first commit

app/models.py

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+from __future__ import annotations
+
+from enum import Enum
+from typing import Literal
+from pydantic import BaseModel, Field
+
+
+class InstallmentType(str, Enum):
+    equal = "equal"
+    decreasing = "decreasing"
+
+
+class OverpaymentEffect(str, Enum):
+    shorten = "shorten"
+    lower_payment = "lower_payment"
+
+
+class RateChange(BaseModel):
+    month: int = Field(ge=1, description="Miesiac od startu kredytu")
+    annual_rate: float = Field(ge=0, le=30, description="Roczne oprocentowanie procentowo")
+
+
+class Overpayment(BaseModel):
+    month: int = Field(ge=1)
+    amount: float = Field(gt=0)
+    repeat: Literal["once", "monthly", "yearly"] = "once"
+    until_month: int | None = Field(default=None, ge=1)
+
+
+class SimulationRequest(BaseModel):
+    principal: float = Field(gt=0)
+    years: int = Field(ge=1, le=50)
+    margin: float = Field(ge=0, le=20, default=2.0)
+    base_rate: float = Field(ge=0, le=30, default=5.75)
+    installment_type: InstallmentType = InstallmentType.equal
+    overpayment_effect: OverpaymentEffect = OverpaymentEffect.shorten
+    rate_changes: list[RateChange] = Field(default_factory=list)
+    overpayments: list[Overpayment] = Field(default_factory=list)
+
+
+class ScheduleRow(BaseModel):
+    month: int
+    rate: float
+    payment: float
+    principal_part: float
+    interest_part: float
+    overpayment: float
+    remaining: float
+
+
+class Summary(BaseModel):
+    months: int
+    total_paid: float
+    total_interest: float
+    total_overpayment: float
+    interest_saved: float
+    months_saved: int
+    baseline_interest: float
+    baseline_months: int
+    average_payment: float
+    max_payment: float
+
+
+class SimulationResponse(BaseModel):
+    schedule: list[ScheduleRow]
+    summary: Summary