app picker: extend App Picker to integrate with mime overrides

- Adds "DMS Opener" as an option (dms-open.desktop)
- Add mime type GO utils
- Add rememberance to App Picker modal

core/internal/desktop/entries.go

@@ -0,0 +1,203 @@
+package desktop
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/AvengeMedia/DankMaterialShell/core/internal/utils"
+)
+
+type Entry struct {
+	ID         string
+	Path       string
+	Name       string
+	Exec       string
+	Icon       string
+	Categories []string
+	MimeTypes  []string
+	NoDisplay  bool
+	Hidden     bool
+	Terminal   bool
+}
+
+type cachedEntry struct {
+	entry   *Entry
+	modTime time.Time
+	size    int64
+}
+
+var (
+	entryCache   = make(map[string]cachedEntry)
+	entryCacheMu sync.Mutex
+
+	listingCache   []*Entry
+	listingExpires time.Time
+	listingCacheMu sync.Mutex
+)
+
+const listingTTL = 5 * time.Second
+
+func applicationDirs() []string {
+	seen := make(map[string]bool)
+	var dirs []string
+
+	add := func(path string) {
+		if path == "" {
+			return
+		}
+		abs, err := filepath.Abs(path)
+		if err != nil {
+			abs = path
+		}
+		if seen[abs] {
+			return
+		}
+		seen[abs] = true
+		dirs = append(dirs, abs)
+	}
+
+	add(filepath.Join(utils.XDGDataHome(), "applications"))
+
+	if env := os.Getenv("XDG_DATA_DIRS"); env != "" {
+		for d := range strings.SplitSeq(env, ":") {
+			add(filepath.Join(strings.TrimSpace(d), "applications"))
+		}
+	} else {
+		add("/usr/local/share/applications")
+		add("/usr/share/applications")
+	}
+
+	home, _ := os.UserHomeDir()
+	if home != "" {
+		add(filepath.Join(home, ".local", "share", "flatpak", "exports", "share", "applications"))
+	}
+	add("/var/lib/flatpak/exports/share/applications")
+	add("/var/lib/snapd/desktop/applications")
+
+	return dirs
+}
+
+func parseEntry(path string, id string) (*Entry, error) {
+	info, err := os.Stat(path)
+	if err != nil {
+		return nil, err
+	}
+
+	entryCacheMu.Lock()
+	if c, ok := entryCache[path]; ok && c.modTime.Equal(info.ModTime()) && c.size == info.Size() {
+		entryCacheMu.Unlock()
+		return c.entry, nil
+	}
+	entryCacheMu.Unlock()
+
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+
+	groups := parseGroups(data)
+	g, ok := groups["Desktop Entry"]
+	if !ok {
+		return nil, nil
+	}
+
+	entry := &Entry{
+		ID:         id,
+		Path:       path,
+		Name:       g.keys["Name"],
+		Exec:       g.keys["Exec"],
+		Icon:       g.keys["Icon"],
+		Categories: splitList(g.keys["Categories"]),
+		MimeTypes:  splitList(g.keys["MimeType"]),
+		NoDisplay:  parseBool(g.keys["NoDisplay"]),
+		Hidden:     parseBool(g.keys["Hidden"]),
+		Terminal:   parseBool(g.keys["Terminal"]),
+	}
+
+	if t := g.keys["Type"]; t != "" && t != "Application" {
+		return nil, nil
+	}
+
+	entryCacheMu.Lock()
+	entryCache[path] = cachedEntry{entry: entry, modTime: info.ModTime(), size: info.Size()}
+	entryCacheMu.Unlock()
+
+	return entry, nil
+}
+
+func relativeID(root, path string) string {
+	rel, err := filepath.Rel(root, path)
+	if err != nil {
+		return filepath.Base(path)
+	}
+	return strings.ReplaceAll(rel, string(filepath.Separator), "-")
+}
+
+func AllEntries() []*Entry {
+	listingCacheMu.Lock()
+	if time.Now().Before(listingExpires) && listingCache != nil {
+		out := listingCache
+		listingCacheMu.Unlock()
+		return out
+	}
+	listingCacheMu.Unlock()
+
+	seen := make(map[string]bool)
+	var entries []*Entry
+
+	for _, dir := range applicationDirs() {
+		_ = filepath.WalkDir(dir, func(path string, d os.DirEntry, err error) error {
+			if err != nil || d.IsDir() {
+				return nil
+			}
+			if !strings.HasSuffix(path, ".desktop") {
+				return nil
+			}
+			id := relativeID(dir, path)
+			if seen[id] {
+				return nil
+			}
+			seen[id] = true
+
+			entry, err := parseEntry(path, id)
+			if err != nil || entry == nil {
+				return nil
+			}
+			entries = append(entries, entry)
+			return nil
+		})
+	}
+
+	listingCacheMu.Lock()
+	listingCache = entries
+	listingExpires = time.Now().Add(listingTTL)
+	listingCacheMu.Unlock()
+
+	return entries
+}
+
+func EntryByID(id string) *Entry {
+	if !strings.HasSuffix(id, ".desktop") {
+		id += ".desktop"
+	}
+	for _, entry := range AllEntries() {
+		if entry.ID == id {
+			return entry
+		}
+	}
+	return nil
+}
+
+func InvalidateCache() {
+	entryCacheMu.Lock()
+	entryCache = make(map[string]cachedEntry)
+	entryCacheMu.Unlock()
+
+	listingCacheMu.Lock()
+	listingCache = nil
+	listingExpires = time.Time{}
+	listingCacheMu.Unlock()
+}

