utils/data_explorer.py

@@ -8,7 +8,9 @@ for each prefix:
 - **Only considers files matching the configured extensions** (default: all
   supported extensions — SAS and text).  All other file types are ignored.
 - Tests read permission with ``head_object`` on the first matching file found
-- Categorises the directory as **Available**, **Blocked**, or **Empty**
+- If the first file is accessible, tests ALL remaining files individually
+- Categorises the directory as **Available**, **Blocked**, **Empty**, and
+  tracks individual file **Exceptions** within available directories
 
 Supported file types
 --------------------
@@ -143,6 +145,9 @@ class AvailableDir:
     prefix: str
     file_count: int
     total_size: int  # bytes
+    accessible_count: int = 0   # files that passed head_object
+    total_count: int = 0        # total .sas7bdat files found
+    accessible_size: int = 0    # total size of accessible files only
 
 
 @dataclass
@@ -161,6 +166,15 @@ class EmptyDir:
     prefix: str
 
 
+@dataclass
+class ExceptionFile:
+    """A specific file that failed permission check within an otherwise available directory."""
+
+    prefix: str   # the directory prefix
+    key: str      # the full S3 key of the failed file
+    error: str    # the error message
+
+
 @dataclass
 class Results:
     """Aggregated exploration results."""
@@ -168,6 +182,7 @@ class Results:
     available: List[AvailableDir] = field(default_factory=list)
     blocked: List[BlockedDir] = field(default_factory=list)
     empty: List[EmptyDir] = field(default_factory=list)
+    exceptions: List[ExceptionFile] = field(default_factory=list)
 
 
 # ---------------------------------------------------------------------------
@@ -218,37 +233,30 @@ def list_objects(
     bucket: str,
     prefix: str,
     extensions: Set[str] | None = None,
-) -> Tuple[str | None, int, int]:
+) -> Tuple[List[Tuple[str, int]], int]:
-    """Recursively list all objects under *prefix* using streaming counters.
+    """Recursively list all objects under *prefix*.
 
     Only objects whose key ends with one of *extensions* (case-insensitive) are
     counted.  All other files are silently skipped.  When *extensions* is
     ``None`` the module-level ``FILE_EXTENSIONS`` set is used.
 
-    Returns ``(first_key, file_count, total_size)`` where *first_key* is the
+    Returns ``(files, total_size)`` where *files* is a list of
-    key of the first matching object found (or ``None`` if no matching files
+    ``(key, size)`` tuples for every matching object and *total_size* is the
-    exist), *file_count* is the total number of matching objects, and
+    sum of their sizes in bytes.
-    *total_size* is the sum of their sizes in bytes.
-
-    Unlike the previous implementation this never accumulates all keys in
-    memory, making it safe for prefixes with millions of objects.
     """
     if extensions is None:
         extensions = FILE_EXTENSIONS
     exts_lower = {e.lower() for e in extensions}
     paginator = s3_client.get_paginator("list_objects_v2")
-    first_key: str | None = None
+    files: List[Tuple[str, int]] = []
-    file_count: int = 0
     total_size: int = 0
     for page in paginator.paginate(Bucket=bucket, Prefix=prefix):
         for obj in page.get("Contents", []):
             if not any(obj["Key"].lower().endswith(ext) for ext in exts_lower):
                 continue
-            if first_key is None:
+            files.append((obj["Key"], obj["Size"]))
-                first_key = obj["Key"]
-            file_count += 1
             total_size += obj["Size"]
-    return first_key, file_count, total_size
+    return files, total_size
 
 
 def check_read_permission(
@@ -305,7 +313,7 @@ def explore_directories(
 
         # --- Recursive listing ------------------------------------------------
         try:
-            first_key, file_count, total_size = list_objects(
+            files, total_size = list_objects(
                 s3, S3_BUCKET, prefix, extensions=extensions,
             )
         except botocore.exceptions.ClientError as exc:
@@ -321,44 +329,77 @@ def explore_directories(
             )
             continue
 
-        if first_key is None:
+        if not files:
             results.empty.append(EmptyDir(prefix=prefix))
             continue
 
