, err
+}
+
+func setupWatcher() (*fsnotify.Watcher, error) {
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		return nil, err
+	}
+
+	go func() {
+		for {
+			select {
+			case event, ok := <-watcher.Events:
+				if !ok {
+					return
+				}
+
+				// chmod events are noisy, ignore them
+				isChmod := event.Has(fsnotify.Chmod)
+
+				// I've seen issues with temporary files, eg. .#name.org generated by emacs
+				// I'll just ignore changes to dotfiles to stay on the safe side
+				isDotFile := strings.HasPrefix(filepath.Base(event.Name), ".")
+
+				if !isChmod && !isDotFile {
+					fmt.Printf("\nFile %s changed, triggering rebuild.\n", event.Name)
+
+					// since new nested directories could be triggering this change, and we need to watch those too
+					// and since re-watching files is a noop, I just re-add the entire src everytime there's a change
+					if err := addAll(watcher); err != nil {
+						fmt.Println("error:", err)
+						return
+					}
+
+					if err := Build(); err != nil {
+						fmt.Println("error:", err)
+						return
+					}
+				}
+
+			case err, ok := <-watcher.Errors:
+				if !ok {
+					return
+				}
+				fmt.Println("error:", err)
+			}
+		}
+	}()
+
+	err = addAll(watcher)
+
+	return watcher, err
+}
+
+// Add the layouts and all source directories to the given watcher
+func addAll(watcher *fsnotify.Watcher) error {
+	err := watcher.Add(LAYOUTS_DIR)
+	// fsnotify watches all files within a dir, but non recursively
+	// this walks through the src dir and adds watches for each found directory
+	filepath.WalkDir(SRC_DIR, func(path string, entry fs.DirEntry, err error) error {
+		if entry.IsDir() {
+			watcher.Add(path)
+		}
+		return nil
+	})
+	return err
+}

go.mod

@@ -9,8 +9,10 @@ require (
 )
 
 require (
+	github.com/fsnotify/fsnotify v1.7.0 // indirect
 	github.com/osteele/liquid v1.3.2 // indirect
 	github.com/osteele/tuesday v1.0.3 // indirect
 	golang.org/x/net v0.0.0-20201224014010-6772e930b67b // indirect
+	golang.org/x/sys v0.4.0 // indirect
 	gopkg.in/yaml.v2 v2.4.0 // indirect
 )

go.sum

@@ -1,5 +1,7 @@
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/fsnotify/fsnotify v1.7.0 h1:8JEhPFa5W2WU7YfeZzPNqzMP6Lwt7L2715Ggo0nosvA=
+github.com/fsnotify/fsnotify v1.7.0/go.mod h1:40Bi/Hjc2AVfZrqy+aj+yEI+/bRxZnMJyTJwOpGvigM=
 github.com/niklasfasching/go-org v1.7.0 h1:vyMdcMWWTe/XmANk19F4k8XGBYg0GQ/gJGMimOjGMek=
 github.com/niklasfasching/go-org v1.7.0/go.mod h1:WuVm4d45oePiE0eX25GqTDQIt/qPW1T9DGkRscqLW5o=
 github.com/osteele/liquid v1.3.2 h1:G+MvVYt1HX2xuv99JgdrhV7zRVdlvFnNi8M5rN8gQmI=
@@ -13,6 +15,8 @@ github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/
 golang.org/x/net v0.0.0-20201224014010-6772e930b67b h1:iFwSg7t5GZmB/Q5TjiEAsdoLDrdJRC1RiF2WhuV29Qw=
 golang.org/x/net v0.0.0-20201224014010-6772e930b67b/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.4.0 h1:Zr2JFtRQNX3BCZ8YtxRE9hNJYC8J6I1MVbMg6owUp18=
+golang.org/x/sys v0.4.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=