Store receipt files under year/MM_DD_dollars.cents naming

Replace flat UUID filenames with a browsable, dated layout (spec.md item 9):
<STORAGE_DIR>/<YYYY>/<MM>_<DD>_<dollars>.<cents><ext>, from the receipt date
and amount. Same date+amount collisions get a _1, _2, … suffix via exclusive
create (race-safe). New uploads only; serving is unaffected (blob-backed).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

internal/web/upload.go

@@ -148,11 +148,11 @@ func (s *Server) handleUpload(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	// Dual-write: file on disk (UUID name) + blob in DB.
+	// Dual-write: file on disk (dated, amount-tagged name) + blob in DB.
 	id := newID()
 	ext := extFor(header.Filename, mimeType)
-	relPath := id + ext
-	if err := s.saveFile(relPath, data); err != nil {
+	relPath, err := s.saveReceiptFile(receiptDate, amountCents, ext, data)
+	if err != nil {
 		s.serverError(w, "save file", err)
 		return
 	}
@@ -216,11 +216,47 @@ func whoLabel(id *int64, set []storage.Lookup) string {
 	return labelFor(*id, set)
 }
 
-func (s *Server) saveFile(relPath string, data []byte) error {
-	if err := os.MkdirAll(s.cfg.StorageDir, 0o700); err != nil {
-		return err
+// saveReceiptFile writes the bytes under
+//
+//	<StorageDir>/<YYYY>/<MM>_<DD>_<dollars>.<cents><ext>
+//
+// using the receipt date and amount. When a file with the same date+amount+ext
+// already exists (legitimately possible — duplicates can be approved), a _1, _2, …
+// suffix is added to the stem. Exclusive create avoids two concurrent uploads
+// racing onto the same name. Returns the storage-relative path actually written
+// (forward-slash separated, as stored in receipts.file_path).
+func (s *Server) saveReceiptFile(date time.Time, amountCents int64, ext string, data []byte) (string, error) {
+	yearDir := fmt.Sprintf("%04d", date.Year())
+	if err := os.MkdirAll(filepath.Join(s.cfg.StorageDir, yearDir), 0o700); err != nil {
+		return "", err
 	}
-	return os.WriteFile(filepath.Join(s.cfg.StorageDir, relPath), data, 0o600)
+	stem := fmt.Sprintf("%02d_%02d_%d.%02d", int(date.Month()), date.Day(), amountCents/100, amountCents%100)
+
+	for i := 0; i < 10000; i++ {
+		name := stem
+		if i > 0 {
+			name += "_" + strconv.Itoa(i)
+		}
+		name += ext
+		rel := filepath.Join(yearDir, name)
+		f, err := os.OpenFile(filepath.Join(s.cfg.StorageDir, rel), os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0o600)
+		if os.IsExist(err) {
+			continue // name taken — try the next suffix
+		}
+		if err != nil {
+			return "", err
+		}
+		_, werr := f.Write(data)
+		cerr := f.Close()
+		if werr != nil {
+			return "", werr
+		}
+		if cerr != nil {
+			return "", cerr
+		}
+		return filepath.ToSlash(rel), nil
+	}
+	return "", fmt.Errorf("could not find a free filename for %s", stem)
 }
 
 func detectMime(data []byte) string {

internal/web/upload_test.go

@@ -107,16 +107,49 @@ func TestUpload_HappyPath_WritesFileAndRow(t *testing.T) {
 		t.Fatalf("CountActive = %d, want 1", n)
 	}
 
