// FlowEditorPage — the public-facing widget Studio (and any
// other host) embeds as its flow surface.
//
// Layout:
//
//   ┌─ Toolbar ─────────────────────────────────────────────┐
//   │ [back] file.yaml ●        [+ Step] [Save] [Run]       │
//   ├──────┬────────────────────────────────────────────────┤
//   │ FLOWS│ [Graph][Text][Run]                             │
//   │  ⟲   │                                                │
//   │      │  (active tab content)                          │
//   │ list │                                                │
//   │      │                                                │
//   └──────┴────────────────────────────────────────────────┘
//                                            └ Properties (overlay)
//
// All three tabs read state from a single [FlowEditorController].
// The graph tab and text tab keep YAML in lockstep — graph
// edits emit fresh YAML; text edits re-parse the graph on
// debounce. The run tab reads the saved-on-disk version
// because that's what the hub's runSavedFlow consumes.

library;

import 'dart:io';

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_code_editor/flutter_code_editor.dart';

import 'editor_controller.dart';
import 'l10n.dart';
import 'model/flow_graph.dart';
import 'run_driver.dart';
import 'tokens.dart';
import 'widgets.dart';
import 'widgets/capability_picker.dart';
import 'widgets/flow_canvas.dart';
import 'widgets/properties_panel.dart';
import 'widgets/run_tab.dart';

/// Compute the flows directory under the operator's home.
String _defaultFlowsDir() {
  final home =
      Platform.environment['HOME'] ??
      Platform.environment['USERPROFILE'] ??
      '.';
  return '$home/.fai/data/flows';
}

class FlowEditorPage extends StatefulWidget {
  /// Pre-load this flow on open. When null, the editor starts
  /// empty and the operator picks from the file list.
  final String? initialFlowName;

  /// Language for inline strings.
  final FlowEditorLocale locale;

  /// Bridge between editor and host's hub. When null, the
  /// Run tab is read-only.
  final FlowRunDriver? runDriver;

  /// Capabilities the operator can drop into a new step.
  /// Studio supplies the list from `HubService.listCapabilities()`.
  /// Empty list = the picker shows a free-form text field.
  final List<String> availableCapabilities;

  const FlowEditorPage({
    super.key,
    this.initialFlowName,
    this.locale = FlowEditorLocale.en,
    this.runDriver,
    this.availableCapabilities = const [],
  });

  @override
  State<FlowEditorPage> createState() => _FlowEditorPageState();
}

class _FlowEditorPageState extends State<FlowEditorPage>
    with TickerProviderStateMixin {
  late final FlowEditorController _controller;
  late final FlowEditorStrings _l;
  late Future<List<_FlowFile>> _files;
  late final TabController _tabs;

  @override
  void initState() {
    super.initState();
    _l = FlowEditorStrings(widget.locale);
    _controller = FlowEditorController();
    _controller.addListener(_onCtrlChanged);
    _tabs = TabController(length: 3, vsync: this);
    _files = _listFiles();
    final initial = widget.initialFlowName;
    if (initial != null && initial.isNotEmpty) {
      WidgetsBinding.instance.addPostFrameCallback((_) async {
        await _openByName(initial);
      });
    }
  }

  @override
  void dispose() {
    _controller.removeListener(_onCtrlChanged);
    _controller.dispose();
    _tabs.dispose();
    super.dispose();
  }

  void _onCtrlChanged() {
    if (mounted) setState(() {});
  }

  // --- file ops ---

  Future<List<_FlowFile>> _listFiles() async {
    final dir = Directory(_defaultFlowsDir());
    if (!dir.existsSync()) return <_FlowFile>[];
    final entries = await dir
        .list()
        .where((e) => e is File && e.path.endsWith('.yaml'))
        .cast<File>()
        .toList();
    final files =
        entries
            .map(
              (f) => _FlowFile(
                name: f.uri.pathSegments.last.replaceAll(
                  RegExp(r'\.yaml$'),
                  '',
                ),
                path: f.path,
                sizeBytes: f.statSync().size,
              ),
            )
            .toList()
          ..sort((a, b) => a.name.compareTo(b.name));
    return files;
  }

  Future<void> _openByName(String name) async {
    final path = '${_defaultFlowsDir()}/$name.yaml';
    final file = File(path);
    if (!file.existsSync()) return;
    final text = await file.readAsString();
    if (!mounted) return;
    _controller.openFlow(name, text);
  }

  Future<void> _openFile(_FlowFile f) async {
    if (_controller.isDirty) {
      final keep = await _confirmDiscard();
      if (keep == false || !mounted) return;
    }
    final text = await File(f.path).readAsString();
    if (!mounted) return;
    _controller.openFlow(f.name, text);
  }

