import "package:flutter/material.dart";

import "../../core/app_state.dart";
import "../../core/app_theme.dart";
import "../../core/models.dart";
import "../../core/seed_courses.dart";
import "../../core/assessment_bank.dart";
import "../../widgets/app_widgets.dart";
import "../dialogue/dialogue_flow.dart";
import "../assessment/assessment_page.dart";
import "../home/home_page.dart";
import "../lesson/lesson_flow.dart";
import "../progress/progress_pages.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.home;
  var route = _ShellRoute.tab;
  _ShellRoute? previousRoute;
  bool dialogueInLesson = false;
  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 showDialogueScene() => setState(() {
    previousRoute = route;
    route = _ShellRoute.scene;
  });

  void showDialogue({bool inLesson = false}) => setState(() {
    previousRoute = route;
    dialogueInLesson = inLesson;
    route = _ShellRoute.dialogue;
  });

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

  void showSettings() => setState(() {
    previousRoute = route;
    route = _ShellRoute.settings;
  });

  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.scene:
        showTab(tab);
      case _ShellRoute.dialogue:
        if (dialogueInLesson) {
          showLesson();
        } else if (previousRoute == _ShellRoute.scene) {
          showDialogueScene();
        } else {
          showTab(tab == AppTab.dialogue ? AppTab.dialogue : tab);
        }
      case _ShellRoute.summary:
        showTab(tab);
      case _ShellRoute.settings:
        showTab(AppTab.progress);
      case _ShellRoute.adaptiveLesson:
        showTab(AppTab.review);
      case _ShellRoute.assessmentPreparation:
        showTab(AppTab.progress);
      case _ShellRoute.assessment:
        if (assessmentPack != null) {
          showAssessment(assessmentPack!);
        } else {
          showTab(AppTab.progress);
        }
      case _ShellRoute.tab:
        if (tab != AppTab.home) {
          showTab(AppTab.home);
        }
    }
  }

  @override
  Widget build(BuildContext context) {
    Widget body;
    switch (route) {
      case _ShellRoute.lesson:
        body = LessonFlow(
          state: widget.state,
          onOpenDialogue: () => showDialogue(inLesson: true),
          onFinish: () => showTab(tab),
        );
      case _ShellRoute.scene:
        body = DialogueScenePage(
          onStart: showDialogue,
          onBack: () => showTab(tab),
        );
      case _ShellRoute.dialogue:
        body = DialoguePage(
          state: widget.state,
          isLessonDialogue: dialogueInLesson,
          onFinished: (summary) {
            if (dialogueInLesson) {
              showLesson();
            } else if (summary != null) {
              showSummary(summary);
            } else {
              handleBack();
            }
          },
        );
      case _ShellRoute.summary:
        body = DialogueSummaryPage(
          summary: dialogueSummary!,
          onHome: () => showTab(AppTab.home),
          onLesson: showLesson,
          onRetry: showDialogue,
          onBack: () => showTab(tab),
        );
      case _ShellRoute.settings:
        body = SettingsPage(
          state: widget.state,
          onBack: () => showTab(AppTab.progress),
        );
      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.progress),
          onStartReplacement: showAssessment,
        );
      case _ShellRoute.assessmentPreparation:
        body = AssessmentPreparationPage(
          state: widget.state,
          pack: assessmentPack!,
          onStart: startAssessment,
          onBack: () => showTab(AppTab.progress),
        );
      case _ShellRoute.tab:
        body = _tabContent();
    }

