import React, { useEffect, useState } from 'react';
import { Plus, Clock, Loader2, Edit, Trash2, X, Filter } from 'lucide-react';
import { api } from '../services/api';
import { Course, Subject, User, ClassInfo } from '../types';
import { sortClasses } from './Dashboard';

export const CourseList: React.FC = () => {
  const [courses, setCourses] = useState<Course[]>([]);
  const [subjects, setSubjects] = useState<Subject[]>([]);
  const [teachers, setTeachers] = useState<User[]>([]); 
  const [classes, setClasses] = useState<ClassInfo[]>([]);
  const [loading, setLoading] = useState(true);
  
  // Filter state
  const [filterSubject, setFilterSubject] = useState('All');

  const [isModalOpen, setIsModalOpen] = useState(false);
  const [formData, setFormData] = useState<{
      courseCode: string, 
      courseName: string, 
      teacherName: string, 
      teacherId: string, 
      className: string, 
      credits: number, 
      capacity: number
  }>({ courseCode: '', courseName: '', teacherName: '', teacherId: '', className: '', credits: 2, capacity: 45 });
  
  const [editId, setEditId] = useState<string | null>(null);

  const currentUser = api.auth.getCurrentUser();
  const isAdmin = currentUser?.role === 'ADMIN';
  const isTeacher = currentUser?.role === 'TEACHER';

  const loadData = async () => {
    setLoading(true);
    try {
      const [c, s, t, cls] = await Promise.all([
         api.courses.getAll(), 
         api.subjects.getAll(),
         api.users.getAll({ role: 'TEACHER' }),
         api.classes.getAll()
      ]);
      
      let filteredCourses = c;
      if (isTeacher) {
          // Teachers only see their own courses
          filteredCourses = c.filter((course: Course) => course.teacherId === currentUser._id || course.teacherName === (currentUser.trueName || currentUser.username));
      }
      
      setCourses(filteredCourses);
      setSubjects(s);
      setTeachers(t);
      
      // Safety check: Ensure cls is array and sort safely
      const safeClasses = Array.isArray(cls) ? cls : [];
      try {
          safeClasses.sort(sortClasses);
      } catch (e) {
          console.warn("Class sort failed", e);
      }
      setClasses(safeClasses);

    } catch (e) { console.error(e); } finally { setLoading(false); }
  };

  useEffect(() => { loadData(); }, []);

  const handleSubmit = async (e: React.FormEvent) => {
    e.preventDefault();
    if (editId) await api.courses.update(editId, formData);
    else {
        try {
            await api.courses.add(formData);
        } catch (e: any) {
            if (e.message.includes('DUPLICATE')) {
                alert('该班级的该科目已经有任课老师了，请勿重复添加。');
                return;
            }
            alert('添加失败');
            return;
        }
    }
    setIsModalOpen(false);
    loadData();
  };

  const handleDelete = async (id: string) => {
    if(confirm('删除课程关联？')) { await api.courses.delete(id); loadData(); }
  };

  const filteredCourses = courses.filter(c => filterSubject === 'All' || c.courseName === filterSubject);

  const handleTeacherSelect = (e: React.ChangeEvent<HTMLSelectElement>) => {
      const tId = e.target.value;
      const t = teachers.find(u => u._id === tId);
      if(t) {
          setFormData({ ...formData, teacherId: tId, teacherName: t.trueName || t.username });
      }
  };

  // If teacher is logged in, default the teacher selection to themselves
  const handleOpenAdd = () => {
      setEditId(null);
      setFormData({ 
          courseCode: '', 
          courseName: '', 
          teacherName: isTeacher ? (currentUser?.trueName || currentUser?.username || '') : '', 
          teacherId: isTeacher ? (currentUser?._id || '') : '',
          className: '', 
          credits: 2, 
          capacity: 45 
      });
      setIsModalOpen(true);
  };

  // Helper to ensure class name is consistent
  const getFullClassName = (c: ClassInfo) => {
      if (c.className && c.grade && c.className.startsWith(c.grade)) return c.className;
      return (c.grade || '') + (c.className || '');
  };

  return (
    <div className="space-y-6">
       <div className="flex flex-col md:flex-row justify-between items-center gap-4">
          <div>
              <h2 className="text-xl font-bold text-gray-800">任课安排</h2>
              <p className="text-xs text-gray-500">在此设置每个班级各科目的任课老师</p>
          </div>
          
          <div className="flex items-center gap-3 w-full md:w-auto">
              <div className="flex items-center bg-white border rounded-lg px-2 py-1.5 flex-1 md:flex-none">
                  <Filter size={16} className="text-gray-400 mr-2"/>
                  <select 
                    className="bg-transparent text-sm outline-none text-gray-700 min-w-[100px]"
                    value={filterSubject}
                    onChange={e => setFilterSubject(e.target.value)}
                  >
                      <option value="All">所有科目</option>
                      {subjects.map(s => <option key={s._id} value={s.name}>{s.name}</option>)}
                  </select>
              </div>
              <button onClick={handleOpenAdd} className="px-4 py-2 bg-indigo-600 text-white rounded-lg flex items-center text-sm hover:bg-indigo-700 transition-colors whitespace-nowrap">
                  <Plus size={16} className="mr-1"/> 绑定新班级
              </button>
          </div>
       </div>