  Future<bool?> _confirmDiscard() {
    return showDialog<bool>(
      context: context,
      builder: (ctx) => AlertDialog(
        title: Text(_l.discardTitle),
        content: Text(_l.discardBody),
        actions: [
          TextButton(
            onPressed: () => Navigator.pop(ctx, false),
            child: Text(_l.discardKeep),
          ),
          TextButton(
            onPressed: () => Navigator.pop(ctx, true),
            child: Text(_l.discardThrow),
          ),
        ],
      ),
    );
  }

  Future<void> _save() async {
    final name = _controller.activeName;
    if (name == null) return;
    _controller.saving = true;
    try {
      final file = File('${_defaultFlowsDir()}/$name.yaml');
      await file.writeAsString(
        _controller.codeController.fullText,
        flush: true,
      );
      if (!mounted) return;
      _controller.markSaved();
      _files = _listFiles();
      setState(() {});
    } catch (e) {
      if (!mounted) return;
      ScaffoldMessenger.of(
        context,
      ).showSnackBar(SnackBar(content: Text(e.toString())));
    } finally {
      _controller.saving = false;
    }
  }

  Future<void> _newFlow() async {
    final name = await showDialog<String>(
      context: context,
      builder: (ctx) => _NewFlowDialog(strings: _l),
    );
    if (name == null || name.isEmpty || !mounted) return;
    final template =
        '''# ${_l.newTemplateComment(name)}

name: $name

inputs:
  text:
    type: text

steps:
  - id: echo
    use: debug.echo@^0
    with:
      message: \$inputs.text

outputs:
  result: \$echo.echoed
''';
    try {
      final dir = Directory(_defaultFlowsDir());
      if (!dir.existsSync()) await dir.create(recursive: true);
      final file = File('${dir.path}/$name.yaml');
      if (file.existsSync()) {
        if (!mounted) return;
        ScaffoldMessenger.of(
          context,
        ).showSnackBar(SnackBar(content: Text(_l.alreadyExists(name))));
        return;
      }
      await file.writeAsString(template, flush: true);
      if (!mounted) return;
      _controller.openFlow(name, template);
      _files = _listFiles();
      setState(() {});
    } catch (e) {
      if (!mounted) return;
      ScaffoldMessenger.of(
        context,
      ).showSnackBar(SnackBar(content: Text(e.toString())));
    }
  }

  Future<void> _refreshFiles() async {
    setState(() => _files = _listFiles());
  }

  Future<void> _addStep() async {
    final picked = await CapabilityPicker.show(
      context,
      capabilities: widget.availableCapabilities,
      strings: _l,
    );
    if (picked == null || !mounted) return;
    final graph = _controller.graph;
    // Generate a fresh id — base on the capability's local
    // name, deduplicating against existing step ids.
    final localPart = picked.split('/').last.split('@').first;
    final baseId = localPart.split('.').last;
    var id = baseId;
    var i = 1;
    while (graph.steps.any((s) => s.id == id)) {
      id = '${baseId}_$i';
      i++;
    }
    _controller.applyGraphEdit(
      graph.withStepAdded(FlowStep(id: id, use: picked, with_: const {})),
    );
    _controller.selectStep(id);
    _tabs.animateTo(0);
  }

  // --- build ---

  @override
  Widget build(BuildContext context) {
    // Keyboard shortcuts: Cmd/Ctrl+S to save, Cmd/Ctrl+Enter
    // to start a run. The text tab also keeps these but the
    // global wrapper covers the graph + run tabs too.
    return Shortcuts(
      shortcuts: <ShortcutActivator, Intent>{
        LogicalKeySet(LogicalKeyboardKey.meta, LogicalKeyboardKey.keyS):
            const _SaveIntent(),
        LogicalKeySet(LogicalKeyboardKey.control, LogicalKeyboardKey.keyS):
            const _SaveIntent(),
        LogicalKeySet(LogicalKeyboardKey.meta, LogicalKeyboardKey.enter):
            const _RunIntent(),
        LogicalKeySet(LogicalKeyboardKey.control, LogicalKeyboardKey.enter):
            const _RunIntent(),
      },
      child: Actions(
        actions: <Type, Action<Intent>>{
          _SaveIntent: CallbackAction<_SaveIntent>(
            onInvoke: (_) {
              if (_controller.activeName != null) _save();
              return null;
            },
          ),
          _RunIntent: CallbackAction<_RunIntent>(
            onInvoke: (_) {
              if (_controller.activeName != null) _tabs.animateTo(2);
              return null;
            },
          ),
        },
        child: Focus(autofocus: true, child: _buildScaffold()),
      ),
    );
  }

