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;
  }
}