       {loading ? <div className="flex justify-center py-10"><Loader2 className="animate-spin text-indigo-600"/></div> : (
         filteredCourses.length > 0 ? (
             <div className="grid grid-cols-1 md:grid-cols-3 gap-6">
                {filteredCourses.map(c => (
                   <div key={c._id || c.id} className="bg-white p-6 rounded-xl border shadow-sm hover:shadow-md transition-shadow relative overflow-hidden group">
                      <div className="absolute top-0 right-0 p-4 opacity-10 font-black text-6xl text-indigo-900 pointer-events-none -mr-4 -mt-4">
                          {c.courseName[0]}
                      </div>
                      
                      <div className="relative z-10">
                          <h3 className="font-bold text-lg text-gray-800 mb-1">{c.className}</h3>
                          <div className="text-indigo-600 font-bold text-md mb-4 flex items-center">
                              {c.courseName}
                          </div>
                          
                          <div className="text-sm text-gray-500 mb-4 space-y-1">
                              <p className="flex items-center"><span className="w-16 text-gray-400">教师:</span> {c.teacherName}</p>
                              {c.courseCode && <p className="flex items-center"><span className="w-16 text-gray-400">代码:</span> {c.courseCode}</p>}
                          </div>

                          <div className="flex gap-2 pt-2 border-t border-gray-50">
                             <button onClick={() => { 
                                 setFormData({ 
                                     courseCode: c.courseCode || '', 
                                     courseName: c.courseName, 
                                     teacherName: c.teacherName, 
                                     teacherId: c.teacherId || '',
                                     className: c.className,
                                     credits: c.credits || 2, 
                                     capacity: c.capacity || 45
                                 }); 
                                 setEditId(c._id || String(c.id)); 
                                 setIsModalOpen(true); 
                             }} className="flex-1 bg-gray-50 text-blue-600 py-1.5 rounded text-sm hover:bg-blue-50 transition-colors font-medium">编辑</button>
                             <button onClick={() => handleDelete(c._id || String(c.id))} className="flex-1 bg-gray-50 text-red-600 py-1.5 rounded text-sm hover:bg-red-50 transition-colors font-medium">解绑</button>
                          </div>
                      </div>
                   </div>
                ))}
             </div>
         ) : (
             <div className="text-center py-12 text-gray-400 bg-white rounded-xl border border-dashed border-gray-200">
                 {isTeacher ? '您尚未绑定任何教学班级，请点击右上角绑定' : '没有找到课程安排'}
             </div>
         )
       )}

       {isModalOpen && (
          <div className="fixed inset-0 bg-black/50 flex items-center justify-center p-4 z-50 backdrop-blur-sm">
             <div className="bg-white p-6 rounded-xl w-full max-w-md shadow-xl animate-in zoom-in-95">
                <h3 className="font-bold mb-4 text-lg text-gray-800">{editId ? '编辑课程关联' : '新增课程关联'}</h3>
                <form onSubmit={handleSubmit} className="space-y-4">
                   <div>
                      <label className="text-sm font-bold text-gray-500 mb-1 block">教学班级</label>
                      <select className="w-full border p-2 rounded-lg focus:ring-2 focus:ring-indigo-500 outline-none" value={formData.className} onChange={e=>setFormData({...formData, className:e.target.value})} required>
                         <option value="">-- 选择班级 --</option>
                         {classes.map(cls => {
                             const fullName = getFullClassName(cls);
                             return <option key={cls._id} value={fullName}>{fullName}</option>;
                         })}
                      </select>
                   </div>

                   <div>
                      <label className="text-sm font-bold text-gray-500 mb-1 block">科目</label>
                      <select className="w-full border p-2 rounded-lg focus:ring-2 focus:ring-indigo-500 outline-none" value={formData.courseName} onChange={e=>setFormData({...formData, courseName:e.target.value})} required>
                         <option value="">-- 选择科目 --</option>
                         {subjects.map(s=><option key={s._id} value={s.name}>{s.name}</option>)}
                      </select>
                   </div>
                   
                   {!isTeacher && (
                       <div>
                          <label className="text-sm font-bold text-gray-500 mb-1 block">任课教师</label>
                          <select 
                            className="w-full border p-2 rounded-lg focus:ring-2 focus:ring-indigo-500 outline-none"
                            value={formData.teacherId}
                            onChange={handleTeacherSelect}
                            required
                          >
                             <option value="">-- 选择教师 --</option>
                             {teachers.map(t => <option key={t._id} value={t._id}>{t.trueName || t.username}</option>)}
                          </select>
                       </div>
                   )}

                   {isTeacher && (
                       <div className="bg-blue-50 p-2 rounded text-sm text-blue-700">
                           您正在将自己 ({formData.teacherName}) 绑定为 {formData.className || '某班'} 的 {formData.courseName || '某科'} 老师。
                       </div>
                   )}

                   <div className="flex gap-3 pt-2">
                       <button type="button" onClick={()=>setIsModalOpen(false)} className="flex-1 border py-2 rounded-lg hover:bg-gray-50">取消</button>
                       <button className="flex-1 bg-indigo-600 text-white py-2 rounded-lg hover:bg-indigo-700 shadow-md">保存</button>
                   </div>
                </form>
             </div>
          </div>
       )}
    </div>
  );
};