// lib/editor/canvas/pen_canvas.dart
//
// Pen-first canvas: ONE shared transform (an InteractiveViewer driven by a
// TransformationController we own) zooms/pans BOTH the PDF page bitmap and the
// ink layer together. A Listener wrapped around the InteractiveViewer reads raw
// pointer kind + pressure and tracks the active pointer COUNT to arbitrate
// draw vs pan/zoom — we own the gesture pipeline, pdfrx never sees gestures.
//
// Gesture arbitration (reimplemented clean-room from Saber's documented model):
//  - A draw gesture is exactly ONE active pointer that is a stylus / inverted
//    stylus, OR (when the user's finger-drawing toggle is on) a single finger.
//  - >= 2 active pointers ALWAYS means pan/zoom (pinch); never draw. If a 2nd
//    pointer lands while a stroke is in progress, that stroke is discarded
//    (accidental palm/finger).
//  - Palm rejection: once any stylus event is seen in a session, finger-drawing
//    is forced OFF so a resting palm/finger pans instead of marking.
//  - While a stroke is active, the InteractiveViewer's pan is disabled so it
//    can't fight the stroke; pinch-zoom still works because a 2nd pointer
//    cancels the stroke first, re-enabling pan/zoom.

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

import 'ink_painters.dart';
import 'pen_stroke.dart';

/// The active tool on the pen canvas.
enum CanvasTool { pen, highlighter, eraser }

class PenCanvas extends StatefulWidget {
  const PenCanvas({
    super.key,
    required this.pageWidget,
    required this.pageSize,
    required this.strokes,
    required this.transformationController,
    required this.tool,
    required this.color,
    required this.strokeWidth,
    required this.onStrokeComplete,
    required this.onEraseStroke,
    this.allowFingerDrawing = false,
    this.minScale = 0.5,
    this.maxScale = 8.0,
  });

  /// The rendered PDF page bitmap, already sized to [pageSize].
  final Widget pageWidget;

  /// On-screen size (at scale 1.0) of the page rectangle in logical pixels.
  /// Ink normalized coords map onto this rectangle.
  final Size pageSize;

  /// Committed strokes for the CURRENT page (normalized coords).
  final List<PenStroke> strokes;

  /// Shared transform driving both page and ink.
  final TransformationController transformationController;

  final CanvasTool tool;
  final Color color;

  /// Pen width as a fraction of page width (so it zooms with the page).
  final double strokeWidth;

  /// Called with a finished stroke (normalized coords) to commit it.
  final void Function(PenStroke stroke) onStrokeComplete;

  /// Called with the index of a committed stroke to erase (stroke-erase).
  final void Function(int strokeIndex) onEraseStroke;

  /// User toggle: allow a single finger to draw. Forced off once a stylus is
  /// seen (palm rejection).
  final bool allowFingerDrawing;

  final double minScale;
  final double maxScale;

  @override
  State<PenCanvas> createState() => _PenCanvasState();
}

class _PenCanvasState extends State<PenCanvas> {
  /// Active (down) pointers by id → their device kind. Size == pointer count.
  final Map<int, PointerDeviceKind> _activePointers = {};

  /// The pointer id currently driving a stroke, or null.
  int? _drawPointer;

  /// In-progress stroke points (normalized).
  final List<PenPoint> _livePoints = [];

  /// Live stroke snapshot handed to the LiveInkPainter; null when idle.
  PenStroke? _liveStroke;

  /// True once any stylus event is seen this session → finger-drawing forced
  /// off so a resting palm pans instead of marking.
  bool _stylusSeen = false;

  /// True when the active stylus reports the eraser signal (barrel button or
  /// inverted stylus), detected on hover/down.
  bool _eraserActive = false;

  bool get _fingerDrawingEnabled =>
      widget.allowFingerDrawing && !_stylusSeen;

  bool _isStylus(PointerDeviceKind kind) =>
      kind == PointerDeviceKind.stylus ||
      kind == PointerDeviceKind.invertedStylus;