-        # --- Permission check -------------------------------------------------
+        file_count = len(files)
-        # Prefer a real object over a zero-byte directory marker (key ending
+
-        # in "/") for the head_object test.  The selected key must also match
+        # --- Permission check on first file -----------------------------------
-        # the extension filter.  If no suitable key is found, fall back to
+        # in "/") for the head_object test.  The listing is already filtered
-        # first_key.
+        # to the requested extensions, so any non-marker key is a valid probe.
+        first_key, _ = files[0]
         test_key = first_key
         if first_key.endswith("/") and total_size > 0:
-            # Re-scan the first page to find a non-marker key matching the extensions
+            for key, size in files:
-            try:
+                if not (key.endswith("/") and size == 0):
-                probe_paginator = s3.get_paginator("list_objects_v2")
+                    test_key = key
-                for probe_page in probe_paginator.paginate(
-                    Bucket=S3_BUCKET, Prefix=prefix, PaginationConfig={"MaxItems": 1000}
-                ):
-                    for obj in probe_page.get("Contents", []):
-                        if (
-                            not (obj["Key"].endswith("/") and obj["Size"] == 0)
-                            and any(obj["Key"].lower().endswith(ext) for ext in exts_lower)
-                        ):
-                            test_key = obj["Key"]
                     break
-                    if test_key != first_key:
-                        break
-            except Exception:
-                pass  # Fall back to first_key
 
         error = check_read_permission(s3, S3_BUCKET, test_key)
-        if error is None:
+        if error is not None:
-            results.available.append(
+            # First file blocked → entire directory is blocked
-                AvailableDir(prefix=prefix, file_count=file_count, total_size=total_size)
-            )
-        else:
             results.blocked.append(
                 BlockedDir(prefix=prefix, file_count=file_count, error=error)
             )
+            continue
+
+        # --- First file accessible → check ALL remaining files ----------------
+        accessible_count = 1  # the first (test_key) already passed
+        accessible_size = 0
+        dir_exceptions: List[ExceptionFile] = []
+
+        # Find the size of the test_key to count it
+        for key, size in files:
+            if key == test_key:
+                accessible_size = size
+                break
+
+        # Build list of remaining files to check
+        remaining = [(key, size) for key, size in files if key != test_key]
+
+        if remaining:
+            if len(remaining) > 10:
+                print(
+                    f"  Verifying access to {file_count} {ext_label} files in {prefix} ...",
+                    file=sys.stderr,
+                )
+
+            for key, size in remaining:
+                file_error = check_read_permission(s3, S3_BUCKET, key)
+                if file_error is None:
+                    accessible_count += 1
+                    accessible_size += size
+                else:
+                    dir_exceptions.append(
+                        ExceptionFile(prefix=prefix, key=key, error=file_error)
+                    )
+
+        else:
+            # Only one file and it passed
+            accessible_size = total_size
+
+        results.available.append(
+            AvailableDir(
+                prefix=prefix,
+                file_count=file_count,
+                total_size=total_size,
+                accessible_count=accessible_count,
+                total_count=file_count,
+                accessible_size=accessible_size,
+            )
+        )
+        results.exceptions.extend(dir_exceptions)
 
     return results
 
@@ -394,7 +435,10 @@ def print_results(results: Results, *, extensions: Set[str] | None = None) -> No
     if results.available:
         for d in results.available:
             print(f"  {d.prefix}")
-            print(f"    Matching files ({ext_label}): {d.file_count} | Total Size: {format_size(d.total_size)}")
+            print(
+                f"    {ext_label} files: {d.accessible_count}/{d.total_count} accessible"
+                f" | Total Size: {format_size(d.accessible_size)}"
+            )
     else:
         print("  (none)")
 
@@ -412,6 +456,16 @@ def print_results(results: Results, *, extensions: Set[str] | None = None) -> No
     else:
         print("  (none)")
 
+    # --- Exceptions ---
+    print()
+    print(f"--- Exceptions ({len(results.exceptions)}) ---")
+    if results.exceptions:
+        for exc in results.exceptions:
+            print(f"  {exc.key}")
+            print(f"    Directory: {exc.prefix} | Error: {exc.error}")
+    else:
+        print("  (none)")
+
     # --- Empty ---
     print()
     print(f"--- Empty / no matching files ({len(results.empty)}) ---")