core/internal/desktop/mime.go

@@ -0,0 +1,311 @@
+package desktop
+
+import (
+	"bufio"
+	"bytes"
+	"os"
+	"path/filepath"
+	"slices"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/AvengeMedia/DankMaterialShell/core/internal/utils"
+)
+
+var (
+	aliasMap      map[string]string
+	subclassMap   map[string][]string
+	aliasLoaded   time.Time
+	aliasReloadMu sync.Mutex
+
+	mimeCacheMap      map[string][]string
+	mimeCacheLoaded   time.Time
+	mimeCacheReloadMu sync.Mutex
+)
+
+const aliasTTL = 60 * time.Second
+const mimeCacheTTL = 10 * time.Second
+
+func mimeDataDirs() []string {
+	var dirs []string
+	seen := make(map[string]bool)
+
+	add := func(p string) {
+		if p == "" || seen[p] {
+			return
+		}
+		seen[p] = true
+		dirs = append(dirs, p)
+	}
+
+	add(filepath.Join(utils.XDGDataHome(), "mime"))
+
+	if env := os.Getenv("XDG_DATA_DIRS"); env != "" {
+		for d := range strings.SplitSeq(env, ":") {
+			add(filepath.Join(strings.TrimSpace(d), "mime"))
+		}
+	} else {
+		add("/usr/local/share/mime")
+		add("/usr/share/mime")
+	}
+
+	return dirs
+}
+
+func loadAliasTables() {
+	aliases := make(map[string]string)
+	subclasses := make(map[string][]string)
+
+	for _, dir := range mimeDataDirs() {
+		readKV(filepath.Join(dir, "aliases"), func(k, v string) {
+			if _, ok := aliases[k]; !ok {
+				aliases[k] = v
+			}
+		})
+		readKV(filepath.Join(dir, "subclasses"), func(k, v string) {
+			subclasses[k] = append(subclasses[k], v)
+		})
+	}
+
+	aliasMap = aliases
+	subclassMap = subclasses
+	aliasLoaded = time.Now()
+}
+
+func readKV(path string, fn func(k, v string)) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return
+	}
+	scanner := bufio.NewScanner(bytes.NewReader(data))
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+		if line == "" || line[0] == '#' {
+			continue
+		}
+		sp := strings.IndexByte(line, ' ')
+		if sp <= 0 {
+			continue
+		}
+		fn(strings.TrimSpace(line[:sp]), strings.TrimSpace(line[sp+1:]))
+	}
+}
+
+func ensureAliasTables() {
+	aliasReloadMu.Lock()
+	defer aliasReloadMu.Unlock()
+
+	if aliasMap == nil || time.Since(aliasLoaded) > aliasTTL {
+		loadAliasTables()
+	}
+}
+
+func loadMimeCache() {
+	merged := make(map[string][]string)
+	seen := make(map[string]map[string]bool)
+
+	for _, dir := range applicationDirs() {
+		data, err := os.ReadFile(filepath.Join(dir, "mimeinfo.cache"))
+		if err != nil {
+			continue
+		}
+		groups := parseGroups(data)
+		g := groups["MIME Cache"]
+		if g == nil {
+			continue
+		}
+		for mime, val := range g.keys {
+			ids := splitList(val)
+			if len(ids) == 0 {
+				continue
+			}
+			if seen[mime] == nil {
+				seen[mime] = make(map[string]bool)
+			}
+			for _, id := range ids {
+				if seen[mime][id] {
+					continue
+				}
+				seen[mime][id] = true
+				merged[mime] = append(merged[mime], id)
+			}
+		}
+	}
+
+	mimeCacheMap = merged
+	mimeCacheLoaded = time.Now()
+}
+
+func ensureMimeCache() {
+	mimeCacheReloadMu.Lock()
+	defer mimeCacheReloadMu.Unlock()
+
+	if mimeCacheMap == nil || time.Since(mimeCacheLoaded) > mimeCacheTTL {
+		loadMimeCache()
+	}
+}
+
+func cacheAppsForMime(mimeType string) []string {
+	ensureMimeCache()
+	return mimeCacheMap[mimeType]
+}
+
+func StripMimeParams(mimeType string) string {
