import React, { useState, useEffect } from 'react';
import { ArrowLeft, BookOpen, ChevronRight, FileText, CheckCircle2, Circle, MessageSquare, AlertCircle, Award, Download } from 'lucide-react';
import VideoPlayer from './VideoPlayer';
import CourseActivity from './CourseActivity';

interface LessonProgress {
  watchedPercentage: number;
  completed: boolean;
}

interface Lesson {
  id: string;
  moduleId: string;
  title: string;
  videoUrl: string;
  videoType: 'youtube' | 'direct';
  order: number;
  content: string;
  progress: LessonProgress;
  note: string;
}

interface Module {
  id: string;
  courseId: string;
  title: string;
  order: number;
  lessons: Lesson[];
}

interface Course {
  id: string;
  title: string;
  description: string;
  thumbnail: string;
  category: string;
  studyMaterialUrl?: string;
}

interface CourseViewProps {
  courseId: string;
  token: string | null;
  onBack: () => void;
  initialLessonId?: string | null;
}

export default function CourseView({ courseId, token, onBack, initialLessonId }: CourseViewProps) {
  const [course, setCourse] = useState<Course | null>(null);
  const [modules, setModules] = useState<Module[]>([]);
  const [activeLesson, setActiveLesson] = useState<Lesson | null>(null);
  const [expandedModules, setExpandedModules] = useState<string[]>([]);
  const [noteContent, setNoteContent] = useState('');
  const [isLoading, setIsLoading] = useState(true);
  const [error, setError] = useState<string | null>(null);
  const [saveStatus, setSaveStatus] = useState<'idle' | 'saving' | 'saved' | 'error'>('idle');
  const [activeActivityModuleId, setActiveActivityModuleId] = useState<string | null>(null);

  useEffect(() => {
    fetchCourseDetails();
  }, [courseId]);

  const fetchCourseDetails = async () => {
    setIsLoading(true);
    setError(null);
    try {
      const res = await fetch(`/api/courses/${courseId}`, {
        headers: {
          'Authorization': `Bearer ${token}`
        }
      });
      if (!res.ok) {
        throw new Error('Falha ao carregar detalhes do curso');
      }
      const data = await res.json();
      setCourse(data.course);
      setModules(data.modules);

      // Default to the selected initial lesson, or the first lesson of the first module
      if (data.modules && data.modules.length > 0) {
        let selectedLsn = null;
        if (initialLessonId) {
          for (const mod of data.modules) {
            const found = mod.lessons?.find((l: any) => l.id === initialLessonId);
            if (found) {
              selectedLsn = found;
              break;
            }
          }
        }
        
        if (!selectedLsn) {
          const firstMod = data.modules[0];
          if (firstMod.lessons && firstMod.lessons.length > 0) {
            selectedLsn = firstMod.lessons[0];
          }
        }
        
        if (selectedLsn) {
          handleSelectLesson(selectedLsn, data.modules.find((m: any) => m.lessons.some((l: any) => l.id === selectedLsn.id))?.id);
        }
      }
    } catch (err: any) {
      setError(err.message || 'Erro inesperado.');
    } finally {
      setIsLoading(false);
    }
  };

  const handleSelectLesson = (lesson: Lesson, moduleId?: string) => {
    setActiveLesson(lesson);
    setNoteContent(lesson.note || '');
    setSaveStatus('idle');
    if (moduleId) {
      setExpandedModules(prev => prev.includes(moduleId) ? prev : [...prev, moduleId]);
    } else {
      // Find module if not passed
      const parentMod = modules.find(m => m.lessons.some(l => l.id === lesson.id));
      if (parentMod) {
        setExpandedModules(prev => prev.includes(parentMod.id) ? prev : [...prev, parentMod.id]);
      }
    }
  };

  const toggleModule = (moduleId: string) => {
    setExpandedModules(prev => 
      prev.includes(moduleId) ? prev.filter(id => id !== moduleId) : [...prev, moduleId]
    );
  };

