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+# Pet Insurance — Code Challenge
+
+A Java coding challenge implementing the calculation logic for a pet health insurance product.
+
+## Build & test
+
+Requires **Java 25** and **Maven 3.x**.
+
+```bash
+# Compile
+mvn compile
+
+# Run all tests
+mvn test
+
+# Full build
+mvn package
+```
+
+## Project structure
+
+```
+src/
+├── main/
+│   ├── java/com/pfefferminzia/petinsurance/
+│   │   ├── animals/          # Animal sealed interface + Dog, Cat, SmallAnimal records
+│   │   ├── calculations/     # InsuranceContract, Calculations, CalculationResult
+│   │   ├── exception/        # InvalidInsuranceContractException
+│   │   └── tariffs/          # TariffOption, TariffConfiguration, TariffLoader
+│   └── resources/
+│       └── tariff.properties # Runtime tariff configuration
+└── test/
+    ├── java/.../calculations/
+    │   └── CalculationsTest.java
+    └── resources/
+        └── tariff.properties # Test tariff configuration (mirrors main)
+```
+
+## Architecture
+
+### Animals
+
+`Animal` is a sealed interface (`permits Dog, Cat, SmallAnimal`). Each type is an immutable record:
+
+- `Dog(LocalDate birthday, String breed)` — identifies with species key `"DOG"`
+- `Cat(LocalDate birthday)` — species key `"CAT"`
+- `SmallAnimal(LocalDate birthday)` — species key `"SMALLANIMAL"`
+
+The interface exposes `birthday()` and `speciesKey()`. Base insurance sums are **not** hardcoded in the animal types; they live in configuration (see below).
+
+### Tariff configuration (`tariff.properties`)
+
+All tariff data is loaded from `tariff.properties` at startup via `TariffLoader.loadFromFile()`, which produces a `TariffConfiguration` record. This makes adding new tariffs, animals, age brackets, or breed adjustments a config-only change.
+
+```properties
+# Animal base insurance sums
+baseSum.DOG=2500.00
+baseSum.CAT=2000.00
+baseSum.SMALLANIMAL=1000.00
+
+# Tariffs: factor,availableFromDate
+tariffs.KOMPAKT=1.0,1970-01-01
+tariffs.OPTIMAL=1.2,1970-01-01
+tariffs.PREMIUM=1.4,2026-07-01
+
+# Age-based premium factors (≤ age → factor; elderlyFactor covers > 7)
+age.2=0.20
+age.5=0.25
+age.7=0.28
+elderlyFactor=0.30
+
+# Dog breed surcharge (positive) / discount (negative)
+breed.DACKEL=-0.1
+breed.BERNHARDINER=0.1
+```
+
+`TariffConfiguration.getTariffFactor(tariffName, startDate)` throws `IllegalStateException` if the chosen tariff is not yet available on the given start date (e.g. PREMIUM before 2026-07-01).
+
+### Calculation flow
+
+1. Build an `InsuranceContract(animal, insuranceStartDate, tariffName)`. The record constructor validates all fields eagerly and throws `InvalidInsuranceContractException` collecting all violations.
+2. Call `Calculations.calculateInsuranceSumAndYearlyPremium(contract)`, which returns a `CalculationResult(insuranceSum, yearlyPremium)`.
+
+**Insurance sum** = `baseSum(animal) × tariffFactor`
+
+**Yearly premium** = `insuranceSum × ageFactor × (1 + breedFactor)`
+
+- `ageFactor` is looked up from the age bracket table based on exact years between `birthday` and `insuranceStartDate`.
+- `breedFactor` only applies to `Dog`; all other animals use 0 (no adjustment).
+
+### Worked examples
+
+| Animal                      | Insurance sum | Yearly premium |
+|-----------------------------|--------------|----------------|
+| Husky, 7y, PREMIUM          | 3500         | 980            |
+| Dackel, 7y, PREMIUM         | 3500         | 882            |
+| Bernhardiner, 7y, PREMIUM   | 3500         | 1078           |
+| Cat, 3y, OPTIMAL            | 2400         | 600            |
+| SmallAnimal, 1y, KOMPAKT    | 1000         | 200            |
+
+All five examples are covered by `CalculationsTest`.
+
+## Extensibility
+
+- **New animal type** — add a record implementing `Animal`, register its base sum in `tariff.properties`.
+- **New tariff** — add one line to `tariff.properties` with a factor and availability date.
+- **New breed adjustment** — add one line to the `breed.*` section.
+- **New age bracket** — add one `age.N` entry; `TariffConfiguration.getAgeFactor` uses a `NavigableMap` ceiling lookup so ordering is automatic.
+- **New calculation** — extend `Calculations` or add a new method; `CalculationResult` can be widened to carry additional fields.