+	if semi := strings.IndexByte(mimeType, ';'); semi >= 0 {
+		mimeType = mimeType[:semi]
+	}
+	return strings.TrimSpace(mimeType)
+}
+
+func canonicalMime(mimeType string) string {
+	ensureAliasTables()
+	mimeType = StripMimeParams(mimeType)
+	if target, ok := aliasMap[mimeType]; ok {
+		return target
+	}
+	return mimeType
+}
+
+func mimeChain(mimeType string) []string {
+	ensureAliasTables()
+
+	root := canonicalMime(mimeType)
+	visited := map[string]bool{root: true}
+	chain := []string{root}
+
+	queue := []string{root}
+	for len(queue) > 0 {
+		cur := queue[0]
+		queue = queue[1:]
+		for _, parent := range subclassMap[cur] {
+			if visited[parent] {
+				continue
+			}
+			visited[parent] = true
+			chain = append(chain, parent)
+			queue = append(queue, parent)
+		}
+	}
+
+	return chain
+}
+
+func entrySupportsMime(entry *Entry, chain []string) bool {
+	for _, m := range entry.MimeTypes {
+		canonical := canonicalMime(m)
+		if slices.Contains(chain, canonical) || slices.Contains(chain, m) {
+			return true
+		}
+	}
+	return false
+}
+
+func GetDefault(mimeType string) string {
+	merged := mergedAssociations()
+	chain := mimeChain(mimeType)
+
+	for _, m := range chain {
+		if id, ok := merged.Defaults[m]; ok {
+			if !slices.Contains(merged.Removed[m], id) {
+				return id
+			}
+		}
+	}
+
+	for _, m := range chain {
+		for _, id := range merged.Added[m] {
+			if !slices.Contains(merged.Removed[m], id) {
+				return id
+			}
+		}
+	}
+
+	for _, m := range chain {
+		for _, id := range cacheAppsForMime(m) {
+			if !slices.Contains(merged.Removed[m], id) {
+				return id
+			}
+		}
+	}
+
+	for _, m := range chain {
+		for _, entry := range AllEntries() {
+			if entry.Hidden || entry.NoDisplay {
+				continue
+			}
+			if slices.Contains(merged.Removed[m], entry.ID) {
+				continue
+			}
+			if entrySupportsMime(entry, []string{m}) {
+				return entry.ID
+			}
+		}
+	}
+
+	return ""
+}
+
+func SetDefault(mimeType, desktopID string) error {
+	return setDefaultAssociation(mimeType, desktopID)
+}
+
+func SetDefaults(mimeTypes []string, desktopID string) error {
+	return setDefaultAssociations(mimeTypes, desktopID)
+}
+
+func AppsForMime(mimeType string) []string {
+	merged := mergedAssociations()
+	chain := mimeChain(mimeType)
+	removed := make(map[string]bool)
+	for _, m := range chain {
+		for _, id := range merged.Removed[m] {
+			removed[id] = true
+		}
+	}
+
+	seen := make(map[string]bool)
+	var out []string
+
+	add := func(id string) {
+		if id == "" || removed[id] || seen[id] {
+			return
+		}
+		seen[id] = true
+		out = append(out, id)
+	}
+
+	for _, m := range chain {
+		if id := merged.Defaults[m]; id != "" {
+			add(id)
+		}
+		for _, id := range merged.Added[m] {
+			add(id)
+		}
+	}
+
+	for _, m := range chain {
+		for _, id := range cacheAppsForMime(m) {
+			add(id)
+		}
+	}
+
+	for _, entry := range AllEntries() {
+		if entry.Hidden {
+			continue
+		}
+		if entrySupportsMime(entry, chain) {
+			add(entry.ID)
+		}
+	}
+
+	return out
+}
+
+func QueryDefaults(mimeTypes []string) map[string]string {
+	out := make(map[string]string, len(mimeTypes))
+	for _, m := range mimeTypes {
+		out[m] = GetDefault(m)
+	}
+	return out
+}

