From 0f4f83e0795fd61795e102c77b5e1d5a9d7a5d9c Mon Sep 17 00:00:00 2001
From: Brett Smith <brettcsmith@brettcsmith.org>
Date: Wed, 27 Dec 2017 12:52:47 -0500
Subject: [PATCH] importers._csv: Refactor header reading into CSVImporterBase.

---
 import2ledger/importers/_csv.py     | 27 ++++++++++++++----
 import2ledger/importers/benevity.py | 44 ++++++++---------------------
 2 files changed, 34 insertions(+), 37 deletions(-)

diff --git a/import2ledger/importers/_csv.py b/import2ledger/importers/_csv.py
index 754c3fa..368471c 100644
--- a/import2ledger/importers/_csv.py
+++ b/import2ledger/importers/_csv.py
@@ -20,15 +20,32 @@ class CSVImporterBase:
     ENTRY_SEED = {}
     COPIED_FIELDS = {}
 
+    @classmethod
+    def _read_header_row(cls, row):
+        return {} if len(row) < cls._HEADER_MAX_LEN else None
+
+    @classmethod
+    def _read_header(cls, input_file):
+        cls._NEEDED_KEYS = cls.NEEDED_FIELDS.union(cls.COPIED_FIELDS)
+        cls._HEADER_MAX_LEN = len(cls._NEEDED_KEYS)
+        header = {}
+        row = None
+        for row in csv.reader(input_file):
+            row_data = cls._read_header_row(row)
+            if row_data is None:
+                break
+            else:
+                header.update(row_data)
+        return header, row
+
     @classmethod
     def can_import(cls, input_file):
-        in_csv = csv.reader(input_file)
-        fields = next(iter(in_csv), [])
-        return cls.NEEDED_FIELDS.union(cls.COPIED_FIELDS).issubset(fields)
+        _, fields = cls._read_header(input_file)
+        return cls._NEEDED_KEYS.issubset(fields or ())
 
     def __init__(self, input_file):
-        self.in_csv = csv.DictReader(input_file)
-        self.entry_seed = {}
+        self.entry_seed, fields = self._read_header(input_file)
+        self.in_csv = csv.DictReader(input_file, fields)
 
     def __iter__(self):
         for row in self.in_csv:
diff --git a/import2ledger/importers/benevity.py b/import2ledger/importers/benevity.py
index 4e5a34d..c304103 100644
--- a/import2ledger/importers/benevity.py
+++ b/import2ledger/importers/benevity.py
@@ -1,9 +1,12 @@
-import csv
-
 from . import _csv
 from .. import strparse
 
 class PaymentImporter(_csv.CSVImporterBase):
+    HEADER_FIELDS = {
+        'Currency': 'currency',
+        'Disbursement ID': 'disbursement_id',
+        'Reference': 'reference',
+    }
     DATE_FIELD = 'Date of Donation'
     NAME_FIELDS = ['Donor First Name', 'Donor Last Name']
     DECIMAL_FIELDS = {
@@ -28,37 +31,14 @@ class PaymentImporter(_csv.CSVImporterBase):
     NOT_SHARED = 'Not shared by donor'
 
     @classmethod
-    def _read_header(cls, source):
-        needed_keys = cls.NEEDED_FIELDS.union(cls.COPIED_FIELDS)
-        header = {}
-        for row in csv.reader(source):
-            row_len = len(row)
-            if row_len < 2:
-                pass
-            elif row_len == 2:
-                header[row[0]] = row[1]
-            elif needed_keys.issubset(row):
-                return header, csv.DictReader(source, row)
-            else:
-                break
-        raise ValueError("source is not a Benevity CSV")
-
-    @classmethod
-    def can_import(cls, input_file):
-        try:
-            header, _ = cls._read_header(input_file)
-        except ValueError:
-            return False
+    def _read_header_row(cls, row):
+        row_len = len(row)
+        if row_len > 2:
+            return None
+        elif row_len == 2 and row[0] in cls.HEADER_FIELDS:
+            return {cls.HEADER_FIELDS[row[0]]: row[1]}
         else:
-            return bool(header)
-
-    def __init__(self, input_file):
-        header, self.in_csv = self._read_header(input_file)
-        self.entry_seed = {
-            'currency': header['Currency'],
-            'disbursement_id': header['Disbursement ID'],
-            'reference': header['Payment Reference'],
-        }
+            return {}
 
     def _read_row(self, row):
         try: