From a1089644579b3bcf661d3c68d1c5201a022a8005 Mon Sep 17 00:00:00 2001
From: Felix Martin <mail@felixm.de>
Date: Mon, 1 Jun 2026 20:15:00 -0400
Subject: [PATCH] Add GET /fs/browse directory-listing endpoint

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 internal/web/settings_handlers.go      | 57 ++++++++++++++++++++
 internal/web/settings_handlers_test.go | 72 ++++++++++++++++++++++++++
 internal/web/web.go                    |  1 +
 3 files changed, 130 insertions(+)

diff --git a/internal/web/settings_handlers.go b/internal/web/settings_handlers.go
index c147391..31d0729 100644
--- a/internal/web/settings_handlers.go
+++ b/internal/web/settings_handlers.go
@@ -2,6 +2,9 @@ package web
 
 import (
 	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
 
 	"antidrift/internal/settings"
 
@@ -61,3 +64,57 @@ func (s *Server) handlePostSettings(c *gin.Context) {
 	s.broadcast()
 	c.JSON(http.StatusOK, req)
 }
+
+type browseEntry struct {
+	Name  string `json:"name"`
+	Path  string `json:"path"`
+	IsDir bool   `json:"is_dir"`
+}
+
+type browseResponse struct {
+	Dir     string        `json:"dir"`
+	Parent  string        `json:"parent"`
+	Entries []browseEntry `json:"entries"`
+}
+
+// handleBrowse lists subdirectories plus .md files under dir, so the UI can build
+// a file picker that returns a real server-side path. Dotfiles are NOT hidden —
+// the default profile lives under ~/.antidrift. Localhost-only daemon; no jail
+// beyond OS permissions (same trust boundary as the rest of the UI).
+func (s *Server) handleBrowse(c *gin.Context) {
+	dir := strings.TrimSpace(c.Query("dir"))
+	if dir == "" {
+		dir = s.browseStart()
+	}
+	dir = filepath.Clean(dir)
+	infos, err := os.ReadDir(dir)
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+		return
+	}
+	resp := browseResponse{Dir: dir, Parent: filepath.Dir(dir), Entries: []browseEntry{}}
+	for _, e := range infos {
+		name := e.Name()
+		full := filepath.Join(dir, name)
+		if e.IsDir() {
+			resp.Entries = append(resp.Entries, browseEntry{Name: name, Path: full, IsDir: true})
+		} else if strings.HasSuffix(name, ".md") {
+			resp.Entries = append(resp.Entries, browseEntry{Name: name, Path: full})
+		}
+	}
+	c.JSON(http.StatusOK, resp)
+}
+
+// browseStart picks the directory of the current knowledge path, else $HOME.
+func (s *Server) browseStart() string {
+	s.settingsMu.Lock()
+	kp := s.settings.KnowledgePath
+	s.settingsMu.Unlock()
+	if kp != "" {
+		return filepath.Dir(kp)
+	}
+	if home, err := os.UserHomeDir(); err == nil {
+		return home
+	}
+	return "/"
+}
diff --git a/internal/web/settings_handlers_test.go b/internal/web/settings_handlers_test.go
index d49ae08..0d02db2 100644
--- a/internal/web/settings_handlers_test.go
+++ b/internal/web/settings_handlers_test.go
@@ -110,3 +110,75 @@ func TestPostSettingsInvalidJSONIs400(t *testing.T) {
 		t.Errorf("applier called on invalid json; want 0, got %d", fa.called)
 	}
 }
+
+func TestBrowseListsDirsAndMarkdown(t *testing.T) {
+	dir := t.TempDir()
+	if err := os.Mkdir(filepath.Join(dir, "sub"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(dir, "profile.md"), []byte("x"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(dir, "notes.txt"), []byte("x"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	s := newTestServer(t)
+	s.SetSettings(filepath.Join(t.TempDir(), "settings.json"), settings.Settings{}, func(settings.Settings) error { return nil })
+	r := s.Router()
+
+	req := httptest.NewRequest(http.MethodGet, "/fs/browse?dir="+dir, nil)
+	w := httptest.NewRecorder()
+	r.ServeHTTP(w, req)
+	if w.Code != http.StatusOK {
+		t.Fatalf("status = %d, want 200", w.Code)
+	}
+	var resp struct {
+		Dir     string `json:"dir"`
+		Parent  string `json:"parent"`
+		Entries []struct {
+			Name  string `json:"name"`
+			Path  string `json:"path"`
+			IsDir bool   `json:"is_dir"`
+		} `json:"entries"`
+	}
+	if err := json.Unmarshal(w.Body.Bytes(), &resp); err != nil {
+		t.Fatalf("decode: %v", err)
+	}
+	if resp.Parent != filepath.Dir(dir) {
+		t.Errorf("parent = %q, want %q", resp.Parent, filepath.Dir(dir))
+	}
+	var names []string
+	for _, e := range resp.Entries {
+		names = append(names, e.Name)
+	}
+	hasSub, hasMd, hasTxt := false, false, false
+	for _, e := range resp.Entries {
+		switch e.Name {
+		case "sub":
+			hasSub = e.IsDir
+		case "profile.md":
+			hasMd = !e.IsDir
+		case "notes.txt":
+			hasTxt = true
+		}
+	}
+	if !hasSub || !hasMd {
+		t.Errorf("missing dir or .md entry; names = %v", names)
+	}
+	if hasTxt {
+		t.Errorf(".txt should be filtered out; names = %v", names)
+	}
+}
+
+func TestBrowseBadDirIs400(t *testing.T) {
+	s := newTestServer(t)
+	s.SetSettings(filepath.Join(t.TempDir(), "settings.json"), settings.Settings{}, func(settings.Settings) error { return nil })
+	r := s.Router()
+	req := httptest.NewRequest(http.MethodGet, "/fs/browse?dir=/no/such/dir/xyz", nil)
+	w := httptest.NewRecorder()
+	r.ServeHTTP(w, req)
+	if w.Code != http.StatusBadRequest {
+		t.Fatalf("status = %d, want 400", w.Code)
+	}
+}
diff --git a/internal/web/web.go b/internal/web/web.go
index 6679b78..ed12747 100644
--- a/internal/web/web.go
+++ b/internal/web/web.go
@@ -77,6 +77,7 @@ func (s *Server) Router() *gin.Engine {
 	r.POST("/knowledge/path", s.handleKnowledgePath)
 	r.GET("/settings", s.handleGetSettings)
 	r.POST("/settings", s.handlePostSettings)
+	r.GET("/fs/browse", s.handleBrowse)
 	return r
 }