refactor podcast schema and generate unique episode paths (#373)

closes #350

fileutil/fileutil.go

@@ -0,0 +1,56 @@
+// TODO: this package shouldn't really exist. we can usually just attempt our normal filesystem operations
+// and handle errors atomically. eg.
+// - Safe could instead be try create file, handle error
+// - Unique could be try create file, on err create file (1), etc
+package fileutil
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strings"
+)
+
+var nonAlphaNumExpr = regexp.MustCompile("[^a-zA-Z0-9_.]+")
+
+func Safe(filename string) string {
+	filename = nonAlphaNumExpr.ReplaceAllString(filename, "")
+	return filename
+}
+
+// try to find a unqiue file (or dir) name. incrementing like "example (1)"
+func Unique(base, filename string) (string, error) {
+	return unique(base, filename, 0)
+}
+
+func unique(base, filename string, count uint) (string, error) {
+	var suffix string
+	if count > 0 {
+		suffix = fmt.Sprintf(" (%d)", count)
+	}
+	path := base + suffix
+	if filename != "" {
+		noExt := strings.TrimSuffix(filename, filepath.Ext(filename))
+		path = filepath.Join(base, noExt+suffix+filepath.Ext(filename))
+	}
+	_, err := os.Stat(path)
+	if os.IsNotExist(err) {
+		return path, nil
+	}
+	if err != nil {
+		return "", err
+	}
+	return unique(base, filename, count+1)
+}
+
+func First(path ...string) (string, error) {
+	var err error
+	for _, p := range path {
+		_, err = os.Stat(p)
+		if err == nil {
+			return p, nil
+		}
+	}
+	return "", err
+}

fileutil/fileutil_test.go

@@ -0,0 +1,56 @@
+package fileutil
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestUniquePath(t *testing.T) {
+	unq := func(base, filename string, count uint) string {
+		r, err := unique(base, filename, count)
+		require.NoError(t, err)
+		return r
+	}
+
+	require.Equal(t, "test/wow.mp3", unq("test", "wow.mp3", 0))
+	require.Equal(t, "test/wow (1).mp3", unq("test", "wow.mp3", 1))
+	require.Equal(t, "test/wow (2).mp3", unq("test", "wow.mp3", 2))
+
+	require.Equal(t, "test", unq("test", "", 0))
+	require.Equal(t, "test (1)", unq("test", "", 1))
+
+	base := filepath.Join(t.TempDir(), "a")
+
+	require.NoError(t, os.MkdirAll(base, os.ModePerm))
+
+	next := base + " (1)"
+	require.Equal(t, next, unq(base, "", 0))
+
+	require.NoError(t, os.MkdirAll(next, os.ModePerm))
+
+	next = base + " (2)"
+	require.Equal(t, next, unq(base, "", 0))
+
+	_, err := os.Create(filepath.Join(base, "test.mp3"))
+	require.NoError(t, err)
+	require.Equal(t, filepath.Join(base, "test (1).mp3"), unq(base, "test.mp3", 0))
+}
+
+func TestFirst(t *testing.T) {
+	base := t.TempDir()
+	name := filepath.Join(base, "test")
+	_, err := os.Create(name)
+	require.NoError(t, err)
+
+	p := func(name string) string {
+		return filepath.Join(base, name)
+	}
+
+	r, err := First(p("one"), p("two"), p("test"), p("four"))
+	require.NoError(t, err)
+	require.Equal(t, p("test"), r)
+
+}