From b1436f1db9b3e567818a59f4bcb83ae4a57435ae Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Thu, 5 Feb 2026 17:39:32 +0000
Subject: [PATCH 1/3] Initial plan


From 3d506d85076e9f88498116b802cb4e71b183afc4 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Thu, 5 Feb 2026 17:43:07 +0000
Subject: [PATCH 2/3] Add parallel copy method to FileHandler with
 comprehensive tests

Co-authored-by: DavidHuber-NOAA <69919478+DavidHuber-NOAA@users.noreply.github.com>
---
 src/wxflow/file_utils.py |  89 ++++++++++++++++
 tests/test_file_utils.py | 215 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 304 insertions(+)

diff --git a/src/wxflow/file_utils.py b/src/wxflow/file_utils.py
index fcdf478..4a80068 100644
--- a/src/wxflow/file_utils.py
+++ b/src/wxflow/file_utils.py
@@ -1,5 +1,6 @@
 import os
 from logging import getLogger
+from multiprocessing import Pool
 from pathlib import Path
 
 from .fsutils import cp, mkdir
@@ -9,6 +10,28 @@
 logger = getLogger(__name__.split('.')[-1])
 
 
+def _copy_single_file(src, dest):
+    """Helper function to copy a single file. Used by multiprocessing.Pool.
+
+    Parameters
+    ----------
+    src : str
+            Source file path
+    dest : str
+            Destination file path
+
+    Returns
+    -------
+    tuple
+            (success: bool, src: str, dest: str, error: Exception or None)
+    """
+    try:
+        cp(src, dest)
+        return (True, src, dest, None)
+    except Exception as ee:
+        return (False, src, dest, ee)
+
+
 class FileHandler:
     """Class to manipulate files in bulk for a given configuration
 
@@ -106,6 +129,72 @@ def _copy_files(filelist, required=True):
                 else:
                     logger.warning(f"Source file '{src}' does not exist, skipping!")
 
