import java.time.LocalDate;
import java.util.Objects;
import java.util.UUID;

/**
 * 证书类：管理员工获得的证书
 */
public class Certificate {
    private String certificateId;     // 证书ID
    private int employeeId;           // 员工ID
    private String title;             // 证书名称
    private String issuingAuthority;  // 发证机构
    private LocalDate issueDate;      // 颁发日期
    private LocalDate expiryDate;     // 到期日期（可选）
    private String description;       // 证书描述
    private String certificateUrl;    // 证书电子版URL（可选）
    private boolean isActive;         // 是否有效
    
    /**
     * 构造函数
     */
    public Certificate(int employeeId, String title, String issuingAuthority, 
                      LocalDate issueDate) {
        validateEmployeeId(employeeId);
        validateTitle(title);
        validateIssuingAuthority(issuingAuthority);
        validateIssueDate(issueDate);
        
        this.certificateId = generateCertificateId();
        this.employeeId = employeeId;
        this.title = title;
        this.issuingAuthority = issuingAuthority;
        this.issueDate = issueDate;
        this.isActive = true;  // 默认为有效证书
        this.description = "";
        this.certificateUrl = null;
    }
    
    /**
     * 构造函数（包含到期日期）
     */
    public Certificate(int employeeId, String title, String issuingAuthority, 
                      LocalDate issueDate, LocalDate expiryDate) {
        this(employeeId, title, issuingAuthority, issueDate);
        
        if (expiryDate != null && expiryDate.isBefore(issueDate)) {
            throw new IllegalArgumentException("到期日期不能早于颁发日期");
        }
        this.expiryDate = expiryDate;
        
        // 如果有到期日期且已过期，则标记为无效
        if (expiryDate != null && expiryDate.isBefore(LocalDate.now())) {
            this.isActive = false;
        }
    }
    
    // 生成证书ID
    private String generateCertificateId() {
        return "CERT-" + UUID.randomUUID().toString().substring(0, 8).toUpperCase();
    }
    
    // 验证方法
    private void validateEmployeeId(int employeeId) {
        if (employeeId <= 0) {
            throw new IllegalArgumentException("员工ID必须为正整数");
        }
    }
    
    private void validateTitle(String title) {
        if (title == null || title.trim().isEmpty()) {
            throw new IllegalArgumentException("证书名称不能为空");
        }
    }
    
    private void validateIssuingAuthority(String issuingAuthority) {
        if (issuingAuthority == null || issuingAuthority.trim().isEmpty()) {
            throw new IllegalArgumentException("发证机构不能为空");
        }
    }
    
    private void validateIssueDate(LocalDate issueDate) {
        if (issueDate == null || issueDate.isAfter(LocalDate.now())) {
            throw new IllegalArgumentException("颁发日期不能晚于当前日期");
        }
    }
    
    /**
     * 检查证书是否过期
     */
    public boolean isExpired() {
        return expiryDate != null && expiryDate.isBefore(LocalDate.now());
    }
    
    /**
     * 检查证书是否仍然有效
     */
    public boolean isValid() {
        return isActive && !isExpired();
    }
    
    /**
     * 更新证书到期日期
     */
    public void updateExpiryDate(LocalDate expiryDate) {
        if (expiryDate != null && expiryDate.isBefore(issueDate)) {
            throw new IllegalArgumentException("到期日期不能早于颁发日期");
        }
        this.expiryDate = expiryDate;
        
        // 更新状态
        if (expiryDate != null && expiryDate.isBefore(LocalDate.now())) {
            this.isActive = false;
        }
    }
    
    // Getter方法
    public String getCertificateId() { return certificateId; }
    public int getEmployeeId() { return employeeId; }
    public String getTitle() { return title; }
    public String getIssuingAuthority() { return issuingAuthority; }
    public LocalDate getIssueDate() { return issueDate; }
    public LocalDate getExpiryDate() { return expiryDate; }
    public String getDescription() { return description; }
    public String getCertificateUrl() { return certificateUrl; }
    public boolean isActive() { return isActive; }
    
    // Setter方法
    public void setTitle(String title) {
        validateTitle(title);
        this.title = title;
    }
    
    public void setIssuingAuthority(String issuingAuthority) {
        validateIssuingAuthority(issuingAuthority);
        this.issuingAuthority = issuingAuthority;
    }
    
    public void setDescription(String description) {
        this.description = description != null ? description : "";
    }
    
    public void setCertificateUrl(String certificateUrl) {
        this.certificateUrl = certificateUrl;
    }
    
    public void activate() {
        this.isActive = true;
    }
    
    public void deactivate() {
        this.isActive = false;
    }
    
    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Certificate that = (Certificate) o;
        return certificateId.equals(that.certificateId);
    }
    
    @Override
    public int hashCode() {
        return Objects.hash(certificateId);
    }
    
    @Override
    public String toString() {
        return String.format("证书[ID: %s, 名称: %s, 员工ID: %d, 发证机构: %s, 状态: %s]",
                certificateId, title, employeeId, issuingAuthority, 
                isValid() ? "有效" : "无效");
    }
}