  const totalLessonsCount = modules.reduce((acc, mod) => acc + mod.lessons.length, 0);
  const completedLessonsCount = modules.reduce((acc, mod) => acc + mod.lessons.filter(l => l.progress?.completed).length, 0);
  const overallProgress = totalLessonsCount === 0 ? 0 : Math.round((completedLessonsCount / totalLessonsCount) * 100);

  const handleReact = async (type: string | null) => {
    if (!activeLesson) return;

    try {
      const res = await fetch(`/api/lessons/${activeLesson.id}/react`, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'Authorization': `Bearer ${token}`
        },
        body: JSON.stringify({ type })
      });

      if (res.ok) {
        // Update local state for lesson reaction
        setModules(prev => prev.map(mod => {
          return {
            ...mod,
            lessons: mod.lessons.map(lsn => {
              if (lsn.id === activeLesson.id) {
                return { ...lsn, reaction: type };
              }
              return lsn;
            })
          };
        }));
      }
    } catch (err) {
      console.error('Error saving reaction:', err);
    }
  };

  const handleProgressUpdate = async (watchedPercentage: number) => {
    if (!activeLesson) return;

    try {
      const res = await fetch(`/api/lessons/${activeLesson.id}/progress`, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'Authorization': `Bearer ${token}`
        },
        body: JSON.stringify({ watchedPercentage })
      });

      if (res.ok) {
        const data = await res.json();
        
        // Update local state for lesson progress
        setModules(prev => prev.map(mod => {
          return {
            ...mod,
            lessons: mod.lessons.map(lsn => {
              if (lsn.id === activeLesson.id) {
                return {
                  ...lsn,
                  progress: {
                    watchedPercentage: Math.max(lsn.progress.watchedPercentage, watchedPercentage),
                    completed: data.completed || lsn.progress.completed
                  }
                };
              }
              return lsn;
            })
          };
        }));

        // Also update the active lesson progress locally
        setActiveLesson(prev => {
          if (!prev) return null;
          return {
            ...prev,
            progress: {
              watchedPercentage: Math.max(prev.progress.watchedPercentage, watchedPercentage),
              completed: data.completed || prev.progress.completed
            }
          };
        });
      }
    } catch (err) {
      console.error('Error saving progress:', err);
    }
  };

  const handleSaveNote = async () => {
    if (!activeLesson) return;
    setSaveStatus('saving');

    try {
      const res = await fetch(`/api/lessons/${activeLesson.id}/notes`, {
        method: 'POST',
        headers: {
          'Content-Type': 'application/json',
          'Authorization': `Bearer ${token}`
        },
        body: JSON.stringify({ content: noteContent })
      });

      if (res.ok) {
        setSaveStatus('saved');
        
        // Update local modules array so state matches
        setModules(prev => prev.map(mod => {
          return {
            ...mod,
            lessons: mod.lessons.map(lsn => {
              if (lsn.id === activeLesson.id) {
                return { ...lsn, note: noteContent };
              }
              return lsn;
            })
          };
        }));

        setTimeout(() => setSaveStatus('idle'), 3000);
      } else {
        setSaveStatus('error');
      }
    } catch (err) {
      setSaveStatus('error');
    }
  };

  if (isLoading) {
    return (
      <div className="flex flex-col items-center justify-center min-h-[60vh] text-zinc-400 space-y-4">
        <div className="w-12 h-12 border-4 border-[#E50914] border-t-transparent rounded-full animate-spin" />
        <p className="text-sm font-semibold tracking-wide">Preparando seu ambiente de estudos...</p>
      </div>
    );
  }

  if (error || !course) {
    return (
      <div className="flex flex-col items-center justify-center min-h-[50vh] text-center max-w-md mx-auto p-4 space-y-4">
        <AlertCircle className="w-12 h-12 text-[#E50914]" />
        <h2 className="text-xl font-bold text-white">Oops! Algo deu errado</h2>
        <p className="text-sm text-zinc-400">{error || 'Não foi possível carregar as informações deste curso.'}</p>
        <button 
          onClick={onBack}
          className="bg-zinc-800 hover:bg-zinc-700 text-white font-bold px-6 py-2 rounded-lg transition-colors flex items-center space-x-2"
        >
          <ArrowLeft className="w-4 h-4" />
          <span>Voltar para cursos</span>
        </button>
      </div>
    );
  }

