From be7eda29e51287d362ae9e743f9667367a5179d3 Mon Sep 17 00:00:00 2001
From: BO ZHANG <bozhang@nao.cas.cn>
Date: Sat, 8 Jun 2024 16:34:11 +0800
Subject: [PATCH] add delete_section

---
 csst_common/io.py | 57 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)

diff --git a/csst_common/io.py b/csst_common/io.py
index b2cf06b..28cb065 100644
--- a/csst_common/io.py
+++ b/csst_common/io.py
@@ -8,7 +8,10 @@ Modified-History:
     2023-12-10, Bo Zhang, created
     2023-12-15, Bo Zhang, added verify_checksum and append_header, add module header
     2023-12-16, Bo Zhang, fixed a bug in finding the first key when reformatting
+    2024-06-08, Bo Zhang, added delete_section
 """
+
+import bisect
 import warnings
 from copy import deepcopy
 from typing import Optional
@@ -134,3 +137,57 @@ def reformat_header(
     h_copy.add_comment(comment, before=first_key)
     h_copy.add_comment("=" * 72, before=first_key)
     return h_copy
+
+
+def delete_section(
+    header: fits.Header,
+    title="WORLD COORDINATE SYSTEM INFORMATION",
+) -> fits.Header:
+    """
+    Delete a section from a fits header.
+
+    This function is used to delete the section of WCS information from the header.
+
+    Parameters
+    ----------
+    header: fits.Header
+        Header.
+    title: str
+        Title of the section to be deleted.
+
+    Returns
+    -------
+    fits.Header
+        Edited header.
+    """
+
+    # find sep lines
+    i_seps = []
+    for i_card, card in enumerate(header.cards):
+        if (
+            card.keyword == "COMMENT"
+            and isinstance(card.value, str)
+            and card.value.startswith("===")
+        ) or i_card == len(header.cards) - 1:
+            i_seps.append(i_card)
+
+    # find section title
+    i_section = -1
+    for i_card, card in enumerate(header.cards):
+        if card.keyword == "COMMENT" and card.value == title:
+            i_section = i_card
+            break
+    if i_section < 0:
+        raise ValueError(f"Title not found: `{title}`")
+
+    # find section start and stop
+    idx = bisect.bisect(i_seps, i_section)
+    i_section_start = i_seps[idx - 1]
+    i_section_stop = i_seps[idx + 1]
+
+    # delete keys in reverse order
+    print(f"Delete keys {i_section_start} to {i_section_stop} ...")
+    for i in range(i_section_stop - 1, i_section_start - 1, -1):
+        del header[i]
+
+    return header
-- 
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