core/internal/desktop/mime_test.go

@@ -0,0 +1,233 @@
+package desktop
+
+import (
+	"os"
+	"path/filepath"
+	"sync"
+	"testing"
+)
+
+func setupFakeXDG(t *testing.T) (configHome, dataHome string) {
+	t.Helper()
+	tmp := t.TempDir()
+	configHome = filepath.Join(tmp, "config")
+	dataHome = filepath.Join(tmp, "data")
+	if err := os.MkdirAll(filepath.Join(dataHome, "applications"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.MkdirAll(configHome, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	t.Setenv("XDG_CONFIG_HOME", configHome)
+	t.Setenv("XDG_DATA_HOME", dataHome)
+	t.Setenv("XDG_DATA_DIRS", dataHome)
+	t.Setenv("XDG_CONFIG_DIRS", configHome)
+	InvalidateCache()
+
+	mimeCacheReloadMu.Lock()
+	mimeCacheMap = nil
+	mimeCacheReloadMu.Unlock()
+	aliasReloadMu.Lock()
+	aliasMap = nil
+	subclassMap = nil
+	aliasReloadMu.Unlock()
+
+	return configHome, dataHome
+}
+
+func writeFile(t *testing.T, path, content string) {
+	t.Helper()
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(path, []byte(content), 0o644); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestParseDesktopEntry(t *testing.T) {
+	_, dataHome := setupFakeXDG(t)
+	writeFile(t, filepath.Join(dataHome, "applications", "test.desktop"), `[Desktop Entry]
+Type=Application
+Name=Test
+Exec=test %f
+Icon=test
+MimeType=application/pdf;image/png;
+Categories=Office;Viewer;
+NoDisplay=false
+`)
+
+	entry := EntryByID("test.desktop")
+	if entry == nil {
+		t.Fatal("entry not found")
+	}
+	if entry.Name != "Test" {
+		t.Errorf("Name = %q", entry.Name)
+	}
+	if len(entry.MimeTypes) != 2 || entry.MimeTypes[0] != "application/pdf" {
+		t.Errorf("MimeTypes = %v", entry.MimeTypes)
+	}
+	if len(entry.Categories) != 2 || entry.Categories[1] != "Viewer" {
+		t.Errorf("Categories = %v", entry.Categories)
+	}
+}
+
+func TestSetGetDefault(t *testing.T) {
+	configHome, dataHome := setupFakeXDG(t)
+	writeFile(t, filepath.Join(dataHome, "applications", "foo.desktop"), `[Desktop Entry]
+Type=Application
+Name=Foo
+MimeType=application/pdf;
+`)
+	writeFile(t, filepath.Join(dataHome, "applications", "bar.desktop"), `[Desktop Entry]
+Type=Application
+Name=Bar
+MimeType=application/pdf;
+`)
+
+	if err := SetDefault("application/pdf", "bar.desktop"); err != nil {
+		t.Fatal(err)
+	}
+
+	if got := GetDefault("application/pdf"); got != "bar.desktop" {
+		t.Errorf("GetDefault = %q want bar.desktop", got)
+	}
+
+	data, err := os.ReadFile(filepath.Join(configHome, "mimeapps.list"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !contains(string(data), "application/pdf=bar.desktop") {
+		t.Errorf("mimeapps.list missing default:\n%s", string(data))
+	}
+}
+
+func TestSetDefaultBypassesMimeSupportCheck(t *testing.T) {
+	configHome, dataHome := setupFakeXDG(t)
+	writeFile(t, filepath.Join(dataHome, "applications", "dms-open.desktop"), `[Desktop Entry]
+Type=Application
+Name=DMS
+MimeType=x-scheme-handler/http;
+`)
+
+	if err := SetDefault("application/pdf", "dms-open.desktop"); err != nil {
+		t.Fatal(err)
+	}
+
+	if got := GetDefault("application/pdf"); got != "dms-open.desktop" {
+		t.Errorf("GetDefault = %q, want dms-open.desktop (native impl must not enforce MimeType= check)", got)
+	}
+