    return PopScope(
      canPop: route == _ShellRoute.tab && tab == AppTab.home,
      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.home_outlined),
                      selectedIcon: Icon(Icons.home),
                      label: "首页",
                    ),
                    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.home:
        return HomePage(
          state: widget.state,
          onStartPrimaryTask: () {
            if (widget.state.reviewIsPrimary) {
              showTab(AppTab.review);
            } else {
              showLesson();
            }
          },
          onOpenDialogue: showDialogueScene,
          onResumeLessonDialogue: () => showDialogue(inLesson: true),
        );
      case AppTab.learn:
        return _LearningMap(
          onOpenLesson: (id) {
            widget.state.openLesson(id);
            showLesson();
          },
          onStartReinforcement: () {
            widget.state.scheduleA0Reinforcement();
            showTab(AppTab.review);
          },
          onOpenReview: () => showTab(AppTab.review),
          state: widget.state,
        );
      case AppTab.dialogue:
        return DialogueScenePage(onStart: showDialogue);
      case AppTab.review:
        return ReviewPage(
          state: widget.state,
          onFinished: () => showTab(AppTab.home),
          onOpenAdaptiveLesson: showAdaptiveLesson,
        );
      case AppTab.progress:
        return ProgressPage(
          state: widget.state,
          onSettings: showSettings,
          onOpenAssessment: showAssessment,
        );
    }
  }
}

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

class _LearningMap extends StatelessWidget {
  const _LearningMap({
    required this.onOpenLesson,
    required this.onStartReinforcement,
    required this.onOpenReview,
    required this.state,
  });
  final ValueChanged<String> onOpenLesson;
  final VoidCallback onStartReinforcement;
  final VoidCallback onOpenReview;
  final AppState state;

  @override
  Widget build(BuildContext context) {
    return AppPage(
      child: SpacedColumn(
        children: [
          const Eyebrow("学习地图 · 按掌握状态推进"),
          Text("从认识到开口", style: Theme.of(context).textTheme.headlineMedium),
          const Text("每节课都围绕一个能完成的小任务。"),
          if (state.reviewBacklog)
            SectionCard(
              tint: AppColors.warm,
              child: SpacedColumn(
                children: [
                  Text(
                    "复习已有积压，今天先完成 ${state.dueReviewCount} 项到期复习，再开启新课。",
                    style: const TextStyle(color: AppColors.warmInk),
                  ),
                  SecondaryButton(label: "先去复习", onPressed: onOpenReview),
                ],
              ),
            ),
          for (final lesson in a0SeedLessons)
            SectionCard(
              tint: lesson.id == state.activeLessonId
                  ? AppColors.softGreen
                  : null,
              onTap:
                  state.isLessonUnlocked(lesson.id) &&
                      (!state.reviewBacklog ||
                          state.completedLessonIds.contains(lesson.id))
                  ? () => onOpenLesson(lesson.id)
                  : null,
              child: Row(
                children: [
                  Icon(
                    state.completedLessonIds.contains(lesson.id)
                        ? Icons.check_circle
                        : state.reviewBacklog
                        ? Icons.lock_outline
                        : state.isLessonUnlocked(lesson.id)
                        ? Icons.play_circle_outline
                        : Icons.lock_outline,
                    color: state.completedLessonIds.contains(lesson.id)
                        ? AppColors.green
                        : AppColors.muted,
                  ),
                  const SizedBox(width: 10),
                  Expanded(
                    child: Column(
                      crossAxisAlignment: CrossAxisAlignment.start,
                      children: [
                        Text(
                          "第 ${lesson.number} 课 · ${lesson.title}",
                          style: const TextStyle(fontWeight: FontWeight.w600),
                        ),
                        const SizedBox(height: 3),
                        Text(
                          lesson.segments.length > 1
                              ? "${lesson.outcome} · 小段 ${lesson.segments.where((segment) => state.isSegmentComplete(segment.id)).length}/${lesson.segments.length}"
                              : lesson.outcome,
                          style: Theme.of(context).textTheme.bodyMedium,
                        ),
                      ],
                    ),
                  ),
                ],
              ),
            ),
          if (state.completedLessonIds.length == a0SeedLessons.length)
            SectionCard(
              tint: AppColors.softGreen,
              child: SpacedColumn(
                children: [
                  const Text(
                    "A0 巩固变式",
                    style: TextStyle(fontSize: 16, fontWeight: FontWeight.w600),
                  ),
                  const Text("换一个人物、地点或情境，继续巩固尚未稳定的核心表达。"),
                  PrimaryButton(
                    label: "安排一题巩固练习",
                    onPressed: onStartReinforcement,
                  ),
                ],
              ),
            ),
        ],
      ),
    );
  }
}