// ChainFlowOutput — type-aware renderer for one entry in
// `runSavedFlow`'s output map. Reads `FlowOutput` and dispatches
// to the right widget:
//
//   - text:    SelectableText for plain text; Markdown widget
//              when the (hinted) MIME is text/markdown.
//   - json:    indented JSON in a code-block container.
//   - bytes:   inline image thumbnail when image/*, otherwise a
//              "{mime}, {size}" summary. Always offers Save-as.
//   - file:    "Open" button → SystemActions.openInOs(uri).
//
// Stateless on purpose: the dialog wraps it; we never own a
// future or a controller here.

import 'dart:io';
import 'dart:typed_data';

import 'package:file_picker/file_picker.dart';
import 'package:flutter/material.dart';
import 'package:flutter_markdown_plus/flutter_markdown_plus.dart';

import '../data/error_presentation.dart';
import '../data/flow_output.dart';
import '../data/format.dart';
import '../data/system_actions.dart';
import '../l10n/app_localizations.dart';
import '../theme/theme.dart';
import '../theme/tokens.dart';

class ChainFlowOutput extends StatelessWidget {
  final FlowOutput output;

  const ChainFlowOutput({super.key, required this.output});

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    switch (output) {
      case FlowOutputText(:final text):
        return _TextView(text: text);
      case FlowOutputJson(:final pretty):
        return _CodeBlock(text: pretty, theme: theme);
      case FlowOutputBytes(:final bytes, :final mimeType):
        return _BytesView(bytes: bytes, mimeType: mimeType);
      case FlowOutputFile(:final uri, :final mimeType):
        return _FileView(uri: uri, mimeType: mimeType);
      case FlowOutputUnknown():
        return _CodeBlock(
          text: AppLocalizations.of(context)!.flowsOutputUnknown,
          theme: theme,
        );
    }
  }
}

/// Plain-text renderer. Auto-detects markdown via a cheap
/// heuristic (leading `#` heading, fenced code block, or
/// numbered/bulleted list) so flows that emit text/markdown
/// without setting an explicit MIME still render formatted.
class _TextView extends StatelessWidget {
  final String text;

  const _TextView({required this.text});

  static final RegExp _markdownHeuristic = RegExp(
    r'(^|\n)(#{1,6}\s|```|\*\s|-\s|\d+\.\s)',
  );

  bool get _looksLikeMarkdown =>
      text.length < 64 * 1024 && _markdownHeuristic.hasMatch(text);

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    if (_looksLikeMarkdown) {
      return Container(
        width: double.infinity,
        padding: const EdgeInsets.all(ChainSpace.md),
        decoration: BoxDecoration(
          color: theme.colorScheme.surfaceContainerHigh,
          borderRadius: BorderRadius.circular(ChainRadius.sm),
          border: Border.all(color: theme.colorScheme.outlineVariant),
        ),
        child: MarkdownBody(
          data: text,
          selectable: true,
          onTapLink: (_, href, _) async {
            if (href != null && href.isNotEmpty) {
              await SystemActions.openInOs(href);
            }
          },
          styleSheet: ChainTheme.markdownStyle(theme),
        ),
      );
    }
    return Container(
      width: double.infinity,
      padding: const EdgeInsets.all(ChainSpace.md),
      decoration: BoxDecoration(
        color: theme.colorScheme.surfaceContainerHigh,
        borderRadius: BorderRadius.circular(ChainRadius.sm),
        border: Border.all(color: theme.colorScheme.outlineVariant),
      ),
      child: SelectableText(
        text,
        style: theme.textTheme.bodyMedium?.copyWith(height: 1.5),
      ),
    );
  }
}

class _CodeBlock extends StatelessWidget {
  final String text;
  final ThemeData theme;

  const _CodeBlock({required this.text, required this.theme});

  @override
  Widget build(BuildContext context) {
    return Container(
      width: double.infinity,
      padding: const EdgeInsets.all(ChainSpace.md),
      decoration: BoxDecoration(
        color: theme.colorScheme.surfaceContainerHigh,
        borderRadius: BorderRadius.circular(ChainRadius.sm),
        border: Border.all(color: theme.colorScheme.outlineVariant),
      ),
      child: SelectableText(
        text,
        style: ChainTheme.mono(size: 12, color: theme.colorScheme.onSurface),
      ),
    );
  }
}

class _BytesView extends StatelessWidget {
  final Uint8List bytes;
  final String mimeType;

  const _BytesView({required this.bytes, required this.mimeType});

  bool get _isImage => mimeType.startsWith('image/');

