package com.learn.config;

import com.learn.security.JwtAuthFilter;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.HttpMethod;
import org.springframework.security.config.annotation.method.configuration.EnableMethodSecurity;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
import org.springframework.security.config.http.SessionCreationPolicy;
import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
import org.springframework.security.crypto.password.PasswordEncoder;
import org.springframework.security.web.SecurityFilterChain;
import org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter;

/**
 * Spring Security 配置（第 1-3 天）
 *
 * 核心设计：
 *   1. 无状态会话（JWT，不依赖 Cookie/Session）
 *   2. 自定义 JWT 过滤器在 UsernamePasswordAuthenticationFilter 之前执行
 *   3. RBAC：ADMIN 可增删改，USER 只能查
 *   4. 公开 /api/auth/** 和 Actuator 端点
 */
@Configuration
@EnableWebSecurity
@EnableMethodSecurity          // 开启方法级安全注解（第 3 天）
public class SecurityConfig {

    private final JwtAuthFilter jwtAuthFilter;

    public SecurityConfig(JwtAuthFilter jwtAuthFilter) {
        this.jwtAuthFilter = jwtAuthFilter;
    }

    @Bean
    public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
        http
            .csrf(csrf -> csrf.disable())                    // 前后端分离，禁用 CSRF
            .sessionManagement(sm -> sm
                .sessionCreationPolicy(SessionCreationPolicy.STATELESS))  // 无状态
            .authorizeHttpRequests(auth -> auth
                // 公开接口
                .requestMatchers("/api/auth/**").permitAll()
                .requestMatchers("/actuator/**").permitAll()
                .requestMatchers("/", "/index.html", "/css/**", "/js/**").permitAll()
                // 查询：USER 及以上
                .requestMatchers(HttpMethod.GET, "/api/students/**").hasAnyRole("ADMIN", "USER")
                // 增删改：仅 ADMIN（第 3 天 RBAC）
                .requestMatchers(HttpMethod.POST, "/api/students/**").hasRole("ADMIN")
                .requestMatchers(HttpMethod.PUT, "/api/students/**").hasRole("ADMIN")
                .requestMatchers(HttpMethod.DELETE, "/api/students/**").hasRole("ADMIN")
                // 其他请求需认证
                .anyRequest().authenticated()
            )
            // 在用户名密码过滤器之前插入 JWT 过滤器
            .addFilterBefore(jwtAuthFilter, UsernamePasswordAuthenticationFilter.class);

        return http.build();
    }

    @Bean
    public PasswordEncoder passwordEncoder() {
        return new BCryptPasswordEncoder();   // BCrypt 加密，不可逆
    }
}