import 'dart:math';

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatefulWidget {
  const MyApp({super.key});

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  TextEditingController categoryController = TextEditingController();
  TextEditingController changeDataController = TextEditingController();
  ScrollController scrollController = ScrollController();
  String resultStr = "";

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text("密码生成器")),
        body: Container(
          padding: EdgeInsets.only(left: 10, right: 10),
          child: ListView(
            scrollDirection: Axis.vertical,
            controller: scrollController,
            children: [
              DefaultTextStyle(
                style: TextStyle(color: Colors.black, fontSize: 20),
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: [
                    Column(
                      crossAxisAlignment: CrossAxisAlignment.start,
                      children: [
                        Text(
                          "C (communication)",
                          style: TextStyle(
                            fontWeight: FontWeight.bold,
                            fontSize: 25,
                            color: Colors.green,
                          ),
                        ),
                        Text("社交类: 该类软件包含以文本，语音，图片，音视频等方式进行社交，典型如微信，qq，电子邮箱 "),
                        SizedBox(height: 20),
                        Text(
                          "T (technology)",
                          style: TextStyle(
                            fontWeight: FontWeight.bold,
                            fontSize: 25,
                            color: Colors.green,
                          ),
                        ),
                        Text(
                          "科技/技术类: 该类软件包含以提供计算机技术等其他工程类技术支持/论坛为主的服务，典型如csdn，华为 ",
                        ),
                        SizedBox(height: 20),
                        Text(
                          "S (shopping)",
                          style: TextStyle(
                            fontWeight: FontWeight.bold,
                            fontSize: 25,
                            color: Colors.green,
                          ),
                        ),
                        Text("购物/外卖类: 该类软件包含各种以线上购买实体商品为主的服务，典型如淘宝，京东 "),
                        SizedBox(height: 20),
                        Text(
                          "EDU (education)",
                          style: TextStyle(
                            fontWeight: FontWeight.bold,
                            fontSize: 25,
                            color: Colors.green,
                          ),
                        ),
                        Text("教育/学习类: 该类软件专注于提供教育，学术，辅导等的支持/资料，典型如扇贝英语，作业帮 "),
                        SizedBox(height: 20),
                        Text(
                          "E (entertainment)",
                          style: TextStyle(
                            fontWeight: FontWeight.bold,
                            fontSize: 25,
                            color: Colors.green,
                          ),
                        ),
                        Text("游戏/娱乐类: 该类软件专注于以提供电子游戏，休闲娱乐为主的服务，典型如王者荣耀，抖音 "),
                        SizedBox(height: 20),
                        Text(
                          "O (other)",
                          style: TextStyle(
                            fontWeight: FontWeight.bold,
                            fontSize: 25,
                            color: Colors.green,
                          ),
                        ),
                        Text("其他: 当一个服务不属于以上任何类别，那么归属于此类，典型如processon，工商银行 "),
                      ],
                    ),
                    SizedBox(height: 20),

                    Row(
                      crossAxisAlignment: CrossAxisAlignment.end,
                      children: [
                        Expanded(flex: 2, child: Text("Category:")),
                        Expanded(
                          flex: 3,
                          child: SizedBox(
                            width: 200,
                            height: 50,
                            child: TextField(controller: categoryController),
                          ),
                        ),
                      ],
                    ),
                    SizedBox(height: 20),
                    Row(
                      crossAxisAlignment: CrossAxisAlignment.end,
                      children: [
                        Expanded(flex: 2, child: Text("Change date: ")),
                        Expanded(
                          flex: 3,
                          child: SizedBox(
                            width: 200,
                            height: 50,
                            child: TextField(controller: changeDataController),
                          ),
                        ),
                      ],
                    ),
                    SizedBox(height: 20),
                    Center(
                      child: GestureDetector(
                        onTap: () {
                          setState(() {
                            resultStr = genPasswd();
                          });
                          WidgetsBinding.instance.addPostFrameCallback((val) {
                            scrollController.jumpTo(
                              scrollController.position.maxScrollExtent,
                            );
                          });
                        },
                        child: Container(
                          width: MediaQuery.of(context).size.width / 2,
                          height: 50,
                          alignment: Alignment.center,
                          decoration: BoxDecoration(
                            color: Color(0xFF8447D5),
                            borderRadius: BorderRadiusGeometry.circular(20),
                          ),
                          child: Text(
                            "generate password",
                            style: TextStyle(fontSize: 18, color: Colors.white),
                          ),
                        ),
                      ),
                    ),

                    resultStr.isEmpty
                        ? SizedBox()
                        : Center(
                            child: Builder(
                              builder: (BuildContext context) {
                                return GestureDetector(
                                  onLongPress: () {
                                    Clipboard.setData(
                                      ClipboardData(text: resultStr),
                                    ).then((val) {
                                      double offsetTop =
                                          MediaQuery.of(context).size.height -
                                          200;
                                      ScaffoldMessenger.of(
                                        context,
                                      ).showSnackBar(
                                        SnackBar(
                                          backgroundColor: Color(0xE4616161),
                                          behavior: SnackBarBehavior.floating,
                                          margin: EdgeInsets.only(
                                            bottom: offsetTop,
                                            left: 100,
                                            right: 100
                                          ),
                                          content: Center(
                                            child: Text("saved to clipboard"),
                                          ),
                                        ),
                                      );
                                    });
                                  },
                                  child: Container(
                                    margin: EdgeInsets.only(top: 10),
                                    child: Text(
                                      resultStr,
                                      style: TextStyle(
                                        fontSize: 30,
                                        fontWeight: FontWeight.w900,
                                        letterSpacing: 2,
                                      ),
                                    ),
                                  ),
                                );
                              },
                            ),
                          ),
                  ],
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }

  String genRandomString(int length) {
    String re = "";
    Random random = Random();

    for (int i = 0; i < length; i++) {
      int de = random.nextInt(2) + 1;

      switch (de) {
        case 1:
          int lowerCase = random.nextInt(122 - 97 + 1) + 97;
          re += String.fromCharCode(lowerCase);
          break;
        case 2:
          int upperCase = random.nextInt(90 - 65 + 1) + 65;
          re += String.fromCharCode(upperCase);
          break;
        default:
          print("Unexpected value: $de");
          break;
      }
    }
    return re;
  }

  String genLowerLetter(int length) {
    String re = "";
    Random random = Random();

    for (int i = 0; i < length; i++) {
      int lowerCase = random.nextInt(122 - 97 + 1) + 97;
      re += String.fromCharCode(lowerCase);
    }
    return re;
  }

  String genPasswd() {
    String categoryText = categoryController.text;
    String dateText = changeDataController.text;
    if (categoryText.isEmpty || dateText.isEmpty) {
      return "Please done the form";
    }

    // verify if the field valid
    // ================== START ==================
    const categoryList = ["C", "T", "S", "EDU", "E", "O"];
    if (!categoryList.contains(categoryText)) {
      return "Category: input not valid";
    }

    if (dateText.length != 4) {
      return "Date: the length must be 4";
    }
    var dateList = dateText.split('');
    for (var i = 0; i < dateList.length; i++) {
      if (!(dateList[i].codeUnitAt(0) >= 48 &&
          dateList[i].codeUnitAt(0) <= 57)) {
        return "Date: all digit must be a number";
      }
    }
    // ================== END ==================

    return "${categoryText}${dateText}${genLowerLetter(2)}_${genRandomString(8)}";
  }
}