  if (activeActivityModuleId) {
    return (
      <CourseActivity 
        token={token}
        moduleId={activeActivityModuleId}
        onBack={() => setActiveActivityModuleId(null)}
        onCompleted={(passed) => {
          if (passed) {
            // Re-fetch course details to update any unlocked certificates if applicable
            fetchCourseDetails();
          }
        }}
      />
    );
  }

  return (
    <div className="space-y-6">
      {/* Back Header */}
      <div className="flex items-center justify-between pb-4 border-b border-white/10">
        <button 
          onClick={onBack}
          className="group flex items-center space-x-2 text-zinc-400 hover:text-white transition-colors font-semibold text-sm cursor-pointer"
        >
          <ArrowLeft className="w-4 h-4 group-hover:-translate-x-1 transition-transform" />
          <span>Voltar ao Catálogo</span>
        </button>
        <span className="text-zinc-500 text-xs font-bold uppercase tracking-widest">{course.category}</span>
      </div>

      {/* Main Grid: Player on left, lessons sidebar on right */}
      <div className="grid grid-cols-1 lg:grid-cols-3 gap-8">
        
        {/* Left Hand: Video & Notes */}
        <div className="lg:col-span-2 space-y-6">
          {activeLesson ? (
            <div className="space-y-4">
              <h2 className="text-xl md:text-2xl font-sans font-extrabold text-white tracking-tight">
                {activeLesson.title}
              </h2>
              
              <VideoPlayer 
                videoUrl={activeLesson.videoUrl}
                videoType={activeLesson.videoType}
                lessonId={activeLesson.id}
                onProgressUpdate={handleProgressUpdate}
                initialProgress={activeLesson.progress?.watchedPercentage || 0}
                reaction={activeLesson.reaction}
                onReact={handleReact}
              />

              {/* Lesson Description Content */}
              {activeLesson.content && (
                <div className="glass-card p-5 rounded-xl space-y-2">
                  <h3 className="text-xs font-bold text-zinc-400 uppercase tracking-widest flex items-center space-x-1.5">
                    <FileText className="w-3.5 h-3.5 text-[#E50914]" />
                    <span>Recursos & Descrição da Aula</span>
                  </h3>
                  <p className="text-zinc-300 text-sm leading-relaxed whitespace-pre-line">
                    {activeLesson.content}
                  </p>
                </div>
              )}

              {/* Notes & Doubts panel */}
              <div className="glass-card p-5 rounded-xl space-y-4">
                <div className="flex items-center justify-between">
                  <h3 className="text-xs font-bold text-zinc-400 uppercase tracking-widest flex items-center space-x-1.5">
                    <MessageSquare className="w-3.5 h-3.5 text-[#E50914]" />
                    <span>Suas Anotações e Dúvidas</span>
                  </h3>
                  {saveStatus === 'saving' && <span className="text-[10px] text-zinc-500">Salvando...</span>}
                  {saveStatus === 'saved' && <span className="text-[10px] text-emerald-500 font-bold">Salvo com sucesso!</span>}
                  {saveStatus === 'error' && <span className="text-[10px] text-red-500 font-bold">Erro ao salvar.</span>}
                </div>
                
                <textarea
                  value={noteContent}
                  onChange={(e) => setNoteContent(e.target.value)}
                  placeholder="Escreva aqui suas anotações pessoais, dúvidas ou resumos sobre esta aula... Seus apontamentos são salvos automaticamente."
                  className="w-full h-32 glass-input rounded-lg p-3 text-sm text-zinc-100 placeholder-zinc-500 focus:outline-none resize-none"
                />