+	data, _ := os.ReadFile(filepath.Join(configHome, "mimeapps.list"))
+	if !contains(string(data), "application/pdf=dms-open.desktop") {
+		t.Errorf("mimeapps.list missing override:\n%s", string(data))
+	}
+}
+
+func TestAliasResolution(t *testing.T) {
+	_, dataHome := setupFakeXDG(t)
+	writeFile(t, filepath.Join(dataHome, "mime", "aliases"), "text/javascript application/javascript\n")
+	writeFile(t, filepath.Join(dataHome, "applications", "editor.desktop"), `[Desktop Entry]
+Type=Application
+Name=Editor
+MimeType=application/javascript;
+`)
+	writeFile(t, filepath.Join(dataHome, "applications", "mimeinfo.cache"), `[MIME Cache]
+application/javascript=editor.desktop;
+`)
+
+	if got := GetDefault("text/javascript"); got != "editor.desktop" {
+		t.Errorf("GetDefault(text/javascript) = %q want editor.desktop (alias resolution)", got)
+	}
+}
+
+func TestSetDefaultsBatch(t *testing.T) {
+	configHome, dataHome := setupFakeXDG(t)
+	writeFile(t, filepath.Join(dataHome, "applications", "dms-open.desktop"), `[Desktop Entry]
+Type=Application
+Name=DMS
+MimeType=x-scheme-handler/http;
+`)
+
+	mimes := []string{
+		"text/plain", "text/x-csrc", "text/x-python",
+		"text/x-shellscript", "application/json",
+	}
+	if err := SetDefaults(mimes, "dms-open.desktop"); err != nil {
+		t.Fatal(err)
+	}
+
+	data, err := os.ReadFile(filepath.Join(configHome, "mimeapps.list"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, m := range mimes {
+		if !contains(string(data), m+"=dms-open.desktop") {
+			t.Errorf("missing %s default in mimeapps.list:\n%s", m, string(data))
+		}
+	}
+}
+
+func TestConcurrentSetDefaultNoCorruption(t *testing.T) {
+	configHome, dataHome := setupFakeXDG(t)
+	writeFile(t, filepath.Join(dataHome, "applications", "app.desktop"), `[Desktop Entry]
+Type=Application
+Name=App
+`)
+
+	mimes := []string{
+		"a/1", "a/2", "a/3", "a/4", "a/5", "a/6", "a/7",
+	}
+
+	var wg sync.WaitGroup
+	for _, m := range mimes {
+		wg.Add(1)
+		go func(m string) {
+			defer wg.Done()
+			if err := SetDefault(m, "app.desktop"); err != nil {
+				t.Errorf("SetDefault(%s) failed: %v", m, err)
+			}
+		}(m)
+	}
+	wg.Wait()
+
+	data, err := os.ReadFile(filepath.Join(configHome, "mimeapps.list"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, m := range mimes {
+		if !contains(string(data), m+"=app.desktop") {
+			t.Errorf("lost write for %s — concurrent writes corrupted file:\n%s", m, string(data))
+		}
+	}
+}
+
+func TestMimeCacheOrdering(t *testing.T) {
+	_, dataHome := setupFakeXDG(t)
+	writeFile(t, filepath.Join(dataHome, "applications", "a.desktop"), `[Desktop Entry]
+Type=Application
+Name=A
+MimeType=image/png;
+`)
+	writeFile(t, filepath.Join(dataHome, "applications", "b.desktop"), `[Desktop Entry]
+Type=Application
+Name=B
+MimeType=image/png;
+`)
+	writeFile(t, filepath.Join(dataHome, "applications", "mimeinfo.cache"), `[MIME Cache]
+image/png=b.desktop;a.desktop;
+`)
+
+	if got := GetDefault("image/png"); got != "b.desktop" {
+		t.Errorf("GetDefault should follow mimeinfo.cache order: got %q want b.desktop", got)
+	}
+}
+
+func contains(haystack, needle string) bool {
+	for i := 0; i+len(needle) <= len(haystack); i++ {
+		if haystack[i:i+len(needle)] == needle {
+			return true
+		}
+	}
+	return false
+}

