/**
 * 控制層注解
 * @Controller 
 */
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Controller {

    String value() default "";
}

/**
 * 請(qǐng)求路徑注解
 * @RequestMapping
 */
@Target({ElementType.METHOD,ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestMapping {

    String value() default "";
}

/**
 * 參數(shù)注解
 * @RequestParam
 */
@Target({ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestParam {

    String value() default "";
}

/**
 * 服務(wù)層注解
 * @Controller
 */
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Service {

    String value() default "";
}

/**
 * 自動(dòng)裝載注解
 * @Autowrited
 */
@Target({ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Autowired {

    String value() default "";
}

/**
 * servlet跳轉(zhuǎn)層
 */
@WebServlet(name = "DispatcherServlet",urlPatterns = "/*", loadOnStartup = 1, initParams = {@WebInitParam(name="scanPackage", value="com.example.mvc")})
public class DispatcherServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    private static final Logger logger = LoggerFactory.getLogger(DispatcherServlet.class);

    /**請(qǐng)求方法映射容器*/
    private static List<RequestHandler> handlerMapping = new ArrayList<>();

    /**
     * 服務(wù)啟動(dòng)的時(shí)候，進(jìn)行初始化，流程如下：
     * 1、掃描指定包下所有的類
     * 2、通過反射將類實(shí)例，放入ioc容器
     * 3、通過Autowired注解，實(shí)現(xiàn)自動(dòng)依賴注入，也就是set類中的屬性
     * 4、通過RequestMapping注解，獲取需要映射的所有方法，然后將類信息存放到容器中
     * @param config
     * @throws ServletException
     */
    @Override
    public void init(ServletConfig config) throws ServletException {
        try {
            //1、掃描指定包下所有的類
            String scanPackage = config.getInitParameter("scanPackage");
            //1、掃描指定包下所有的類
            List<String> classNames = doScan(scanPackage);
            //2、初始化所有類實(shí)例，放入ioc容器，也就是map對(duì)象中
            Map<String, Object> iocMap = doInstance(classNames);
            //3、實(shí)現(xiàn)自動(dòng)依賴注入
            doAutowired(iocMap);
            //5、初始化方法mapping
            initHandleMapping(iocMap);
        } catch (Exception e) {
            logger.error("dispatcher-servlet類初始化失敗!",e);
            throw new ServletException(e.getMessage());
        }
    }


    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
        doPost(request, response);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
        //跳轉(zhuǎn)
        doDispatch(request, response);
    }

    /**
     * 掃描指定包下的類文件
     * @param packageName
     * @return
     */
    private List<String> doScan(String packageName){
        if(StringUtils.isBlank(packageName)){
            throw new RuntimeException("mvc配置文件中指定掃描包名為空!");
        }
        return PackageHelper.getClassName(packageName);
    }

    private Map<String, Object> doInstance(List<String> classNames) {
        Map<String, Object> iocMap = new HashMap<>();
        if(!CollectionUtils.isNotEmpty(classNames)){
            throw new RuntimeException("獲取的類為空!");
        }
        for (String className : classNames) {
            try {
                //通過反射機(jī)制構(gòu)造對(duì)象
                Class<?> clazz = Class.forName(className);
                if(clazz.isAnnotationPresent(Controller.class)){
                    //將類名第一個(gè)字母小寫
                    String baneName = firstLowerCase(clazz.getSimpleName());
                    iocMap.put(baneName, clazz.newInstance());
                }else if(clazz.isAnnotationPresent(Service.class)){
                    //服務(wù)層注解判斷
                    Service service = clazz.getAnnotation(Service.class);
                    String beanName = service.value();
                    //如果該注解上沒有自定義類名，則默認(rèn)首字母小寫
                    if(StringUtils.isBlank(beanName)){
                        beanName = clazz.getName();
                    }
                    Object instance = clazz.newInstance();
                    iocMap.put(beanName, instance);
                    //如果注入的是接口，可以巧妙的用接口的類型作為key
                    Class<?>[] interfaces = clazz.getInterfaces();
                    for (Class<?> clazzInterface : interfaces) {
                        iocMap.put(clazzInterface.getName(), instance);
                    }
                }
            } catch (Exception e) {
                logger.error("初始化mvc-ioc容器失敗!",e);
                throw new RuntimeException("初始化mvc-ioc容器失敗!");
            }
        }
        return iocMap;
    }

    /**
     * 實(shí)現(xiàn)自動(dòng)依賴注入
     * @throws Exception
     */
    private void doAutowired(Map<String, Object> iocMap) {
        if(!MapUtils.isNotEmpty(iocMap)){
            throw new RuntimeException("初始化實(shí)現(xiàn)自動(dòng)依賴失敗，ioc為空!");
        }
        for(Map.Entry<String, Object> entry : iocMap.entrySet()){
            //獲取對(duì)象下所有的屬性
            Field[] fields = entry.getValue().getClass().getDeclaredFields();
            for (Field field : fields) {
                //判斷字段上有沒有@Autowried注解，有的話才注入
                if(field.isAnnotationPresent(Autowired.class)){
                    try {
                        Autowired autowired = field.getAnnotation(Autowired.class);
                        //獲取注解上有沒有自定義值
                        String beanName = autowired.value().trim();
                        if(StringUtils.isBlank(beanName)){
                            beanName = field.getType().getName();
                        }
                        //如果想要訪問到私有的屬性，我們要強(qiáng)制授權(quán)
                        field.setAccessible(true);
                        field.set(entry.getValue(), iocMap.get(beanName));
                    } catch (Exception e) {
                        logger.error("初始化實(shí)現(xiàn)自動(dòng)依賴注入失敗!",e);
                        throw new RuntimeException("初始化實(shí)現(xiàn)自動(dòng)依賴注入失敗");
                    }
                }
            }
        }
    }