+    @staticmethod
+    def copy_parallel(filelist, num_processes=None):
+        """Function to copy files in parallel using multiprocessing.Pool
+
+        Parameters
+        ----------
+        filelist : list
+                List of lists of [src, dest]
+        num_processes : int, optional
+                Number of processes to use for parallel copying.
+                If None, uses the number of CPUs on the machine.
+        """
+        FileHandler._copy_files_parallel(filelist, required=True, num_processes=num_processes)
+
+    @staticmethod
+    def _copy_files_parallel(filelist, required=True, num_processes=None):
+        """Function to copy files in parallel using multiprocessing.Pool
+
+        `filelist` should be in the form:
+        - [src, dest]
+
+        Parameters
+        ----------
+        filelist : list
+                List of lists of [src, dest]
+        required : bool, optional
+                Flag to indicate if the src file is required to exist. Default is True
+        num_processes : int, optional
+                Number of processes to use for parallel copying.
+                If None, uses the number of CPUs on the machine.
+        """
+        # Validate filelist format
+        for sublist in filelist:
+            if len(sublist) != 2:
+                raise IndexError(
+                    f"List must be of the form ['src', 'dest'], not {sublist}")
+
+        # Check that all required source files exist before starting any copies
+        for sublist in filelist:
+            src = sublist[0]
+            if not os.path.exists(src):
+                if required:
+                    logger.exception(f"Source file '{src}' does not exist and is required, ABORT!")
+                    raise FileNotFoundError(f"Source file '{src}' does not exist")
+                else:
+                    logger.warning(f"Source file '{src}' does not exist, skipping!")
+
+        # Filter out files where source doesn't exist (for optional copies)
+        valid_files = [sublist for sublist in filelist if os.path.exists(sublist[0])]
+
+        if not valid_files:
+            logger.warning("No valid files to copy")
+            return
+
+        # Use multiprocessing.Pool to copy files in parallel
+        with Pool(processes=num_processes) as pool:
+            results = pool.starmap(_copy_single_file, valid_files)
+
+        # Check if any copies failed
+        for i, (success, src, dest, error) in enumerate(results):
+            if not success:
+                logger.exception(f"Error copying {src} to {dest}: {error}")
+                raise error
+            else:
+                logger.info(f'Copied {src} to {dest}')
+
     @staticmethod
     def _make_dirs(dirlist):
         """Function to make all directories specified in the list
diff --git a/tests/test_file_utils.py b/tests/test_file_utils.py
index 54a13f0..ed7d8c0 100644
--- a/tests/test_file_utils.py
+++ b/tests/test_file_utils.py
@@ -263,3 +263,218 @@ def test_link_file_bad(tmp_path, create_dirs_and_files_for_test_link):
     bad_config = {'link_req': bad_link_list}
     with pytest.raises(FileNotFoundError):
         FileHandler(bad_config).sync()
+
+
+def test_copy_parallel_basic(tmp_path):
+    """
+    Test basic parallel copy functionality
+    Parameters
+    ----------
+    tmp_path - pytest fixture
+    """
+    # Create input directory and files
+    input_dir_path = tmp_path / 'parallel_input'
+    config = {'mkdir': [input_dir_path]}
+    FileHandler(config).sync()
+
+    # Create multiple test files with some content
+    src_files = []
+    for i in range(10):
+        src_file = input_dir_path / f'file_{i}.txt'
+        src_file.write_text(f'Content of file {i}\n' * 100)
+        src_files.append(src_file)
+
+    # Create output directory
+    output_dir_path = tmp_path / 'parallel_output'
+    config = {'mkdir': [output_dir_path]}
+    FileHandler(config).sync()
+
+    # Create copy list
+    copy_list = []
+    dest_files = []
+    for i, src in enumerate(src_files):
+        dest = output_dir_path / f'file_{i}.txt'
+        copy_list.append([src, dest])
+        dest_files.append(dest)
+
+    # Perform parallel copy
+    FileHandler.copy_parallel(copy_list)
+
+    # Verify all files were copied
+    for src, dest in zip(src_files, dest_files):
+        assert os.path.isfile(dest), f"Destination file {dest} does not exist"
+        # Verify content matches
+        assert src.read_text() == dest.read_text(), f"Content mismatch for {dest}"
+
+
+def test_copy_parallel_with_num_processes(tmp_path):
+    """
+    Test parallel copy with specific number of processes
+    Parameters
+    ----------
+    tmp_path - pytest fixture
+    """
+    # Create input directory and files
+    input_dir_path = tmp_path / 'parallel_input'
+    config = {'mkdir': [input_dir_path]}
+    FileHandler(config).sync()
+
+    # Create test files
+    src_files = []
+    for i in range(5):
+        src_file = input_dir_path / f'file_{i}.txt'
+        src_file.write_text(f'Content {i}')
+        src_files.append(src_file)
+
+    # Create output directory
+    output_dir_path = tmp_path / 'parallel_output'
+    config = {'mkdir': [output_dir_path]}
+    FileHandler(config).sync()
+
+    # Create copy list
+    copy_list = []
+    for i, src in enumerate(src_files):
+        dest = output_dir_path / f'file_{i}.txt'
+        copy_list.append([src, dest])
+
+    # Perform parallel copy with 2 processes
+    FileHandler.copy_parallel(copy_list, num_processes=2)
+
+    # Verify all files were copied
+    for i, src in enumerate(src_files):
+        dest = output_dir_path / f'file_{i}.txt'
+        assert os.path.isfile(dest)
+        assert src.read_text() == dest.read_text()
+
+
+def test_copy_parallel_error_propagation(tmp_path):
+    """
+    Test that errors in one copy cause the parent call to fail
+    Parameters
+    ----------
+    tmp_path - pytest fixture
+    """
+    # Create input directory and files
+    input_dir_path = tmp_path / 'parallel_input'
+    config = {'mkdir': [input_dir_path]}
+    FileHandler(config).sync()
+
+    # Create valid source files
+    src_files = []
+    for i in range(3):
+        src_file = input_dir_path / f'file_{i}.txt'
+        src_file.write_text(f'Content {i}')
+        src_files.append(src_file)
+
+    # Create copy list with bad destination (unwritable directory)
+    copy_list = []
+    for i, src in enumerate(src_files):
+        # Try to copy to an invalid location
+        dest = "/dev/null/invalid_path.txt"
+        copy_list.append([src, dest])
+
+    # Attempt parallel copy - should fail
+    with pytest.raises(OSError):
+        FileHandler.copy_parallel(copy_list)
+
+
+def test_copy_parallel_missing_required_file(tmp_path):
+    """
+    Test that missing required source files cause the parent call to fail
+    Parameters
+    ----------
+    tmp_path - pytest fixture
+    """
+    # Create input directory
+    input_dir_path = tmp_path / 'parallel_input'
+    config = {'mkdir': [input_dir_path]}
+    FileHandler(config).sync()
+
+    # Create one valid file and reference one that doesn't exist
+    valid_file = input_dir_path / 'valid.txt'
+    valid_file.write_text('Valid content')
+    missing_file = input_dir_path / 'missing.txt'
+
+    # Create output directory
+    output_dir_path = tmp_path / 'parallel_output'
+    config = {'mkdir': [output_dir_path]}
+    FileHandler(config).sync()
+
+    # Create copy list with missing file
+    copy_list = [
+        [valid_file, output_dir_path / 'valid.txt'],
+        [missing_file, output_dir_path / 'missing.txt']
+    ]
+
+    # Attempt parallel copy - should fail due to missing file
+    with pytest.raises(FileNotFoundError, match=f"Source file '{missing_file}' does not exist"):
+        FileHandler.copy_parallel(copy_list)
+
+
+def test_copy_parallel_file_integrity(tmp_path):
+    """
+    Test that parallel copies are identical to their sources
+    Parameters
+    ----------
+    tmp_path - pytest fixture
+    """
+    import hashlib
+
+    # Create input directory
+    input_dir_path = tmp_path / 'parallel_input'
+    config = {'mkdir': [input_dir_path]}
+    FileHandler(config).sync()
+
+    # Create files with larger content to ensure integrity
+    src_files = []
+    src_hashes = []
+    for i in range(5):
+        src_file = input_dir_path / f'file_{i}.txt'
+        # Create larger content
+        content = f'Line {i}\n' * 10000
+        src_file.write_text(content)
+        src_files.append(src_file)
+        # Calculate hash
+        hash_obj = hashlib.sha256()
+        hash_obj.update(content.encode())
+        src_hashes.append(hash_obj.hexdigest())
+
+    # Create output directory
+    output_dir_path = tmp_path / 'parallel_output'
+    config = {'mkdir': [output_dir_path]}
+    FileHandler(config).sync()
+
+    # Create copy list
+    copy_list = []
+    dest_files = []
+    for i, src in enumerate(src_files):
+        dest = output_dir_path / f'file_{i}.txt'
+        copy_list.append([src, dest])
+        dest_files.append(dest)
+
+    # Perform parallel copy
+    FileHandler.copy_parallel(copy_list)
+
+    # Verify file integrity using hashes
+    for i, dest in enumerate(dest_files):
+        assert os.path.isfile(dest)
+        content = dest.read_text()
+        hash_obj = hashlib.sha256()
+        hash_obj.update(content.encode())
+        dest_hash = hash_obj.hexdigest()
+        assert dest_hash == src_hashes[i], f"Hash mismatch for {dest}"
+
+
+def test_copy_parallel_invalid_format(tmp_path):
+    """
+    Test that invalid copy list format raises appropriate error
+    Parameters
+    ----------
+    tmp_path - pytest fixture
+    """
+    # Create a copy list with invalid format
+    bad_copy_list = [['only_one_item']]
+
+    # Attempt parallel copy with bad format - should fail
+    with pytest.raises(IndexError, match="List must be of the form"):
+        FileHandler.copy_parallel(bad_copy_list)