core/internal/desktop/mimeapps.go

@@ -0,0 +1,226 @@
+package desktop
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"os"
+	"path/filepath"
+	"slices"
+	"sort"
+	"strings"
+	"sync"
+
+	"github.com/AvengeMedia/DankMaterialShell/core/internal/utils"
+)
+
+var mimeappsWriteMu sync.Mutex
+
+const (
+	groupDefaults = "Default Applications"
+	groupAdded    = "Added Associations"
+	groupRemoved  = "Removed Associations"
+)
+
+type MimeAssociations struct {
+	Defaults map[string]string
+	Added    map[string][]string
+	Removed  map[string][]string
+}
+
+func newAssociations() *MimeAssociations {
+	return &MimeAssociations{
+		Defaults: make(map[string]string),
+		Added:    make(map[string][]string),
+		Removed:  make(map[string][]string),
+	}
+}
+
+func mimeappsSearchPaths() []string {
+	var paths []string
+	seen := make(map[string]bool)
+
+	add := func(p string) {
+		if p == "" || seen[p] {
+			return
+		}
+		seen[p] = true
+		paths = append(paths, p)
+	}
+
+	add(filepath.Join(utils.XDGConfigHome(), "mimeapps.list"))
+
+	if env := os.Getenv("XDG_CONFIG_DIRS"); env != "" {
+		for d := range strings.SplitSeq(env, ":") {
+			add(filepath.Join(strings.TrimSpace(d), "mimeapps.list"))
+		}
+	} else {
+		add("/etc/xdg/mimeapps.list")
+	}
+
+	add(filepath.Join(utils.XDGDataHome(), "applications", "mimeapps.list"))
+
+	if env := os.Getenv("XDG_DATA_DIRS"); env != "" {
+		for d := range strings.SplitSeq(env, ":") {
+			add(filepath.Join(strings.TrimSpace(d), "applications", "mimeapps.list"))
+		}
+	} else {
+		add("/usr/local/share/applications/mimeapps.list")
+		add("/usr/share/applications/mimeapps.list")
+	}
+
+	return paths
+}
+
+func mimeappsWritePath() string {
+	return filepath.Join(utils.XDGConfigHome(), "mimeapps.list")
+}
+
+func readAssociations(path string) (*MimeAssociations, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+
+	groups := parseGroups(data)
+	assoc := newAssociations()
+
+	if g := groups[groupDefaults]; g != nil {
+		for mime, val := range g.keys {
+			parts := splitList(val)
+			if len(parts) > 0 {
+				assoc.Defaults[mime] = parts[0]
+			}
+		}
+	}
+
+	if g := groups[groupAdded]; g != nil {
+		for mime, val := range g.keys {
+			assoc.Added[mime] = splitList(val)
+		}
+	}
+
+	if g := groups[groupRemoved]; g != nil {
+		for mime, val := range g.keys {
+			assoc.Removed[mime] = splitList(val)
+		}
+	}
+
+	return assoc, nil
+}
+
+func mergedAssociations() *MimeAssociations {
+	merged := newAssociations()
+
+	for _, path := range mimeappsSearchPaths() {
+		assoc, err := readAssociations(path)
+		if err != nil {
+			continue
+		}
+		for mime, app := range assoc.Defaults {
+			if _, ok := merged.Defaults[mime]; !ok {
+				merged.Defaults[mime] = app
+			}
+		}
+		for mime, apps := range assoc.Added {
+			merged.Added[mime] = append(merged.Added[mime], apps...)
+		}
+		for mime, apps := range assoc.Removed {
+			merged.Removed[mime] = append(merged.Removed[mime], apps...)
+		}
+	}
+
+	return merged
+}
+
+func writeUserMimeapps(update func(*MimeAssociations)) error {
+	mimeappsWriteMu.Lock()
+	defer mimeappsWriteMu.Unlock()
+
+	path := mimeappsWritePath()
+
+	assoc, err := readAssociations(path)
+	if err != nil {
+		if !os.IsNotExist(err) {
+			return err
+		}
+		assoc = newAssociations()
+	}
+
+	update(assoc)
+
+	var buf bytes.Buffer
+	w := bufio.NewWriter(&buf)
+
+	writeSection := func(name string, entries map[string]string) {
+		fmt.Fprintf(w, "[%s]\n", name)
+		keys := make([]string, 0, len(entries))
+		for k := range entries {
+			keys = append(keys, k)
+		}
+		sort.Strings(keys)
+		for _, k := range keys {
+			fmt.Fprintf(w, "%s=%s\n", k, entries[k])
+		}
+		fmt.Fprintln(w)
+	}
+
+	flatten := func(m map[string][]string) map[string]string {
+		out := make(map[string]string, len(m))
+		for k, list := range m {
+			out[k] = strings.Join(list, ";") + ";"
+		}
+		return out
+	}
+
+	writeSection(groupDefaults, assoc.Defaults)
+	writeSection(groupAdded, flatten(assoc.Added))
+	writeSection(groupRemoved, flatten(assoc.Removed))
+
+	if err := w.Flush(); err != nil {
+		return err
+	}
+
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		return err
+	}
+	return os.WriteFile(path, buf.Bytes(), 0o644)
+}
+
+func setDefaultAssociation(mimeType, desktopID string) error {
+	return setDefaultAssociations([]string{mimeType}, desktopID)
+}
+
+func setDefaultAssociations(mimeTypes []string, desktopID string) error {
+	if !strings.HasSuffix(desktopID, ".desktop") {
+		desktopID += ".desktop"
+	}
+	return writeUserMimeapps(func(assoc *MimeAssociations) {
+		for _, mimeType := range mimeTypes {
+			if mimeType == "" {
+				continue
+			}
+			assoc.Defaults[mimeType] = desktopID
+			existing := assoc.Added[mimeType]
+			if !slices.Contains(existing, desktopID) {
+				assoc.Added[mimeType] = append(existing, desktopID)
+			}
+			removed, ok := assoc.Removed[mimeType]
+			if !ok {
+				continue
+			}
+			filtered := removed[:0]
+			for _, id := range removed {
+				if id != desktopID {
+					filtered = append(filtered, id)
+				}
+			}
+			switch {
+			case len(filtered) == 0:
+				delete(assoc.Removed, mimeType)
+			default:
+				assoc.Removed[mimeType] = filtered
+			}
+		}
+	})
+}

