Add a one billing period free trial

This will run a empty metering on the first bill and archive the
usage records. After the first billing period the adapter will
begin billing usage as normal.

csp_billing_adapter/adapter.py

@@ -259,15 +259,29 @@ def event_loop_handler(
         cache['next_bill_time']
     )
 
+    trial_remaining = cache.get('trial_remaining', 0)
+
     if now >= string_to_date(cache['next_bill_time']):
-        log.info('Attempt a billing cycle update')
-        process_metering(
-            hook,
-            config,
-            now,
-            cache,
-            csp_config
-        )
+        if trial_remaining > 0:
+            log.info('Attempt a free trial billing cycle update')
+            process_metering(
+                hook,
+                config,
+                now,
+                cache,
+                csp_config,
+                empty_metering=True,
+                free_trial=True
+            )
+        else:
+            log.info('Attempt a billing cycle update')
+            process_metering(
+                hook,
+                config,
+                now,
+                cache,
+                csp_config
+            )
     elif now >= string_to_date(cache['next_reporting_time']):
         log.info('Attempt a reporting cycle update')
         process_metering(

csp_billing_adapter/bill_utils.py

@@ -485,7 +485,8 @@ def process_metering(
     now: datetime.datetime,
     cache: dict,
     csp_config: dict,
-    empty_metering: bool = False
+    empty_metering: bool = False,
+    free_trial: bool = False
 ) -> None:
     """
     Handle the CSP metering process, updating the csp_config and cache
@@ -628,7 +629,7 @@ def process_metering(
         csp_config['billing_api_access_ok'] = True
         csp_config['expire'] = next_reporting_time
 
-        if not empty_metering:
+        if not empty_metering or free_trial:
             # Usage was billed
             next_bill_time = date_to_string(
                 get_next_bill_time(
@@ -674,3 +675,6 @@ def process_metering(
             except Exception as error:
                 # Non-fatal error is only logged
                 log.exception(error)
+
+        if free_trial:
+            cache['trial_remaining'] = cache['trial_remaining'] - 1

csp_billing_adapter/csp_cache.py

@@ -60,7 +60,8 @@ def create_cache(hook, config: Config) -> dict:
         'next_bill_time': date_to_string(next_bill_time),
         'next_reporting_time': date_to_string(next_reporting_time),
         'usage_records': [],
-        'last_bill': {}
+        'last_bill': {},
+        'trial_remaining': 1
     }
 
     try:

tests/unit/test_adapter.py

@@ -251,6 +251,7 @@ def test_event_loop_handler(
     assert cache['usage_records'] != []
     assert len(cache['usage_records']) == 1
     assert cache['last_bill'] == {}
+    assert cache['trial_remaining'] == 1
 
     # Similarly the meter_billing() call should have succeeded
     # not triggered the generation of a new bill.
@@ -324,6 +325,7 @@ def test_event_loop_handler(
     assert cache != {}
     assert cache['usage_records'] == []
     assert cache['last_bill'] != {}
+    assert cache['trial_remaining'] == 0
     assert 'dimensions' in cache['last_bill']
     assert 'billing_status' in cache['last_bill']
     assert 'metering_time' in cache['last_bill']