Birthday problem

beancount_reds_plugins/effective_date/effective_date.py

@@ -16,7 +16,12 @@
 # to enable the older transaction-level hacky plugin, now renamed to effective_date_transaction
 # __plugins__ = ['effective_date', 'effective_date_transaction']
 
-LINK_FORMAT = 'edate-{date}-{random}'
+DEFAULT_FORMATS = {
+    'LINK_FORMAT': 'edate-{date}-{rand}',
+    'DATE_FORMAT': '%y%m%d',
+    'RANDOM_LEN': 3,
+}
+HEX_BASE = 16
 
 
 def has_valid_effective_date(posting):
@@ -44,18 +49,52 @@ def cleaned(p):
     return effective_date_entry
 
 
+def rand_counter(n=10, repr=int):
+    values = [x for x in range(n)]
+    random.shuffle(values)
+    i = 0
+
+    while i < n:
+        value = values[i]
+        i += 1
+        yield repr(value)
+
+
 def build_config(config):
+    # Config may contain more than just accounts, but the non-account
+    # configurations are not valid account names.
     holding_accts = {}
+    formats = {}
     if config:
         holding_accts = literal_eval(config)
+        formats = {k: holding_accts.pop(k, None) or v
+                   for k, v in DEFAULT_FORMATS.items()}
+
     if not holding_accts:
         if DEBUG:
             print("effective_date: Using default config", file=sys.stderr)
         holding_accts = {
                 'Expenses': {'earlier': 'Liabilities:Hold:Expenses', 'later': 'Assets:Hold:Expenses'},
                 'Income':   {'earlier': 'Assets:Hold:Income', 'later': 'Liabilities:Hold:Income'},
                 }
-    return holding_accts
+        formats = DEFAULT_FORMATS | formats
+
+    def hexformat(i):
+        return hex(i)[2:].zfill(formats['RANDOM_LEN'])
+
+    return holding_accts, formats, hexformat
+
+
+def make_link(entry_date, formats, hexformat, rand_gens):
+    date_str = entry_date.strftime(formats['DATE_FORMAT'])
+    # Fail collision test: rand_str = ''.join(random.choice(string.ascii_uppercase) for i in range(3))
+    if date_str not in rand_gens:
+        rand_gens[date_str] = rand_counter(
+            HEX_BASE**formats['RANDOM_LEN'], hexformat)
+    rand_str = next(rand_gens[date_str])
+
+    link = formats['LINK_FORMAT'].format(date=date_str, rand=rand_str)
+    return link
 
 
 def effective_date(entries, options_map, config):
@@ -73,8 +112,8 @@ def effective_date(entries, options_map, config):
     """
     start_time = time.time()
     errors = []
-    holding_accts = build_config(config)
-
+    holding_accts, formats, hexformat = build_config(config)
+    rand_gens = {}
     interesting_entries = []
     filtered_entries = []
     new_accounts = set()
@@ -94,9 +133,7 @@ def effective_date(entries, options_map, config):
     # entries, and thus links each set of effective date entries
     interesting_entries_linked = []
     for entry in interesting_entries:
-        rand_string = ''.join(random.choice(string.ascii_lowercase) for i in range(3))
-        date = str(entry.date).replace('-', '')[2:]
-        link = LINK_FORMAT.format(date=str(date), random=rand_string)
+        link = make_link(entry.date, formats, hexformat, rand_gens)
         new_entry = entry._replace(links=(entry.links or set()) | set([link]))
         interesting_entries_linked.append(new_entry)
 
@@ -261,7 +298,7 @@ def effective_date_transaction(entries, options_map, config):
 
         if found:
             rand_string = ''.join(random.choice(string.ascii_uppercase) for i in range(5))
-            link = LINK_FORMAT.format(rand_string)
+            link = DEFAULT_FORMATS['LINK_FORMAT'].format(rand_string)
             # modified_entry = data.entry_replace(entry, postings=modified_entry_postings,
             #                                     links=(entry.links or set()) | set([link]))
             modified_entry = entry._replace(postings=modified_entry_postings,