added meta subcommand

this command parses and prints out the metadata. Also I've used an
alternate spelling of "go wide" that I've been finding slightly more
legible these days.

arrange.go

@@ -92,7 +92,7 @@ func Parse(in <-chan string) <-chan Media {
 	out := make(chan Media)
 	go func() {
 		for path := range in {
-			f, err := _parse(path)
+			f, err := ParseFile(path)
 			if err != nil {
 				switch err.(type) {
 				case NotMedia:
@@ -149,7 +149,8 @@ func Move(in <-chan Media, root string) <-chan error {
 	return out
 }
 
-func _parse(path string) (Media, error) {
+// ParseFile extracts metadata from single file.
+func ParseFile(path string) (Media, error) {
 	ext := strings.ToLower(filepath.Ext(path))
 	var r Media
 	hash := md5.New()

cmd/am/main.go

@@ -7,9 +7,10 @@ import (
 	"os"
 )
 
-const usage = "am <arr|clean|help> [flags]"
+const usage = "am <arr|clean|meta> [flags]"
 const arrUsage = "am arr [-h|-cores=N] <in> <out>"
 const cleanUsage = "am clean [-h|-cores=N] <directory>"
+const metaUsage = "am meta [-h|-cores=N] <file0> <file1> ... <fileN>"
 
 type stats struct {
 	total int
@@ -53,6 +54,13 @@ func main() {
 			fmt.Fprintf(os.Stderr, "problem cleaning: %v\n", err)
 			os.Exit(1)
 		}
+	case "m", "meta":
+		args := flag.Args()
+		if len(args) < 1 {
+			fmt.Fprintf(os.Stderr, "%s\n", metaUsage)
+			os.Exit(1)
+		}
+		meta(args)
 	default:
 		fmt.Fprintf(os.Stderr, "%s\n", usage)
 		os.Exit(1)

cmd/am/meta.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"runtime"
+	"sync"
+
+	"mcquay.me/arrange"
+)
+
+func meta(files []string) {
+	workers := runtime.NumCPU()
+	if *cores != 0 {
+		workers = *cores
+	}
+	fc := make(chan arrange.Media)
+
+	go func() {
+		wg := &sync.WaitGroup{}
+		s := make(chan bool, workers)
+		for _, f := range files {
+			wg.Add(1)
+			go func(pth string) {
+				s <- true
+				pf, err := arrange.ParseFile(pth)
+				if err != nil {
+					log.Printf("%+v", err)
+				}
+
+				fc <- pf
+				<-s
+				wg.Done()
+			}(f)
+		}
+		wg.Wait()
+		close(fc)
+	}()
+	for f := range fc {
+		fmt.Printf("%+v: %v\n", f.Time, f.Path)
+	}
+}