core/internal/desktop/parser.go

@@ -0,0 +1,80 @@
+package desktop
+
+import (
+	"bufio"
+	"bytes"
+	"strings"
+)
+
+type group struct {
+	keys map[string]string
+}
+
+func parseGroups(data []byte) map[string]*group {
+	groups := make(map[string]*group)
+	var current *group
+
+	scanner := bufio.NewScanner(bytes.NewReader(data))
+	scanner.Buffer(make([]byte, 64*1024), 1024*1024)
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+		if line == "" || line[0] == '#' {
+			continue
+		}
+
+		if line[0] == '[' && strings.HasSuffix(line, "]") {
+			name := line[1 : len(line)-1]
+			g, ok := groups[name]
+			if !ok {
+				g = &group{keys: make(map[string]string)}
+				groups[name] = g
+			}
+			current = g
+			continue
+		}
+
+		if current == nil {
+			continue
+		}
+
+		eq := strings.IndexByte(line, '=')
+		if eq <= 0 {
+			continue
+		}
+
+		key := strings.TrimSpace(line[:eq])
+		if bracket := strings.IndexByte(key, '['); bracket > 0 {
+			key = key[:bracket]
+		}
+		if _, ok := current.keys[key]; ok {
+			continue
+		}
+		current.keys[key] = strings.TrimSpace(line[eq+1:])
+	}
+
+	return groups
+}
+
+func splitList(value string) []string {
+	if value == "" {
+		return nil
+	}
+	parts := strings.Split(value, ";")
+	out := make([]string, 0, len(parts))
+	for _, p := range parts {
+		p = strings.TrimSpace(p)
+		if p == "" {
+			continue
+		}
+		out = append(out, p)
+	}
+	return out
+}
+
+func parseBool(value string) bool {
+	switch strings.ToLower(strings.TrimSpace(value)) {
+	case "true", "1", "yes":
+		return true
+	}
+	return false
+}

core/internal/server/apppicker/handlers.go

@@ -3,6 +3,7 @@ package apppicker
 import (
 	"net"
 
+	"github.com/AvengeMedia/DankMaterialShell/core/internal/desktop"
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/log"
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/models"
 )
@@ -32,7 +33,7 @@ func handleOpen(conn net.Conn, req models.Request, manager *Manager) {
 	event := OpenEvent{
 		Target:      target,
 		RequestType: models.GetOr(req, "requestType", "url"),
-		MimeType:    models.GetOr(req, "mimeType", ""),
+		MimeType:    desktop.StripMimeParams(models.GetOr(req, "mimeType", "")),
 	}
 