  /// Normalize stylus pressure to [0,1], or null when the device reports no
  /// usable pressure range (then perfect_freehand simulates pressure).
  double? _normalizedPressure(PointerEvent event) {
    if (!_isStylus(event.kind)) return null;
    if (event.pressureMin == event.pressureMax) return null;
    final range = event.pressureMax - event.pressureMin;
    return ((event.pressure - event.pressureMin) / range).clamp(0.0, 1.0);
  }

  /// The eraser signal: barrel/secondary button held, or an inverted stylus.
  bool _isEraserSignal(PointerEvent event) =>
      event.buttons == kSecondaryButton ||
      event.kind == PointerDeviceKind.invertedStylus;

  /// Decide whether the gesture currently forming should DRAW.
  /// True iff exactly one active pointer AND (stylus OR finger-drawing on).
  bool _shouldDraw(PointerDeviceKind kind) {
    if (_activePointers.length != 1) return false;
    if (_isStylus(kind)) return true;
    if (kind == PointerDeviceKind.mouse) return true;
    if (kind == PointerDeviceKind.touch) return _fingerDrawingEnabled;
    return false;
  }

  // --- Coordinate mapping ---------------------------------------------------

  /// Map a global pointer position into normalized page coords using the
  /// shared transform (inverse) and this widget's geometry.
  PenPoint? _toNormalized(Offset globalPosition, double? pressure) {
    final box = context.findRenderObject() as RenderBox?;
    if (box == null) return null;
    final local = box.globalToLocal(globalPosition);

    // Undo the InteractiveViewer transform to get scene (untransformed) coords.
    final scene = widget.transformationController.toScene(local);

    final nx = scene.dx / widget.pageSize.width;
    final ny = scene.dy / widget.pageSize.height;
    return PenPoint(nx, ny, pressure);
  }

  // --- Stroke lifecycle -----------------------------------------------------

  void _startStroke(PointerDownEvent event) {
    _drawPointer = event.pointer;
    _livePoints.clear();
    final p = _toNormalized(event.position, _normalizedPressure(event));
    if (p != null) _livePoints.add(p);

    if (_eraserActive || widget.tool == CanvasTool.eraser) {
      _eraseAt(p);
      // Keep the stroke pointer reserved so moves keep erasing, but don't paint.
      setState(() => _liveStroke = null);
      return;
    }
    _updateLiveStroke();
  }

  void _extendStroke(PointerMoveEvent event) {
    final p = _toNormalized(event.position, _normalizedPressure(event));
    if (p == null) return;

    if (_eraserActive || widget.tool == CanvasTool.eraser) {
      _eraseAt(p);
      return;
    }
    _livePoints.add(p);
    _updateLiveStroke();
  }

  void _endStroke() {
    if (_drawPointer == null) return;
    final wasEraser = _eraserActive || widget.tool == CanvasTool.eraser;
    if (!wasEraser && _livePoints.isNotEmpty) {
      widget.onStrokeComplete(
        PenStroke(
          points: List.of(_livePoints),
          color: _currentColor().toARGB32(),
          width: widget.strokeWidth,
          kind: _currentKind(),
        ),
      );
    }
    _drawPointer = null;
    _livePoints.clear();
    setState(() => _liveStroke = null);
  }

  /// Discard the in-progress stroke without committing (palm/2nd-finger).
  void _cancelStroke() {
    _drawPointer = null;
    _livePoints.clear();
    setState(() => _liveStroke = null);
  }

  void _updateLiveStroke() {
    setState(() {
      _liveStroke = PenStroke(
        points: List.of(_livePoints),
        color: _currentColor().toARGB32(),
        width: widget.strokeWidth,
        kind: _currentKind(),
      );
    });
  }

  PenStrokeKind _currentKind() =>
      widget.tool == CanvasTool.highlighter
          ? PenStrokeKind.highlighter
          : PenStrokeKind.pen;

  Color _currentColor() => widget.tool == CanvasTool.highlighter
      ? widget.color.withAlpha(0x80)
      : widget.color;