  Widget _buildScaffold() {
    final theme = Theme.of(context);
    return Scaffold(
      body: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          _Toolbar(
            strings: _l,
            activeName: _controller.activeName,
            dirty: _controller.isDirty,
            saving: _controller.isSaving,
            running: _controller.isRunning,
            onBack: Navigator.of(context).canPop()
                ? () => Navigator.of(context).maybePop()
                : null,
            onSave: _controller.activeName != null ? _save : null,
            onAddStep: _controller.activeName != null ? _addStep : null,
            onNew: _newFlow,
            onRun: _controller.activeName != null
                ? () => _tabs.animateTo(2)
                : null,
          ),
          const Divider(height: 1),
          Expanded(
            child: Row(
              crossAxisAlignment: CrossAxisAlignment.stretch,
              children: [
                SizedBox(
                  width: 240,
                  child: _FileList(
                    filesFuture: _files,
                    activeName: _controller.activeName,
                    strings: _l,
                    onOpen: _openFile,
                    onRefresh: _refreshFiles,
                  ),
                ),
                const VerticalDivider(width: 1),
                Expanded(
                  child: _controller.activeName == null
                      ? _EmptyState(strings: _l)
                      : _tabbedBody(theme),
                ),
              ],
            ),
          ),
        ],
      ),
    );
  }

  Widget _tabbedBody(ThemeData theme) {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: [
        Container(
          color: theme.colorScheme.surfaceContainerLowest,
          child: TabBar(
            controller: _tabs,
            isScrollable: true,
            tabAlignment: TabAlignment.start,
            tabs: [
              Tab(
                text: _l.tabGraph,
                icon: const Icon(Icons.account_tree, size: 16),
              ),
              Tab(text: _l.tabText, icon: const Icon(Icons.notes, size: 16)),
              Tab(
                text: _l.tabRun,
                icon: const Icon(Icons.play_arrow, size: 16),
              ),
            ],
          ),
        ),
        Expanded(
          child: TabBarView(
            controller: _tabs,
            // Disable the lateral swipe gesture so it doesn't
            // race with the canvas's pan handlers.
            physics: const NeverScrollableScrollPhysics(),
            children: [
              _graphTab(theme),
              _textTab(theme),
              RunTab(
                controller: _controller,
                strings: _l,
                driver: widget.runDriver,
              ),
            ],
          ),
        ),
      ],
    );
  }

  Widget _graphTab(ThemeData theme) {
    // When a step is selected, show the properties panel on
    // the right as a fixed sidebar. Selection is owned by
    // the controller and ChangeNotifier rebuilds drive the
    // panel show / hide.
    return Row(
      crossAxisAlignment: CrossAxisAlignment.stretch,
      children: [
        Expanded(child: FlowCanvas(controller: _controller)),
        if (_controller.selectedStepId != null) ...[
          const VerticalDivider(width: 1),
          SizedBox(
            width: 320,
            child: PropertiesPanel(
              controller: _controller,
              strings: _l,
              availableCapabilities: widget.availableCapabilities,
            ),
          ),
        ],
      ],
    );
  }

  Widget _textTab(ThemeData theme) {
    final mono = TextStyle(
      fontFamily: 'JetBrains Mono',
      fontSize: 13,
      height: 1.45,
      color: theme.colorScheme.onSurface,
    );
    return CodeTheme(
      data: CodeThemeData(styles: _yamlStyle(theme)),
      child: CodeField(
        controller: _controller.codeController,
        textStyle: mono,
        expands: true,
        minLines: null,
        maxLines: null,
        gutterStyle: GutterStyle(
          textStyle: mono.copyWith(color: theme.colorScheme.onSurfaceVariant),
          background: theme.colorScheme.surfaceContainer,
          showLineNumbers: true,
        ),
        background: theme.colorScheme.surface,
      ),
    );
  }

  Map<String, TextStyle> _yamlStyle(ThemeData theme) {
    final cs = theme.colorScheme;
    final monoBase = TextStyle(
      fontFamily: 'JetBrains Mono',
      fontSize: 13,
      height: 1.45,
    );
    return {
      'root': monoBase.copyWith(color: cs.onSurface),
      // YAML key — bright primary so the structure pops at a
      // glance. attr is the highlight grammar's key token.
      'attr': monoBase.copyWith(color: cs.primary, fontWeight: FontWeight.w600),
      'string': monoBase.copyWith(color: cs.tertiary),
      'number': monoBase.copyWith(color: cs.secondary),
      'bullet': monoBase.copyWith(color: cs.onSurfaceVariant),
      'literal': monoBase.copyWith(color: cs.secondary),
      'comment': monoBase.copyWith(
        color: cs.onSurfaceVariant,
        fontStyle: FontStyle.italic,
      ),
      'meta': monoBase.copyWith(color: cs.secondary),
    };
  }
}

