feat(fusion_accounting_reports): partner-grouped engine method

Adds engine.compute_partner_grouped(period, account_type=...) that
returns per-partner aggregations with aging buckets (current/1-30/
31-60/61-90/90+). SQL-direct for performance — single GROUP BY query
with conditional sum per bucket.

Foundation for the 3 partner-grouped reports landing in commit 3:
Aged Receivable, Aged Payable, Partner Ledger.

Made-with: Cursor

fusion_accounting_reports/models/fusion_report_engine.py

@@ -14,7 +14,7 @@ Internal pipeline (per report run):
 """
 
 import logging
-from datetime import date
+from datetime import date, timedelta
 
 from odoo import _, api, models
 from odoo.exceptions import ValidationError
@@ -118,6 +118,130 @@ class FusionReportEngine(models.AbstractModel):
             limit=500,
         )
 
+    @api.model
+    def compute_partner_grouped(
+        self, period: Period, *, account_type: str = 'asset_receivable',
+        comparison: str = 'none', company_id: int | None = None,
+    ) -> dict:
+        """Per-partner aggregation report (Aged Receivable, Aged Payable,
+        Partner Ledger).
+
+        Returns a dict with ``rows`` = list of partner-level aggregates.
+        Each row has the partner_id, partner_name, total residual, and
+        aging buckets: current / 1-30 / 31-60 / 61-90 / 90+ days past
+        ``period.date_to``.
+
+        SQL-direct for performance: a single GROUP BY query with conditional
+        sum per bucket. Only un-reconciled, posted lines with non-zero
+        residual at the as-of date are included.
+        """
+        company_id = company_id or self.env.company.id
+
+        accounts = self.env['account.account'].sudo().search([
+            ('account_type', '=', account_type),
+            ('company_ids', 'in', company_id),
+        ])
+        if not accounts:
+            return {
+                'report_type': 'partner_grouped',
+                'account_type': account_type,
+                'period': {
+                    'date_from': str(period.date_from),
+                    'date_to': str(period.date_to),
+                    'label': period.label,
+                },
+                'rows': [],
+                'total': 0.0,
+                'partner_count': 0,
+            }
+
+        as_of = period.date_to
+        d30 = as_of - timedelta(days=30)
+        d60 = as_of - timedelta(days=60)
+        d90 = as_of - timedelta(days=90)
+
+        self.env.cr.execute(
+            """
+            SELECT
+                COALESCE(p.id, 0) AS partner_id,
+                COALESCE(p.name, '(no partner)') AS partner_name,
+                SUM(aml.amount_residual) AS total_residual,
+                SUM(CASE
+                        WHEN aml.date_maturity >= %s
+                          OR aml.date_maturity IS NULL
+                        THEN aml.amount_residual ELSE 0
+                    END) AS bucket_current,
+                SUM(CASE
+                        WHEN aml.date_maturity < %s
+                         AND aml.date_maturity >= %s
+                        THEN aml.amount_residual ELSE 0
+                    END) AS bucket_1_30,
+                SUM(CASE
+                        WHEN aml.date_maturity < %s
+                         AND aml.date_maturity >= %s
+                        THEN aml.amount_residual ELSE 0
+                    END) AS bucket_31_60,
+                SUM(CASE
+                        WHEN aml.date_maturity < %s
+                         AND aml.date_maturity >= %s
+                        THEN aml.amount_residual ELSE 0
+                    END) AS bucket_61_90,
+                SUM(CASE
+                        WHEN aml.date_maturity < %s
+                        THEN aml.amount_residual ELSE 0
+                    END) AS bucket_90_plus,
+                COUNT(*) AS line_count
+            FROM account_move_line aml
+            LEFT JOIN res_partner p ON p.id = aml.partner_id
+            WHERE aml.account_id = ANY(%s)
+              AND aml.parent_state = 'posted'
+              AND aml.reconciled = false
+              AND aml.amount_residual != 0
+              AND aml.company_id = %s
+              AND aml.date <= %s
+            GROUP BY p.id, p.name
+            HAVING SUM(aml.amount_residual) != 0
+            ORDER BY total_residual DESC
+            """,
+            (
+                as_of,
+                as_of, d30,
+                d30, d60,
+                d60, d90,
+                d90,
+                list(accounts.ids), company_id, as_of,
+            ),
+        )
+
+        rows = []
+        for r in self.env.cr.dictfetchall():
+            rows.append({
+                'partner_id': r['partner_id'] or False,
+                'partner_name': r['partner_name'] or '(no partner)',
+                'total': float(r['total_residual'] or 0),
+                'bucket_current': float(r['bucket_current'] or 0),
+                'bucket_1_30': float(r['bucket_1_30'] or 0),
+                'bucket_31_60': float(r['bucket_31_60'] or 0),
+                'bucket_61_90': float(r['bucket_61_90'] or 0),
+                'bucket_90_plus': float(r['bucket_90_plus'] or 0),
+                'line_count': r['line_count'],
+            })
+
+        total = sum(r['total'] for r in rows)
+        return {
+            'report_type': 'partner_grouped',
+            'account_type': account_type,
+            'period': {
+                'date_from': str(period.date_from),
+                'date_to': str(period.date_to),
+                'label': period.label,
+            },
+            'company_id': company_id,
+            'rows': rows,
+            'total': total,
+            'partner_count': len(rows),
+        }
+
     # ============================================================
     # PRIVATE HELPERS
     # ============================================================

fusion_accounting_reports/tests/test_fusion_report_engine.py

@@ -90,6 +90,23 @@ class TestFusionReportEngine(TransactionCase):
         )
         self.assertIsInstance(rows, list)
 
+    def test_compute_partner_grouped_receivable(self):
+        period = Period(date(2025, 1, 1), date(2025, 12, 31), 'Test')
+        result = self.env['fusion.report.engine'].compute_partner_grouped(
+            period, account_type='asset_receivable',
+        )
+        self.assertEqual(result['report_type'], 'partner_grouped')
+        self.assertEqual(result['account_type'], 'asset_receivable')
+        self.assertIn('rows', result)
+        self.assertIn('total', result)
+        self.assertIn('partner_count', result)
+        if result['rows']:
+            for key in (
+                'partner_name', 'total', 'bucket_current', 'bucket_1_30',
+                'bucket_31_60', 'bucket_61_90', 'bucket_90_plus',
+            ):
+                self.assertIn(key, result['rows'][0])
+
     def test_no_report_raises_validation_error(self):
         period = Period(date(2026, 1, 1), date(2026, 12, 31), 'Test 2026')
         # Inactivate any pre-existing GL definitions so the lookup