import 'dart:math';

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

import '../../theming/app_theme.dart';
import 'pm_document_view.dart';
import 'pm_node.dart';

/// Renders a ProseMirror table. Flutter's built-in `Table` cannot span cells,
/// so `flutter_layout_grid` places each cell explicitly, honouring
/// colspan/rowspan via a simple HTML-style occupancy scan.
class PmTableView extends StatelessWidget {
  final PmTable node;

  static const double _minColumnWidth = 140;

  const PmTableView({required this.node, super.key});

  @override
  Widget build(BuildContext context) {
    final rows = node.children.whereType<PmTableRow>().toList();
    if (rows.isEmpty) return const SizedBox.shrink();

    final occupied = <int, Set<int>>{};
    final placements = <Widget>[];
    var columnCount = 0;

    for (var r = 0; r < rows.length; r++) {
      var col = 0;
      for (final cell in rows[r].children.whereType<PmTableCell>()) {
        while (occupied[r]?.contains(col) ?? false) {
          col++;
        }
        placements.add(
          GridPlacement(
            columnStart: col,
            columnSpan: cell.colspan,
            rowStart: r,
            rowSpan: cell.rowspan,
            child: _cell(context, cell),
          ),
        );
        for (var dr = 0; dr < cell.rowspan; dr++) {
          final set = occupied[r + dr] ??= <int>{};
          for (var dc = 0; dc < cell.colspan; dc++) {
            set.add(col + dc);
          }
        }
        col += cell.colspan;
        columnCount = max(columnCount, col);
      }
    }
    if (columnCount == 0) return const SizedBox.shrink();

    return LayoutBuilder(
      builder: (context, constraints) {
        final available = constraints.maxWidth.isFinite
            ? constraints.maxWidth
            : _minColumnWidth * columnCount;
        final columnWidth = max(_minColumnWidth, available / columnCount);
        final totalWidth = columnWidth * columnCount;

        final grid = SizedBox(
          width: totalWidth,
          child: LayoutGrid(
            columnSizes: List.filled(columnCount, fixed(columnWidth)),
            rowSizes: List.filled(rows.length, auto),
            children: placements,
          ),
        );

        if (totalWidth <= available) return grid;
        return SingleChildScrollView(
          scrollDirection: Axis.horizontal,
          child: grid,
        );
      },
    );
  }

  Widget _cell(BuildContext context, PmTableCell cell) {
    final theme = Theme.of(context);
    return DecoratedBox(
      decoration: BoxDecoration(
        color: cell.header ? theme.colorScheme.surfaceContainerHighest : null,
        border: Border.all(color: theme.colorScheme.outlineVariant),
      ),
      child: Padding(
        padding: const EdgeInsets.all(AppSpacing.sm),
        child: pmBlocks(cell.children, gap: AppSpacing.xs),
      ),
    );
  }
}