From 544788edcc4a657f9dec983a4d55fc833df464fb Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Thu, 5 Feb 2026 17:44:14 +0000
Subject: [PATCH 3/3] Address code review feedback: remove unused loop variable
 and move import

Co-authored-by: DavidHuber-NOAA <69919478+DavidHuber-NOAA@users.noreply.github.com>
---
 src/wxflow/file_utils.py | 2 +-
 tests/test_file_utils.py | 3 +--
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/wxflow/file_utils.py b/src/wxflow/file_utils.py
index 4a80068..e9663c0 100644
--- a/src/wxflow/file_utils.py
+++ b/src/wxflow/file_utils.py
@@ -188,7 +188,7 @@ def _copy_files_parallel(filelist, required=True, num_processes=None):
             results = pool.starmap(_copy_single_file, valid_files)
 
         # Check if any copies failed
-        for i, (success, src, dest, error) in enumerate(results):
+        for success, src, dest, error in results:
             if not success:
                 logger.exception(f"Error copying {src} to {dest}: {error}")
                 raise error
diff --git a/tests/test_file_utils.py b/tests/test_file_utils.py
index ed7d8c0..c385648 100644
--- a/tests/test_file_utils.py
+++ b/tests/test_file_utils.py
@@ -1,3 +1,4 @@
+import hashlib
 import logging
 import os
 
@@ -418,8 +419,6 @@ def test_copy_parallel_file_integrity(tmp_path):
     ----------
     tmp_path - pytest fixture
     """
-    import hashlib
-
     # Create input directory
     input_dir_path = tmp_path / 'parallel_input'
     config = {'mkdir': [input_dir_path]}