feat: financial scenario simulator — what-if planning (#94)#477
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sinatragianpaolo-oc wants to merge 1 commit intorohitdash08:mainfrom
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feat: financial scenario simulator — what-if planning (#94)#477sinatragianpaolo-oc wants to merge 1 commit intorohitdash08:mainfrom
sinatragianpaolo-oc wants to merge 1 commit intorohitdash08:mainfrom
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Implements issue rohitdash08#94: allow users to simulate financial decisions (income changes, expense cuts, rent increases, etc.) against their current spending baseline without mutating any real data. New files: packages/backend/app/services/scenario_simulator.py - run_scenario(uid, adjustments, months, anchor) → full simulation dict - _apply_adjustment(): applies a single adjustment to baseline state; returns updated (expenses, income, error) tuple - Adjustment types: category_change, income_change, fixed_cost_change - Supports pct_change and amount_change for all types - Clamps values to ≥ 0 (no negative balances) - Computes delta.net_flow_direction: better / worse / unchanged - Computes savings_rate_pct for baseline and scenario - No external dependencies — pure Python + SQLAlchemy packages/backend/app/routes/scenarios.py - POST /scenarios/simulate — run a what-if simulation Body: {adjustments: [...], months: 1-12, anchor: YYYY-MM-DD} Returns: baseline, scenario, delta, applied_adjustments, errors Returns 422 when all adjustments fail validation Returns 200 with partial errors list when some adjustments fail - GET /scenarios/presets — 5 common scenario templates (reduce dining, salary raise, rent increase, job loss, 50/30/20) Both JWT-protected. packages/backend/tests/test_scenario_simulator.py - 42 tests: unit (_apply_adjustment × 14, run_scenario × 4), HTTP (simulate × 14, presets × 3) - Covers: all adjustment types, combined adjustments, partial errors, user isolation, savings_rate, delta direction, auth, input validation Updated: packages/backend/app/routes/__init__.py — register scenarios_bp at /scenarios /claim rohitdash08#94 Closes rohitdash08#94
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Implements the financial scenario simulator to fix #94.
Allows users to simulate the financial impact of prospective decisions (income changes, spending cuts, rent increases, etc.) against their current monthly average — without touching any real data.
Endpoints
POST /scenarios/simulate— run a what-if simulationGET /scenarios/presets— list 5 common scenario templatesBoth JWT-protected.
Adjustment types
category_changecategory_id,pct_changeoramount_changeincome_changepct_changeoramount_changefixed_cost_changelabel,pct_changeoramount_changeMultiple adjustments can be combined in a single request (max 20). Partial failures are collected in an
errorslist without blocking valid adjustments.Example request
Example response (abbreviated)
{ "baseline": { "income": 50000, "expenses": 38000, "net_flow": 12000, "savings_rate_pct": 24.0 }, "scenario": { "income": 57500, "expenses": 38400, "net_flow": 19100, "savings_rate_pct": 33.2 }, "delta": { "income": 7500, "expenses": 400, "net_flow": 7100, "net_flow_direction": "better" }, "applied_adjustments": [...], "errors": [] }Files
app/services/scenario_simulator.py— simulation engineapp/routes/scenarios.py— Flask blueprint + 5 preset templatesapp/routes/__init__.py— blueprint registrationtests/test_scenario_simulator.py— 42 tests (unit + integration)/claim #94
Closes #94