Merge branch 'main' of https://git.joeac.net/joeac/schist

1 files changed, 26 insertions, 0 deletions

diff --git a/requirements/catalogue/req-030.md b/requirements/catalogue/req-030.md
new file mode 100644
index 0000000..e09a281
--- /dev/null
+++ b/requirements/catalogue/req-030.md
@@ -0,0 +1,26 @@
+# req-030
+
+Schist must implement the procedure described below as `calculate_bucket_balance`.
+
+## calculate_bucket_balance
+
+Inputs:
+
+-   A bucket name, `name`
+
+1. If no bucket exists with the name, `name`, then return empty.
+2. If more than one bucket exists with the name, `name`, then panic.
+3. Let `bucket` be the bucket with the given name.
+4. Let `cache_key = bucket.balance_cache_key`.
+5. Let `is_up_to_date` be the result of the procedure,
+   `is_bucket_balance_up_to_date(bucket)`, as described in req-035.
+6. If `is_up_to_date = TRUE`, then return `bucket.balance`.
+7. Carry out the procedure, `update_bucket_drips(bucket)`, as described in
+   req-037.
+8. Let `transaction_sum` be the sum over the property, `amount`, of all
+   transactions `t` such that `t.bucket_id = bucket.id`.
+9.  Let `drip_sum` be the sum over the property, `amount`, of all drips `d` such
+   that `d.bucket_id = bucket.id`.
+10. Return `drip_sum - transaction_sum`.
+
+Source: req-029