moving get_fmap_type to utils

Author: birajstha

CPAC/utils/datasource.py

@@ -377,67 +377,9 @@ def create_fmap_datasource(fmap_dct, wf_name="fmap_datasource"):
 
 def get_fmap_phasediff_metadata(data_config_scan_params):
     """Return the scan parameters for a field map phasediff scan."""
-    def get_fmap_type(metadata):
-    """Determine the type of field map from metadata.
-
-    reference: https://bids-specification.readthedocs.io/en/latest/modality-specific-files/magnetic-resonance-imaging-data.html#case-1-phase-difference-map-and-at-least-one-magnitude-image
-
-    Parameters
-    ----------
-    metadata : dict or str
-        Metadata dictionary or path to a JSON file containing metadata.
-
-    Returns
-    -------
-    str or None
-        Returns the type of field map as a string:
-        - "phasediff" for phase difference maps with two echo times
-        - "phase" for single echo phase maps
-        - "fieldmap" for field maps with units like Hz, rad/s, T, or Tesla
-        - "epi" for EPI field maps with phase encoding direction
-    """
-
-    if not isinstance(metadata, dict):
-        if isinstance(metadata, str) and ".json" in metadata:
-            import json
-
-            try:
-                with open(metadata, "r", encoding="utf-8") as f:
-                    metadata = json.load(f)
-            except (FileNotFoundError, json.JSONDecodeError):
-                return None
-        else:
-            return None
-
-    # Check for required BIDS fields only
-    match (
-        "EchoTime1" in metadata,
-        "EchoTime2" in metadata,
-        "EchoTime" in metadata,
-        "Units" in metadata,
-        "PhaseEncodingDirection" in metadata,
-    ):
-        case (True, True, _, _, _):
-            # Case 1: Phase-difference map (REQUIRED: EchoTime1 AND EchoTime2)
-            return "phasediff"
-        case (False, False, True, _, _):
-            # Case 2: Single phase map (REQUIRED: EchoTime, but NOT EchoTime1/2)
-            return "phase"
-        case (_, _, _, True, _):
-            # Case 3: Direct field mapping (REQUIRED: Units)
-            units = metadata["Units"].lower()
-            if units in ["hz", "rad/s", "t", "tesla", "hertz"]:
-                return "fieldmap"
-        case (_, _, _, _, True):
-            # Case 4: EPI field maps (REQUIRED: PhaseEncodingDirection)
-            pe_dir = metadata["PhaseEncodingDirection"]
-            if pe_dir in ["i", "i-", "j", "j-", "k", "k-"]:
-                return "epi"
-        case _:
-            return None
-
-    return None
 
+    from CPAC.utils.utils import get_fmap_type
+    
     if (
         not isinstance(data_config_scan_params, dict)
         and ".json" in data_config_scan_params

CPAC/utils/utils.py

@@ -2657,3 +2657,65 @@ def flip_orientation_code(code):
     """Reverts an orientation code by flipping R↔L, A↔P, and I↔S."""
     flip_dict = {"R": "L", "L": "R", "A": "P", "P": "A", "I": "S", "S": "I"}
     return "".join(flip_dict[c] for c in code)
+
+
+def get_fmap_type(metadata):
+    """Determine the type of field map from metadata.
+
+    reference: https://bids-specification.readthedocs.io/en/latest/modality-specific-files/magnetic-resonance-imaging-data.html#case-1-phase-difference-map-and-at-least-one-magnitude-image
+
+    Parameters
+    ----------
+    metadata : dict or str
+        Metadata dictionary or path to a JSON file containing metadata.
+
+    Returns
+    -------
+    str or None
+        Returns the type of field map as a string:
+        - "phasediff" for phase difference maps with two echo times
+        - "phase" for single echo phase maps
+        - "fieldmap" for field maps with units like Hz, rad/s, T, or Tesla
+        - "epi" for EPI field maps with phase encoding direction
+    """
+
+    if not isinstance(metadata, dict):
+        if isinstance(metadata, str) and ".json" in metadata:
+            import json
+
+            try:
+                with open(metadata, "r", encoding="utf-8") as f:
+                    metadata = json.load(f)
+            except (FileNotFoundError, json.JSONDecodeError):
+                return None
+        else:
+            return None
+
+    # Check for required BIDS fields only
+    match (
+        "EchoTime1" in metadata,
+        "EchoTime2" in metadata,
+        "EchoTime" in metadata,
+        "Units" in metadata,
+        "PhaseEncodingDirection" in metadata,
+    ):
+        case (True, True, _, _, _):
+            # Case 1: Phase-difference map (REQUIRED: EchoTime1 AND EchoTime2)
+            return "phasediff"
+        case (False, False, True, _, _):
+            # Case 2: Single phase map (REQUIRED: EchoTime, but NOT EchoTime1/2)
+            return "phase"
+        case (_, _, _, True, _):
+            # Case 3: Direct field mapping (REQUIRED: Units)
+            units = metadata["Units"].lower()
+            if units in ["hz", "rad/s", "t", "tesla", "hertz"]:
+                return "fieldmap"
+        case (_, _, _, _, True):
+            # Case 4: EPI field maps (REQUIRED: PhaseEncodingDirection)
+            pe_dir = metadata["PhaseEncodingDirection"]
+            if pe_dir in ["i", "i-", "j", "j-", "k", "k-"]:
+                return "epi"
+        case _:
+            return None
+
+    return None