package com.hfl.mvcframework.servlet.v2;
import com.hfl.mvcframework.annotation.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.net.URL;
import java.util.*;
/**
 * Created by Tom on 2019/3/24.
 */
public class HfDispatcherServlet extends HttpServlet{
    //保存application.properties配置文件中的内容
    private Properties contextConfig = new Properties();
    //保存扫描的所有的类名
    private List<String> classNames = new ArrayList<String>();
    //传说中的IOC容器，我们来揭开它的神秘面纱
    //为了简化程序，暂时不考虑ConcurrentHashMap
    // 主要还是关注设计思想和原理
    private Map<String,Object> ioc = new HashMap<String,Object>();
    //保存url和Method的对应关系
//    private Map<String,Method> handlerMapping = new HashMap<String,Method>();
    //思考：为什么不用Map
    //你用Map的话，key，只能是url
    //Handler 本身的功能就是把url和method对应关系，已经具备了Map的功能
    //根据设计原则：冗余的感觉了，单一职责，最少知道原则，帮助我们更好的理解
    private List<Handler> handlerMapping = new ArrayList<Handler>();
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doPost(req,resp);
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //6、调用，运行阶段
        try {
            doDispatch(req,resp);
        } catch (Exception e) {
            e.printStackTrace();
            resp.getWriter().write("500 Exection,Detail : " + Arrays.toString(e.getStackTrace()));
        }
    }
    private void doDispatch(HttpServletRequest req, HttpServletResponse resp) throws Exception {
        Handler handler = getHandler(req);
        if(handler == null){
//        if(!this.handlerMapping.containsKey(url)){
            resp.getWriter().write("404 Not Found!!!");
            return;
        }
        //获得方法的形参列表
        Class<?> [] paramTypes = handler.getParamTypes();
        Object [] paramValues = new Object[paramTypes.length];
        Map<String,String[]> params = req.getParameterMap();
        for (Map.Entry<String, String[]> parm : params.entrySet()) {
            String value = Arrays.toString(parm.getValue()).replaceAll("\\[|\\]","")
                    .replaceAll("\\s",",");
            if(!handler.paramIndexMapping.containsKey(parm.getKey())){continue;}
            int index = handler.paramIndexMapping.get(parm.getKey());
            paramValues[index] = convert(paramTypes[index],value);
        }
        if(handler.paramIndexMapping.containsKey(HttpServletRequest.class.getName())) {
            int reqIndex = handler.paramIndexMapping.get(HttpServletRequest.class.getName());
            paramValues[reqIndex] = req;
        }
        if(handler.paramIndexMapping.containsKey(HttpServletResponse.class.getName())) {
            int respIndex = handler.paramIndexMapping.get(HttpServletResponse.class.getName());
            paramValues[respIndex] = resp;
        }
        Object returnValue = handler.method.invoke(handler.controller,paramValues);
        if(returnValue == null || returnValue instanceof Void){ return; }
        resp.getWriter().write(returnValue.toString());
    }
    private Handler getHandler(HttpServletRequest req) {
        if(handlerMapping.isEmpty()){return null;}
        //绝对路径
        String url = req.getRequestURI();
        //处理成相对路径
        String contextPath = req.getContextPath();
        url = url.replaceAll(contextPath,"").replaceAll("/+","/");
        for (Handler handler : this.handlerMapping) {
            Matcher matcher = handler.getPattern().matcher(url);
            if(!matcher.matches()){ continue;}
            return handler;
        }
        return null;
    }
    //url传过来的参数都是String类型的，HTTP是基于字符串协议
    //只需要把String转换为任意类型就好
    private Object convert(Class<?> type,String value){
        //如果是int
        if(Integer.class == type){
            return Integer.valueOf(value);
        }
        else if(Double.class == type){
            return Double.valueOf(value);
        }
        //如果还有double或者其他类型，继续加if
        //这时候，我们应该想到策略模式了
        //在这里暂时不实现，希望小伙伴自己来实现
        return value;
    }
    //初始化阶段
    @Override
    public void init(ServletConfig config) throws ServletException {
        //1、加载配置文件
        doLoadConfig(config.getInitParameter("contextConfigLocation"));
        //2、扫描相关的类
        doScanner(contextConfig.getProperty("scanPackage"));
        //3、初始化扫描到的类，并且将它们放入到ICO容器之中
        doInstance();
