chandra_acis.py: Add function "get_chips()"

1 files changed, 31 insertions, 4 deletions

diff --git a/scripts/chandra_acis.py b/scripts/chandra_acis.py
index 2dcc62e..6170b40 100755
--- a/scripts/chandra_acis.py
+++ b/scripts/chandra_acis.py
@@ -8,6 +8,8 @@
 
 """
 Determine the Chandra ACIS type for the given observation.
+
+TODO: move these methods to module `acis.py`
 """
 
 import argparse
@@ -17,15 +19,15 @@ import re
 from setup_pfiles import setup_pfiles
 
 
-def get_acis_type(infile):
+def get_acis_type(filepath):
     """
     Determine the Chandra ACIS type (``I`` or ``S``) according the
     active ACIS chips.
 
     Parameters
     ----------
-    infile : str
-        Filename of the FITS file
+    filepath : str
+        Path to the input FITS file
 
     Returns
     -------
@@ -34,7 +36,7 @@ def get_acis_type(infile):
     """
     subprocess.check_call(["punlearn", "dmkeypar"])
     detnam = subprocess.check_output([
-        "dmkeypar", "infile=%s" % infile, "keyword=DETNAM", "echo=yes"
+        "dmkeypar", "infile=%s" % filepath, "keyword=DETNAM", "echo=yes"
     ]).decode("utf-8").strip()
     if re.match(r"^ACIS-0123", detnam):
         return "I"
@@ -44,6 +46,31 @@ def get_acis_type(infile):
         raise ValueError("unknown chip combination: %s" % detnam)
 
 
+def get_chips(filepath, sep=":"):
+    """
+    Get the corresponding chips of interest according to the active ACIS type.
+
+    Parameters
+    ----------
+    filepath : str
+        Path to the input FITS file
+    sep : str, optional
+        Separator to join the chip ranges, e.g., 0:3, 0-3
+
+    Returns
+    -------
+    chips : str
+        ``0:3`` if ACIS-I, ``7`` if ACIS-S, otherwise, ``ValueError`` raised.
+    """
+    acis_type = get_acis_type(filepath)
+    if acis_type == "I":
+        return sep.join(["0", "3"])
+    elif acis_type == "S":
+        return "7"
+    else:
+        raise ValueError("unknown ACIS type")
+
+
 def main():
     parser = argparse.ArgumentParser(description="Determine Chandra ACIS type")
     parser.add_argument("-b", "--brief", dest="brief",