// --- shortcuts ---

class _SaveIntent extends Intent {
  const _SaveIntent();
}

class _RunIntent extends Intent {
  const _RunIntent();
}

// --- toolbar ---

class _Toolbar extends StatelessWidget {
  final FlowEditorStrings strings;
  final String? activeName;
  final bool dirty;
  final bool saving;
  final bool running;
  final VoidCallback? onBack;
  final VoidCallback? onSave;
  final VoidCallback? onAddStep;
  final VoidCallback onNew;
  final VoidCallback? onRun;
  const _Toolbar({
    required this.strings,
    required this.activeName,
    required this.dirty,
    required this.saving,
    required this.running,
    required this.onBack,
    required this.onSave,
    required this.onAddStep,
    required this.onNew,
    required this.onRun,
  });

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return Container(
      padding: const EdgeInsets.symmetric(
        horizontal: FaiSpace.md,
        vertical: FaiSpace.sm,
      ),
      color: theme.colorScheme.surfaceContainer,
      child: Row(
        children: [
          if (onBack != null) ...[
            IconButton(
              icon: const Icon(Icons.arrow_back, size: 18),
              tooltip: strings.backTooltip,
              onPressed: onBack,
            ),
            const SizedBox(width: FaiSpace.xs),
          ],
          Text(
            activeName == null ? strings.emptyTitle : '${activeName!}.yaml',
            style: theme.textTheme.titleSmall?.copyWith(
              fontFamily: 'monospace',
              fontWeight: FontWeight.w600,
            ),
          ),
          if (dirty)
            Padding(
              padding: const EdgeInsets.only(left: FaiSpace.xs),
              child: Icon(
                Icons.circle,
                size: 8,
                color: theme.colorScheme.primary,
              ),
            ),
          const Spacer(),
          FilledButton.tonalIcon(
            onPressed: onNew,
            icon: const Icon(Icons.add, size: 16),
            label: Text(strings.newFlow),
          ),
          const SizedBox(width: FaiSpace.sm),
          if (onAddStep != null)
            FilledButton.tonalIcon(
              onPressed: onAddStep,
              icon: const Icon(Icons.add_box_outlined, size: 16),
              label: Text(strings.addStep),
            ),
          const SizedBox(width: FaiSpace.sm),
          FilledButton.tonalIcon(
            onPressed: saving ? null : onSave,
            icon: saving
                ? const SizedBox(
                    width: 14,
                    height: 14,
                    child: CircularProgressIndicator(strokeWidth: 2),
                  )
                : const Icon(Icons.save_outlined, size: 16),
            label: Text(strings.save),
          ),
          const SizedBox(width: FaiSpace.sm),
          FilledButton.icon(
            onPressed: onRun,
            icon: running
                ? const SizedBox(
                    width: 14,
                    height: 14,
                    child: CircularProgressIndicator(strokeWidth: 2),
                  )
                : const Icon(Icons.play_arrow, size: 18),
            label: Text(strings.run),
          ),
        ],
      ),
    );
  }
}

// --- file list ---

class _FlowFile {
  final String name;
  final String path;
  final int sizeBytes;
  const _FlowFile({
    required this.name,
    required this.path,
    required this.sizeBytes,
  });
}

class _FileList extends StatelessWidget {
  final Future<List<_FlowFile>> filesFuture;
  final String? activeName;
  final FlowEditorStrings strings;
  final void Function(_FlowFile) onOpen;
  final VoidCallback onRefresh;

  const _FileList({
    required this.filesFuture,
    required this.activeName,
    required this.strings,
    required this.onOpen,
    required this.onRefresh,
  });

