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

import '../../app/app_controller.dart';
import '../../domain/school_term.dart';
import 'school_session.dart';

class SchoolAuthPage extends StatefulWidget {
  const SchoolAuthPage({
    super.key,
    required this.session,
    required this.controller,
  });
  final SchoolSession session;
  final AppController controller;
  @override
  State<SchoolAuthPage> createState() => _SchoolAuthPageState();
}

class _SchoolAuthPageState extends State<SchoolAuthPage> {
  bool _saving = false;
  SchoolTerm? _termChoice;
  @override
  void initState() {
    super.initState();
    widget.session.addListener(_changed);
    WidgetsBinding.instance.addPostFrameCallback((_) {
      if (!mounted) return;
      widget.session.setReadingActive(true);
      _changed();
    });
  }

  void _changed() {
    if (!mounted) return;
    setState(() {});
    final s = widget.session;
    final courses = s.pendingDraft, exams = s.pendingExams;
    final generation = s.pageGeneration;
    final route = ModalRoute.of(context);
    if (s.needsTermSelection || _saving || (courses == null && exams == null)) {
      return;
    }
    _saving = true;
    WidgetsBinding.instance.addPostFrameCallback((_) async {
      if (!mounted) {
        _saving = false;
        return;
      }
      // The session draft must still belong to the same page after navigation.
      if (generation != s.pageGeneration ||
          courses != s.pendingDraft ||
          exams != s.pendingExams) {
        _saving = false;
        _changed();
        return;
      }
      if (courses != null) {
        await widget.controller.applyImport(courses, confirmedEmpty: false);
      }
      if (exams != null) await widget.controller.applyExams(exams);
      final success = widget.controller.lastError == null;
      final acknowledged = s.saved(
        success: success,
        generation: generation,
        draft: courses,
        exams: exams,
      );
      _saving = false;
      if (!mounted) return;
      if (!acknowledged) {
        _changed();
        return;
      }
      if (success && route?.isCurrent == true) {
        Navigator.of(context).pop();
        ScaffoldMessenger.of(context).showSnackBar(
          SnackBar(
            content: Text(exams == null ? '课表已导入；请核对学期开始日。' : '考试信息已更新'),
          ),
        );
      } else {
        setState(() {});
      }
    });
  }

  @override
  void dispose() {
    widget.session.removeListener(_changed);
    widget.session.setReadingActive(false);
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    final s = widget.session;
    return Scaffold(
      appBar: AppBar(
        title: const Text('学校认证'),
        actions: [
          IconButton(
            tooltip: '重新认证',
            onPressed: _saving ? null : s.openAuthentication,
            icon: const Icon(Icons.refresh_rounded),
          ),
          IconButton(
            tooltip: '读取当前页面',
            onPressed: _saving || s.needsTermSelection
                ? null
                : s.readCurrentPage,
            icon: const Icon(Icons.sync_rounded),
          ),
        ],
      ),
      body: Column(
        children: [
          if (s.busy || _saving) const LinearProgressIndicator(minHeight: 2),
          Container(
            width: double.infinity,
            padding: const EdgeInsets.all(12),
            color: const Color(0xFFEFF6FF),
            child: Text(
              s.message,
              style: const TextStyle(fontSize: 12, height: 1.5),
            ),
          ),
          Expanded(
            child: Stack(
              children: [
                WebViewWidget(controller: s.web),
                if (s.needsTermSelection)
                  Positioned.fill(child: _termPicker(s)),
                if (!s.needsTermSelection && (s.finding || _saving))
                  Positioned.fill(
                    child: ColoredBox(
                      color: const Color(0xFFF5F9FE),
                      child: Center(
                        child: Column(
                          mainAxisSize: MainAxisSize.min,
                          children: [
                            const CircularProgressIndicator(),
                            const SizedBox(height: 20),
                            Text(
                              _saving
                                  ? '正在保存，请稍候'
                                  : (s.requestingExams
                                        ? '正在查找考试安排，请稍候'
                                        : '正在查找课表，请稍候'),
                            ),
                          ],
                        ),
                      ),
                    ),
                  ),
              ],
            ),
          ),
        ],
      ),
    );
  }

  Widget _termPicker(SchoolSession session) {
    final choices = session.termChoices;
    final preferred =
        _termChoice ??
        session.selectedTerm ??
        widget.controller.snapshot.schoolTerm ??
        choices.first;
    final selected = choices.contains(preferred) ? preferred : choices.first;
    return Material(
      color: const Color(0xFFF5F9FE),
      child: SafeArea(
        child: Padding(
          padding: const EdgeInsets.fromLTRB(20, 16, 20, 20),
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.stretch,
            children: [
              const Text(
                '选择学校学期',
                style: TextStyle(fontSize: 22, fontWeight: FontWeight.w700),
              ),
              const SizedBox(height: 8),
              Text(session.requestingExams ? '将读取这个学期的考试安排。' : '将读取这个学期的课程表。'),
              const SizedBox(height: 12),
              Expanded(
                child: ListView.builder(
                  itemCount: choices.length,
                  itemBuilder: (context, index) {
                    final term = choices[index];
                    final isSelected = term == selected;
                    return ListTile(
                      title: Text(term.label),
                      selected: isSelected,
                      leading: Icon(
                        isSelected
                            ? Icons.radio_button_checked
                            : Icons.radio_button_off,
                      ),
                      onTap: () => setState(() => _termChoice = term),
                    );
                  },
                ),
              ),
              const SizedBox(height: 12),
              FilledButton(
                onPressed: () => session.selectTerm(selected),
                child: const Text('导入所选学期'),
              ),
              TextButton(
                onPressed: () => Navigator.of(context).pop(),
                child: const Text('取消'),
              ),
            ],
          ),
        ),
      ),
    );
  }
}