        //4、完成依赖注入
        doAutowired();
        //5、初始化HandlerMapping
        initHandlerMapping();
        System.out.println("Hf Spring framework is init.");
    }
    //初始化url和Method的一对一对应关系
    private void initHandlerMapping() {
        if(ioc.isEmpty()){ return; }
        for (Map.Entry<String, Object> entry : ioc.entrySet()) {
            Class<?> clazz = entry.getValue().getClass();
            if(!clazz.isAnnotationPresent(HfController.class)){continue;}
            //保存写在类上面的@HfRequestMapping("/demo")
            String baseUrl = "";
            if(clazz.isAnnotationPresent(HfRequestMapping.class)){
                HfRequestMapping requestMapping = clazz.getAnnotation(HfRequestMapping.class);
                baseUrl = requestMapping.value();
            }
            //默认获取所有的public方法
            for (Method method : clazz.getMethods()) {
                if(!method.isAnnotationPresent(HfRequestMapping.class)){continue;}
                HfRequestMapping requestMapping = method.getAnnotation(HfRequestMapping.class);
                //优化
                // //demo///query
                String regex = ("/" + baseUrl + "/" + requestMapping.value())
                        .replaceAll("/+","/");
                Pattern pattern = Pattern.compile(regex);
                this.handlerMapping.add(new Handler(pattern,entry.getValue(),method));
//                handlerMapping.put(url,method);
                System.out.println("Mapped :" + pattern + "," + method);
            }
        }
    }
    //自动依赖注入
    private void doAutowired() {
        if(ioc.isEmpty()){return;}
        for (Map.Entry<String, Object> entry : ioc.entrySet()) {
            //Declared 所有的，特定的 字段，包括private/protected/default
            //正常来说，普通的OOP编程只能拿到public的属性
            Field[] fields = entry.getValue().getClass().getDeclaredFields();
            for (Field field : fields) {
                if(!field.isAnnotationPresent(HfAutowired.class)){continue;}
                HfAutowired autowired = field.getAnnotation(HfAutowired.class);
                //如果用户没有自定义beanName，默认就根据类型注入
                //这个地方省去了对类名首字母小写的情况的判断，这个作为课后作业
                //小伙伴们自己去完善
                String beanName = autowired.value().trim();
                if("".equals(beanName)){
                    //获得接口的类型，作为key待会拿这个key到ioc容器中去取值
                    beanName = field.getType().getName();
                }
                //如果是public以外的修饰符，只要加了@Autowired注解，都要强制赋值
                //反射中叫做暴力访问， 强吻
                field.setAccessible(true);
                try {
                    //用反射机制，动态给字段赋值
                    field.set(entry.getValue(),ioc.get(beanName));
                } catch (IllegalAccessException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    private void doInstance() {
        //初始化，为DI做准备
        if(classNames.isEmpty()){return;}
        try {
            for (String className : classNames) {
                Class<?> clazz = Class.forName(className);
                //什么样的类才需要初始化呢？
                //加了注解的类，才初始化，怎么判断？
                //为了简化代码逻辑，主要体会设计思想，只举例 @Controller和@Service,
                // @Componment...就一一举例了
                if(clazz.isAnnotationPresent(HfController.class)){
                    Object instance = clazz.newInstance();
                    //Spring默认类名首字母小写
                    String beanName = toLowerFirstCase(clazz.getSimpleName());
                    ioc.put(beanName,instance);
                }else if(clazz.isAnnotationPresent(HfService.class)){
                    //1、自定义的beanName
                    HfService service = clazz.getAnnotation(HfService.class);
                    String beanName = service.value();
                    //2、默认类名首字母小写
                    if("".equals(beanName.trim())){
                        beanName = toLowerFirstCase(clazz.getSimpleName());
                    }
                    Object instance = clazz.newInstance();
                    ioc.put(beanName,instance);
                    //3、根据类型自动赋值,投机取巧的方式
                    for (Class<?> i : clazz.getInterfaces()) {
                        if(ioc.containsKey(i.getName())){
                            throw new Exception("The “" + i.getName() + "” is exists!!");