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return Container(
      color: theme.colorScheme.surface,
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          Container(
            padding: const EdgeInsets.symmetric(
              horizontal: FaiSpace.md,
              vertical: FaiSpace.xs,
            ),
            decoration: BoxDecoration(
              border: Border(bottom: BorderSide(color: theme.dividerColor)),
            ),
            child: Row(
              children: [
                Expanded(
                  child: Text(
                    strings.listHeader,
                    style: theme.textTheme.labelSmall?.copyWith(
                      color: theme.colorScheme.onSurfaceVariant,
                      letterSpacing: 0.6,
                    ),
                  ),
                ),
                IconButton(
                  onPressed: onRefresh,
                  tooltip: strings.refresh,
                  icon: const Icon(Icons.refresh, size: 16),
                  visualDensity: VisualDensity.compact,
                  padding: EdgeInsets.zero,
                  constraints: const BoxConstraints(
                    minWidth: 28,
                    minHeight: 28,
                  ),
                ),
              ],
            ),
          ),
          Expanded(child: _buildBody(context, theme)),
        ],
      ),
    );
  }

  Widget _buildBody(BuildContext context, ThemeData theme) {
    return FutureBuilder<List<_FlowFile>>(
      future: filesFuture,
      builder: (context, snap) {
        if (snap.connectionState == ConnectionState.waiting) {
          return const Center(child: CircularProgressIndicator());
        }
        if (snap.hasError) {
          return Padding(
            padding: const EdgeInsets.all(FaiSpace.md),
            child: FaiErrorBox(error: snap.error, isError: true),
          );
        }
        final files = snap.data ?? <_FlowFile>[];
        if (files.isEmpty) {
          return Padding(
            padding: const EdgeInsets.all(FaiSpace.md),
            child: FaiEmptyState(
              icon: Icons.folder_outlined,
              title: strings.listEmptyTitle,
              hint: strings.listEmptyBody,
            ),
          );
        }
        return ListView.builder(
          padding: const EdgeInsets.symmetric(vertical: FaiSpace.xs),
          itemCount: files.length,
          itemBuilder: (_, i) {
            final f = files[i];
            final isActive = f.name == activeName;
            return InkWell(
              onTap: () => onOpen(f),
              child: Container(
                padding: const EdgeInsets.symmetric(
                  horizontal: FaiSpace.md,
                  vertical: FaiSpace.sm,
                ),
                decoration: BoxDecoration(
                  color: isActive ? theme.colorScheme.secondaryContainer : null,
                  border: Border(
                    left: BorderSide(
                      width: 3,
                      color: isActive
                          ? theme.colorScheme.primary
                          : Colors.transparent,
                    ),
                  ),
                ),
                child: Column(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: [
                    Text(
                      f.name,
                      style: theme.textTheme.bodyMedium?.copyWith(
                        fontWeight: FontWeight.w500,
                      ),
                      overflow: TextOverflow.ellipsis,
                    ),
                    Text(
                      '${f.sizeBytes} B',
                      style: theme.textTheme.bodySmall?.copyWith(
                        color: theme.colorScheme.onSurfaceVariant,
                      ),
                    ),
                  ],
                ),
              ),
            );
          },
        );
      },
    );
  }
}

// --- empty state ---

class _EmptyState extends StatelessWidget {
  final FlowEditorStrings strings;
  const _EmptyState({required this.strings});

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return Container(
      color: theme.colorScheme.surface,
      child: Center(
        child: Padding(
          padding: const EdgeInsets.all(FaiSpace.xl),
          child: FaiEmptyState(
            icon: Icons.description_outlined,
            title: strings.emptyTitle,
            hint: strings.emptyBody,
          ),
        ),
      ),
    );
  }
}

// --- new flow dialog ---

class _NewFlowDialog extends StatefulWidget {
  final FlowEditorStrings strings;
  const _NewFlowDialog({required this.strings});

  @override
  State<_NewFlowDialog> createState() => _NewFlowDialogState();
}

class _NewFlowDialogState extends State<_NewFlowDialog> {
  final _controller = TextEditingController();
  String? _error;

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  void _submit() {
    final name = _controller.text.trim();
    if (!RegExp(r'^[a-z0-9_-]+$').hasMatch(name)) {
      setState(() => _error = widget.strings.newDialogHelper);
      return;
    }
    Navigator.pop(context, name);
  }

  @override
  Widget build(BuildContext context) {
    return AlertDialog(
      title: Text(widget.strings.newDialogTitle),
      content: TextField(
        autofocus: true,
        controller: _controller,
        decoration: InputDecoration(
          labelText: widget.strings.newDialogLabel,
          helperText: widget.strings.newDialogHelper,
          errorText: _error,
          border: const OutlineInputBorder(),
        ),
        onSubmitted: (_) => _submit(),
      ),
      actions: [
        TextButton(
          onPressed: () => Navigator.pop(context),
          child: Text(widget.strings.newDialogCancel),
        ),
        FilledButton(
          onPressed: _submit,
          child: Text(widget.strings.newDialogCreate),
        ),
      ],
    );
  }
}