import "package:flutter/material.dart";

import "../../core/app_state.dart";
import "../../core/app_theme.dart";
import "../../core/models.dart";
import "../../core/courses/courses.dart";
import "../dialogue/dialogue_flow.dart";
import "../assessment/assessment_page.dart";
import "../home/home_page.dart";
import "../lesson/lesson_flow.dart";
import "../profile/profile_page.dart";
import "../review/review_page.dart";

class LearningShell extends StatefulWidget {
  const LearningShell({super.key, required this.state});
  final AppState state;

  @override
  State<LearningShell> createState() => _LearningShellState();
}

class _LearningShellState extends State<LearningShell> {
  AppTab tab = AppTab.learn;
  var route = _ShellRoute.tab;
  _ShellRoute? previousRoute;
  bool dialogueInLesson = false;
  String sceneId = 'a0-meet';
  AssessmentPack? assessmentPack;
  DialogueSummaryData? dialogueSummary;

  void showTab(AppTab value) => setState(() {
    tab = value;
    route = _ShellRoute.tab;
    previousRoute = null;
  });

  void showLesson() => setState(() {
    previousRoute = route;
    route = _ShellRoute.lesson;
  });

  void showDialogue({bool inLesson = false, String? scene}) => setState(() {
    previousRoute = route;
    dialogueInLesson = inLesson;
    if (scene != null) sceneId = scene;
    route = _ShellRoute.dialogue;
  });

  void showSummary(DialogueSummaryData summary) => setState(() {
    previousRoute = route;
    dialogueSummary = summary;
    route = _ShellRoute.summary;
  });

  void showAssessment(AssessmentPack pack) => setState(() {
    previousRoute = route;
    assessmentPack = pack;
    route = _ShellRoute.assessmentPreparation;
  });

  void startAssessment() => setState(() {
    previousRoute = route;
    route = _ShellRoute.assessment;
  });

  void showAdaptiveLesson() => setState(() {
    previousRoute = route;
    route = _ShellRoute.adaptiveLesson;
  });

  void handleBack() {
    switch (route) {
      case _ShellRoute.lesson:
        showTab(tab);
      case _ShellRoute.dialogue:
        if (dialogueInLesson) {
          showLesson();
        } else {
          showTab(tab);
        }
      case _ShellRoute.summary:
        showTab(tab);
      case _ShellRoute.adaptiveLesson:
        showTab(AppTab.review);
      case _ShellRoute.assessmentPreparation:
        showTab(AppTab.profile);
      case _ShellRoute.assessment:
        if (assessmentPack != null) {
          showAssessment(assessmentPack!);
        } else {
          showTab(AppTab.profile);
        }
      case _ShellRoute.tab:
        if (tab != AppTab.learn) {
          showTab(AppTab.learn);
        }
    }
  }

  @override
  Widget build(BuildContext context) {
    Widget body;
    switch (route) {
      case _ShellRoute.lesson:
        body = LessonFlow(
          // 换课或换段时重建，避免上一段的听力选择和播放状态沿用过来。
          key: ValueKey(
            '${widget.state.activeLessonId}-'
            '${widget.state.activeSegmentIndexFor(widget.state.activeLessonId)}',
          ),
          state: widget.state,
          onOpenDialogue: () => showDialogue(inLesson: true),
          onFinish: () => showTab(tab),
        );
      case _ShellRoute.dialogue:
        body = DialoguePage(
          key: ValueKey(dialogueInLesson ? 'lesson' : 'scene-$sceneId'),
          state: widget.state,
          isLessonDialogue: dialogueInLesson,
          sceneId: sceneId,
          onFinished: (summary) {
            if (dialogueInLesson) {
              showLesson();
            } else if (summary != null) {
              showSummary(summary);
            } else {
              handleBack();
            }
          },
        );
      case _ShellRoute.summary:
        body = DialogueSummaryPage(
          summary: dialogueSummary!,
          onHome: () => showTab(AppTab.learn),
          onLesson: showLesson,
          onRetry: () => showDialogue(scene: sceneId),
          onBack: () => showTab(tab),
        );
      case _ShellRoute.adaptiveLesson:
        body = AdaptiveLessonPage(
          state: widget.state,
          onFinished: () => showTab(AppTab.review),
        );
      case _ShellRoute.assessment:
        body = AssessmentPage(
          state: widget.state,
          pack: assessmentPack!,
          onFinished: () => showTab(AppTab.profile),
          onStartReplacement: showAssessment,
        );
      case _ShellRoute.assessmentPreparation:
        body = AssessmentPreparationPage(
          state: widget.state,
          pack: assessmentPack!,
          onStart: startAssessment,
          onBack: () => showTab(AppTab.profile),
        );
      case _ShellRoute.tab:
        body = _tabContent();
    }

    return PopScope(
      canPop: route == _ShellRoute.tab && tab == AppTab.learn,
      onPopInvokedWithResult: (didPop, _) {
        if (!didPop) {
          handleBack();
        }
      },
      child: AnimatedBuilder(
        animation: widget.state,
        builder: (context, _) => Scaffold(
          body: body,
          bottomNavigationBar: route == _ShellRoute.tab
              ? NavigationBar(
                  selectedIndex: tab.index,
                  height: 70,
                  indicatorColor: AppColors.softGreen,
                  onDestinationSelected: (index) =>
                      showTab(AppTab.values[index]),
                  destinations: const [
                    NavigationDestination(
                      icon: Icon(Icons.menu_book_outlined),
                      selectedIcon: Icon(Icons.menu_book),
                      label: "学习",
                    ),
                    NavigationDestination(
                      icon: Icon(Icons.chat_bubble_outline),
                      selectedIcon: Icon(Icons.chat_bubble),
                      label: "对话",
                    ),
                    NavigationDestination(
                      icon: Icon(Icons.refresh_outlined),
                      selectedIcon: Icon(Icons.refresh),
                      label: "复习",
                    ),
                    NavigationDestination(
                      icon: Icon(Icons.person_outline),
                      selectedIcon: Icon(Icons.person),
                      label: "我的",
                    ),
                  ],
                )
              : null,
        ),
      ),
    );
  }

  Widget _tabContent() {
    switch (tab) {
      case AppTab.learn:
        return HomePage(
          state: widget.state,
          onStartLesson: showLesson,
          onOpenLesson: (id) {
            widget.state.openLesson(id);
            showLesson();
          },
          onStartReview: () => showTab(AppTab.review),
          onResumeLessonDialogue: () => showDialogue(inLesson: true),
          onStartReinforcement: () {
            widget.state.scheduleA0Reinforcement();
            showTab(AppTab.review);
          },
          onOpenAssessment: (packId) {
            final pack = a0AssessmentPacks
                .where((item) => item.id == packId)
                .firstOrNull;
            if (pack != null) showAssessment(pack);
          },
        );
      case AppTab.dialogue:
        return DialogueScenePage(
          state: widget.state,
          onStart: (id) => showDialogue(scene: id),
        );
      case AppTab.review:
        return ReviewPage(
          state: widget.state,
          onFinished: () => showTab(AppTab.learn),
          onOpenAdaptiveLesson: showAdaptiveLesson,
        );
      case AppTab.profile:
        return ProfilePage(
          state: widget.state,
          onOpenAssessment: showAssessment,
          onOpenReview: () => showTab(AppTab.review),
        );
    }
  }
}

enum _ShellRoute {
  tab,
  lesson,
  dialogue,
  summary,
  adaptiveLesson,
  assessmentPreparation,
  assessment,
}