                        }
                        //把接口的类型直接当成key了
                        ioc.put(i.getName(),instance);
                    }
                }else {
                    continue;
                }
            }
        }catch (Exception e){
            e.printStackTrace();
        }
    }
    //如果类名本身是小写字母，确实会出问题
    //但是我要说明的是：这个方法是我自己用，private的
    //传值也是自己传，类也都遵循了驼峰命名法
    //默认传入的值，存在首字母小写的情况，也不可能出现非字母的情况
    //为了简化程序逻辑，就不做其他判断了，大家了解就OK
    //其实用写注释的时间都能够把逻辑写完了
    private String toLowerFirstCase(String simpleName) {
        char [] chars = simpleName.toCharArray();
        //之所以加，是因为大小写字母的ASCII码相差32，
        // 而且大写字母的ASCII码要小于小写字母的ASCII码
        //在Java中，对char做算学运算，实际上就是对ASCII码做算学运算
        chars[0] += 32;
        return String.valueOf(chars);
    }
    //扫描出相关的类
    private void doScanner(String scanPackage) {
        //scanPackage = com.gupaoedu.demo ，存储的是包路径
        //转换为文件路径，实际上就是把.替换为/就OK了
        //classpath
        URL url = this.getClass().getClassLoader().getResource("/" + scanPackage.replaceAll("\\.","/"));
        File classPath = new File(url.getFile());
        for (File file : classPath.listFiles()) {
            if(file.isDirectory()){
                doScanner(scanPackage + "." + file.getName());
            }else{
                if(!file.getName().endsWith(".class")){ continue;}
                String className = (scanPackage + "." + file.getName().replace(".class",""));
                classNames.add(className);
            }
        }
    }
    //加载配置文件
    private void doLoadConfig(String contextConfigLocation) {
        //直接从类路径下找到Spring主配置文件所在的路径
        //并且将其读取出来放到Properties对象中
        //相对于scanPackage=com.gupaoedu.demo 从文件中保存到了内存中
        InputStream fis = this.getClass().getClassLoader().getResourceAsStream(contextConfigLocation);
        try {
            contextConfig.load(fis);
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if(null != fis){
                try {
                    fis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    //保存一个url和一个Method的关系
    public class Handler {
        //必须把url放到HandlerMapping才好理解吧
        private Pattern pattern;  //正则
        private Method method;
        private Object controller;
        private Class<?> [] paramTypes;
        public Pattern getPattern() {
            return pattern;
        }
        public Method getMethod() {
            return method;
        }
        public Object getController() {
            return controller;
        }
        public Class<?>[] getParamTypes() {
            return paramTypes;
        }
        //形参列表
        //参数的名字作为key,参数的顺序，位置作为值
        private Map<String,Integer> paramIndexMapping;
        public Handler(Pattern pattern, Object controller, Method method) {
            this.pattern = pattern;
            this.method = method;
            this.controller = controller;
            paramTypes = method.getParameterTypes();
            paramIndexMapping = new HashMap<String, Integer>();
            putParamIndexMapping(method);
        }
        private void putParamIndexMapping(Method method){
            //提取方法中加了注解的参数
            //把方法上的注解拿到，得到的是一个二维数组
            //因为一个参数可以有多个注解，而一个方法又有多个参数
            Annotation [] [] pa = method.getParameterAnnotations();
            for (int i = 0; i < pa.length ; i ++) {
                for(Annotation a : pa[i]){
                    if(a instanceof HfRequestParam){
                        String paramName = ((HfRequestParam) a).value();
                        if(!"".equals(paramName.trim())){
                            paramIndexMapping.put(paramName, i);
                        }
                    }
                }
            }
            //提取方法中的request和response参数
            Class<?> [] paramsTypes = method.getParameterTypes();
            for (int i = 0; i < paramsTypes.length ; i ++) {
                Class<?> type = paramsTypes[i];
                if(type == HttpServletRequest.class ||
                        type == HttpServletResponse.class){
                    paramIndexMapping.put(type.getName(),i);
                }
            }
        }
    }
}