 	if categories, ok := models.Get[[]any](req, "categories"); ok {

core/internal/server/mime/handlers.go

@@ -0,0 +1,154 @@
+package mime
+
+import (
+	"fmt"
+	"net"
+
+	"github.com/AvengeMedia/DankMaterialShell/core/internal/desktop"
+	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/models"
+	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/params"
+)
+
+type defaultResult struct {
+	MimeType  string `json:"mimeType"`
+	DesktopID string `json:"desktopId"`
+}
+
+type appsResult struct {
+	MimeType   string   `json:"mimeType"`
+	DesktopIDs []string `json:"desktopIds"`
+}
+
+type queryResult struct {
+	Defaults map[string]string `json:"defaults"`
+}
+
+func HandleRequest(conn net.Conn, req models.Request) {
+	switch req.Method {
+	case "mime.getDefault":
+		handleGetDefault(conn, req)
+	case "mime.setDefault":
+		handleSetDefault(conn, req)
+	case "mime.setDefaults":
+		handleSetDefaults(conn, req)
+	case "mime.appsForMime":
+		handleAppsForMime(conn, req)
+	case "mime.queryDefaults":
+		handleQueryDefaults(conn, req)
+	case "mime.invalidate":
+		desktop.InvalidateCache()
+		models.Respond(conn, req.ID, models.SuccessResult{Success: true})
+	default:
+		models.RespondError(conn, req.ID, fmt.Sprintf("unknown method: %s", req.Method))
+	}
+}
+
+func handleGetDefault(conn net.Conn, req models.Request) {
+	mimeType, err := mimeParam(req.Params, "mimeType")
+	if err != nil {
+		models.RespondError(conn, req.ID, err.Error())
+		return
+	}
+	models.Respond(conn, req.ID, defaultResult{
+		MimeType:  mimeType,
+		DesktopID: desktop.GetDefault(mimeType),
+	})
+}
+
+func handleSetDefault(conn net.Conn, req models.Request) {
+	mimeType, err := mimeParam(req.Params, "mimeType")
+	if err != nil {
+		models.RespondError(conn, req.ID, err.Error())
+		return
+	}
+	desktopID, err := params.StringNonEmpty(req.Params, "desktopId")
+	if err != nil {
+		models.RespondError(conn, req.ID, err.Error())
+		return
+	}
+	if err := desktop.SetDefault(mimeType, desktopID); err != nil {
+		models.RespondError(conn, req.ID, err.Error())
+		return
+	}
+	models.Respond(conn, req.ID, models.SuccessResult{Success: true})
+}
+
+func handleSetDefaults(conn net.Conn, req models.Request) {
+	desktopID, err := params.StringNonEmpty(req.Params, "desktopId")
+	if err != nil {
+		models.RespondError(conn, req.ID, err.Error())
+		return
+	}
+	mimeTypes, err := mimeListParam(req, "mimeTypes")
+	if err != nil {
+		models.RespondError(conn, req.ID, err.Error())
+		return
+	}
+	if err := desktop.SetDefaults(mimeTypes, desktopID); err != nil {
+		models.RespondError(conn, req.ID, err.Error())
+		return
+	}
+	models.Respond(conn, req.ID, models.SuccessResult{Success: true})
+}
+
+func handleAppsForMime(conn net.Conn, req models.Request) {
+	mimeType, err := mimeParam(req.Params, "mimeType")
+	if err != nil {
+		models.RespondError(conn, req.ID, err.Error())
+		return
+	}
+	ids := desktop.AppsForMime(mimeType)
+	if ids == nil {
+		ids = []string{}
+	}
+	models.Respond(conn, req.ID, appsResult{
+		MimeType:   mimeType,
+		DesktopIDs: ids,
+	})
+}
+
+func handleQueryDefaults(conn net.Conn, req models.Request) {
+	mimeTypes, err := mimeListParam(req, "mimeTypes")
+	if err != nil {
+		models.RespondError(conn, req.ID, err.Error())
+		return
+	}
+	models.Respond(conn, req.ID, queryResult{
+		Defaults: desktop.QueryDefaults(mimeTypes),
+	})
+}
+
+func mimeParam(p map[string]any, key string) (string, error) {
+	raw, err := params.StringNonEmpty(p, key)
+	if err != nil {
+		return "", err
+	}
+	canonical := desktop.StripMimeParams(raw)
+	if canonical == "" {
+		return "", fmt.Errorf("invalid '%s' parameter", key)
+	}
+	return canonical, nil
+}
+
+func mimeListParam(req models.Request, key string) ([]string, error) {
+	raw, ok := models.Get[[]any](req, key)
+	if !ok {
+		return nil, fmt.Errorf("missing or invalid '%s' parameter", key)
+	}
+	out := make([]string, 0, len(raw))
+	for _, v := range raw {
+		s, ok := v.(string)
+		if !ok {
+			continue
+		}
+		canonical := desktop.StripMimeParams(s)
+		if canonical == "" {
+			continue
+		}
+		out = append(out, canonical)
+	}
+	if len(out) == 0 {
+		return nil, fmt.Errorf("no valid mime types provided")
+	}
+	return out, nil
+}

core/internal/server/router.go

@@ -16,6 +16,7 @@ import (
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/freedesktop"
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/location"
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/loginctl"
+	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/mime"
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/models"
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/server/network"
 	serverPlugins "github.com/AvengeMedia/DankMaterialShell/core/internal/server/plugins"
@@ -92,6 +93,11 @@ func RouteRequest(conn net.Conn, req models.Request) {
 		return
 	}
 
+	if strings.HasPrefix(req.Method, "mime.") {
+		mime.HandleRequest(conn, req)
+		return
+	}
+
 	if strings.HasPrefix(req.Method, "browser.") || strings.HasPrefix(req.Method, "apppicker.") {
 		if appPickerManager == nil {
 			models.RespondError(conn, req.ID, "apppicker manager not initialized")