Feat: add CSV file parsing support (#5989)

### What problem does this PR solve?

Add CSV file parsing support #4552, #5849, #5870

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

deepdoc/parser/excel_parser.py

 #
 
 import logging
-from openpyxl import load_workbook, Workbook
 import sys
 from io import BytesIO
 
-from rag.nlp import find_codec
-
 import pandas as pd
+from openpyxl import Workbook, load_workbook
+
+from rag.nlp import find_codec
 
 
 class RAGFlowExcelParser:
+
     @staticmethod
     def _load_excel_to_workbook(file_like_object):
+        if isinstance(file_like_object, bytes):
+            file_like_object = BytesIO(file_like_object)
+
+        # Read first 4 bytes to determine file type
+        file_like_object.seek(0)
+        file_head = file_like_object.read(4)
+        file_like_object.seek(0)
+
+        if not (file_head.startswith(b'PK\x03\x04') or file_head.startswith(b'\xD0\xCF\x11\xE0')):
+            logging.info("****wxy: Not an Excel file, converting CSV to Excel Workbook")
+
+            try:
+                file_like_object.seek(0)
+                df = pd.read_csv(file_like_object)
+                return RAGFlowExcelParser._dataframe_to_workbook(df)
+
+            except Exception as e_csv:
+                raise Exception(f"****wxy: Failed to parse CSV and convert to Excel Workbook: {e_csv}")
+
         try:
             return load_workbook(file_like_object)
         except Exception as e:
             logging.info(f"****wxy: openpyxl load error: {e}, try pandas instead")
             try:
+                file_like_object.seek(0)
                 df = pd.read_excel(file_like_object)
-                wb = Workbook()
-                ws = wb.active
-                ws.title = "Data"
-                for col_num, column_name in enumerate(df.columns, 1):
-                    ws.cell(row=1, column=col_num, value=column_name)
-                for row_num, row in enumerate(df.values, 2):
-                    for col_num, value in enumerate(row, 1):
-                        ws.cell(row=row_num, column=col_num, value=value)
-                return wb
+                return RAGFlowExcelParser._dataframe_to_workbook(df)
             except Exception as e_pandas:
-                raise Exception(f"****wxy: pandas read error: {e_pandas}, original openpyxl error: {e}")
+                raise Exception(f"****wxy: pandas.read_excel error: {e_pandas}, original openpyxl error: {e}")
+
+    @staticmethod
+    def _dataframe_to_workbook(df):
+        wb = Workbook()
+        ws = wb.active
+        ws.title = "Data"
+
+        for col_num, column_name in enumerate(df.columns, 1):
+            ws.cell(row=1, column=col_num, value=column_name)
+
+        for row_num, row in enumerate(df.values, 2):
+            for col_num, value in enumerate(row, 1):
+                ws.cell(row=row_num, column=col_num, value=value)
+
+        return wb
 
     def html(self, fnm, chunk_rows=256):
         file_like_object = BytesIO(fnm) if not isinstance(fnm, str) else fnm
                 tb += f"<table><caption>{sheetname}</caption>"
                 tb += tb_rows_0
                 for r in list(
-                  rows[1 + chunk_i * chunk_rows: 1 + (chunk_i + 1) * chunk_rows]
+                    rows[1 + chunk_i * chunk_rows: 1 + (chunk_i + 1) * chunk_rows]
                 ):
                     tb += "<tr>"
                     for i, c in enumerate(r):
 if __name__ == "__main__":
     psr = RAGFlowExcelParser()
     psr(sys.argv[1])
-

rag/app/naive.py

                                       callback=callback)
         res = tokenize_table(tables, doc, is_english)
 
-    elif re.search(r"\.xlsx?$", filename, re.IGNORECASE):
+    elif re.search(r"\.(csv|xlsx?)$", filename, re.IGNORECASE):
         callback(0.1, "Start to parse.")
         excel_parser = ExcelParser()
         if parser_config.get("html4excel"):
 if __name__ == "__main__":
     import sys
 
-
     def dummy(prog=None, msg=""):
         pass
 
-
     chunk(sys.argv[1], from_page=0, to_page=10, callback=dummy)