    /**
     * 初始化方法mapping
     */
    private void initHandleMapping(Map<String, Object> iocMap){
        if(!MapUtils.isNotEmpty(iocMap)){
            throw new RuntimeException("初始化實(shí)現(xiàn)自動(dòng)依賴失敗，ioc為空");
        }
        for(Map.Entry<String, Object> entry:iocMap.entrySet()){
            Class<?> clazz = entry.getValue().getClass();
            //判斷是否是controller層
            if(!clazz.isAnnotationPresent(Controller.class)){
                continue;
            }
            String baseUrl = null;
            //判斷類有沒有requestMapping注解
            if(clazz.isAnnotationPresent(RequestMapping.class)){
                RequestMapping requestMapping = clazz.getAnnotation(RequestMapping.class);
                baseUrl= requestMapping.value();
            }
            Method[] methods = clazz.getMethods();
            for (Method method : methods) {
                //判斷方法上有沒有requestMapping
                if(!method.isAnnotationPresent(RequestMapping.class)){
                    continue;
                }
                RequestMapping requestMethodMapping = method.getAnnotation(RequestMapping.class);
                //"/+",表示將多個(gè)"/"轉(zhuǎn)換成"/"
                String regex = (baseUrl + requestMethodMapping.value()).replaceAll("/+", "/");
                Pattern pattern = Pattern.compile(regex);
                handlerMapping.add(new RequestHandler(pattern, entry.getValue(), method));
            }
        }
    }

    /**
     * servlet請(qǐng)求跳轉(zhuǎn)
     * @param request
     * @param response
     * @throws IOException
     */
    private void doDispatch(HttpServletRequest request, HttpServletResponse response) throws IOException {
        try {
            request.setCharacterEncoding("UTF-8");
            response.setHeader("Cache-Control", "no-cache");
            response.setHeader("Pragma", "no-cache");
            response.setDateHeader("Expires", -1);
            response.setContentType("text/html");
            response.setHeader("content-type", "text/html;charset=UTF-8");
            response.setCharacterEncoding("UTF-8");
            RequestHandler handle = getHandleMapping(request);
            if(Objects.isNull(handle)){
                //異常請(qǐng)求地址
                logger.warn("異常請(qǐng)求地址!地址:" + request.getRequestURI());
                response.getWriter().append("error request url");
                return;
            }
            //獲取參數(shù)列表
            Object[] paramValues = RequestParamHelper.buildRequestParam(handle, request, response);
            Object result = handle.getMethod().invoke(handle.getController(), paramValues);
            if(result != null){
                PrintWriter out = response.getWriter();
                out.println(result);
                out.flush();
                out.close();
            }
        } catch (Exception e) {
            logger.error("接口請(qǐng)求失敗!",e);
            PrintWriter out = response.getWriter();
            out.println("請(qǐng)求異常,請(qǐng)稍后再試");
            out.flush();
            out.close();
        }
    }

    /**
     * 將類名第一個(gè)字母小寫
     * @param clazzName
     * @return
     */
    private String firstLowerCase(String clazzName){
        char[] chars = clazzName.toCharArray();
        chars[0] += 32;
        return String.valueOf(chars);
    }


    /**
     * 獲取用戶請(qǐng)求方法名
     * 與handlerMapping中的路徑名進(jìn)行匹配
     * @param request
     * @return
     */
    private RequestHandler getHandleMapping(HttpServletRequest request){
        if(CollectionUtils.isNotEmpty(handlerMapping)){
            //獲取用戶請(qǐng)求路徑
            String url = request.getRequestURI();
            String contextPath = request.getContextPath();
            String serviceUrl = url.replace(contextPath, "").replaceAll("/+", "/");
            for (RequestHandler handle : handlerMapping) {
                //正則匹配請(qǐng)求方法名
                Matcher matcher = handle.getPattern().matcher(serviceUrl);
                if(matcher.matches()){
                    return handle;
                }
            }
        }
        return null;
    }
}

@Controller
@RequestMapping("/user")
public class LoginController {

    @Autowired
    private UserService userService;

    /**
     * 用戶登錄
     * @param request
     * @param response
     * @param userName
     * @param userPwd
     * @return
     */
    @RequestMapping("/login")
    public String login(HttpServletRequest request, HttpServletResponse response,
                        @RequestParam("userName") String userName,
                        @RequestParam("userPwd") String userPwd){
        boolean result = userService.login(userName, userPwd);
        if(result){
            return "登錄成功！";
        } else {
            return "登錄失??！";
        }
    }
}

public interface UserService {

    /**
     * 登錄
     * @param userName
     * @param userPwd
     * @return
     */
    boolean login(String userName, String userPwd);
}

@Service
public class UserServiceImpl implements UserService {

    @Override
    public boolean login(String userName, String userPwd) {
        if("zhangsan".equals(userName) && "123456".equals(userPwd)){
            return true;
        } else {
            return false;
        }
    }
}