fire-planner/fire_planner/api/schemas.py

"""Pydantic response/request schemas for the HTTP API.

Mirror the SQLAlchemy ORM but keep them de-coupled — the API surface is a
contract for the frontend; we don't want migrations to silently change
JSON shape.
"""
from __future__ import annotations

from datetime import date, datetime
from decimal import Decimal
from typing import Any

from pydantic import BaseModel, ConfigDict, Field


class _Base(BaseModel):
    model_config = ConfigDict(from_attributes=True)


# ── scenarios ────────────────────────────────────────────────────────


class ScenarioOut(_Base):
    id: int
    external_id: str
    kind: str
    name: str | None
    description: str | None
    parent_scenario_id: int | None
    jurisdiction: str
    strategy: str
    leave_uk_year: int
    glide_path: str
    spending_gbp: Decimal
    horizon_years: int
    nw_seed_gbp: Decimal
    savings_per_year_gbp: Decimal
    config_json: dict[str, Any]
    created_at: datetime


class ScenarioCreate(BaseModel):
    """Body for POST /scenarios — user-defined scenario."""
    name: str = Field(min_length=1, max_length=200)
    description: str | None = None
    parent_scenario_id: int | None = None
    jurisdiction: str
    strategy: str
    leave_uk_year: int = Field(ge=0, le=60)
    glide_path: str
    spending_gbp: Decimal = Field(gt=0)
    horizon_years: int = Field(ge=5, le=100, default=60)
    nw_seed_gbp: Decimal = Field(ge=0)
    savings_per_year_gbp: Decimal = Field(ge=0, default=Decimal("0"))
    config_json: dict[str, Any] = Field(default_factory=dict)


class ScenarioPatch(BaseModel):
    """Body for PATCH /scenarios/{id} — all fields optional."""
    name: str | None = None
    description: str | None = None
    jurisdiction: str | None = None
    strategy: str | None = None
    leave_uk_year: int | None = None
    glide_path: str | None = None
    spending_gbp: Decimal | None = None
    horizon_years: int | None = None
    nw_seed_gbp: Decimal | None = None
    savings_per_year_gbp: Decimal | None = None
    config_json: dict[str, Any] | None = None


# ── projections ──────────────────────────────────────────────────────


class ProjectionPoint(_Base):
    year_idx: int
    p10_portfolio_gbp: Decimal
    p25_portfolio_gbp: Decimal
    p50_portfolio_gbp: Decimal
    p75_portfolio_gbp: Decimal
    p90_portfolio_gbp: Decimal
    p50_withdrawal_gbp: Decimal
    p50_tax_gbp: Decimal
    survival_rate: Decimal


class ScenarioProjection(BaseModel):
    """Latest MC run + per-year fan-chart series for a scenario."""
    scenario_id: int
    external_id: str
    mc_run_id: int
    run_at: datetime
    n_paths: int
    success_rate: Decimal
    p10_ending_gbp: Decimal
    p50_ending_gbp: Decimal
    p90_ending_gbp: Decimal
    median_lifetime_tax_gbp: Decimal
    median_years_to_ruin: Decimal | None
    yearly: list[ProjectionPoint]


# ── net worth ────────────────────────────────────────────────────────


class AccountSnapshotOut(_Base):
    account_id: str
    account_name: str
    account_type: str
    currency: str
    snapshot_date: date
    market_value: Decimal
    market_value_gbp: Decimal
    cost_basis_gbp: Decimal | None


class NetWorthCurrent(BaseModel):
    """Snapshot at one point in time (latest by default)."""
    snapshot_date: date
    total_gbp: Decimal
    accounts: list[AccountSnapshotOut]


class NetWorthHistoryPoint(BaseModel):
    snapshot_date: date
    total_gbp: Decimal
    by_account: dict[str, Decimal]


class NetWorthHistory(BaseModel):
    """Per-day NW totals + per-account breakdown for a stacked area chart."""
    points: list[NetWorthHistoryPoint]


# ── life events ──────────────────────────────────────────────────────


class LifeEventOut(_Base):
    id: int
    scenario_id: int
    kind: str
    name: str
    year_start: int
    year_end: int | None
    delta_gbp_per_year: Decimal
    one_time_amount_gbp: Decimal | None
    enabled: bool
    payload: dict[str, Any] | None
    created_at: datetime


class LifeEventCreate(BaseModel):
    kind: str
    name: str = Field(min_length=1, max_length=200)
    year_start: int = Field(ge=0, le=100)
    year_end: int | None = Field(default=None, ge=0, le=100)
    delta_gbp_per_year: Decimal = Decimal("0")
    one_time_amount_gbp: Decimal | None = None
    enabled: bool = True
    payload: dict[str, Any] | None = None


class LifeEventPatch(BaseModel):
    kind: str | None = None
    name: str | None = None
    year_start: int | None = None
    year_end: int | None = None
    delta_gbp_per_year: Decimal | None = None
    one_time_amount_gbp: Decimal | None = None
    enabled: bool | None = None
    payload: dict[str, Any] | None = None


# ── goals ────────────────────────────────────────────────────────────


class GoalOut(_Base):
    id: int
    scenario_id: int
    kind: str
    name: str
    target_amount_gbp: Decimal | None
    target_year: int | None
    comparator: str
    success_threshold: Decimal
    enabled: bool
    payload: dict[str, Any] | None
    created_at: datetime


class GoalCreate(BaseModel):
    kind: str
    name: str = Field(min_length=1, max_length=200)
    target_amount_gbp: Decimal | None = None
    target_year: int | None = Field(default=None, ge=0, le=100)
    comparator: str = ">="
    success_threshold: Decimal = Field(default=Decimal("0.95"), ge=0, le=1)
    enabled: bool = True
    payload: dict[str, Any] | None = None


# ── simulate / compare ───────────────────────────────────────────────


class SimulateRequest(BaseModel):
    """Sync, non-persisted simulate. Used by the React UI for what-if."""
    jurisdiction: str
    strategy: str
    leave_uk_year: int = Field(ge=0, le=60)
    glide_path: str = "rising"
    spending_gbp: Decimal = Field(gt=0)
    nw_seed_gbp: Decimal = Field(ge=0)
    savings_per_year_gbp: Decimal = Decimal("0")
    horizon_years: int = Field(ge=5, le=100, default=60)
    floor_gbp: Decimal | None = None
    n_paths: int = Field(ge=100, le=50_000, default=5_000)
    seed: int = 42


class SimulateResult(BaseModel):
    success_rate: Decimal
    p10_ending_gbp: Decimal
    p50_ending_gbp: Decimal
    p90_ending_gbp: Decimal
    median_lifetime_tax_gbp: Decimal
    median_years_to_ruin: Decimal | None
    elapsed_seconds: Decimal
    yearly: list[ProjectionPoint]


class CompareRequest(BaseModel):
    scenarios: list[SimulateRequest] = Field(min_length=2, max_length=5)


class CompareResult(BaseModel):
    results: list[SimulateResult]