BaseballNumber.java

package baseball.model;


import java.util.*;

public class BaseballNumber {
    static final int LENGTH = 3;
    private final List<Integer> digits;

    private BaseballNumber(List<Integer> digits) {
        this.digits = List.copyOf(digits);
    }

    public static BaseballNumber fromString(String raw) {
        String input = raw.trim();
        validate(input);

        List<Integer> digits = new ArrayList<>();
        for (char c : input.toCharArray()) {
            digits.add(c - '0');
        }
        return new BaseballNumber(digits);
    }

    public static BaseballNumber random() {
        List<Integer> pool = new ArrayList<>();
        for (int i = 1; i <= 9; i++) {
            pool.add(i);
        }
        Collections.shuffle(pool);
        return new BaseballNumber(pool.subList(0, LENGTH));
    }

    private static void validate(String input) {
        validateLength(input);
        validateElements(input);
    }

    private static void validateLength(String input) {
        if (input.length() != LENGTH) {
            throw new IllegalArgumentException("입력 숫자는 " + LENGTH + "자리여야 합니다.");
        }
    }

    private static void validateElements(String input) {
        Set<Character> uniqueChars = new HashSet<>();
        for (char c : input.toCharArray()) {
            validateRange(c);
            validateUniqueness(uniqueChars, c);
            uniqueChars.add(c);
        }
    }

    private static void validateRange(char c) {
        if (c < '1' || c > '9') {
            throw new IllegalArgumentException("1 에서 9 사이의 숫자만 입력 가능합니다.");
        }
    }

    private static void validateUniqueness(Set<Character> uniqueChars, char c) {
        if (uniqueChars.contains(c)) {
            throw new IllegalArgumentException("중복되지 않은 숫자여야 합니다.");
        }
    }

    public int size() {
        return digits.size();
    }

    public int digitAt(int index) {
        return digits.get(index);
    }

    public boolean contains(int digit) {
        return digits.contains(digit);
    }
}