  /// Stroke-erase: remove the first committed stroke within proximity of [p].
  void _eraseAt(PenPoint? p) {
    if (p == null) return;
    final radius = widget.strokeWidth * 2; // normalized radius
    for (var i = widget.strokes.length - 1; i >= 0; i--) {
      final stroke = widget.strokes[i];
      for (final sp in stroke.points) {
        final dx = sp.x - p.x;
        final dy = sp.y - p.y;
        if (dx * dx + dy * dy < radius * radius) {
          widget.onEraseStroke(i);
          return;
        }
      }
    }
  }

  // --- Listener callbacks ---------------------------------------------------

  void _onPointerHover(PointerHoverEvent event) {
    if (_isStylus(event.kind)) {
      _stylusSeen = true;
      // Detect eraser (barrel button / inverted) while hovering.
      _eraserActive = _isEraserSignal(event);
    }
  }

  void _onPointerDown(PointerDownEvent event) {
    if (event.kind == PointerDeviceKind.trackpad) return;
    if (_isStylus(event.kind)) _stylusSeen = true;

    _activePointers[event.pointer] = event.kind;

    // A 2nd pointer arriving during a stroke = pinch/palm → cancel the stroke
    // and let the InteractiveViewer take over pan/zoom.
    if (_activePointers.length >= 2) {
      if (_drawPointer != null) _cancelStroke();
      return;
    }

    // Single pointer: decide draw vs pan. Eraser is on if this stylus down
    // signals it (barrel button / inverted), or hover already flagged it.
    if (_isStylus(event.kind)) {
      _eraserActive = _eraserActive || _isEraserSignal(event);
    } else {
      _eraserActive = false;
    }

    if (_shouldDraw(event.kind)) {
      _startStroke(event);
    }
  }

  void _onPointerMove(PointerMoveEvent event) {
    if (event.pointer != _drawPointer) return;
    if (_activePointers.length >= 2) return; // pinch owns it
    _extendStroke(event);
  }

  void _onPointerUp(PointerUpEvent event) {
    final wasDrawer = event.pointer == _drawPointer;
    _activePointers.remove(event.pointer);
    if (wasDrawer) _endStroke();
  }

  void _onPointerCancel(PointerCancelEvent event) {
    final wasDrawer = event.pointer == _drawPointer;
    _activePointers.remove(event.pointer);
    if (wasDrawer) _cancelStroke();
  }

  @override
  Widget build(BuildContext context) {
    // Pan only when NOT mid-stroke; while drawing we suppress IV pan so it
    // can't fight the stroke. (A 2nd finger cancels the stroke first, so pinch
    // re-enables pan/zoom immediately.)
    final panEnabled = _drawPointer == null;

    return Listener(
      onPointerHover: _onPointerHover,
      onPointerDown: _onPointerDown,
      onPointerMove: _onPointerMove,
      onPointerUp: _onPointerUp,
      onPointerCancel: _onPointerCancel,
      child: InteractiveViewer(
        transformationController: widget.transformationController,
        minScale: widget.minScale,
        maxScale: widget.maxScale,
        panEnabled: panEnabled,
        scaleEnabled: true,
        constrained: false,
        boundaryMargin: const EdgeInsets.all(double.infinity),
        child: SizedBox(
          width: widget.pageSize.width,
          height: widget.pageSize.height,
          child: Stack(
            children: [
              // PDF page bitmap.
              Positioned.fill(child: widget.pageWidget),
              // Committed ink (static layer, isolated repaint).
              Positioned.fill(
                child: RepaintBoundary(
                  child: CustomPaint(
                    painter: StaticInkPainter(
                      strokes: widget.strokes,
                      pageSize: widget.pageSize,
                    ),
                  ),
                ),
              ),
              // Live ink (current stroke only, isolated repaint).
              Positioned.fill(
                child: RepaintBoundary(
                  child: CustomPaint(
                    painter: LiveInkPainter(
                      stroke: _liveStroke,
                      pageSize: widget.pageSize,
                    ),
                  ),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}