Complete refactor to clean up project

lib/features/sheet_viewer/widgets/touch_navigation_layer.dart

@@ -0,0 +1,126 @@
+import 'package:flutter/material.dart';
+
+import '../../../core/models/config.dart';
+import 'pdf_page_display.dart';
+
+/// Callback for page turn events.
+typedef PageTurnCallback = void Function(int delta);
+
+/// Gesture layer for touch-based navigation over PDF pages.
+///
+/// Touch zones:
+/// - Top 2cm: Toggle fullscreen (or exit if in fullscreen + top-right corner)
+/// - Left side: Turn page backward (-1 or -2 in two-page mode)
+/// - Right side: Turn page forward (+1 or +2 in two-page mode)
+class TouchNavigationLayer extends StatelessWidget {
+  final PdfPageDisplay pageDisplay;
+  final Config config;
+  final VoidCallback onToggleFullscreen;
+  final VoidCallback onExit;
+  final PageTurnCallback onPageTurn;
+
+  const TouchNavigationLayer({
+    super.key,
+    required this.pageDisplay,
+    required this.config,
+    required this.onToggleFullscreen,
+    required this.onExit,
+    required this.onPageTurn,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return GestureDetector(
+      behavior: HitTestBehavior.opaque,
+      onTapUp: (details) => _handleTap(context, details),
+      child: pageDisplay,
+    );
+  }
+
+  void _handleTap(BuildContext context, TapUpDetails details) {
+    final mediaQuery = MediaQuery.of(context);
+    final position = details.localPosition;
+
+    // Calculate physical measurements for consistent touch zones
+    final pixelsPerCm = _calculatePixelsPerCm(mediaQuery.devicePixelRatio);
+    final touchZoneHeight = 2 * pixelsPerCm;
+    final touchZoneWidth = 2 * pixelsPerCm;
+
+    final screenWidth = mediaQuery.size.width;
+    final screenCenter = screenWidth / 2;
+
+    // Get page sizes for accurate touch zone calculation
+    final (leftPageSize, rightPageSize) = pageDisplay.calculateScaledPageSizes(
+      mediaQuery.size,
+    );
+
+    // Check top zone first
+    if (position.dy < touchZoneHeight) {
+      _handleTopZoneTap(position, screenWidth, touchZoneWidth);
+      return;
+    }
+
+    // Handle page turning based on tap position
+    _handlePageTurnTap(position, screenCenter, leftPageSize, rightPageSize);
+  }
+
+  void _handleTopZoneTap(
+    Offset position,
+    double screenWidth,
+    double touchZoneWidth,
+  ) {
+    // Top-right corner in fullscreen mode = exit
+    if (config.fullscreen && position.dx >= screenWidth - touchZoneWidth) {
+      onExit();
+    } else {
+      onToggleFullscreen();
+    }
+  }
+
+  void _handlePageTurnTap(
+    Offset position,
+    double screenCenter,
+    Size leftPageSize,
+    Size? rightPageSize,
+  ) {
+    final isLeftSide = position.dx < screenCenter;
+
+    if (config.twoPageMode) {
+      _handleTwoPageModeTap(
+        position,
+        screenCenter,
+        leftPageSize,
+        rightPageSize,
+      );
+    } else {
+      // Single page mode: simple left/right
+      onPageTurn(isLeftSide ? -1 : 1);
+    }
+  }
+
+  void _handleTwoPageModeTap(
+    Offset position,
+    double screenCenter,
+    Size leftPageSize,
+    Size? rightPageSize,
+  ) {
+    final leftEdge = screenCenter - leftPageSize.width / 2;
+    final rightEdge = screenCenter + (rightPageSize?.width ?? 0) / 2;
+
+    if (position.dx < leftEdge) {
+      onPageTurn(-2);
+    } else if (position.dx < screenCenter) {
+      onPageTurn(-1);
+    } else if (position.dx > rightEdge) {
+      onPageTurn(2);
+    } else {
+      onPageTurn(1);
+    }
+  }
+
+  double _calculatePixelsPerCm(double devicePixelRatio) {
+    const baseDpi = 160.0; // Android baseline DPI
+    const cmPerInch = 2.54;
+    return (devicePixelRatio * baseDpi) / cmPerInch;
+  }
+}