                <div className="flex justify-end">
                  <button
                    onClick={handleSaveNote}
                    disabled={saveStatus === 'saving'}
                    className="glass-btn-secondary text-white font-bold text-xs px-4 py-2 rounded-lg cursor-pointer"
                  >
                    Salvar Anotações
                  </button>
                </div>
              </div>
            </div>
          ) : (
            <div className="h-[40vh] glass-card rounded-xl flex flex-col items-center justify-center text-zinc-500 text-center p-6">
              <BookOpen className="w-12 h-12 text-zinc-700 mb-2" />
              <p className="text-sm font-semibold text-zinc-400">Nenhuma aula cadastrada neste curso ainda.</p>
              <p className="text-xs text-zinc-600 mt-1">O administrador adicionará conteúdo em breve!</p>
            </div>
          )}
        </div>

        {/* Right Hand: Interactive Modules Accordion */}
        <div className="space-y-4">
          <div className="glass-card p-4 rounded-xl space-y-3">
            <div>
              <h3 className="font-sans font-extrabold text-sm text-white tracking-tight">Conteúdo do Curso</h3>
              <p className="text-xs text-zinc-500 font-medium mt-1">{course.title}</p>
            </div>
            
            {course.studyMaterialUrl && (
              <a 
                href={course.studyMaterialUrl} 
                target="_blank" 
                rel="noreferrer"
                className="flex items-center justify-center gap-2 w-full glass-btn-secondary text-[#E50914] text-xs font-bold py-2 px-3 rounded-lg hover:scale-[1.02] transition-all"
              >
                <Download className="w-4 h-4" />
                Baixar Material de Estudo
              </a>
            )}
          </div>

          {/* Overall Progress Block */}
          <div className="glass-card rounded-xl p-4 mb-4 border border-white/5 flex items-center justify-between">
            <div className="flex items-center space-x-3">
              <div className="relative w-10 h-10 flex items-center justify-center flex-shrink-0">
                <svg viewBox="0 0 36 36" className="w-10 h-10 -rotate-90 absolute inset-0">
                  <path className="text-zinc-800" strokeWidth="3" stroke="currentColor" fill="none" d="M18 2.0845 a 15.9155 15.9155 0 0 1 0 31.831 a 15.9155 15.9155 0 0 1 0 -31.831" />
                  <path className="text-[#E50914] transition-all duration-1000 ease-out" strokeDasharray={`${overallProgress}, 100`} strokeWidth="3" strokeLinecap="round" stroke="currentColor" fill="none" d="M18 2.0845 a 15.9155 15.9155 0 0 1 0 31.831 a 15.9155 15.9155 0 0 1 0 -31.831" />
                </svg>
                <span className="text-[10px] font-bold text-white z-10">{overallProgress}%</span>
              </div>
              <div>
                <h4 className="text-sm font-bold text-white">Meu progresso</h4>
                <p className="text-xs text-zinc-500">{completedLessonsCount} de {totalLessonsCount} {totalLessonsCount === 1 ? 'aula' : 'aulas'}</p>
              </div>
            </div>
          </div>

          <div className="space-y-3">
            {modules.map((mod, modIdx) => {
              const isExpanded = expandedModules.includes(mod.id);
              const moduleTotal = mod.lessons.length;
              const moduleCompleted = mod.lessons.filter(l => l.progress?.completed).length;
              const isModuleFullyCompleted = moduleTotal > 0 && moduleTotal === moduleCompleted;
              const moduleProgressPercent = moduleTotal > 0 ? Math.round((moduleCompleted / moduleTotal) * 100) : 0;

