Implement client cost attribution

src/fin_hub/coupling/ops_hub.py

@@ -6,6 +6,8 @@ from collections import defaultdict
 from dataclasses import dataclass
 from typing import Iterable
 
+from fin_hub.attribution import optional_attribution
+
 
 @dataclass(frozen=True)
 class ServiceCostLine:
@@ -15,6 +17,19 @@ class ServiceCostLine:
     amount: float
     currency: str
     source: str
+    client_id: str | None = None
+    application_id: str | None = None
+    app_instance_id: str | None = None
+    cost_attribution_key: str | None = None
+
+    def __post_init__(self) -> None:
+        attribution = optional_attribution(
+            self.client_id, self.application_id, self.app_instance_id
+        )
+        expected_key = attribution.key if attribution else None
+        if self.cost_attribution_key not in (None, expected_key):
+            raise ValueError("cost_attribution_key does not match its attribution dimensions")
+        object.__setattr__(self, "cost_attribution_key", expected_key)
 
 
 def build_service_cost_report(
@@ -22,6 +37,7 @@ def build_service_cost_report(
 ) -> dict:
     by_service: dict[str, dict] = {}
     totals_by_month: dict[str, float] = defaultdict(float)
+    by_attribution: dict[tuple[str, str], dict] = {}
     for line in lines:
         bucket = by_service.setdefault(
             line.service_id,
@@ -37,11 +53,31 @@ def build_service_cost_report(
         bucket["months"][line.period_month] = month_total
         bucket["total"] += line.amount
         totals_by_month[line.period_month] += line.amount
+        key = (line.cost_attribution_key or "unattributed", line.currency)
+        attribution = by_attribution.setdefault(
+            key,
+            {
+                "cost_attribution_key": line.cost_attribution_key,
+                "client_id": line.client_id,
+                "application_id": line.application_id,
+                "app_instance_id": line.app_instance_id,
+                "currency": line.currency,
+                "months": {},
+                "total": 0.0,
+            },
+        )
+        attribution["months"][line.period_month] = (
+            attribution["months"].get(line.period_month, 0.0) + line.amount
+        )
+        attribution["total"] += line.amount
     services = sorted(by_service.values(), key=lambda item: item["total"], reverse=True)
     return {
         "source_hub": "fin-hub",
         "target_hub": "ops-hub",
         "signal": "service_cost_attribution",
         "services": services,
+        "attributions": sorted(
+            by_attribution.values(), key=lambda item: item["total"], reverse=True
+        ),
         "totals_by_month": dict(sorted(totals_by_month.items())),
-    }
+    }