Preserve media metadata across STRM path renames

internal/service/media_path_alias.go

@@ -0,0 +1,101 @@
+package service
+
+import (
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+)
+
+// strmPathAliases returns sibling STRM names that can represent the same media
+// item when keep_ext is toggled on or off.
+//
+// Both directions are supported:
+//
+//	foo.strm      <-> foo.mkv.strm
+//	foo.strm      <-> foo.mp4.strm
+//
+// The caller must still verify that the aliases are no longer present on disk.
+// keep_ext intentionally allows foo.mkv.strm and foo.mp4.strm to coexist as
+// two real versions, so an existing sibling must never be absorbed.
+func strmPathAliases(path string) []string {
+	clean := filepath.Clean(strings.TrimSpace(path))
+	if clean == "" || clean == "." || !strings.EqualFold(filepath.Ext(clean), ".strm") {
+		return nil
+	}
+	base := mediaSidecarBase(clean)
+	if base == "" {
+		return nil
+	}
+	name := filepath.Base(clean)
+	stem := strings.TrimSuffix(name, filepath.Ext(name))
+	lastExt := strings.ToLower(filepath.Ext(stem))
+	_, hasVideoExt := videoExtensions[lastExt]
+	hasVideoExt = hasVideoExt && !strings.EqualFold(lastExt, ".strm")
+
+	dir := filepath.Dir(clean)
+	out := make([]string, 0, len(videoExtensions)+1)
+	seen := make(map[string]struct{}, len(videoExtensions)+1)
+	add := func(candidate string) {
+		candidate = filepath.Clean(candidate)
+		if candidate == "" || candidate == "." || samePath(candidate, clean) {
+			return
+		}
+		key := strings.ToLower(candidate)
+		if _, ok := seen[key]; ok {
+			return
+		}
+		seen[key] = struct{}{}
+		out = append(out, candidate)
+	}
+	if hasVideoExt {
+		// Current keep_ext shape: the only legacy shape is the stripped name.
+		add(filepath.Join(dir, base+".strm"))
+		return out
+	}
+	// Stripped shape: an old keep_ext file may use any configured video ext.
+	exts := make([]string, 0, len(videoExtensions))
+	for ext := range videoExtensions {
+		if strings.EqualFold(ext, ".strm") {
+			continue
+		}
+		exts = append(exts, strings.ToLower(ext))
+	}
+	sort.Strings(exts)
+	for _, ext := range exts {
+		add(filepath.Join(dir, base+ext+".strm"))
+		if upper := strings.ToUpper(ext); upper != ext {
+			add(filepath.Join(dir, base+upper+".strm"))
+		}
+	}
+	return out
+}
+
+// missingSTRMPathAliases keeps only aliases which no longer exist on disk.
+// This is the key protection for keep_ext=true multi-version libraries: an
+// existing foo.mp4.strm is a real second version, not a rename tombstone.
+func missingSTRMPathAliases(path string) []string {
+	aliases := strmPathAliases(path)
+	if len(aliases) == 0 {
+		return nil
+	}
+	out := make([]string, 0, len(aliases))
+	for _, alias := range aliases {
+		if _, err := os.Lstat(alias); err == nil {
+			continue
+		} else if !os.IsNotExist(err) {
+			continue
+		}
+		out = append(out, alias)
+	}
+	return out
+}
+
+func liveSTRMPathAlias(path string) bool {
+	for _, alias := range strmPathAliases(path) {
+		if info, err := os.Stat(alias); err == nil && !info.IsDir() {
+			return true
+		}
+	}
+	return false
+}