              return (
                <div 
                  key={mod.id} 
                  className="glass-card rounded-xl overflow-hidden border border-white/5"
                >
                  {/* Module Title bar (Clickable) */}
                  <button 
                    onClick={() => toggleModule(mod.id)}
                    className="w-full text-left px-4 py-3.5 flex items-center justify-between hover:bg-white/5 transition-colors"
                  >
                    <div className="flex items-center space-x-3">
                      <div className="relative w-8 h-8 flex items-center justify-center flex-shrink-0">
                        <svg viewBox="0 0 36 36" className="w-8 h-8 -rotate-90 absolute inset-0">
                          <path className="text-zinc-800" strokeWidth="3" stroke="currentColor" fill="none" d="M18 2.0845 a 15.9155 15.9155 0 0 1 0 31.831 a 15.9155 15.9155 0 0 1 0 -31.831" />
                          <path className="text-[#E50914] transition-all duration-1000 ease-out" strokeDasharray={`${moduleProgressPercent}, 100`} strokeWidth="3" strokeLinecap="round" stroke="currentColor" fill="none" d="M18 2.0845 a 15.9155 15.9155 0 0 1 0 31.831 a 15.9155 15.9155 0 0 1 0 -31.831" />
                        </svg>
                        <span className="text-[8px] font-bold text-white z-10">{moduleProgressPercent}%</span>
                      </div>
                      <div>
                        <h4 className="font-sans font-bold text-xs text-zinc-200 tracking-tight leading-snug line-clamp-1">
                          {mod.title}
                        </h4>
                        <p className="text-[10px] text-zinc-500 mt-0.5">
                          {moduleTotal} {moduleTotal === 1 ? 'aula' : 'aulas'}
                        </p>
                      </div>
                    </div>
                  </button>

                  {/* Lessons list inside module */}
                  {isExpanded && (
                    <div className="px-4 pb-3">
                      <div className="ml-2 border-l border-zinc-700 pl-4 py-1 space-y-1">
                        {mod.lessons.length === 0 ? (
                          <div className="py-2 text-xs text-zinc-600 italic">Nenhuma aula neste módulo.</div>
                        ) : (
                          mod.lessons.map(lesson => {
                            const isActive = activeLesson?.id === lesson.id;
                            const isLsnCompleted = lesson.progress?.completed;

                            return (
                              <button
                                key={lesson.id}
                                onClick={() => handleSelectLesson(lesson, mod.id)}
                                className="relative w-full py-2.5 text-left flex items-start space-x-3 group"
                              >
                                {/* Timeline Dot indicator overlaying the border */}
                                <div className={`absolute -left-[21px] top-3.5 w-2 h-2 rounded-full ring-4 ring-[#141414] ${
                                  isLsnCompleted ? 'bg-emerald-500' : isActive ? 'bg-[#E50914]' : 'bg-zinc-600'
                                }`} />

                                <div className="space-y-0.5">
                                  <span className={`font-medium text-xs leading-snug line-clamp-2 transition-colors ${
                                    isActive ? 'text-[#E50914] font-bold' : 'text-zinc-400 group-hover:text-zinc-200'
                                  }`}>
                                    {lesson.order}. {lesson.title}
                                  </span>
                                </div>
                              </button>
                            );
                          })
                        )}

                        {/* Module Activity Button (End of Timeline) */}
                        {mod.lessons.length > 0 && (
                          <div className="relative pt-4 pb-1">
                            <div className="absolute -left-[21px] top-[22px] w-2 h-2 rounded-full bg-zinc-700 ring-4 ring-[#141414]" />
                            <button
                              onClick={() => isModuleFullyCompleted && setActiveActivityModuleId(mod.id)}
                              disabled={!isModuleFullyCompleted}
                              className={`w-full flex items-center justify-center space-x-2 transition-all py-2.5 px-3 rounded-lg text-xs font-extrabold uppercase tracking-wider shadow-md border ${
                                isModuleFullyCompleted 
                                  ? 'glass-btn-primary hover:scale-[1.02] text-white cursor-pointer border-transparent' 
                                  : 'bg-zinc-800/50 text-zinc-500 cursor-not-allowed border-zinc-700/50'
                              }`}
                              title={!isModuleFullyCompleted ? "Conclua todas as aulas deste módulo para liberar a avaliação" : ""}
                            >
                              <Award className="w-4 h-4 flex-shrink-0" />
                              <span className="truncate">Avaliação do Módulo</span>
                            </button>
                          </div>
                        )}
                      </div>
                    </div>
                  )}
                </div>
              );
            })}
          </div>
        </div>

      </div>
    </div>
  );
}