// lib/editor/engine/stroke_geometry.dart
//
// Single source of stroke outline geometry for both screen render and export.
// The recipe is lifted verbatim from the proven live
// `ink_painters.buildStrokePath` (lib/editor/canvas/ink_painters.dart): points
// are scaled from normalized page coords to pixels, perfect_freehand produces
// the outline, and a closed fill Path is built. Keeping ONE implementation here
// kills the hairline-export divergence (R7).

import 'dart:ui';

import 'package:perfect_freehand/perfect_freehand.dart' as pf;

import 'stroke_model.dart';

/// Builds a closed, fillable outline [Path] for one [stroke], scaled into the
/// pixel space of [pageSize] (which maps normalized [0,1] coords to pixels).
///
/// [isComplete] should be false for the in-progress live stroke so freehand
/// tapers the trailing end correctly, and true for committed strokes.
///
/// Returns an empty [Path] when the stroke has no points (or freehand produces
/// no outline).
Path buildStrokeOutline(
  EditorStroke stroke,
  Size pageSize, {
  required bool isComplete,
}) {
  final path = Path();
  if (stroke.points.isEmpty) return path;

  final pixelWidth = stroke.width * pageSize.width;

  final hasRealPressure = stroke.points.any((p) => p.pressure != null);
  final isHighlighter = stroke.tool == EditorTool.highlighter;

  final pfPoints = stroke.points
      .map(
        (p) => pf.Point(
          p.x * pageSize.width,
          p.y * pageSize.height,
          p.pressure ?? 0.5,
        ),
      )
      .toList();

  final outline = pf.getStroke(
    pfPoints,
    size: pixelWidth,
    // Highlighter keeps a constant width (no thinning); pen thins (0.7),
    // matching the live recipe.
    thinning: isHighlighter ? 0.0 : 0.7,
    smoothing: 0.5,
    streamline: 0.5,
    // Real stylus pressure -> don't simulate; no pressure -> let freehand fake
    // it based on velocity (highlighter never simulates).
    simulatePressure: !hasRealPressure && !isHighlighter,
    isComplete: isComplete,
  );

  if (outline.isEmpty) return path;
  path.moveTo(outline.first.x, outline.first.y);
  for (var i = 1; i < outline.length; i++) {
    path.lineTo(outline[i].x, outline[i].y);
  }
  path.close();
  return path;
}