-	// File written to disk (dual-write).
-	entries, err := os.ReadDir(s.cfg.StorageDir)
+	// File written to disk under the receipt-year subdir with a dated, amount-
+	// tagged name (date 2026-06-01, amount 12.34 -> 2026/06_01_12.34.png).
+	entries, err := os.ReadDir(filepath.Join(s.cfg.StorageDir, "2026"))
 	if err != nil {
 		t.Fatal(err)
 	}
 	if len(entries) != 1 {
-		t.Fatalf("storage dir has %d files, want 1", len(entries))
+		t.Fatalf("year dir has %d files, want 1", len(entries))
 	}
-	if !strings.HasSuffix(entries[0].Name(), ".png") {
-		t.Errorf("stored file name = %q, want .png suffix", entries[0].Name())
+	if entries[0].Name() != "06_01_12.34.png" {
+		t.Errorf("stored file name = %q, want 06_01_12.34.png", entries[0].Name())
+	}
+}
+
+func TestUpload_SameDateAmount_DisambiguatesFilename(t *testing.T) {
+	s := testServerWithStore(t)
+	cat := aCategoryID(t, s)
+	post := func() {
+		body, ct := multipartUpload(t,
+			map[string]string{"amount": "12.34", "receipt_date": "2026-06-01", "category_id": cat},
+			"receipt", "receipt.png", fakePNG())
+		req := httptest.NewRequest(http.MethodPost, "/upload", body)
+		req.Header.Set("Content-Type", ct)
+		req.AddCookie(authCookie(t, s))
+		rec := httptest.NewRecorder()
+		s.Routes().ServeHTTP(rec, req)
+		if rec.Code != http.StatusOK {
+			t.Fatalf("status = %d; body=%s", rec.Code, rec.Body.String())
+		}
+	}
+	post()
+	post() // same date + amount → must not overwrite the first file
+
+	entries, err := os.ReadDir(filepath.Join(s.cfg.StorageDir, "2026"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	got := map[string]bool{}
+	for _, e := range entries {
+		got[e.Name()] = true
+	}
+	if !got["06_01_12.34.png"] || !got["06_01_12.34_1.png"] {
+		t.Errorf("expected both base and _1 files, got %v", got)
 	}
 }
 

spec.md

@@ -212,3 +212,32 @@ Where the rates come from (this is the only maintenance cost of the feature):
 (Balance/spend indicator: dropped. The Anthropic API has no remaining-balance
 endpoint, and a cumulative-spend readout was not wanted. Per-query cost above is
 the only cost surface.)
+
+9. Human-readable on-disk file layout
+
+Replace the flat UUID filenames with a dated, amount-tagged layout under the
+storage root, so the files directory is browsable on its own:
+
+    <STORAGE_DIR>/<YYYY>/<MM>_<DD>_<dollars>.<cents>.<ext>
+
+  - Year folder and MM/DD come from the RECEIPT date (not upload date); dollars
+    and cents come from amount_cents (cents zero-padded to two digits, dollars not
+    padded). Example: a $42.50 JPEG dated 2026-06-08 → 2026/06_08_42.50.jpeg.
+  - The amount's decimal dot and the extension dot coexist fine — the extension is
+    just the final dot-segment ("jpeg"); the stem is "06_08_42.50". (If that ever
+    feels ambiguous, the accepted alternatives are an underscore "06_08_42_50" or
+    bare cents "06_08_4250" — pick one and keep it consistent.)
+  - All path components derive only from the date and amount (digits, underscores,
+    one dot), never from the user-supplied original filename, so there is no path-
+    traversal surface. original_filename stays as metadata in the DB.
+  - Collisions (same date + amount + ext — legitimately possible since duplicates
+    can be approved) get a numeric suffix on the STEM, starting at _1: the second
+    file becomes "06_08_42.50_1.jpeg", the third "_2", etc. Use exclusive create
+    (O_CREATE|O_EXCL) and increment the suffix on "already exists" so two concurrent
+    uploads can't race onto the same name.
+  - The chosen relative path is stored in receipts.file_path as today; the dual
+    write still also stores the bytes as the DB blob, and serving continues to work
+    from the blob regardless of the on-disk name.
+  - Applies to NEW uploads only — existing UUID-named files keep their file_path;
+    no backfill/rename of historical files in scope.
+  - saveFile must create the year subdirectory (MkdirAll) before writing.