Add filesystem inventory model

Append-only chunked node arena with stable NodeIDs, intrusive child
lists, per-directory category totals and batched ancestor propagation.

internal/inventory/category.go

@@ -0,0 +1,117 @@
+package inventory
+
+import "strings"
+
+// Category is a coarse file classification used for colouring and stats.
+type Category uint8
+
+const (
+	CatOther Category = iota
+	CatImage
+	CatVideo
+	CatAudio
+	CatArchive
+	CatDiskImage
+	CatDatabase
+	CatCode
+	CatDocument
+	CatExecutable
+	CatLog
+	CatCache
+	NumCategories
+)
+
+var categoryNames = [NumCategories]string{
+	"Other", "Image", "Video", "Audio", "Archive", "Disk image", "Database",
+	"Source code", "Document", "Executable", "Log", "Cache",
+}
+
+func (c Category) String() string {
+	if c < NumCategories {
+		return categoryNames[c]
+	}
+	return "Other"
+}
+
+// ParseCategory resolves a category by (case-insensitive) name or prefix.
+func ParseCategory(s string) (Category, bool) {
+	s = strings.ToLower(strings.TrimSpace(s))
+	for i, n := range categoryNames {
+		ln := strings.ToLower(n)
+		if ln == s || strings.ReplaceAll(ln, " ", "") == s || strings.HasPrefix(ln, s) && len(s) >= 3 {
+			return Category(i), true
+		}
+	}
+	switch s {
+	case "vm", "virtual machine", "disk":
+		return CatDiskImage, true
+	case "db":
+		return CatDatabase, true
+	case "src", "source":
+		return CatCode, true
+	case "exe", "binary":
+		return CatExecutable, true
+	}
+	return 0, false
+}
+
+var extCategory = map[string]Category{}
+
+func init() {
+	add := func(c Category, exts string) {
+		for _, e := range strings.Fields(exts) {
+			extCategory[e] = c
+		}
+	}
+	add(CatImage, "jpg jpeg png gif bmp tif tiff webp heic heif raw cr2 cr3 nef arw dng svg ico psd xcf avif jxl orf rw2")
+	add(CatVideo, "mp4 mkv mov avi wmv flv webm m4v mpg mpeg ts m2ts vob 3gp ogv mts")
+	add(CatAudio, "mp3 flac wav ogg oga opus m4a aac wma aiff aif alac mid midi")
+	add(CatArchive, "zip tar gz tgz bz2 tbz xz txz zst zstd 7z rar lz lz4 lzma cab deb rpm apk jar war cpio pkg snap whl gem")
+	add(CatDiskImage, "iso img qcow qcow2 vmdk vdi vhd vhdx hdd ova ovf dmg raw vmem vmsn nvram sav")
+	add(CatDatabase, "db sqlite sqlite3 db3 mdb accdb frm ibd myd myi ldf mdf ndf dbf wal kdbx realm lmdb rdb aof")
+	add(CatCode, "c h cc cpp cxx hpp hh go rs py pyc js mjs cjs ts tsx jsx java kt kts scala rb php pl pm sh bash zsh fish lua swift m mm cs fs vb r jl hs ml ex exs erl clj dart sql css scss sass less html htm vue svelte json yaml yml toml xml proto gradle cmake mk ipynb o a lib obj class")
+	add(CatDocument, "pdf doc docx odt rtf txt md rst tex xls xlsx ods csv tsv ppt pptx odp epub mobi djvu pages numbers key org adoc")
+	add(CatExecutable, "exe dll so dylib bin msi app elf ko sys efi appimage com")
+	add(CatLog, "log journal")
+	add(CatCache, "cache tmp temp swp bak old part crdownload")
+}
+
+// CategoryFor classifies a file by its (lower-case) extension and by
+// whether it lives beneath a cache or log directory.
+func CategoryFor(ext string, inCache, inLog bool) Category {
+	c, ok := extCategory[ext]
+	switch {
+	case inCache && (!ok || c == CatOther || c == CatCode):
+		return CatCache
+	case inLog && (!ok || c == CatArchive || c == CatOther):
+		return CatLog
+	case ok:
+		return c
+	}
+	return CatOther
+}
+
+// PathHints reports whether a directory path contains a cache or log
+// component. It is evaluated once per directory, not per file.
+func PathHints(path string) (inCache, inLog bool) {
+	lp := strings.ToLower(path)
+	for _, part := range strings.FieldsFunc(lp, func(r rune) bool { return r == '/' || r == '\\' }) {
+		switch part {
+		case "cache", ".cache", "caches", "__pycache__", ".npm", ".gradle", "inetcache", "temp", "tmp":
+			inCache = true
+		case "log", "logs", ".logs", "journal":
+			inLog = true
+		}
+	}
+	return
+}
+
+// Ext returns the lower-case extension of name without the dot ("" if none,
+// or if the name is a dotfile like ".bashrc").
+func Ext(name string) string {
+	i := strings.LastIndexByte(name, '.')
+	if i <= 0 || i == len(name)-1 || len(name)-i > 16 {
+		return ""
+	}
+	return strings.ToLower(name[i+1:])
+}