Added some more documentation to ETL scripts

stm_etl/AS400_Invoice_Interface.py

@@ -1,9 +1,44 @@
 '''
-Attempting to automatically close invoices in the AS400 using data from Jomar.. weee...
+AS400 Invoice Interface - Jomar to AS400 Invoice Synchronization
 
 Created on: 2017-11-20
-
 @author: Wes
+
+PURPOSE:
+    Pushes invoice data from Jomar ERP into the AS400 so that invoices can be
+    automatically closed on the AS400 side without manual entry.
+
+USAGE:
+    python AS400_Invoice_Interface.py <date>
+
+    The date argument (format matching Jomar's RDATLS field) selects which
+    invoices to extract. Typically run daily for the current invoice date.
+
+PROCESSING LOGIC:
+    1. Extract from Jomar (MSSQL via SQLAlchemy):
+        - Query joins invoice rolls (txuyre01), roll/tag master (TXRYRT00),
+          order header (TXUYUV00), and shipment table (TXUYLS00) to build a
+          row set of: invoice number, invoice line, ticket, AS400 order number,
+          invoiced yards, finished yards, ship date, and invoice date.
+        - Only pulls invoices matching the supplied date.
+        - Excludes FREIGHT items and sales return (SR) lines.
+
+    2. Load into AS400 (pyodbc via iSeries ODBC):
+        - Backs up existing rows from STMDATA.JSIINV to WES.JSIINV_BAK
+          (only when running against production library).
+        - Deletes all current rows from STMDATA.JSIINV (staging table).
+        - Inserts each extracted row into STMDATA.JSIINV.
+        - Rows missing a ticket number, order number, or with non-numeric
+          tickets (e.g. credits) are skipped and collected as exceptions.
+
+    3. Exception handling:
+        - Exception rows are written to a temporary CSV (AII_ERRORS_{date}.csv).
+        - CSV is emailed to RECIPIENTS, then deleted from disk.
+
+OUTPUT:
+    - STMDATA.JSIINV populated on the AS400 for downstream invoice closure.
+    - Log file at D:\AS400_Invoice_Interface.log
+    - Email alert with exception CSV if any rows were skipped.
 '''
 import pyodbc, time, logging, sys, os, StringIO, csv, sqlite3
 from sqlalchemy import create_engine