  /// Reasonable default filename for the Save dialog. Strips the
  /// MIME up to the slash and uses the suffix when known
  /// (image/png → output.png), otherwise a generic `.bin`.
  String _defaultFilename() {
    final slash = mimeType.indexOf('/');
    if (slash < 0 || slash == mimeType.length - 1) return 'output.bin';
    final sub = mimeType.substring(slash + 1);
    // Strip common parameter suffixes (`png; charset=...`).
    final semi = sub.indexOf(';');
    final ext = semi < 0 ? sub : sub.substring(0, semi);
    // `vnd.openxmlformats-…wordprocessingml.document` → docx.
    if (ext.contains('wordprocessingml')) return 'output.docx';
    if (ext.contains('spreadsheetml')) return 'output.xlsx';
    if (ext.contains('presentationml')) return 'output.pptx';
    return 'output.$ext';
  }

  Future<void> _save(BuildContext context) async {
    final l = AppLocalizations.of(context)!;
    final path = await FilePicker.saveFile(
      dialogTitle: l.flowsOutputSaveAsTitle,
      fileName: _defaultFilename(),
    );
    if (path == null) return;
    try {
      await File(path).writeAsBytes(bytes, flush: true);
      if (!context.mounted) return;
      ScaffoldMessenger.of(
        context,
      ).showSnackBar(SnackBar(content: Text(l.flowsOutputSavedAt(path))));
    } catch (e) {
      if (!context.mounted) return;
      showFaiErrorSnack(context, 'flows.output.save', e);
    }
  }

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final l = AppLocalizations.of(context)!;
    return Container(
      width: double.infinity,
      padding: const EdgeInsets.all(ChainSpace.md),
      decoration: BoxDecoration(
        color: theme.colorScheme.surfaceContainerHigh,
        borderRadius: BorderRadius.circular(ChainRadius.sm),
        border: Border.all(color: theme.colorScheme.outlineVariant),
      ),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          if (_isImage) ...[
            ConstrainedBox(
              constraints: const BoxConstraints(maxHeight: 240),
              child: ClipRRect(
                borderRadius: BorderRadius.circular(ChainRadius.sm),
                child: Image.memory(bytes, fit: BoxFit.contain),
              ),
            ),
            const SizedBox(height: ChainSpace.sm),
          ],
          Text(
            '${mimeType.isEmpty ? l.flowsOutputBytesUnknownMime : mimeType}'
            ' · ${humanBytes(bytes.length)}',
            style: theme.textTheme.bodySmall?.copyWith(
              color: theme.colorScheme.onSurfaceVariant,
            ),
          ),
          const SizedBox(height: ChainSpace.sm),
          OutlinedButton.icon(
            icon: const Icon(Icons.save_alt, size: 16),
            label: Text(l.flowsOutputSaveAs),
            onPressed: () => _save(context),
          ),
        ],
      ),
    );
  }
}

class _FileView extends StatelessWidget {
  final String uri;
  final String mimeType;

  const _FileView({required this.uri, required this.mimeType});

  Future<void> _open(BuildContext context) async {
    // Most file-URIs come from modules that wrote a temp/output
    // path on the host. SystemActions normalises `file://` for
    // open-in-OS on all three platforms.
    final target = uri.startsWith('file://') ? uri.substring(7) : uri;
    final r = await SystemActions.openInOs(target);
    if (!context.mounted || r.ok) return;
    showFaiErrorSnack(
      context,
      'flows.output.open',
      r.stderr.isEmpty ? 'open failed' : r.stderr,
    );
  }

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    final l = AppLocalizations.of(context)!;
    return Container(
      width: double.infinity,
      padding: const EdgeInsets.all(ChainSpace.md),
      decoration: BoxDecoration(
        color: theme.colorScheme.surfaceContainerHigh,
        borderRadius: BorderRadius.circular(ChainRadius.sm),
        border: Border.all(color: theme.colorScheme.outlineVariant),
      ),
      child: Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        children: [
          SelectableText(
            uri,
            style: ChainTheme.mono(size: 11, color: theme.colorScheme.primary),
          ),
          if (mimeType.isNotEmpty) ...[
            const SizedBox(height: 4),
            Text(
              mimeType,
              style: theme.textTheme.bodySmall?.copyWith(
                color: theme.colorScheme.onSurfaceVariant,
              ),
            ),
          ],
          const SizedBox(height: ChainSpace.sm),
          OutlinedButton.icon(
            icon: const Icon(Icons.open_in_new, size: 16),
            label: Text(l.flowsOutputOpen),
            onPressed: () => _open(context),
          ),
        ],
      ),
    );
  }
}