Mini-challenge: Bộ kiểm thực mượn ấn phẩm với custom exception

import java.util.*;
import java.util.stream.Collectors;

public class BorrowValidatorApp {

    public record ValidationError(String field, String code, String message) {
        public ValidationError {
            Objects.requireNonNull(field, "field must not be null");
            Objects.requireNonNull(code, "code must not be null");
            Objects.requireNonNull(message, "message must not be null");
        }
    }

    public static class ValidationException extends RuntimeException {
        private final List<ValidationError> errors;

        public ValidationException(List<ValidationError> errors) {
            super("Yeu cau chua du lieu khong hop le: " + errors.size() + " loi");
            this.errors = List.copyOf(errors); // Bao ve tinh bat bien
        }

        public List<ValidationError> getErrors() {
            return errors;
        }

        @Override
        public String getMessage() {
            return errors.stream()
                .map(err -> String.format("%s [%s]: %s", err.field(), err.code(), err.message()))
                .collect(Collectors.joining("\n  - ", "Kiem tra du lieu that bai:\n  - ", ""));
        }
    }

    public record BorrowRequest(String memberId, String assetId, int durationDays, String note) { }

    public static class BorrowRequestValidator {
        public void validate(BorrowRequest request) {
            Objects.requireNonNull(request, "request must not be null");
            List<ValidationError> errors = new ArrayList<>();

            // 1. Kiem tra memberId
            if (request.memberId() == null || request.memberId().isBlank()) {
                errors.add(new ValidationError("memberId", "REQUIRED", "Ma the ban doc khong duoc de trong"));
            } else if (!request.memberId().startsWith("MEM-") || request.memberId().length() < 6 || request.memberId().length() > 12) {
                errors.add(new ValidationError("memberId", "FORMAT", "Ma the ban doc phai bat dau bang 'MEM-' va dai 6-12 ky tu"));
            }

            // 2. Kiem tra assetId
            if (request.assetId() == null || request.assetId().isBlank()) {
                errors.add(new ValidationError("assetId", "REQUIRED", "Ma an pham khong duoc de trong"));
            } else if (!request.assetId().startsWith("ITEM-")) {
                errors.add(new ValidationError("assetId", "FORMAT", "Ma an pham phai bat dau bang tien to 'ITEM-'"));
            }

            // 3. Kiem tra durationDays
            if (request.durationDays() < 1 || request.durationDays() > 30) {
                errors.add(new ValidationError("durationDays", "RANGE", "Thoi gian muon phai tu 1 den 30 ngay, nhan duoc: " + request.durationDays()));
            }

            // 4. Kiem tra note
            if (request.note() != null && request.note().length() > 100) {
                errors.add(new ValidationError("note", "MAX_LENGTH", "Ghi chu khong duoc vuot qua 100 ky tu"));
            }

            // Neu co loi, nem ngoai le gom tat ca
            if (!errors.isEmpty()) {
                throw new ValidationException(errors);
            }
        }
    }

    public static class BorrowController {
        private final BorrowRequestValidator validator = new BorrowRequestValidator();

        public String submitBorrow(BorrowRequest request) {
            try {
                validator.validate(request);
                return "{\"status\": \"SUCCESS\", \"message\": \"Yeu cau muon sach da duoc ghi nhan thanh cong\"}";
            } catch (ValidationException ex) {
                // Mo phong format JSON tra ve cho client
                String errorsJson = ex.getErrors().stream()
                    .map(err -> String.format("{\"field\": \"%s\", \"code\": \"%s\", \"detail\": \"%s\"}",
                        err.field(), err.code(), err.message()))
                    .collect(Collectors.joining(",\n    ", "[\n    ", "\n  ]"));

                return String.format("{\n  \"status\": \"BAD_REQUEST\",\n  \"errorCount\": %d,\n  \"errors\": %s\n}",
                    ex.getErrors().size(), errorsJson);
            }
        }
    }

    public static void main(String[] args) {
        BorrowController controller = new BorrowController();

        BorrowRequest invalidReq = new BorrowRequest("LIB-12", "BOOK-99", -5, "Muon gap");
        System.out.println("--- KICH BAN 1: DU LIEU KHONG HOP LE ---");
        System.out.println("Controller Response:\n" + controller.submitBorrow(invalidReq));

        System.out.println();

        BorrowRequest validReq = new BorrowRequest("MEM-10023", "ITEM-5021", 14, "Nghien cuu khoa hoc");
        System.out.println("--- KICH BAN 2: DU LIEU HOP LE ---");
        System.out.println("Controller Response:\n" + controller.submitBorrow(validReq));
    }
}